In that case, you should be able to simply create a DLL in C# that contains your form as a public type and then reference that DLL in your Delphi project. I'd recommend using the Windows Control Library item template for the C# project if it's available. That will provide all the references required by Windows Forms by default. You'll just have to remove the user control that is added by default and then add your form. That project will then build to a DLL that you can reference in your Delphi project in the same way as you would any other .NET assembly.