VB.Net 变量声明

发布于 2024-09-04 22:39:09 字数 395 浏览 7 评论 0原文

我注意到，即使同时打开 Option Strict 和 Option Explicit ，这两个编译器也不会出现任何编译器警告或错误：

    Dim x As Exception = New Exception("this is a test")
    Dim y = New Exception("this is another test")

我的问题是，使用第一种方式（参见变量 x）还是第二种方式（参见变量 y）？我的猜测是，VB 不需要 As 子句，因为变量已就地初始化，因此编译器可以推断类型。

我倾向于喜欢第一种方式，因为它只是“感觉”正确，并且与 C# 等其他语言更一致，只是想知道一种方式是否优于另一种方式是否有充分的理由。我想这确实是个人选择。

原文

I notice that both of these compile without any compiler warnings or errors, even with Option Strict and Option Explicit both turned on:

    Dim x As Exception = New Exception("this is a test")
    Dim y = New Exception("this is another test")

My question is, is it more proper to use the first way (see variable x) or the second way (see variable y)? My guess is that VB doesn't need the As clause since the variable is being initialized in place, so the compiler can infer the type.

I tend to like the first way as it just "feels" right and is more consistent with other languages like C#, just wondered if there was some good reason for one way over the other. I guess it's really personal choice.

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骑趴 2024-09-11 22:39:09

看看 Option Infer On 的奇妙之处吧，编译器会自动计算出“y”的类型。自 VS2008 起可用。通过关闭它，您会得到您正在寻找的错误：

Option Strict On
Option Infer Off

Module Module1
    Sub Main()
        Dim x As Exception = New Exception("this is a test")
        Dim y = New Exception("this is another test")   ''# error BC30209
        Dim z As New Exception("this is a third test")
    End Sub
End Module

Behold the wonder of Option Infer On, the compiler figures out the type of "y" automatically. Available since VS2008. You'll get the error you are looking for by turning it off:

Option Strict On
Option Infer Off

Module Module1
    Sub Main()
        Dim x As Exception = New Exception("this is a test")
        Dim y = New Exception("this is another test")   ''# error BC30209
        Dim z As New Exception("this is a third test")
    End Sub
End Module

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