Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static TSource LastOrDefault(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);
public static TSource LastOrDefault<TSource>(this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);
public static TSource? LastOrDefault<TSource>(this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);
static member LastOrDefault : seq<'Source> * Func<'Source, bool> -> 'Source
<Extension()>
Public Function LastOrDefault(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As TSource
Type Parameters
The type of the elements of source
.
A function to test each element for a condition.
ReturnsTSource
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.
source
or predicate
is null
.
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.
double[] numbers = { 49.6, 52.3, 51.0, 49.4, 50.2, 48.3 };
double last50 = numbers.LastOrDefault(n => Math.Round(n) == 50.0);
Console.WriteLine("The last number that rounds to 50 is {0}.", last50);
double last40 = numbers.LastOrDefault(n => Math.Round(n) == 40.0);
Console.WriteLine(
"The last number that rounds to 40 is {0}.",
last40 == 0.0 ? "<DOES NOT EXIST>" : last40.ToString());
/*
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>.
*/
' 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.
Console.WriteLine(output.ToString)
' 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]
Remarks
The default value for reference and nullable types is null
.
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