Queryable.Average Method

Definition

Namespace:

System.Linq

Assembly:

System.Linq.Queryable.dll

Computes the average of a sequence of numeric values.

Overloads

Average(IQueryable<Single>)	Computes the average of a sequence of Single values.
Average(IQueryable<Nullable<Int64>>)	Computes the average of a sequence of nullable Int64 values.
Average(IQueryable<Nullable<Int32>>)	Computes the average of a sequence of nullable Int32 values.
Average(IQueryable<Nullable<Double>>)	Computes the average of a sequence of nullable Double values.
Average(IQueryable<Nullable<Single>>)	Computes the average of a sequence of nullable Single values.
Average(IQueryable<Int64>)	Computes the average of a sequence of Int64 values.
Average(IQueryable<Int32>)	Computes the average of a sequence of Int32 values.
Average(IQueryable<Double>)	Computes the average of a sequence of Double values.
Average(IQueryable<Decimal>)	Computes the average of a sequence of Decimal values.
Average(IQueryable<Nullable<Decimal>>)	Computes the average of a sequence of nullable Decimal values.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>)	Computes the average of a sequence of Single values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>)	Computes the average of a sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>)	Computes the average of a sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>)	Computes the average of a sequence of nullable Double values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>)	Computes the average of a sequence of nullable Int32 values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>)	Computes the average of a sequence of Int64 values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>)	Computes the average of a sequence of Int32 values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>)	Computes the average of a sequence of Double values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>)	Computes the average of a sequence of Decimal values that is obtained by invoking a projection function on each element of the input sequence.
Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>)	Computes the average of a sequence of nullable Decimal values that is obtained by invoking a projection function on each element of the input sequence.

Average(IQueryable<Single>)

Source:

Queryable.cs

Computes the average of a sequence of Single values.

public:
[System::Runtime::CompilerServices::Extension]
 static float Average(System::Linq::IQueryable<float> ^ source);

public static float Average (this System.Linq.IQueryable<float> source);

static member Average : System.Linq.IQueryable<single> -> single

<Extension()>
Public Function Average (source As IQueryable(Of Single)) As Single

Parameters

source

IQueryable<Single>

A sequence of Single values to calculate the average of.

Returns

Single

The average of the sequence of values.

Exceptions

ArgumentNullException

source is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.

Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

Remarks

The Average(IQueryable<Single>) method generates a MethodCallExpression that represents calling Average(IQueryable<Single>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Single>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Nullable<Int64>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Int64 values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<Nullable<long>> ^ source);

public static double? Average (this System.Linq.IQueryable<long?> source);

static member Average : System.Linq.IQueryable<Nullable<int64>> -> Nullable<double>

<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Long))) As Nullable(Of Double)

Parameters

source

IQueryable<Nullable<Int64>>

A sequence of nullable Int64 values to calculate the average of.

Returns

Nullable<Double>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source is null.

Examples

The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.

Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

Remarks

The Average(IQueryable<Nullable<Int64>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Int64>>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Int64>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Nullable<Int32>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Int32 values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<Nullable<int>> ^ source);

public static double? Average (this System.Linq.IQueryable<int?> source);

static member Average : System.Linq.IQueryable<Nullable<int>> -> Nullable<double>

<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Integer))) As Nullable(Of Double)

Parameters

source

IQueryable<Nullable<Int32>>

A sequence of nullable Int32 values to calculate the average of.

Returns

Nullable<Double>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source is null.

Examples

The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.

Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

Remarks

The Average(IQueryable<Nullable<Int32>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Int32>>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Int32>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Nullable<Double>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Double values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<Nullable<double>> ^ source);

public static double? Average (this System.Linq.IQueryable<double?> source);

static member Average : System.Linq.IQueryable<Nullable<double>> -> Nullable<double>

<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Double))) As Nullable(Of Double)

Parameters

source

IQueryable<Nullable<Double>>

A sequence of nullable Double values to calculate the average of.

Returns

Nullable<Double>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source is null.

Examples

The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.

Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

Remarks

The Average(IQueryable<Nullable<Double>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Double>>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Double>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Nullable<Single>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Single values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<float> Average(System::Linq::IQueryable<Nullable<float>> ^ source);

public static float? Average (this System.Linq.IQueryable<float?> source);

static member Average : System.Linq.IQueryable<Nullable<single>> -> Nullable<single>

<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Single))) As Nullable(Of Single)

Parameters

source

IQueryable<Nullable<Single>>

A sequence of nullable Single values to calculate the average of.

Returns

Nullable<Single>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source is null.

Examples

The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.

Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

Remarks

The Average(IQueryable<Nullable<Single>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Single>>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Single>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Int64>)

Source:

Queryable.cs

Computes the average of a sequence of Int64 values.

public:
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<long> ^ source);

public static double Average (this System.Linq.IQueryable<long> source);

static member Average : System.Linq.IQueryable<int64> -> double

<Extension()>
Public Function Average (source As IQueryable(Of Long)) As Double

Parameters

source

IQueryable<Int64>

A sequence of Int64 values to calculate the average of.

