Dear Adm-inf,
Thank you for your query.
Your question really has nothing to do with the Revit API.
It is a pure C# .NET issue.
I assume you wish to make use of the .NET Windows Forms library?
If so, you should search the Internet for something like 'c# windows forms':
https://duckduckgo.com/?q=c%23+windows+forms&ia=web
There are only a few thousand tutorials on that topic out there waiting for you.
That said, several of the Revit SDK samples also display Windows forms to prompt the user for input, as do many of The Building Coder samples.
The last time I implemented anything myself to prompt the user for input via a Windows form may have been for in the subsidiary external settings command for the HoloLens escape path waypoint JSON exporter:
http://thebuildingcoder.typepad.com/blog/2016/09/hololens-escape-path-waypoint-json-exporter.html
Subsidiary external settings command
- Display modal Windows form
- Implement form validation using ErrorProvider class, Validating and Validated events
- Store add-in option settings in XML using the .NET System.Configuration.ApplicationSettingsBase class
- Store add-in option settings in JSON using custom solution and JavaScriptSerializer class
The entire add-in project including the Visual Studio solution, add-in manifest and entire source code is available from the ExportWaypointsJson GitHub repository:
https://github.com/jeremytammik/ExportWaypointsJson
I hope this helps.
Best regards,
Jeremy