Enumerable.LongCount Method (System.Linq) (original) (raw)
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Returns an Int64 that represents how many elements in a sequence satisfy a condition.
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generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static long LongCount(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);public static long LongCount<TSource>(this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);static member LongCount : seq<'Source> * Func<'Source, bool> -> int64<Extension()>
Public Function LongCount(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As LongType Parameters
TSource
The type of the elements of source.
Parameters
predicate
A function to test each element for a condition.
Returns
A number that represents how many elements in the sequence satisfy the condition in the predicate function.
Exceptions
source or predicate is null.
Examples
The following code example demonstrates how to use LongCount(IEnumerable, Func<TSource,Boolean>) to count the elements in an array that satisfy a condition.
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.
*/
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.
Console.WriteLine($"There are {count} animals over age {Age}")
End Sub
' This code produces the following output:
'
' There are 2 animals over age 3
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.