I’m trying to create a form by inheriting from another form I have already created. The reason for this is that the original form actually has 3 states, and an inheritance structure will make it easier to debug, understand and improve.
The problem is that my Visual Studio 2008 Forms designer doesn’t play nice with this idea. Instead of a form I can design I get this error message:
The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: InheritedForm — The base class ‘MyBaseForm’ could not be loaded. Ensure the assembly has been referenced and that all projects have been built.
Basically I can’t see my inherited form in the designer, but the original form works as it should in the designer.
This was very frustrating, so to make sure the problem was not VS2008’s fault I created a fresh clean Forms project (.net 2.0) and created a form which I called Form1 and another form (Form2) that inherited from Form1. This project work just fine. I can see Form1 in the designer and in my Form2 I can see a label I have added to Form1 but cannot move it in Form2 as it belongs to Form 1.
The result from my test proves that my Visual Studio indeed works; just not in my original project that needs it to work. Another thing I tried was to create an inherited From through the Inheritance Picker when you use the VS2008 Guide to create an inherited form. On my test project I can see all the forms I have created, but in my original I can’t choose anything. I tried to browse to the exe file in my bin folder, but it does not give my any forms to choose.
I have also tried rebuilding the project, cleaning the project and restarting VS2008 hoping it was in some weird state, but nothing helps. I will not dismiss the idea that I have some weird project setup that might interfere with the Designer, since the project file is somewhat old and has a lot of files and elements. But due to the error descriptions I got, I find this unlikely (Still investigating this).
I have been scouring the internet to the point where I get the same articles, forums or blogs no matter what I put into the search field in Google or doing link browsing, with no success. Do any of you have an idea or suggestion as to what could cause my problem? Any help, hint or suggestions at this point is highly appreciated.
Thank you in advance.
I figured out the problem. I was working on Hans Passant suggestion when a colleague of mine thought that he wanted a go on my issue and started up the same program on his computer. To our surprise his designer worked on the same project. We both was baffled by it until we looked at our build configurations.
What I forgot to mention in my question, is that our particular project need to build for either x64 or 86x platforms, due to 3rd party dll’s. This is normally not a problem for the designer when working with normal forms, but when it comes to inherited forms, the designer actually needs to run the base form in order to show the inherited form.
My colleagues build configuration was set to x86 and mine to x64. We are both running VS2008(86x) versions, which means that the designer is most likely build in a 86x platform. Our conclusion was that if we build the forms to x64, the designer don’t know how to run it. So I tried changing my target platform from 64x to 86x, and after I closed my forms in VS and did a rebuild on the project, the designer worked again.
To be sure I tried testing it with a new empty clean project. I created 2 forms: one base and one that inherit from base. By default the build configuration is ‘AnyCPU’ and the designer works fine. But when I changed the configuration to ‘x64’ the designer failed again as expected. And switching to ‘x86’ solved the problem as expected.
So when using inherited forms in a platform specific project, always design in the project platform version equal to your VS2008 platform version (x86 in my case. I don’t actually know if there is a x64 version of visual studio 2008). I still can’t use the Inheritance Picker for some reason in my original project, but inherit in code works like a charm.