Visual Studio cannot open a designer for the file because the class within it does not inherit from a class that can be visually designed
Visual Studio loaded the class, but the designer for that class could not be loaded.
The class can be designed, but it is not the first class in the file. Visual Studio requires that designers use the first class in the file.
To correct this error
- Move the class code so that it is the first class in the file, and then load the designer again.