VS2012 designer cannot open form after inheriting from another form

Question

I have a base form BaseForm which I use for saving settings. This form have no controls in it and it's opened in the designer as an empty form. However, when I inherit this form, the designer refuses to open the newly created form in the designer (there's no button View in Designer). What may be the problem ? Thanks

Answer 1

The problem is with the .csproj file.

Every form has a signature in the file like this

<Compile Include="Opers\MyForm.cs">
  <SubType>Form</SubType>
</Compile>

The SubType element says that this is actually a form and in my file this was deleted for some reason.