Form inheritance should be abstract - forms

Question

Here my code
GeneralLesson.cs: it's just a .cs file, no .Designer.cs or .resx file
public /*abstract*/ class GeneralLesson : Form
{
public GeneralLesson()
{
this.StartPosition = SS.FrmStartPos;//If I want to change it later, I just change it here and all the children will get the change
}
protected override void OnFormClosing(FormClosingEventArgs e)
{
base.OnFormClosing(e);
if (e.CloseReason == CloseReason.WindowsShutDown) return;
SS.LearningDay = 0; //SS is my static class that hold the static variables.
SS.FrmMain.Show();
}
}
SentLesson.cs: This is actually a windows form, with .Designer.cs and .resx file
public partial class _Sent_Lesson : GeneralLesson
{
public _Sent_Lesson()
{
InitializeComponent();
richTextBox1.Text = "under construction";
}
}
So it actually serves my purpose well. my SentLesson window inherits the constructor and OnFormClosing from GeneralLesson. But the problem is I can't design my SentLesson window any more, it shows as the picture below:
Maybe I do it wrong. But I don't want to create GeneralLesson as a Window because I don't design any control on it, I just want to override some function like OnFormClosing or the Constructor. Is there any way I can do this without making GeneralLesson as a Window.
Thanks for reading.

Answer 1

I finally got the solution. Even though the abstract parent form still works logically, but the children form can't be designed any further with Visual Studio designer. So I have to inherit forms the Visual Studio way.
As you can see, Visual Studio provides us Inherited Form to create Children form. So I create GeneralLesson.cs as Windows Form, and SentLesson.cs as Inherited Form. So SentLesson inherits constructor and OnFormClosing from GeneralLesson and the designer of SentLesson no longer shows error.
If you want the Children form can access some controls from the Parent form, say Parent's "Button A". Just set the Parent's "Button A" 's Modifiers in properties window from Private to Protected. Then you can do anything with Button A in the Children form.
Thank for your reading.