Access return value from VBA Function in .NET?

Question

I have the following code in VBA (which resides in an Excel 2007 Workbook):

Public Function Multiply(a As Double, b As Double) As Double
    Multiply = a * b
End Function

If I invoke Multiply from other VBA code, it returns the correct value. However, when I call Multiply from C#:

var excel = new Application {Visible = true};
excel.Workbooks.Open(filename);
var returned = excel.Run("Sheet1.Multiply", (Double) a, (Double) b);

... the multiplication takes place (I can verify this by adding tracing to the Multiply function in VBA) but the returned value isn't available in my C# code; returned is always null.

Could someone please tell me how to get at the return value of Multiply from my C# code?

Answer 1

Try modifying your Multiply function to code below

Public Function Multiply(a As Double, b As Double) As Double

return a * b

End Function

Answer 2

Have you tried moving your function to a regular module in excel (not a sheet module) ?

Tim