Queryable.LongCount Queryable.LongCount Queryable.LongCount Queryable.LongCount Method

Definizione

Restituisce un Int64 che rappresenta il numero di elementi nella sequenza.Returns an Int64 that represents the number of elements in sequence.

Overload

LongCount<TSource>(IQueryable<TSource>) LongCount<TSource>(IQueryable<TSource>) LongCount<TSource>(IQueryable<TSource>) LongCount<TSource>(IQueryable<TSource>)

Restituisce un Int64 che rappresenta il numero totale di elementi in una sequenza.Returns an Int64 that represents the total number of elements in a sequence.

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

Restituisce un Int64 che rappresenta il numero di elementi in una sequenza che soddisfa una condizione.Returns an Int64 that represents the number of elements in a sequence that satisfy a condition.

LongCount<TSource>(IQueryable<TSource>) LongCount<TSource>(IQueryable<TSource>) LongCount<TSource>(IQueryable<TSource>) LongCount<TSource>(IQueryable<TSource>)

Restituisce un Int64 che rappresenta il numero totale di elementi in una sequenza.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

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.

Restituisce

Numero di elementi in source.The number of elements in source.

Eccezioni

Il numero di elementi supera MaxValue.The number of elements exceeds MaxValue.

Esempi

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

Commenti

Il LongCount<TSource>(IQueryable<TSource>) metodo genera un MethodCallExpression che rappresenta una chiamata LongCount<TSource>(IQueryable<TSource>) stesso come un metodo generico costruito.The LongCount<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling LongCount<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 LongCount<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 LongCount<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 e restituisce un Int64.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>>) LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)

Restituisce un Int64 che rappresenta il numero di elementi in una sequenza che soddisfa una condizione.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

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 in source che soddisfano la condizione nella funzione predicativa.The number of elements in source that satisfy the condition in the predicate function.

Eccezioni

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

Il numero di elementi corrispondenti supera MaxValue.The number of matching elements exceeds MaxValue.

Esempi

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

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 LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) metodo genera un MethodCallExpression che rappresenta una chiamata LongCount<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) stesso come un metodo generico costruito.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. 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 LongCount<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 LongCount<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 da predicate e restituisce un Int64.The expected behavior is that it counts the number of items in source that satisfy the condition specified by predicate and returns an Int64.

Si applica a