Why code generation was failed when save the designer level changes?

I had two collection one is column and another one is BaseStyleCollection and I had two forms. One form inherited another form.

public partial class Form2 : Form1
{

   public Form2()
   {
       InitializeComponent();
   }
}

public partial class Form1
{

   public Form1()
   {
       InitializeComponent();
   }
}

I have added my custom control in Form1 and add the (BaseStyles and columns) for my control in designer and BaseStyles and ColumnCollection attribute was DesignerSerializationVisibility.Contentand both are derived fromIList.

. Now i try to edit the childform in designer level and save the changes, i got the following error message

Stack trace for Columns collection:

Stack trace for BaseStyle:

This kind of changes occurring when make the changes for my control and save the changes in Form2 .

please suggest me. Why this kind of changes occurs? Is this reason for the exception? 

Thanks in advance,

Mohanraj G