Inheritance cannot be shown in the designer

Question

Today I am facing a problem. Properly.
I create a general form,
Public class Form1: Form
Then I create another form of inheritance,
Public class From2: Form1.
Form 2 cannot be shown in the VS constructor, the error message "all classes in the file cannot be developed" (this error message is translated from Chinese, the Chinese message is 文件 中 的 类 都 不能 进行 设计). <b> "But this program can be compiled successfully, and when it works, both Form1 and From2 can work.

Can anybody help me? Thanks.

I am not a native speaker of English. Hope I described my question clearly.

Answer 1

This is a limitation with the designer. You can get around this by adding an intermediate derived form that defines types. I explained this in a blog post:

http://adamhouldsworth.blogspot.com/2010/02/winforms-visual-inheritance-limitations.html

Answer 2

I wanted to give a more specific answer as a complement to Adam's message .

BaseForm is the name of your generic form; GenericClass one of the possible type parameters.

BaseForm<T> might look like this:

 public class BaseForm<T> : Form { } 

First you need a base class. This is actually the part that you probably already used before you came across this issue.

Then you use this intermediate implementation.

 public class SampleFormIntermediate : BaseForm<GenericClass> { public SampleFormIntermediate() { InitializeComponent(); } } 

And you need to use this class for the designer of Visual Studio. And only that. I would recommend decorating this with the compiler directive, so it will only be used in Debug mode:

 public partial class SampleForm : SampleFormIntermediate { } 

Using this Visual Studio "understands" what to open in the designer and how to open it.