Returns

Double

The average of the sequence of values.

Exceptions

ArgumentNullException

source is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.

Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

Remarks

The Average(IQueryable<Int64>) method generates a MethodCallExpression that represents calling Average(IQueryable<Int64>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Int64>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Int32>)

Source:

Queryable.cs

Computes the average of a sequence of Int32 values.

public:
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<int> ^ source);

public static double Average (this System.Linq.IQueryable<int> source);

static member Average : System.Linq.IQueryable<int> -> double

<Extension()>
Public Function Average (source As IQueryable(Of Integer)) As Double

Parameters

source

IQueryable<Int32>

A sequence of Int32 values to calculate the average of.

Returns

Double

The average of the sequence of values.

Exceptions

ArgumentNullException

source is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.

Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

Remarks

The Average(IQueryable<Int32>) method generates a MethodCallExpression that represents calling Average(IQueryable<Int32>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Int32>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Double>)

Source:

Queryable.cs

Computes the average of a sequence of Double values.

public:
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<double> ^ source);

public static double Average (this System.Linq.IQueryable<double> source);

static member Average : System.Linq.IQueryable<double> -> double

<Extension()>
Public Function Average (source As IQueryable(Of Double)) As Double

Parameters

source

IQueryable<Double>

A sequence of Double values to calculate the average of.

Returns

Double

The average of the sequence of values.

Exceptions

ArgumentNullException

source is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.

Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

Remarks

The Average(IQueryable<Double>) method generates a MethodCallExpression that represents calling Average(IQueryable<Double>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Double>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Decimal>)

Source:

Queryable.cs

Computes the average of a sequence of Decimal values.

public:
[System::Runtime::CompilerServices::Extension]
 static System::Decimal Average(System::Linq::IQueryable<System::Decimal> ^ source);

public static decimal Average (this System.Linq.IQueryable<decimal> source);

static member Average : System.Linq.IQueryable<decimal> -> decimal

<Extension()>
Public Function Average (source As IQueryable(Of Decimal)) As Decimal

Parameters

source

IQueryable<Decimal>

A sequence of Decimal values to calculate the average of.

Returns

Decimal

The average of the sequence of values.

Exceptions

ArgumentNullException

source is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average(IQueryable<Int32>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

List<int> grades = new List<int> { 78, 92, 100, 37, 81 };

double average = grades.AsQueryable().Average();

Console.WriteLine("The average grade is {0}.", average);

// This code produces the following output:
//
// The average grade is 77.6.

Dim grades As New List(Of Integer)(New Integer() {78, 92, 100, 37, 81})

Dim average As Double = grades.AsQueryable().Average()

MsgBox(String.Format("The average grade is {0}.", average))

' This code produces the following output:
'
' The average grade is 77.6.

Remarks

The Average(IQueryable<Decimal>) method generates a MethodCallExpression that represents calling Average(IQueryable<Decimal>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Decimal>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average(IQueryable<Nullable<Decimal>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Decimal values.

public:
[System::Runtime::CompilerServices::Extension]
 static Nullable<System::Decimal> Average(System::Linq::IQueryable<Nullable<System::Decimal>> ^ source);

public static decimal? Average (this System.Linq.IQueryable<decimal?> source);

static member Average : System.Linq.IQueryable<Nullable<decimal>> -> Nullable<decimal>

<Extension()>
Public Function Average (source As IQueryable(Of Nullable(Of Decimal))) As Nullable(Of Decimal)

Parameters

source

IQueryable<Nullable<Decimal>>

A sequence of nullable Decimal values to calculate the average of.

Returns

Nullable<Decimal>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source is null.

Examples

The following code example demonstrates how to use Average(IQueryable<Nullable<Int64>>) to calculate the average of a sequence of values.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, substitute the elements of the source sequence with elements of the appropriate numerical type.

long?[] longs = { null, 10007L, 37L, 399846234235L };

double? average = longs.AsQueryable().Average();

Console.WriteLine("The average is {0}.", average);

// This code produces the following output:
//
// The average is 133282081426.333.

Dim longs() As Nullable(Of Long) = {Nothing, 10007L, 37L, 399846234235L}

Dim average As Nullable(Of Double) = longs.AsQueryable().Average()

MsgBox(String.Format("The average is {0}.", average))

' This code produces the following output:
'
' The average is 133282081426.333.

Remarks

The Average(IQueryable<Nullable<Decimal>>) method generates a MethodCallExpression that represents calling Average(IQueryable<Nullable<Decimal>>) itself. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average(IQueryable<Nullable<Decimal>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>)

Source:

Queryable.cs

Computes the average of a sequence of Single values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static float Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, float> ^> ^ selector);

public static float Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,float>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, single>> -> single

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Single))) As Single

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Single>>

A projection function to apply to each element.

