Enumerable.LongCount メソッド

定義

シーケンス内の要素数を表す Int64 を返します。Returns an Int64 that represents the number of elements in a sequence.

オーバーロード

LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

シーケンス内で条件を満たす要素の数を表す Int64 を返します。Returns an Int64 that represents how many elements in a sequence satisfy a condition.

LongCount<TSource>(IEnumerable<TSource>)

シーケンス内の要素の合計数を表す Int64 を返します。Returns an Int64 that represents the total number of elements in a sequence.

LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

シーケンス内で条件を満たす要素の数を表す Int64 を返します。Returns an Int64 that represents how many elements in a sequence satisfy a condition.

public:
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 Long

型パラメーター

TSource

source の要素の型。The type of the elements of source.

パラメーター

source
IEnumerable<TSource>

カウントする要素が格納されている IEnumerable<T>An IEnumerable<T> that contains the elements to be counted.

predicate
Func<TSource,Boolean>

各要素が条件を満たしているかどうかをテストする関数。A function to test each element for a condition.

戻り値

Int64

述語関数の条件を満たす、シーケンス内の要素数を表す数値。A number that represents how many elements in the sequence satisfy the condition in the predicate function.

例外

source または predicatenull です。source or predicate is null.

一致する要素数が MaxValue を超えています。The number of matching elements exceeds MaxValue.

次のコード例は、LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) を使用して、条件を満たす配列内の要素をカウントする方法を示しています。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.

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

注釈

結果が MaxValueを超えると予想される場合は、Count ではなく、このメソッドを使用します。Use this method rather than Count when you expect the result to be greater than MaxValue.

クエリ式の構文 Visual Basic、Aggregate Into LongCount() 句は LongCountの呼び出しに変換します。In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount.

こちらもご覧ください

LongCount<TSource>(IEnumerable<TSource>)

シーケンス内の要素の合計数を表す Int64 を返します。Returns an Int64 that represents the total number of elements in a sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static long LongCount(System::Collections::Generic::IEnumerable<TSource> ^ source);
public static long LongCount<TSource> (this System.Collections.Generic.IEnumerable<TSource> source);
static member LongCount : seq<'Source> -> int64
<Extension()>
Public Function LongCount(Of TSource) (source As IEnumerable(Of TSource)) As Long

型パラメーター

TSource

source の要素の型。The type of the elements of source.

パラメーター

source
IEnumerable<TSource>

カウントする要素が格納されている IEnumerable<T>An IEnumerable<T> that contains the elements to be counted.

戻り値

Int64

ソース シーケンスの要素数。The number of elements in the source sequence.

例外

sourcenull です。source is null.

要素数が MaxValue を超えています。The number of elements exceeds MaxValue.

次のコード例は、LongCount<TSource>(IEnumerable<TSource>) を使用して配列内の要素をカウントする方法を示しています。The following code example demonstrates how to use LongCount<TSource>(IEnumerable<TSource>) to count the elements in an array.

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

long count = fruits.LongCount();

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

/*
 This code produces the following output:

 There are 6 fruits in the collection.
*/
' Create an array of strings.
Dim fruits() As String =
{"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Get the number of items in the array.
Dim count As Long = fruits.LongCount()

' Display the result.
Console.WriteLine($"There are {count} fruits in the collection.")

' This code produces the following output:
'
' There are 6 fruits in the collection.

注釈

結果が MaxValueを超えると予想される場合は、Count ではなく、このメソッドを使用します。Use this method rather than Count when you expect the result to be greater than MaxValue.

クエリ式の構文 Visual Basic、Aggregate Into LongCount() 句は LongCountの呼び出しに変換します。In Visual Basic query expression syntax, an Aggregate Into LongCount() clause translates to an invocation of LongCount.

こちらもご覧ください

適用対象