LongCount(TSource) Method (IQueryable(TSource))

Queryable.LongCount<TSource> Method (IQueryable<TSource>)


Returns an Int64 that represents the total number of elements in a sequence.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

public static long LongCount<TSource>(
	this IQueryable<TSource> source


Type: System.Linq.IQueryable<TSource>

An IQueryable<T> that contains the elements to be counted.

Return Value

Type: System.Int64

The number of elements in source.

Type Parameters


The type of the elements of source.

Exception Condition

source is null.


The number of elements exceeds MaxValue.

The LongCount<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling LongCount<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 LongCount<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. The expected behavior is that it counts the number of items in source and returns an Int64.

The following code example demonstrates how to use LongCount<TSource>(IQueryable<TSource>) to count the elements in an array.

string[] fruits = { "apple", "banana", "mango", 
                      "orange", "passionfruit", "grape" };

long count = fruits.AsQueryable().LongCount();

Console.WriteLine("There are {0} fruits in the collection.", count);

    This code produces the following output:

    There are 6 fruits in the collection.

Universal Windows Platform
Available since 4.5
.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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