Queryable.Count Queryable.Count Queryable.Count Queryable.Count Method

定義

シーケンス内の要素の数を返します。Returns the number of elements in a sequence.

オーバーロード

Count<TSource>(IQueryable<TSource>) Count<TSource>(IQueryable<TSource>) Count<TSource>(IQueryable<TSource>) Count<TSource>(IQueryable<TSource>)

シーケンス内の要素の数を返します。Returns the number of elements in a sequence.

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

条件を満たす、指定されたシーケンス内の要素の数を返します。Returns the number of elements in the specified sequence that satisfies a condition.

Count<TSource>(IQueryable<TSource>) Count<TSource>(IQueryable<TSource>) Count<TSource>(IQueryable<TSource>) Count<TSource>(IQueryable<TSource>)

シーケンス内の要素の数を返します。Returns the number of elements in a sequence.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static int Count(System::Linq::IQueryable<TSource> ^ source);
public static int Count<TSource> (this System.Linq.IQueryable<TSource> source);
static member Count : System.Linq.IQueryable<'Source> -> int
<Extension()>
Public Function Count(Of TSource) (source As IQueryable(Of TSource)) As Integer

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>

IQueryable<T>カウントする要素を格納しています。The IQueryable<T> that contains the elements to be counted.

戻り値

入力シーケンス内の要素数。The number of elements in the input sequence.

例外

要素数sourceよりも大きいMaxValueします。The number of elements in source is larger than MaxValue.

次のコード例は、使用する方法を示しますCount<TSource>(IQueryable<TSource>)シーケンス内の要素をカウントします。The following code example demonstrates how to use Count<TSource>(IQueryable<TSource>) to count the elements in a sequence.

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

int numberOfFruits = fruits.AsQueryable().Count();

Console.WriteLine(
    "There are {0} items in the array.",
    numberOfFruits);

// This code produces the following output:
//
// There are 6 items in the array. 

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

Dim numberOfFruits As Integer = fruits.AsQueryable().Count()

MsgBox(String.Format( _
    "There are {0} items in the array.", _
    numberOfFruits))

' This code produces the following output:
'
' There are 6 items in the array. 

注釈

Count<TSource>(IQueryable<TSource>)メソッドを生成、MethodCallExpression呼び出しを表すCount<TSource>(IQueryable<TSource>)として構築されたジェネリック メソッド自体。The Count<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Count<TSource>(IQueryable<TSource>) itself as a constructed generic method. これは、後、渡します、MethodCallExpressionExecute<TResult>(Expression)のメソッド、IQueryProviderによって表される、Providerのプロパティ、sourceパラメーター。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

呼び出し元を表す式ツリーを実行した結果として発生するクエリの動作Count<TSource>(IQueryable<TSource>)の型の実装によって異なります、sourceパラメーター。The query behavior that occurs as a result of executing an expression tree that represents calling Count<TSource>(IQueryable<TSource>) depends on the implementation of the type of the source parameter. 想定される動作は内の項目の数をカウントsourceします。The expected behavior is that it counts the number of items in source.

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

条件を満たす、指定されたシーケンス内の要素の数を返します。Returns the number of elements in the specified sequence that satisfies a condition.

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

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>

IQueryable<T>カウントする要素を格納しています。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シーケンス内の要素の数。The number of elements in the sequence that satisfies the condition in the predicate function.

例外

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

要素数sourceよりも大きいMaxValueします。The number of elements in source is larger than MaxValue.

次のコード例は、使用する方法を示しますCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)条件を満たす、シーケンス内の要素をカウントします。The following code example demonstrates how to use Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) to count the elements in a sequence that satisfy a condition.

class Pet
{
    public string Name { get; set; }
    public bool Vaccinated { get; set; }
}

public static void CountEx2()
{
    // Create an array of Pet objects.
    Pet[] pets = { new Pet { Name="Barley", Vaccinated=true },
                   new Pet { Name="Boots", Vaccinated=false },
                   new Pet { Name="Whiskers", Vaccinated=false } };

    // Count the number of unvaccinated pets in the array.
    int numberUnvaccinated =
        pets.AsQueryable().Count(p => p.Vaccinated == false);

    Console.WriteLine(
        "There are {0} unvaccinated animals.",
        numberUnvaccinated);
}

// This code produces the following output:
//
// There are 2 unvaccinated animals.

Structure Pet
    Public Name As String
    Public Vaccinated As Boolean
End Structure

Shared Sub CountEx2()
    ' Create an array of Pet objects.
    Dim pets() As Pet = {New Pet With {.Name = "Barley", .Vaccinated = True}, _
                   New Pet With {.Name = "Boots", .Vaccinated = False}, _
                   New Pet With {.Name = "Whiskers", .Vaccinated = False}}

    ' Count the number of unvaccinated pets in the array.
    Dim numberUnvaccinated As Integer = pets.AsQueryable().Count(Function(p) p.Vaccinated = False)

    MsgBox(String.Format("There are {0} unvaccinated animals.", numberUnvaccinated))
End Sub

' This code produces the following output:
'
' There are 2 unvaccinated animals.

注釈

このメソッドは、少なくとも 1 つのパラメーター型のExpression<TDelegate>型引数は、のいずれか、Func<T,TResult>型。This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. ラムダ式で、これらのパラメーターを渡すことができますにコンパイルされると、Expression<TDelegate>します。For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)メソッドを生成、MethodCallExpression呼び出しを表すCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)として構築されたジェネリック メソッド自体。The Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) method generates a MethodCallExpression that represents calling Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) itself as a constructed generic method. これは、後、渡します、MethodCallExpressionExecute<TResult>(Expression)のメソッド、IQueryProviderによって表される、Providerのプロパティ、sourceパラメーター。It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

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

適用対象