VB.NET Expression类代码示例

OStack程序员社区-中国程序员成长平台 › 门户 › 编程› VB.NET›VB.NET教程

原作者: [db:作者] 来自: [db:来源] 收藏邀请

本文整理汇总了VB.NET中System.Linq.Expressions.Expression类的典型用法代码示例。如果您正苦于以下问题：VB.NET Expression类的具体用法？VB.NET Expression怎么用？VB.NET Expression使用的例子？那么恭喜您, 这里精选的类代码示例或许可以为您提供帮助。

在下文中一共展示了Expression类的1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，您的评价将有助于我们的系统推荐出更棒的VB.NET代码示例。

示例1: GetType

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

' The block expression enables you to execute several expressions sequentually.
' When the block expression is executed,
' it returns the value of the last expression in the sequence.
Dim blockExpr As BlockExpression = Expression.Block(
    Expression.Call(
        Nothing,
        GetType(Console).GetMethod("Write", New Type() {GetType(String)}),
        Expression.Constant("Hello ")
       ),
    Expression.Call(
        Nothing,
        GetType(Console).GetMethod("WriteLine", New Type() {GetType(String)}),
        Expression.Constant("World!")
        ),
    Expression.Constant(42)
)

Console.WriteLine("The result of executing the expression tree:")
' The following statement first creates an expression tree,
' then compiles it, and then executes it.           
Dim result = Expression.Lambda(Of Func(Of Integer))(blockExpr).Compile()()

' Print the expressions from the block expression.
Console.WriteLine("The expressions from the block expression:")
For Each expr In blockExpr.Expressions
    Console.WriteLine(expr.ToString())
Next

' Print the result of the tree execution.
Console.WriteLine("The return value of the block expression:")
Console.WriteLine(result)

开发者ID:VB.NET开发者，项目名称:System.Linq.Expressions，代码行数:34，代码来源:Expression

输出：

The result of executing the expression tree:
Hello World!

The expressions from the block expression:
Write("Hello ")
WriteLine("World!")
42

The return value of the block expression:
42

注：本文中的System.Linq.Expressions.Expression类示例整理自Github/MSDocs等源码及文档管理平台，相关代码片段筛选自各路编程大神贡献的开源项目，源码版权归原作者所有，传播和使用请参考对应项目的License；未经允许，请勿转载。