Cannot add an object to Windows Forms .VB

[Hubert_Los]

Hello,

I have created a program in visual studio. The program creates a button on the ribbon that calls the program. Now I would like to create a simple API, but I can't add any object to the form in VS. An error appears:

"Object reference not set to an instance of an object."

Program based on template from SDK/Developertools.

Can I create an API based on it?

[Frederick_Law]

Create API?  Application Programming Interface?

You're using API to make addin.

Form are UI, User Interface.

Looks like something wrong with your Visual Studio.

How are you adding object to Form?  By VB program?

[Hubert_Los]

Yes, you are right, I mean UI.

I created a new project from the template, set net.freamwork

add Form

I drag elements from the toolbox into the form.

error appears.

This problem does not appear if I select a new project "Windows Form App(.Net Freamwork)"

[Michael.Navara]

It looks like an issue in VisulaStudio or project (corrupted project or item templates?). You can try to create new project based on template ClassLibrary (.Net Freamwork) and create form with controls. If it works, the issue is in the project.

[Hubert_Los]

My template was in "developertools.msi". Oddly, it is not correct.

"You can try to create a new project based on the ClassLibrary (.Net Freamwork) template and create a form with controls."
It works.

I will try reinstalling Visual Studio

Maybe someone could provide me with the template. It can also be in c#, because I also have a problem with the template working correctly in c#.
The same simple code works in VB but in c# unfortunately not.

[Hubert_Los · Accepted solution]

I used template from Inventor 2025. Now it works