Queryable.Last Method

Definition

Namespace:

System.Linq

Assembly:

System.Linq.Queryable.dll

Returns the last element in a sequence.

Overloads

Last<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)	Returns the last element of a sequence that satisfies a specified condition.
Last<TSource>(IQueryable<TSource>)	Returns the last element in a sequence.

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

Source:

Queryable.cs

Returns the last element of a sequence that satisfies a specified condition.

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

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

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

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

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

An IQueryable<T> to return an element from.

predicate

Expression<Func<TSource,Boolean>>

A function to test each element for a condition.

Returns

TSource

The last element in source that passes the test specified by predicate.

Exceptions

ArgumentNullException

source or predicate is null.

InvalidOperationException

No element satisfies the condition in predicate.

-or-

The source sequence is empty.

Examples

The following code example demonstrates how to use Last<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) to return the last element of an array that satisfies a condition.

int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54,
                    83, 23, 87, 67, 12, 19 };

// Get the last number in the array that is greater than 80.
int last = numbers.AsQueryable().Last(num => num > 80);

Console.WriteLine(last);

/*
    This code produces the following output:

    87
*/

Dim numbers() As Integer = {9, 34, 65, 92, 87, 435, 3, 54, _
                    83, 23, 87, 67, 12, 19}

' Get the last number in the array that is greater than 80.
Dim last As Integer = numbers.AsQueryable().Last(Function(num) num > 80)

MsgBox(last)

' This code produces the following output:
' 87

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 Last<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling Last<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 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 Last<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the last element in source that satisfies the condition specified by predicate.

Last<TSource>(IQueryable<TSource>)

Source:

Queryable.cs

Returns the last element in a sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource Last(System::Linq::IQueryable<TSource> ^ source);

public static TSource Last<TSource> (this System.Linq.IQueryable<TSource> source);

static member Last : System.Linq.IQueryable<'Source> -> 'Source

<Extension()>
Public Function Last(Of TSource) (source As IQueryable(Of TSource)) As TSource

Type Parameters

TSource

The type of the elements of source.

Parameters

source

IQueryable<TSource>

An IQueryable<T> to return the last element of.

Returns

TSource

The value at the last position in source.

Exceptions

ArgumentNullException

source is null.

InvalidOperationException

The source sequence is empty.

Examples

The following code example demonstrates how to use Last<TSource>(IQueryable<TSource>) to return the last element of an array.

int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54,
                    83, 23, 87, 67, 12, 19 };

int last = numbers.AsQueryable().Last();

Console.WriteLine(last);

/*
    This code produces the following output:

    19
*/

Dim numbers() As Integer = {9, 34, 65, 92, 87, 435, 3, 54, _
                    83, 23, 87, 67, 12, 19}

Dim last As Integer = numbers.AsQueryable().Last()

MsgBox(last)

' This code produces the following output:
' 19

Remarks

The Last<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Last<TSource>(IQueryable<TSource>) 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 Last<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. The expected behavior is that it returns the last element in source.