Expression.Label Yöntem

Tanım

Ad Alanı:

System.Linq.Expressions

Bütünleştirilmiş Kod:

System.Linq.Expressions.dll

LabelTarget Bir etiketi temsil eden bir oluşturur.

Aşırı Yüklemeler

Label()	Void türüne sahip ve adı olmayan bir etiketi temsil eden bir LabelTarget oluşturur.
Label(LabelTarget)	LabelExpression Varsayılan değer olmadan bir etiketi temsil eden bir oluşturur.
Label(String)	Void türüne ve verilen ada sahip bir etiketi temsil eden bir LabelTarget oluşturur.
Label(Type)	Verilen türe sahip bir etiketi temsil eden bir LabelTarget oluşturur.
Label(LabelTarget, Expression)	Verilen varsayılan değere sahip bir etiketi temsil eden bir LabelExpression oluşturur.
Label(Type, String)	Verilen tür ve ada sahip bir etiketi temsil eden bir LabelTarget oluşturur.

Label()

Kaynak:

LabelTarget.cs

Void türüne sahip ve adı olmayan bir etiketi temsil eden bir LabelTarget oluşturur.

public:
 static System::Linq::Expressions::LabelTarget ^ Label();

public static System.Linq.Expressions.LabelTarget Label ();

static member Label : unit -> System.Linq.Expressions.LabelTarget

Public Shared Function Label () As LabelTarget

Döndürülenler

LabelTarget

Yeni LabelTarget.

Örnekler

Aşağıdaki örnekte, nesne içeren LabelTarget bir ifadenin nasıl oluşturulacağı gösterilmektedir.

// Add the following directive to the file:
// using System.Linq.Expressions;

// A label expression of the void type that is the target for Expression.Return().
LabelTarget returnTarget = Expression.Label();

// This block contains a GotoExpression that represents a return statement with no value.
// It transfers execution to a label expression that is initialized with the same LabelTarget as the GotoExpression.
// The types of the GotoExpression, label expression, and LabelTarget must match.
BlockExpression blockExpr =
    Expression.Block(
        Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) }), Expression.Constant("Return")),
        Expression.Return(returnTarget),
        Expression.Call(typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) }), Expression.Constant("Other Work")),
        Expression.Label(returnTarget)
    );

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action>(blockExpr).Compile()();

// This code example produces the following output:
//
// Return

// "Other Work" is not printed because
// the Return expression transfers execution from Expression.Return(returnTarget)
// to Expression.Label(returnTarget).

' Add the following directive to the file:
' Imports System.Linq.Expressions  

' A label expression of the void type that is the target for Expression.Return().
Dim returnTarget As LabelTarget = Expression.Label()

' This block contains a GotoExpression that represents a return statement with no value.
' It transfers execution to a label expression that is initialized with the same LabelTarget as the GotoExpression.
' The types of the GotoExpression, label expression, and LabelTarget must match.
Dim blockExpr As BlockExpression =
      Expression.Block(
          Expression.Call(GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}), Expression.Constant("Return")),
          Expression.Return(returnTarget),
          Expression.Call(GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}), Expression.Constant("Other Work")),
          Expression.Label(returnTarget)
      )

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
Expression.Lambda(Of Action)(blockExpr).Compile()()

' This code example produces the following output:
'
' Return

' "Other Work" is not printed because 
' the Return expression transfers execution from Return(returnTarget)
' to Expression.Label(returnTarget).

Label(LabelTarget)

Kaynak:

LabelExpression.cs

LabelExpression Varsayılan değer olmadan bir etiketi temsil eden bir oluşturur.

public:
 static System::Linq::Expressions::LabelExpression ^ Label(System::Linq::Expressions::LabelTarget ^ target);

public static System.Linq.Expressions.LabelExpression Label (System.Linq.Expressions.LabelTarget target);

static member Label : System.Linq.Expressions.LabelTarget -> System.Linq.Expressions.LabelExpression

Public Shared Function Label (target As LabelTarget) As LabelExpression

Parametreler

target

LabelTarget

Bununla LabelTargetLabelExpression ilişkilendirilecek.

Döndürülenler

LabelExpression

LabelExpression Varsayılan değeri olmayan bir.

Label(String)

Kaynak:

LabelTarget.cs

Void türüne ve verilen ada sahip bir etiketi temsil eden bir LabelTarget oluşturur.

public:
 static System::Linq::Expressions::LabelTarget ^ Label(System::String ^ name);

public static System.Linq.Expressions.LabelTarget Label (string? name);

static member Label : string -> System.Linq.Expressions.LabelTarget

Public Shared Function Label (name As String) As LabelTarget

Parametreler

name

String

Etiketin adı.

