Optional parameters in managed C++/CLI methods

Question

How can I declare a managed method in C++/CLI that has an optional parameter when used from C#?

I\'ve decorated the parameter with both an Optional and a DefaultPara

Answer 1

There is a trick to make this working (workaround). the magic word is nullable, as for nullable types the default is always "null" (.HasValue == false).

Example:

C++ CLI in header:

String^ test([Optional] Nullable boolTest);

C++ CLI in .cpp file:

String^ YourClass::test(Nullable boolTest)
{
    if (!boolTest.HasValue) { boolTest = true; }
    return (boolTest ? gcnew String("True") : gcnew String("False"));
}

to Test it in C#:

MessageBox.Show(YourClass.test());

Note that [Optional] in the example above is located in the namespace System::Runtime::InteropServices. To access it, add the following line:

using namespace System::Runtime::InteropServices;