VB.NET 可选参数如何工作'在幕后'?它们是否符合 CLS? [英] How Do VB.NET Optional Parameters work 'Under the hood'? Are they CLS-Compliant?

问题描述

假设我们有以下方法声明:

Let's say we have the following method declaration:

Public Function MyMethod(ByVal param1 As Integer, _
    Optional ByVal param2 As Integer = 0, _
    Optional ByVal param3 As Integer = 1) As Integer

    Return param1 + param2 + param3
End Function

VB.NET 如何使可选参数在 CLR 范围内工作?可选参数是否符合 CLS?

How does VB.NET make the optional parameters work within the confines of the CLR? Are optional parameters CLS-Compliant?

推荐答案

有趣的是，这是通过反射器获得的反编译的 C# 代码.

Interestingly, this is the decompiled C# code, obtained via reflector.

public int MyMethod(int param1, 
                   [Optional, DefaultParameterValue(0)] int param2, 
                   [Optional, DefaultParameterValue(1)] int param3)
{
    return ((param1 + param2) + param3);
}

注意 Optional 和 DefaultParameterValue 属性.尝试将它们放在 C# 方法中.你会发现你仍然需要向方法传递值.然而在 VB 代码中，它变成了 Default！话虽如此，我个人从未在 VB 代码中使用过 Default.感觉就像一个黑客.方法重载对我有用.

Notice the Optional and DefaultParameterValue attributes. Try putting them in C# methods. You will find that you are still required to pass values to the method. In VB code however, its turned into Default! That being said, I personally have never use Default even in VB code. It feels like a hack. Method overloading does the trick for me.

不过，在处理 Excel Interop 时，默认确实有帮助，这在 C# 中直接使用开箱即用是一件很痛苦的事情.

Default does help though, when dealing with the Excel Interop, which is a pain in the ass to use straight out of the box in C#.

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