Question

One of the libraries I’m using defines this in C#:

public ushort GetParameterSet(string name, out ParameterSet parameterSet)

I’m trying to call this from F#:

let parameterSet = new ParameterSet();
let retVal = currentPanel.GetParameterSet(name, ref parameterSet);

However, even though the parameterSet is set to an instance of that
class with valid data in the C# method, it does not change in F#.

What am I missing here?

Answer 1

Try

// let parameterSet = null;
let retval, parameterSet = currentPanel.GetParamterSet(name);

You shouldn’t pass an instance as ref parameter, when the method expects an out parameter (which upon calling should be an unassigned reference preceded by the out keyword).