Queryable.SkipWhile Method

Definition

Namespace:

System.Linq

Assembly:

System.Linq.Queryable.dll

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

Overloads

SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.
SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32,Boolean>>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.

SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)

Source:

Queryable.cs

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.

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

public static System.Linq.IQueryable<TSource> SkipWhile<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,bool>> predicate);

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

<Extension()>
Public Function SkipWhile(Of TSource) (source As IQueryable(Of TSource), predicate As Expression(Of Func(Of TSource, Boolean))) As IQueryable(Of TSource)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

An IQueryable<T> to return elements from.

predicate

Expression<Func<TSource,Boolean>>

A function to test each element for a condition.

Returns

IQueryable<TSource>

An IQueryable<T> that contains elements from source starting at the first element in the linear series that does not pass the test specified by predicate.

Exceptions

ArgumentNullException

source or predicate is null.

Examples

The following code example demonstrates how to use SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) to skip elements of an array as long as a condition is true.

int[] grades = { 59, 82, 70, 56, 92, 98, 85 };

// Get all grades less than 80 by first
// sorting the grades in descending order and then
// taking all the grades after the first grade
// that is less than 80.
IEnumerable<int> lowerGrades =
    grades.AsQueryable()
    .OrderByDescending(grade => grade)
    .SkipWhile(grade => grade >= 80);

Console.WriteLine("All grades below 80:");
foreach (int grade in lowerGrades)
    Console.WriteLine(grade);

/*
    This code produces the following output:

    All grades below 80:
    70
    59
    56
*/

Dim grades() As Integer = {59, 82, 70, 56, 92, 98, 85}

' Get all grades less than 80 by first  sorting the grades 
' in descending order and then taking all the grades that 
' occur after the first grade that is less than 80.
Dim lowerGrades = grades.AsQueryable() _
    .OrderByDescending(Function(grade) grade) _
    .SkipWhile(Function(grade) grade >= 80)

Dim output As New System.Text.StringBuilder
output.AppendLine("All grades below 80:")
For Each grade As Integer In lowerGrades
    output.AppendLine(grade)
Next

' Display the output.
MsgBox(output.ToString())

' This code produces the following output:

' All grades below 80:
' 70
' 59
' 56

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 SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(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 SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) depends on the implementation of the type of the source parameter. The expected behavior is that it applies predicate to each element in source until it finds an element for which predicate returns false. That element and all the remaining elements are returned.

SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32,Boolean>>)

Source:

Queryable.cs

Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.

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

public static System.Linq.IQueryable<TSource> SkipWhile<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,int,bool>> predicate);

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

<Extension()>
Public Function SkipWhile(Of TSource) (source As IQueryable(Of TSource), predicate As Expression(Of Func(Of TSource, Integer, Boolean))) As IQueryable(Of TSource)

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

An IQueryable<T> to return elements from.

predicate

Expression<Func<TSource,Int32,Boolean>>

A function to test each element for a condition; the second parameter of this function represents the index of the source element.

Returns

IQueryable<TSource>

An IQueryable<T> that contains elements from source starting at the first element in the linear series that does not pass the test specified by predicate.

Exceptions

ArgumentNullException

source or predicate is null.

Examples

The following code example demonstrates how to use SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32,Boolean>>) to skip elements of an array as long as a condition that depends on the element's index is true.

int[] amounts = { 5000, 2500, 9000, 8000,
                    6500, 4000, 1500, 5500 };

// Skip over amounts in the array until the first amount
// that is less than or equal to the product of its
// index in the array and 1000. Take the remaining items.
IEnumerable<int> query =
    amounts.AsQueryable()
    .SkipWhile((amount, index) => amount > index * 1000);

foreach (int amount in query)
    Console.WriteLine(amount);

/*
    This code produces the following output:

    4000
    1500
    5500
*/

Dim amounts() As Integer = {5000, 2500, 9000, 8000, _
                    6500, 4000, 1500, 5500}

' Skip over amounts in the array until the first amount
' that is less than or equal to the product of its
' index in the array and 1000. Take the remaining items.
Dim query = amounts.AsQueryable() _
    .SkipWhile(Function(amount, index) amount > index * 1000)

Dim output As New System.Text.StringBuilder
For Each amount As Integer In query
    output.AppendLine(amount)
Next

' Display the output.
MsgBox(output.ToString())

' This code produces the following output:

' 4000
' 1500
' 5500

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 SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32,Boolean>>) method generates a MethodCallExpression that represents calling SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32,Boolean>>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(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 SkipWhile<TSource>(IQueryable<TSource>, Expression<Func<TSource,Int32,Boolean>>) depends on the implementation of the type of the source parameter. The expected behavior is that it applies predicate to each element in source until it finds an element for which predicate returns false. That element and all the remaining elements are returned. The index of each source element is provided as the second argument to predicate.