如何VB.NET可选参数工作“引擎盖下”？他们是符合CLS？ [英] How Do VB.NET Optional Parameters work 'Under the hood'? Are they CLS-Compliant?

问题描述

比方说，我们有以下的方法声明：

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

如何VB.NET使可选参数的CLR的范围内开展工作？可选参数符合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，这是反编译的C＃code，通过反射得到。

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);
}

注意选配和DefaultParameterValue属性。尝试把它们在C＃中的方法。你会发现，你仍然需要将值传递给该方法。在VB code然而，它变成默认的！话虽这么说，我个人从来不使用默认值，即使在VB code。这感觉就像一个黑客。方法重载的伎俩我。

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.

默认确实有助于不过，当使用Excel互操作，这是一个痛苦的屁股直使用的开箱即用在C＃中。处理

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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