Enumerable.LastOrDefault<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)
Syntax
'Declaration
<ExtensionAttribute> _
Public Shared Function LastOrDefault(Of TSource) ( _
source As IEnumerable(Of TSource), _
predicate As Func(Of TSource, Boolean) _
) As TSource
public static TSource LastOrDefault<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate
)
Type Parameters
- TSource
The type of the elements of source.
Parameters
- source
Type: System.Collections.Generic.IEnumerable<TSource>
An IEnumerable<T> to return an element from.
- predicate
Type: System.Func<TSource, Boolean>
A function to test each element for a condition.
Return Value
Type: TSource
default (TSource) if the sequence is empty or if no elements pass the test in the predicate function; otherwise, the last element that passes the test in the predicate function.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | source or predicate is nulla null reference (Nothing in Visual Basic). |
Remarks
The default value for reference and nullable types is nulla null reference (Nothing in Visual Basic).
Examples
The following code example demonstrates how to use LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) by passing in a predicate. In the second call to the method, there is no element in the sequence that satisfies the condition.
' Create an array of doubles.
Dim numbers() As Double = {49.6, 52.3, 51.0, 49.4, 50.2, 48.3}
' Get the last item whose value rounds to 50.0.
Dim number50 As Double = _
numbers.LastOrDefault(Function(n) Math.Round(n) = 50.0)
Dim output As New System.Text.StringBuilder
output.AppendLine("The last number that rounds to 50 is " & number50)
' Get the last item whose value rounds to 40.0.
Dim number40 As Double = _
numbers.LastOrDefault(Function(n) Math.Round(n) = 40.0)
Dim text As String = IIf(number40 = 0.0, _
"[DOES NOT EXIST]", _
number40.ToString())
output.AppendLine("The last number that rounds to 40 is " & text)
' Display the output.
outputBlock.Text &= output.ToString() & vbCrLf
' This code produces the following output:
'
' The last number that rounds to 50 is 50.2
' The last number that rounds to 40 is [DOES NOT EXIST]
double[] numbers = { 49.6, 52.3, 51.0, 49.4, 50.2, 48.3 };
double last50 = numbers.LastOrDefault(n => Math.Round(n) == 50.0);
outputBlock.Text += String.Format("The last number that rounds to 50 is {0}.", last50) + "\n";
double last40 = numbers.LastOrDefault(n => Math.Round(n) == 40.0);
outputBlock.Text += String.Format(
"The last number that rounds to 40 is {0}.",
last40 == 0.0 ? "<DOES NOT EXIST>" : last40.ToString()) + "\n";
/*
This code produces the following output:
The last number that rounds to 50 is 50.2.
The last number that rounds to 40 is <DOES NOT EXIST>.
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.