Queryable.Count Método

Definición

Devuelve el número de elementos de una secuencia.Returns the number of elements in a sequence.

Sobrecargas

Count<TSource>(IQueryable<TSource>)

Devuelve el número de elementos de una secuencia.Returns the number of elements in a sequence.

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

Devuelve el número de elementos de la secuencia especificada que satisfacen una condición.Returns the number of elements in the specified sequence that satisfies a condition.

Count<TSource>(IQueryable<TSource>)

Devuelve el número de elementos de una secuencia.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

Parámetros de tipo

TSource

Tipo de los elementos de source.The type of the elements of source.

Parámetros

source
IQueryable<TSource>

IQueryable<T> que contiene los elementos que se van a contar.The IQueryable<T> that contains the elements to be counted.

Devoluciones

Int32

El número de elementos de la secuencia de entrada.The number of elements in the input sequence.

Excepciones

source es null.source is null.

El número de elementos de source es mayor que MaxValue.The number of elements in source is larger than MaxValue.

Ejemplos

En el ejemplo de código siguiente se muestra cómo usar Count<TSource>(IQueryable<TSource>) para contar los elementos de una secuencia.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.

Comentarios

El Count<TSource>(IQueryable<TSource>) método genera un MethodCallExpression que representa la llamada a Count<TSource>(IQueryable<TSource>) sí mismo como un método genérico construido.The Count<TSource>(IQueryable<TSource>) method generates a MethodCallExpression that represents calling Count<TSource>(IQueryable<TSource>) itself as a constructed generic method. A continuación, pasa el MethodCallExpression al Execute<TResult>(Expression) método de IQueryProvider representado por la Provider propiedad del source parámetro.It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

El comportamiento de la consulta que se produce como resultado de ejecutar un árbol de expresión que representa Count<TSource>(IQueryable<TSource>) la llamada depende de la implementación del tipo del source parámetro.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. El comportamiento esperado es que cuente el número de elementos de source .The expected behavior is that it counts the number of items in source.

Se aplica a

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

Devuelve el número de elementos de la secuencia especificada que satisfacen una condición.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

Parámetros de tipo

TSource

Tipo de los elementos de source.The type of the elements of source.

Parámetros

source
IQueryable<TSource>

IQueryable<T> que contiene los elementos que se van a contar.An IQueryable<T> that contains the elements to be counted.

predicate
Expression<Func<TSource,Boolean>>

Función para probar cada elemento de una condición.A function to test each element for a condition.

Devoluciones

Int32

El número de elementos de la secuencia que satisfacen la condición de la función de predicado.The number of elements in the sequence that satisfies the condition in the predicate function.

Excepciones

source o predicate es null.source or predicate is null.

El número de elementos de source es mayor que MaxValue.The number of elements in source is larger than MaxValue.

Ejemplos

En el ejemplo de código siguiente se muestra cómo usar Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) para contar los elementos de una secuencia que satisfacen una condición.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.

Comentarios

Este método tiene al menos un parámetro de tipo Expression<TDelegate> cuyo argumento de tipo es uno de los Func<T,TResult> tipos.This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. Para estos parámetros, puede pasar una expresión lambda y se compilará en un Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

El Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) método genera un MethodCallExpression que representa la llamada a Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) sí mismo como un método genérico construido.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. A continuación, pasa el MethodCallExpression al Execute<TResult>(Expression) método de IQueryProvider representado por la Provider propiedad del source parámetro.It then passes the MethodCallExpression to the Execute<TResult>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

El comportamiento de la consulta que se produce como resultado de ejecutar un árbol de expresión que representa Count<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) la llamada depende de la implementación del tipo del source parámetro.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. El comportamiento esperado es que cuente el número de elementos de source que satisfacen la condición especificada por predicate .The expected behavior is that it counts the number of items in source that satisfy the condition specified by predicate.

Se aplica a