Queryable.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 sequence.

オーバーロード

LongCount<TSource>(IQueryable<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>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)

条件を満たす、シーケンス内の要素の数を表す Int64 を返します。Returns an Int64 that represents the number of elements in a sequence that satisfy a condition.

LongCount<TSource>(IQueryable<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::Linq::IQueryable<TSource> ^ source);
public static long LongCount<TSource> (this System.Linq.IQueryable<TSource> source);
static member LongCount : System.Linq.IQueryable<'Source> -> int64
<Extension()>
Public Function LongCount(Of TSource) (source As IQueryable(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
IQueryable<TSource>

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

戻り値

source にある要素の数。The number of elements in source.

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>(IQueryable<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>(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.
*/

Dim fruits() As String = {"apple", "banana", "mango", _
                      "orange", "passionfruit", "grape"}

Dim count As Long = fruits.AsQueryable().LongCount()

MsgBox(String.Format("There are {0} fruits in the collection.", count))

' This code produces the following output:

' There are 6 fruits in the collection.

注釈

LongCount<TSource>(IQueryable<TSource>) メソッドは、構築されたジェネリックメソッドとしての呼び出し LongCount<TSource>(IQueryable<TSource>) 自体を表す MethodCallExpression を生成します。The LongCount<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling LongCount<TSource>(IQueryable<TSource>) itself as a constructed generic method. 次に、source パラメーターの Provider プロパティによって表される IQueryProviderExecute<TResult>(Expression) メソッドに MethodCallExpression を渡します。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

LongCount<TSource>(IQueryable<TSource>) の呼び出しを表す式ツリーを実行した結果として発生するクエリ動作は、source パラメーターの型の実装によって異なります。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. 期待される動作は、source 内の項目の数をカウントし、Int64を返すことです。The expected behavior is that it counts the number of items in source and returns an Int64.

LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)

条件を満たす、シーケンス内の要素の数を表す Int64 を返します。Returns an Int64 that represents the number of elements in a sequence that satisfy a condition.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static long LongCount(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, bool> ^> ^ predicate);
public static long LongCount<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,bool>> predicate);
static member LongCount : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, bool>> -> int64
<Extension()>
Public Function LongCount(Of TSource) (source As IQueryable(Of TSource), predicate As Expression(Of 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
IQueryable<TSource>

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

predicate
Expression<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

述語関数の条件を満たす、source の要素数。The number of elements in source that 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>(IQueryable<TSource>, Expression<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>(IQueryable<TSource>, Expression<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;

    // Count the number of Pet objects where Pet.Age is greater than 3.
    long count = pets.AsQueryable().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

Shared Sub LongCountEx2()
    Dim pets() As Pet = {New Pet With {.Name = "Barley", .Age = 8}, _
                       New Pet With {.Name = "Boots", .Age = 4}, _
                       New Pet With {.Name = "Whiskers", .Age = 1}}

    Const Age As Integer = 3

    ' Count the number of Pet objects where Pet.Age is greater than 3.
    Dim count As Long = pets.AsQueryable().LongCount(Function(Pet) Pet.Age > Age)

    MsgBox(String.Format("There are {0} animals over age {1}.", count, Age))
End Sub

' This code produces the following output:

' There are 2 animals over age 3.

注釈

このメソッドには、型引数が Func<T,TResult> 型の1つである Expression<TDelegate> 型のパラメーターが少なくとも1つ含まれています。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. これらのパラメーターでは、ラムダ式を渡すことができ、Expression<TDelegate>にコンパイルされます。For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) メソッドは、構築されたジェネリックメソッドとしての呼び出し LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 自体を表す MethodCallExpression を生成します。The LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) itself as a constructed generic method. 次に、source パラメーターの Provider プロパティによって表される IQueryProviderExecute<TResult>(Expression) メソッドに MethodCallExpression を渡します。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) の呼び出しを表す式ツリーを実行した結果として発生するクエリ動作は、source パラメーターの型の実装によって異なります。The query behavior that occurs as a result of executing an expression tree that represents calling LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) depends on the implementation of the type of the source parameter. 期待される動作は、predicate によって指定された条件を満たす source 内の項目の数をカウントし、Int64を返すことです。The expected behavior is that it counts the number of items in source that satisfy the condition specified by predicate and returns an Int64.

適用対象