Enumerable.LastOrDefault Enumerable.LastOrDefault Enumerable.LastOrDefault Enumerable.LastOrDefault Method

Definition

Returns the last element of a sequence, or a default value if no element is found.

Overloads

LastOrDefault<TSource>(IEnumerable<TSource>) LastOrDefault<TSource>(IEnumerable<TSource>) LastOrDefault<TSource>(IEnumerable<TSource>) LastOrDefault<TSource>(IEnumerable<TSource>)

Returns the last element of a sequence, or a default value if the sequence contains no elements.

LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.

LastOrDefault<TSource>(IEnumerable<TSource>) LastOrDefault<TSource>(IEnumerable<TSource>) LastOrDefault<TSource>(IEnumerable<TSource>) LastOrDefault<TSource>(IEnumerable<TSource>)

Returns the last element of a sequence, or a default value if the sequence contains no elements.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static TSource LastOrDefault(System::Collections::Generic::IEnumerable<TSource> ^ source);
public static TSource LastOrDefault<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);
static member LastOrDefault : seq<'Source> -> 'Source
<Extension()>
Public Function LastOrDefault(Of TSource) (source As IEnumerable(Of TSource)) As TSource
Type Parameters
TSource

The type of the elements of source.

Parameters
source
IEnumerable<TSource>

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

Returns
TSource TSource TSource TSource

default(TSource) if the source sequence is empty; otherwise, the last element in the IEnumerable<T>.

Exceptions

Examples

The following code example demonstrates how to use LastOrDefault<TSource>(IEnumerable<TSource>) on an empty array.

string[] fruits = { };
string last = fruits.LastOrDefault();
Console.WriteLine(
    String.IsNullOrEmpty(last) ? "<string is null or empty>" : last);

/*
 This code produces the following output:

 <string is null or empty>
*/

' Create an empty array.
Dim fruits() As String = {}

' Get the last item in the array, or a
' default value if there are no items.
Dim last As String = fruits.LastOrDefault()

' Display the result.
MsgBox(IIf(String.IsNullOrEmpty(last),
       "<string is Nothing or empty>",
       last))

' This code produces the following output:
'
' <string is Nothing or empty>

Sometimes the value of default(TSource) is not the default value that you want to use if the collection contains no elements. Instead of checking the result for the unwanted default value and then changing it if necessary, you can use the DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource) method to specify the default value that you want to use if the collection is empty. Then, call Last<TSource>(IEnumerable<TSource>) to obtain the last element. The following code example uses both techniques to obtain a default value of 1 if a collection of numeric days of the month is empty. Because the default value for an integer is 0, which does not correspond to any day of the month, the default value must be specified as 1 instead. The first result variable is checked for the unwanted default value after the query has finished executing. The second result variable is obtained by using DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource) to specify a default value of 1.

List<int> daysOfMonth = new List<int> { };

// Setting the default value to 1 after the query.
int lastDay1 = daysOfMonth.LastOrDefault();
if (lastDay1 == 0)
{
    lastDay1 = 1;
}
Console.WriteLine("The value of the lastDay1 variable is {0}", lastDay1);

// Setting the default value to 1 by using DefaultIfEmpty() in the query.
int lastDay2 = daysOfMonth.DefaultIfEmpty(1).Last();
Console.WriteLine("The value of the lastDay2 variable is {0}", lastDay2);

/*
 This code produces the following output:
 
 The value of the lastDay1 variable is 1
 The value of the lastDay2 variable is 1
*/
Dim daysOfMonth As New List(Of Integer)(New Integer() {})

' Setting the default value to 1 after the query.
Dim lastDay1 As Integer = daysOfMonth.LastOrDefault()
If lastDay1 = 0 Then
    lastDay1 = 1
End If
MsgBox(String.Format("The value of the lastDay1 variable is {0}", lastDay1))

' Setting the default value to 1 by using DefaultIfEmpty() in the query.
Dim lastDay2 As Integer = daysOfMonth.DefaultIfEmpty(1).Last()
MsgBox(String.Format("The value of the lastDay2 variable is {0}", lastDay2))

' This code produces the following output:
'
' The value of the lastDay1 variable is 1
' The value of the lastDay2 variable is 1

Remarks

The default value for reference and nullable types is null.

The LastOrDefault method does not provide a way to specify a default value. If you want to specify a default value other than default(TSource), use the DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource) method as described in the Example section.

LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

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);
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
TSource

The type of the elements of source.

Parameters
source
IEnumerable<TSource>

An IEnumerable<T> to return an element from.

predicate
Func<TSource,Boolean>

A function to test each element for a condition.

Returns
TSource TSource TSource 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.

Exceptions

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.

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.
MsgBox(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.

Applies to