.NET Framework Class Library
EnumerableLongCountTSource Method (IEnumerableTSource, FuncTSource, Boolean)

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

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)
Syntax
<[%$TOPIC/bb548914_en-us_VS_110_2_0_0_0_0%]> _
Public Shared Function LongCount(Of TSource) ( _
	source As [%$TOPIC/bb548914_en-us_VS_110_2_0_0_0_1%](Of TSource), _
	predicate As [%$TOPIC/bb548914_en-us_VS_110_2_0_0_0_2%](Of TSource, [%$TOPIC/bb548914_en-us_VS_110_2_0_0_0_3%]) _
) As [%$TOPIC/bb548914_en-us_VS_110_2_0_0_0_4%]
public static [%$TOPIC/bb548914_en-us_VS_110_2_0_1_0_0%] LongCount<TSource>(
	this [%$TOPIC/bb548914_en-us_VS_110_2_0_1_0_1%]<TSource> source,
	[%$TOPIC/bb548914_en-us_VS_110_2_0_1_0_2%]<TSource, [%$TOPIC/bb548914_en-us_VS_110_2_0_1_0_3%]> predicate
)
[[%$TOPIC/bb548914_en-us_VS_110_2_0_2_0_0%]]
public:
generic<typename TSource>
static [%$TOPIC/bb548914_en-us_VS_110_2_0_2_0_1%] LongCount(
	[%$TOPIC/bb548914_en-us_VS_110_2_0_2_0_2%]<TSource>^ source, 
	[%$TOPIC/bb548914_en-us_VS_110_2_0_2_0_3%]<TSource, [%$TOPIC/bb548914_en-us_VS_110_2_0_2_0_4%]>^ predicate
)
static member LongCount : 
        source:[%$TOPIC/bb548914_en-us_VS_110_2_0_3_0_0%]<'TSource> * 
        predicate:[%$TOPIC/bb548914_en-us_VS_110_2_0_3_0_1%]<'TSource, [%$TOPIC/bb548914_en-us_VS_110_2_0_3_0_2%]> -> [%$TOPIC/bb548914_en-us_VS_110_2_0_3_0_3%]

Type Parameters

TSource

The type of the elements of source.

Parameters

source
Type: System.Collections.GenericIEnumerableTSource

An IEnumerableT that contains the elements to be counted.

predicate
Type: SystemFuncTSource, Boolean

A function to test each element for a condition.

Return Value

Type: SystemInt64
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 IEnumerableTSource. 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).
Exceptions
ExceptionCondition
ArgumentNullException

source or predicate is .

OverflowException

The number of matching elements exceeds MaxValue.

Remarks

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.

Examples

The following code example demonstrates how to use LongCountTSource(IEnumerableTSource, FuncTSource, Boolean) to count the elements in an array that satisfy a condition.

Structure Pet
        Public Name As String 
        Public Age As Integer 
    End Structure 

    Sub LongCountEx2()
        ' Create a list of Pet objects. 
        Dim pets As New List(Of Pet)(New Pet() _
                             {New Pet With {.Name = "Barley", .Age = 8}, _
                              New Pet With {.Name = "Boots", .Age = 4}, _
                              New Pet With {.Name = "Whiskers", .Age = 1}})

        ' Determine the number of elements in the list 
        ' where the pet's age is greater than a constant value (3). 
        Const Age As Integer = 3
        Dim count As Long = _
            pets.LongCount(Function(pet) pet.Age > Age)

        ' Display the result.
        MsgBox("There are " & count & " animals over age " & Age)
    End Sub 

    ' This code produces the following output: 
    ' 
    ' There are 2 animals over age 3
class Pet
            {
                public string Name { get; set; }
                public int Age { get; set; }
            }

            public static void LongCountEx2()
            {
                Pet[] pets = { new Pet { Name="Barley", Age=8 },
                               new Pet { Name="Boots", Age=4 },
                               new Pet { Name="Whiskers", Age=1 } };

                const int Age = 3;

                long count = pets.LongCount(pet => pet.Age > Age);

                Console.WriteLine("There are {0} animals over age {1}.", count, Age);
            }

            /*
             This code produces the following output:

             There are 2 animals over age 3.
            */
Version Information

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1
Platforms

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.