与C＃语法相对应的VB是什么？ [英] What is the VB equivalent of this C# syntax, dealing with delegates?

问题描述

可以使用VB 9.0将以下C＃代码转换为VB.NET吗？

Is it possible to translate the following C# code into VB.NET, using VB 9.0?

delegate Stream StreamOpenerDelegate(String name);

void Exec1()
{
    WorkMethod( x => File.OpenRead(x));
}

void Exec2()
{
    StreamOpenerDelegate opener = x => return File.OpenRead(x) ;
    WorkMethod(opener);
}

我可以这样做吗？：

Private Delegate Function StreamOpenerDelegate(ByVal name As String) As Stream

Private Sub WorkMethod(ByVal d As StreamOpenerDelegate)
    ''
End Sub

Private Sub Exec1()
    Me.WorkMethod(Function (ByVal x As String) 
        Return File.OpenRead(x)
    End Function)
End Sub

Private Sub Exec2()
    Dim opener As StreamOpenerDelegate = Function (ByVal x As String) 
        Return File.OpenRead(x)
    End Function
    Me.WorkMethod(opener)
End Sub

我试图写一些文档，但我不知道VB语法。通常我使用反射器进行翻译，但我不确定它是否正常工作这个案例。我也不清楚我在哪里需要行连续字符。

I'm trying to write some documentation, but I don't know VB syntax. Often I use Reflector to translate it, but I'm not sure it's working in this case. I'm also not clear on where I would need line continuation characters.

ANSWER br>
在VB9中，不可能有多行lambdas（或Sub lambdas，我没有问过）。在VB9中，所有lambdas都返回一个值，并且必须是单个表达式。 VB10中的这种变化。 VB10将允许上述语法，但VB9不会。在VB9中，如果逻辑涉及多个代码行，那么它不能是一个lambda;您必须将其放入一个命名的函数中并明确引用。像这样：

ANSWER
In VB9, it's not possible to have multi-line lambdas (or Sub lambdas, which I did not ask about). In VB9, all lambdas return a value, and must be a single expression. This changes in VB10. VB10 will allow the above syntax, but VB9 will not. In VB9, if the logic involves multiple code lines, it must not be a lambda; you must put it into a named Function and reference it explicitly. Like this:

Private Delegate Function StreamOpenerDelegate(ByVal name As String) As Stream

Private Sub WorkMethod(ByVal d As StreamOpenerDelegate)
    ''
End Sub

Function MyStreamOpener(ByVal entryName As String) As Stream
    '' possibly multiple lines here
    Return File.OpenRead(entryName)
End Function

Private Sub Exec1()
    Me.WorkMethod(AddressOf MyStreamOpener)
End Sub

网站： Mike McIntyre的博客

推荐答案

这应该工作：

Private Sub Exec1()
    Me.WorkMethod(Function (x) File.OpenRead(x))
End Sub

Private Sub Exec2()
    Dim opener As StreamOpenerDelegate = Function (x) File.OpenRead(x)

    Me.WorkMethod(opener)
End Sub

您需要行连续字符来拆分单行语句成多行，如下所示：

You need the line continuation character to split a single line statement into multiple lines, like so:

Private Sub Exec1()
    Me.WorkMethod(Function (x) _
                    File.OpenRead(x))
End Sub

Private Sub Exec2()
    Dim opener As StreamOpenerDelegate = Function (x) _
                                           File.OpenRead(x)

    Me.WorkMethod(opener)
End Sub

无论如何，在 VS2010 某些字符之后有隐式行延续。所以我不用担心太多了。

In any case, in VS2010 there is implicit line continuation after certain characters. So I wouldn't worry about it too much.

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