vb.net - 使用类型别名来定义类型别名

Question

作为DRY(Don't Repeat Yourself)的狂热信徒，我只写了这段代码:

Imports SimpleDict = System.Collections.Generic.Dictionary(Of String, String)
Imports ListOfSimpleDicts = System.Collections.Generic.List(Of SimpleDict)
Imports DictOfSimpleDicts = System.Collections.Generic.Dictionary(Of String, SimpleDict)

我立即收到错误消息，“类型‘SimpleDict’未定义。”在最后两行。有没有办法避免在我的类型别名中重复我自己？

[附录] 24 小时后，我不得不将 SimpleDict 更改为别名 Dictionary(Of String, HashSet)。好消息是，由于我使用的是别名，我的更改会传播到我使用过的所有地方，但不幸的是，我仍然需要自己更改其他两行。

Answer 1

From the VB specification

Imports statements make names available in a source file, but do not declare anything in the global namespace's declaration space. The scope of the names imported by an Imports statement extends over the namespace member declarations contained in the source file. The scope of an Imports statement specifically does not include other Imports statements, nor does it include other source files. Imports statements may not refer to one another.

In this example, the last Imports statement is in error because it is not affected by the first import alias.

Imports R1 = N1 ' OK.
Imports R2 = N1.N2 ' OK.
Imports R3 = R1.N2 ' Error: Can't refer to R1.

我不确定你可以做什么。我唯一能想到的是将 SimpleDict 定义为 System.Collections.Generic.Dictionary(Of String, String) 的类，不确定这是否适合您因为你必须创建一个类。

Imports ListOfSimpleDicts = System.Collections.Generic.List(Of RootNamespace.SimpleDict)
Imports DictOfSimpleDicts = System.Collections.Generic.Dictionary(Of String, RootNamespace.SimpleDict)

Public Class SimpleDict
    Inherits System.Collections.Generic.Dictionary(Of String, String)
End Class