How to call method written in VB.NET from C# with optional arguments

Question

Hi,

I have a method written in VB.NET. It looks like this:

Shared Sub SomeMethod(ByVal Id As Guid, 
                      Optional ByVal str1 As String = "foo", 
                      Optional ByVal str2 As String = "")

I want to call this method from C# 3.0 and I want it to use its default arguments. I tried passing System.Reflection.Missing.Value, but I cannot cast it as String.

Is there any way to do that?

Thanks in advance for help.

Answer 1

No, in C#3 you simply have to pass all parameters. C#4 will have optional and named parameters.

You could off course create a few overloaded variations, but that is only an approximation.

Answer 2

Without using C# 4.0 (which adds support for optional parameters) you can't use them; if you run your code through FxCop you will see Optional parameters specifically flagged for their inability to be consumed by C#.

Answer 3

if you want to retrieve optional parameters' values you can use reflection, this information is stored in custom attribute at corresponding parameter