本文整理汇总了VB.NET中System.Linq.Expressions.Expression.Label方法的典型用法代码示例。如果您正苦于以下问题：VB.NET Expression.Label方法的具体用法？VB.NET Expression.Label怎么用？VB.NET Expression.Label使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类System.Linq.Expressions.Expression的用法示例。
在下文中一共展示了Expression.Label方法的2个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的VB.NET代码示例。
示例1: Type
' 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()()输出：
Return "Other Work" is not printed because the Return expression transfers execution from Return(returnTarget) to Expression.Label(returnTarget).
示例2: ParameterExpression
' 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)输出：
120