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Enumerable::LongCount<TSource> Method (IEnumerable<TSource>, Func<TSource, Boolean>)

Returns an Int64 that represents how many elements in a sequence satisfy a condition.

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

[ExtensionAttribute]
public:
generic<typename TSource>
static long long LongCount(
	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> that contains the elements to be counted.

predicate
Type: System::Func<TSource, Boolean>

A function to test each element for a condition.

Return Value

Type: System::Int64
A number that represents how many elements in the sequence satisfy the condition 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. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

ExceptionCondition
ArgumentNullException

source or predicate is nullptr.

OverflowException

The number of matching elements exceeds MaxValue.

Use this method rather than Count when you expect the result to be greater than MaxValue.

In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount.

The following code example demonstrates how to use LongCount<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) to count the elements in an array that satisfy a condition.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8
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