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

Definizione

Restituisce il numero di elementi in una sequenza.Returns the number of elements in a sequence.

Overload

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

Restituisce il numero di elementi in una sequenza.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>>)

Restituisce il numero di elementi nella sequenza che soddisfa una condizione specificata.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>)

Restituisce il numero di elementi in una sequenza.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

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

Parametri

source
IQueryable<TSource>

Il IQueryable<T> che contiene gli elementi da contare.The IQueryable<T> that contains the elements to be counted.

Restituisce

Numero di elementi nella sequenza di input.The number of elements in the input sequence.

Eccezioni

Il numero di elementi in source è maggiore di MaxValue.The number of elements in source is larger than MaxValue.

Esempi

Esempio di codice seguente viene illustrato come utilizzare Count<TSource>(IQueryable<TSource>) per contare gli elementi in una sequenza.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. 

Commenti

Il Count<TSource>(IQueryable<TSource>) metodo genera un MethodCallExpression che rappresenta una chiamata Count<TSource>(IQueryable<TSource>) stesso come un metodo generico costruito.The Count<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Count<TSource>(IQueryable<TSource>) itself as a constructed generic method. Passa quindi il MethodCallExpression per il Execute<TResult>(Expression) metodo del IQueryProvider rappresentato dal Provider proprietà del source parametro.It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

Il comportamento delle query che si verifica in seguito all'esecuzione di un albero delle espressioni che rappresenta una chiamata Count<TSource>(IQueryable<TSource>) dipende dall'implementazione del tipo del source parametro.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. Il comportamento previsto è che conta il numero di elementi in source.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>>)

Restituisce il numero di elementi nella sequenza che soddisfa una condizione specificata.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

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

Parametri

source
IQueryable<TSource>

Un IQueryable<T> che contiene gli elementi da contare.An IQueryable<T> that contains the elements to be counted.

predicate
Expression<Func<TSource,Boolean>>

Funzione per testare ogni elemento rispetto a una condizione.A function to test each element for a condition.

Restituisce

Il numero di elementi nella sequenza che soddisfa la condizione nella funzione predicativa.The number of elements in the sequence that satisfies the condition in the predicate function.

Eccezioni

source o predicate è null.source or predicate is null.

Il numero di elementi in source è maggiore di MaxValue.The number of elements in source is larger than MaxValue.

Esempi

Esempio di codice seguente viene illustrato come utilizzare Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) per contare gli elementi in una sequenza che soddisfa una condizione.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.

Commenti

Questo metodo ha almeno un parametro di tipo Expression<TDelegate> il cui argomento tipo è uno del Func<T,TResult> tipi.This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. Per questi parametri, è possibile passare in un'espressione lambda e verrà compilata per un Expression<TDelegate>.For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

Il Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) metodo genera un MethodCallExpression che rappresenta una chiamata Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) stesso come un metodo generico costruito.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. Passa quindi il MethodCallExpression per il Execute<TResult>(Expression) metodo del IQueryProvider rappresentato dal Provider proprietà del source parametro.It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

Il comportamento delle query che si verifica in seguito all'esecuzione di un albero delle espressioni che rappresenta una chiamata Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) dipende dall'implementazione del tipo del source parametro.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. Il comportamento previsto è che conta il numero di elementi in source che soddisfano la condizione specificata dal predicate.The expected behavior is that it counts the number of items in source that satisfy the condition specified by predicate.

Si applica a