Form class inheritance

If i create abstract class A that inherits from Form, and make class B that inherits from class A.

I can see the designer of class A. (Empty Form).

But class B is my object, class A only abstract.

But i can't see designer of class B. Get error screen that says:

"

1 Error
Why am I seeing this page?
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: MemoryAccessDlg --- The base class 'TLGUI.formControlsInterface' could not be loaded. Ensure the assembly has been referenced and that all projects have been built.

 
Instances of this error (1)
1.Hide Call Stack
at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.EnsureDocument(IDesignerSerializationManager manager)
at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager)
at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager)
at System.ComponentModel.Design.Serialization.BasicDesignerLoader.BeginLoad(IDesignerLoaderHost host)

" What should i do to see the designer of class B?