Queryable.LastOrDefault<TSource> Method (IQueryable<TSource>, Expression<Func<TSource, Boolean>>)


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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)

public static TSource LastOrDefault<TSource>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, bool>> predicate


Type: System.Linq.IQueryable<TSource>

An IQueryable<T> to return an element from.

Type: System.Linq.Expressions.Expression<Func<TSource, Boolean>>

A function to test each element for a condition.

Return Value

Type: TSource

default(TSource) if source is empty or if no elements pass the test in the predicate function; otherwise, the last element of source that passes the test in the predicate function.

Type Parameters


The type of the elements of source.

Exception Condition

source or predicate is null.

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 LastOrDefault<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling LastOrDefault<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 LastOrDefault<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 that satisfies the condition specified by predicate. It returns a default value if there is no such element in source.

The following code example demonstrates how to use LastOrDefault<TSource>(IQueryable<TSource>, Expression<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 };

// Get the last number in the array that rounds to 50.0,
// or else the default value for type double (0.0).
double last50 =
    numbers.AsQueryable().LastOrDefault(n => Math.Round(n) == 50.0);

Console.WriteLine("The last number that rounds to 50 is {0}.", last50);

// Get the last number in the array that rounds to 40.0,
// or else the default value for type double (0.0).
double last40 =
    numbers.AsQueryable().LastOrDefault(n => Math.Round(n) == 40.0);

    "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].

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1
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