Döndürülenler

LabelTarget

Yeni LabelTarget.

Label(Type)

Kaynak:

LabelTarget.cs

Verilen türe sahip bir etiketi temsil eden bir LabelTarget oluşturur.

public:
 static System::Linq::Expressions::LabelTarget ^ Label(Type ^ type);

public static System.Linq.Expressions.LabelTarget Label (Type type);

static member Label : Type -> System.Linq.Expressions.LabelTarget

Public Shared Function Label (type As Type) As LabelTarget

Parametreler

type

Type

Etikete atlarken geçirilen değerin türü.

Döndürülenler

LabelTarget

Yeni LabelTarget.

Örnekler

Aşağıdaki örnekte, döngü ifadesinde bir LabelTarget nesnenin nasıl kullanılacağı gösterilmektedir.

// Add the following directive to the file:
// using System.Linq.Expressions;

// Creating a parameter expression.
ParameterExpression value = Expression.Parameter(typeof(int), "value");

// Creating an expression to hold a local variable.
ParameterExpression result = Expression.Parameter(typeof(int), "result");

// Creating a label to jump to from a loop.
LabelTarget label = Expression.Label(typeof(int));

// Creating a method body.
BlockExpression block = Expression.Block(
    new[] { result },
    Expression.Assign(result, Expression.Constant(1)),
        Expression.Loop(
           Expression.IfThenElse(
               Expression.GreaterThan(value, Expression.Constant(1)),
               Expression.MultiplyAssign(result,
                   Expression.PostDecrementAssign(value)),
               Expression.Break(label, result)
           ),
       label
    )
);

// Compile and run an expression tree.
int factorial = Expression.Lambda<Func<int, int>>(block, value).Compile()(5);

Console.WriteLine(factorial);

// This code example produces the following output:
//
// 120

' Add the following directive to the file:
' Imports System.Linq.Expressions  

' Creating a parameter expression.
Dim value As ParameterExpression =
    Expression.Parameter(GetType(Integer), "value")

' Creating an expression to hold a local variable. 
Dim result As ParameterExpression =
    Expression.Parameter(GetType(Integer), "result")

' Creating a label to jump to from a loop.
Dim label As LabelTarget = Expression.Label(GetType(Integer))

' Creating a method body.
Dim block As BlockExpression = Expression.Block(
    New ParameterExpression() {result},
    Expression.Assign(result, Expression.Constant(1)),
    Expression.Loop(
        Expression.IfThenElse(
            Expression.GreaterThan(value, Expression.Constant(1)),
            Expression.MultiplyAssign(result,
                Expression.PostDecrementAssign(value)),
            Expression.Break(label, result)
        ),
        label
    )
)

' Compile an expression tree and return a delegate.
Dim factorial As Integer =
    Expression.Lambda(Of Func(Of Integer, Integer))(block, value).Compile()(5)

Console.WriteLine(factorial)

' This code example produces the following output:
'
' 120

Label(LabelTarget, Expression)

Kaynak:

LabelExpression.cs

Verilen varsayılan değere sahip bir etiketi temsil eden bir LabelExpression oluşturur.

public:
 static System::Linq::Expressions::LabelExpression ^ Label(System::Linq::Expressions::LabelTarget ^ target, System::Linq::Expressions::Expression ^ defaultValue);

public static System.Linq.Expressions.LabelExpression Label (System.Linq.Expressions.LabelTarget target, System.Linq.Expressions.Expression? defaultValue);

static member Label : System.Linq.Expressions.LabelTarget * System.Linq.Expressions.Expression -> System.Linq.Expressions.LabelExpression

Public Shared Function Label (target As LabelTarget, defaultValue As Expression) As LabelExpression

Parametreler

target

LabelTarget

Bununla LabelTargetLabelExpression ilişkilendirilecek.

defaultValue

Expression

Etikete normal denetim akışı üzerinden ulaşıldığında bunun LabelExpression değeri.

Döndürülenler

LabelExpression

Verilen varsayılan değere sahip A LabelExpression .

Label(Type, String)

Kaynak:

LabelTarget.cs

Verilen tür ve ada sahip bir etiketi temsil eden bir LabelTarget oluşturur.

public:
 static System::Linq::Expressions::LabelTarget ^ Label(Type ^ type, System::String ^ name);

public static System.Linq.Expressions.LabelTarget Label (Type type, string? name);

static member Label : Type * string -> System.Linq.Expressions.LabelTarget

Public Shared Function Label (type As Type, name As String) As LabelTarget

Parametreler

type

Type

Etikete atlarken geçirilen değerin türü.

name

String

Etiketin adı.

Döndürülenler

LabelTarget

Yeni LabelTarget.