Queryable.Select Queryable.Select Queryable.Select Queryable.Select Method

Definição

Projeta cada elemento de uma sequência em um novo formulário.Projects each element of a sequence into a new form.

Sobrecargas

Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>)

Projeta cada elemento de uma sequência em um novo formulário, incorporando o índice do elemento.Projects each element of a sequence into a new form by incorporating the element's index.

Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>)

Projeta cada elemento de uma sequência em um novo formulário.Projects each element of a sequence into a new form.

Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>)

Projeta cada elemento de uma sequência em um novo formulário, incorporando o índice do elemento.Projects each element of a sequence into a new form by incorporating the element's index.

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

Parâmetros de tipo

TSource

O tipo dos elementos de source.The type of the elements of source.

TResult

O tipo do valor retornado pela função representada por selector.The type of the value returned by the function represented by selector.

Parâmetros

source
IQueryable<TSource>

Uma sequência de valores a serem projetados.A sequence of values to project.

selector
Expression<Func<TSource,Int32,TResult>>

Uma função de projeção a ser aplicada a cada elemento.A projection function to apply to each element.

Retornos

IQueryable<TResult>

Um IQueryable<T> cujos elementos são o resultado da invocação de uma função de transformação em cada elemento de source.An IQueryable<T> whose elements are the result of invoking a projection function on each element of source.

Exceções

source ou selector é null.source or selector is null.

Exemplos

O exemplo de código a seguir demonstra como usar Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) em uma sequência de valores de projeto e usar o índice de cada elemento no formulário projetado.The following code example demonstrates how to use Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) to project over a sequence of values and use the index of each element in the projected form.

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

// Project an anonymous type that contains the
// index of the string in the source array, and
// a string that contains the same number of characters
// as the string's index in the source array.
var query =
    fruits.AsQueryable()
    .Select((fruit, index) =>
                new { index, str = fruit.Substring(0, index) });

foreach (var obj in query)
    Console.WriteLine("{0}", obj);

/*
    This code produces the following output:

    { index = 0, str =  }
    { index = 1, str = b }
    { index = 2, str = ma }
    { index = 3, str = ora }
    { index = 4, str = pass }
    { index = 5, str = grape }
*/

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

' Project an anonymous type that contains the
' index of the string in the source array, and
' a string that contains the same number of characters
' as the string's index in the source array.
Dim query = _
    fruits.AsQueryable() _
    .Select(Function(fruit, index) New With {index, .str = fruit.Substring(0, index)})

Dim output As New System.Text.StringBuilder
For Each obj In query
    output.AppendLine(obj.ToString())
Next

' Display the output.
MsgBox(output.ToString())

' This code produces the following output:

' { index = 0, str =  }
' { index = 1, str = b }
' { index = 2, str = ma }
' { index = 3, str = ora }
' { index = 4, str = pass }
' { index = 5, str = grape }

Comentários

Esse método tem pelo menos um parâmetro do tipo Expression<TDelegate> cujo argumento de tipo é um do 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 esses parâmetros, você pode passar em uma expressão lambda e ele será compilado em um Expression<TDelegate>.For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

O Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) método gera uma MethodCallExpression que representa a chamada Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) a próprio como um método genérico construído.The Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) method generates a MethodCallExpression that represents calling Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) itself as a constructed generic method. Em seguida, ele passa a MethodCallExpression para o CreateQuery(Expression) método da IQueryProvider representado pela Provider propriedade do source parâmetro.It then passes the MethodCallExpression to the CreateQuery(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

O comportamento de consulta que ocorre como resultado da execução de uma árvore de expressão que representa a chamada Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) dependem da implementação do tipo do source parâmetro.The query behavior that occurs as a result of executing an expression tree that represents calling Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,Int32,TResult>>) depend on the implementation of the type of the source parameter. O comportamento esperado é que ela invoca selector em cada elemento de source para projetá-lo em um formato diferente.The expected behavior is that it invokes selector on each element of source to project it into a different form.

Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>)

Projeta cada elemento de uma sequência em um novo formulário.Projects each element of a sequence into a new form.

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

Parâmetros de tipo

TSource

O tipo dos elementos de source.The type of the elements of source.

TResult

O tipo do valor retornado pela função representada por selector.The type of the value returned by the function represented by selector.

Parâmetros

source
IQueryable<TSource>

Uma sequência de valores a serem projetados.A sequence of values to project.

selector
Expression<Func<TSource,TResult>>

Uma função de projeção a ser aplicada a cada elemento.A projection function to apply to each element.

Retornos

IQueryable<TResult>

Um IQueryable<T> cujos elementos são o resultado da invocação de uma função de transformação em cada elemento de source.An IQueryable<T> whose elements are the result of invoking a projection function on each element of source.

Exceções

source ou selector é null.source or selector is null.

Exemplos

O exemplo de código a seguir demonstra como usar Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) ao projeto em uma sequência de valores.The following code example demonstrates how to use Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) to project over a sequence of values.

List<int> range =
    new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

// Project the square of each int value.
IEnumerable<int> squares =
    range.AsQueryable().Select(x => x * x);

foreach (int num in squares)
    Console.WriteLine(num);

/*
    This code produces the following output:

    1
    4
    9
    16
    25
    36
    49
    64
    81
    100
*/

Dim range As New List(Of Integer)(New Integer() {1, 2, 3, 4, 5, 6, 7, 8, 9, 10})

' Project the square of each int value.
Dim squares As IEnumerable(Of Integer) = _
    range.AsQueryable().Select(Function(x) x * x)

Dim output As New System.Text.StringBuilder
For Each num As Integer In squares
    output.AppendLine(num)
Next

' Display the output.
MsgBox(output.ToString())

' This code produces the following output:

' 1
' 4
' 9
' 16
' 25
' 36
' 49
' 64
' 81
' 100

Comentários

Esse método tem pelo menos um parâmetro do tipo Expression<TDelegate> cujo argumento de tipo é um do 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 esses parâmetros, você pode passar em uma expressão lambda e ele será compilado em um Expression<TDelegate>.For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

O Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) método gera uma MethodCallExpression que representa a chamada Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) a próprio como um método genérico construído.The Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) method generates a MethodCallExpression that represents calling Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) itself as a constructed generic method. Em seguida, ele passa a MethodCallExpression para o CreateQuery(Expression) método da IQueryProvider representado pela Provider propriedade do source parâmetro.It then passes the MethodCallExpression to the CreateQuery(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

O comportamento de consulta que ocorre como resultado da execução de uma árvore de expressão que representa a chamada Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) depende da implementação do tipo do source parâmetro.The query behavior that occurs as a result of executing an expression tree that represents calling Select<TSource,TResult>(IQueryable<TSource>, Expression<Func<TSource,TResult>>) depends on the implementation of the type of the source parameter. O comportamento esperado é que ela invoca selector em cada elemento de source para projetá-lo em um formato diferente.The expected behavior is that it invokes selector on each element of source to project it into a different form.

Aplica-se a