Expression.Goto 方法

定义

命名空间:

System.Linq.Expressions

程序集:

System.Linq.Expressions.dll

创建一个表示“go to”语句的 GotoExpression。

重载

Goto(LabelTarget, Expression, Type)	创建一个表示具有指定类型的“go to”语句的 GotoExpression。 可以指定在跳转时传递给标签的值。
Goto(LabelTarget, Type)	创建一个表示具有指定类型的“go to”语句的 GotoExpression。
Goto(LabelTarget)	创建一个表示“go to”语句的 GotoExpression。
Goto(LabelTarget, Expression)	创建一个表示“go to”语句的 GotoExpression。 可以指定在跳转时传递给标签的值。

Goto(LabelTarget, Expression, Type)

Source:

GotoExpression.cs

创建一个表示具有指定类型的“go to”语句的 GotoExpression。 可以指定在跳转时传递给标签的值。

public:
 static System::Linq::Expressions::GotoExpression ^ Goto(System::Linq::Expressions::LabelTarget ^ target, System::Linq::Expressions::Expression ^ value, Type ^ type);

public static System.Linq.Expressions.GotoExpression Goto (System.Linq.Expressions.LabelTarget target, System.Linq.Expressions.Expression? value, Type type);

static member Goto : System.Linq.Expressions.LabelTarget * System.Linq.Expressions.Expression * Type -> System.Linq.Expressions.GotoExpression

Public Shared Function Goto (target As LabelTarget, value As Expression, type As Type) As GotoExpression

参数

target

LabelTarget

LabelTarget 将跳至的 GotoExpression。

value

Expression

将在跳转时传递给关联标签的值。

type

Type

要将 Type 属性设置为与其相等的 Type。

返回

GotoExpression

一个 GotoExpression，其 Kind 等于 Goto，其 Target 属性设置为 target，并且其 Type 属性设置为 type，此外还有一个在跳转时将传递给目标标签的 value。

Goto(LabelTarget, Type)

Source:

GotoExpression.cs

创建一个表示具有指定类型的“go to”语句的 GotoExpression。

public:
 static System::Linq::Expressions::GotoExpression ^ Goto(System::Linq::Expressions::LabelTarget ^ target, Type ^ type);

public static System.Linq.Expressions.GotoExpression Goto (System.Linq.Expressions.LabelTarget target, Type type);

static member Goto : System.Linq.Expressions.LabelTarget * Type -> System.Linq.Expressions.GotoExpression

Public Shared Function Goto (target As LabelTarget, type As Type) As GotoExpression

参数

target

LabelTarget

LabelTarget 将跳至的 GotoExpression。

type

Type

要将 Type 属性设置为与其相等的 Type。

返回

GotoExpression

一个 GotoExpression，其 Kind 等于 Goto，其 Target 属性设置为指定值，并且其 Type 属性设置为 type，此外还有一个在跳转时将传递给目标标签的 null 值。

Goto(LabelTarget)

Source:

GotoExpression.cs

创建一个表示“go to”语句的 GotoExpression。

public:
 static System::Linq::Expressions::GotoExpression ^ Goto(System::Linq::Expressions::LabelTarget ^ target);

public static System.Linq.Expressions.GotoExpression Goto (System.Linq.Expressions.LabelTarget target);

static member Goto : System.Linq.Expressions.LabelTarget -> System.Linq.Expressions.GotoExpression

Public Shared Function Goto (target As LabelTarget) As GotoExpression

参数

target

LabelTarget

LabelTarget 将跳至的 GotoExpression。

返回

GotoExpression

一个 GotoExpression，其 Kind 等于 Goto，其 Target 属性设置为指定值，此外还有一个在跳转时将传递给目标标签的 null 值。

示例

以下示例演示如何创建包含 GotoExpression 对象的表达式。

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

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

// This block contains a GotoExpression.
// 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("GoTo")),
        Expression.Goto(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:
//
// GoTo

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

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

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

' This block contains a GotoExpression.
' 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("GoTo")),
          Expression.Goto(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:
'
' GoTo

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

Goto(LabelTarget, Expression)

Source:

GotoExpression.cs

创建一个表示“go to”语句的 GotoExpression。 可以指定在跳转时传递给标签的值。

public:
 static System::Linq::Expressions::GotoExpression ^ Goto(System::Linq::Expressions::LabelTarget ^ target, System::Linq::Expressions::Expression ^ value);

public static System.Linq.Expressions.GotoExpression Goto (System.Linq.Expressions.LabelTarget target, System.Linq.Expressions.Expression? value);

static member Goto : System.Linq.Expressions.LabelTarget * System.Linq.Expressions.Expression -> System.Linq.Expressions.GotoExpression

Public Shared Function Goto (target As LabelTarget, value As Expression) As GotoExpression

参数

target

LabelTarget

LabelTarget 将跳至的 GotoExpression。

value

Expression

将在跳转时传递给关联标签的值。

返回

GotoExpression

一个 GotoExpression，其 Kind 等于 Goto，并且其 Target 属性设置为 target，此外还有一个在跳转时将传递给目标标签的 value。