context.Instance().ParentForm has wrong type

[Linkelf]

Hi all! I have a form with controls and non-visual components. Some of them implements interface MyInterface and some have a MyInterface Property.
Task is : select MyIntrerface Property for control in property grid from all components that implement MyInterface.

Descibe code:

interface MyInterface {}

public class ControlClass : UserControl
{
  MyInterface MyInterfaceProvider {get; set;}
}

public class ComponentClass : Component, MyInterface{}

public  class MainForm:Form
{
 ControlClass _myControl;
 ComponentClass _myComponent;
 [...]
}

I wrote a typeconverter to perform string <=> MyInterface types conversation:

public class InterfaceTypeConverter: TypeConverter{

  public override  
      StandardValuesCollection GetStandardValues(
                                                       ITypeDescriptorContext context){
   [...checks]
  // try to obtain ParentForm for getting _myComponent;
  ComponentParentForm = (context.Instance() as _myControl).ParentForm;

  MainForm MF = ComponentParentForm as MainForm;
  [...]
}
 [...]
}

I have:

MF == null

but

_myComponent.Pa rentForm is MainForm

but

ComponentParent Form is Form

!! ComponentParent Form is not MainForm !!

ComponentParent Form.Name == "MainForm"

How i can get ComponentParent Form with MainForm type ?

[Linkelf]

Problem Solved !
I cant and dont need convert ParentForm into MainForm type. All components i needed place in ComponentParent Form.Container. Components