Returns

Single

The average of the sequence of values.

Exceptions

ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Single>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Single values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<float> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<float>> ^> ^ selector);

public static float? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,float?>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<single>>> -> Nullable<single>

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Single)))) As Nullable(Of Single)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Nullable<Single>>>

A projection function to apply to each element.

Returns

Nullable<Single>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source or selector is null.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Single>>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Int64 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<long>> ^> ^ selector);

public static double? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,long?>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<int64>>> -> Nullable<double>

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Long)))) As Nullable(Of Double)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Nullable<Int64>>>

A projection function to apply to each element.

Returns

Nullable<Double>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source or selector is null.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int64>>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Double values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<double>> ^> ^ selector);

public static double? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,double?>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<double>>> -> Nullable<double>

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Double)))) As Nullable(Of Double)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Nullable<Double>>>

A projection function to apply to each element.

Returns

Nullable<Double>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source or selector is null.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Double>>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Int32 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<double> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<int>> ^> ^ selector);

public static double? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,int?>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<int>>> -> Nullable<double>

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Integer)))) As Nullable(Of Double)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Nullable<Int32>>>

A projection function to apply to each element.

Returns

Nullable<Double>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source or selector is null.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Int32>>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>)

Source:

Queryable.cs

Computes the average of a sequence of Int64 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, long> ^> ^ selector);

public static double Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,long>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, int64>> -> double

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Long))) As Double

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Int64>>

A projection function to apply to each element.

Returns

Double

The average of the sequence of values.

Exceptions

ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int64>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>)

Source:

Queryable.cs

Computes the average of a sequence of Int32 values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, int> ^> ^ selector);

public static double Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,int>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, int>> -> double

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Integer))) As Double

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Int32>>

A projection function to apply to each element.

Returns

Double

The average of the sequence of values.

Exceptions

ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>)

Source:

Queryable.cs

Computes the average of a sequence of Double values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static double Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, double> ^> ^ selector);

public static double Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,double>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, double>> -> double

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Double))) As Double

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Double>>

A projection function to apply to each element.

Returns

Double

The average of the sequence of values.

Exceptions

ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Double>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>)

Source:

Queryable.cs

Computes the average of a sequence of Decimal values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Decimal Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, System::Decimal> ^> ^ selector);

public static decimal Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,decimal>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, decimal>> -> decimal

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Decimal))) As Decimal

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values that are used to calculate an average.

selector

Expression<Func<TSource,Decimal>>

A projection function to apply to each element.

Returns

Decimal

The average of the sequence of values.

Exceptions

ArgumentNullException

source or selector is null.

InvalidOperationException

source contains no elements.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Decimal>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.

Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>)

Source:

Queryable.cs

Computes the average of a sequence of nullable Decimal values that is obtained by invoking a projection function on each element of the input sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static Nullable<System::Decimal> Average(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, Nullable<System::Decimal>> ^> ^ selector);

public static decimal? Average<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,decimal?>> selector);

static member Average : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, Nullable<decimal>>> -> Nullable<decimal>

<Extension()>
Public Function Average(Of TSource) (source As IQueryable(Of TSource), selector As Expression(Of Func(Of TSource, Nullable(Of Decimal)))) As Nullable(Of Decimal)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

A sequence of values to calculate the average of.

selector

Expression<Func<TSource,Nullable<Decimal>>>

A projection function to apply to each element.

Returns

Nullable<Decimal>

The average of the sequence of values, or null if the source sequence is empty or contains only null values.

Exceptions

ArgumentNullException

source or selector is null.

Examples

The following code example demonstrates how to use Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32>>) to calculate the average String length in a sequence of values of type String.

Note

This code example uses an overload of the method that's different from the specific overload that this article describes. To extend the example to the overload that this article describes, change the body of the selector function.

string[] fruits = { "apple", "banana", "mango", "orange", "passionfruit", "grape" };

// Determine the average string length in the array.
double average = fruits.AsQueryable().Average(s => s.Length);

Console.WriteLine("The average string length is {0}.", average);

// This code produces the following output:
//
// The average string length is 6.5.

Dim fruits() As String = {"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Determine the average string length in the array.
Dim average As Double = fruits.AsQueryable().Average(Function(s) s.Length)

MsgBox(String.Format("The average string length is {0}.", average))

' This code produces the following output:
'
' The average string length is 6.5.

Remarks

This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

The Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) method generates a MethodCallExpression that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) itself as a constructed generic method. It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Average<TSource>(IQueryable<TSource>, Expression<Func<TSource,Nullable<Decimal>>>) depends on the implementation of the type of the source parameter. The expected behavior is that it calculates the average of the values in source after invoking selector on each value.