I have:

public interface IMyControl
{
    string MyProperty {get; set;}    
}

public class MyControl : UserControl, IMyControl
{
    public string MyProperty {get; set;}


}

public static class InstanceManager
{
    public static object GetInstanceOfType(Type type)
    {
        if (type.Name == "IMyControl")
             return new MyControl(); 
    }
}

I want:

1) See IMyControl interface on toolbox
2) Have ability to drag IMyControl on aform or control designer
3) When i`ve dragged IMyControl interface from toolbox on aform or control designer, following code should be generated in SomeForm.Designer.cs file:

this.iMyControl1= InstanceManager.GetInstanceOfType(typeof(IMyControl));

// ...

((UserControl)this.iMyControl1).Location = new System.Drawing.Point(94, 119);
((UserControl)this.iMyControl1).Name = "iMyControl1";
((UserControl)this.iMyControl1).Size = new System.Drawing.Size(75, 23);
((UserControl)this.iMyControl1).TabIndex = 0;
iMyControl1.MyProperty = "MyText";


// ...

private IMyControl iMyControl1;

Please show me way and maybe code snippets or working opensource examples. Can I use DesignerAttribute, DesignerSerializerAttribute, ToolboxItemAttribute?

Is my question unclear? If so, please ask me what unclear.

That's a fair question indeed !

I have been thinking of something like this for very long time. It could be very usefull thing to have such an ability, because as I understand it helps us to abstract our user interface from concreete control implementations. Using the feature we could constract a form from some IInputBox, ILabel, IAny... "controls" and then plug concreete implemetations using this.iMyControl1= InstanceManager.GetInstanceOfType(typeof(IMyControl)); in the form designer .cs file. That is a cool thing !!!. We can plug any concreete controls that implement particular interface, so one form beeing constructed once - can look and behave differently depending on plugged concreete controls.

Looking forward to hear an answer to this post. It is very interesting to know your opinion about all that said above
Thank you.

Yes, abstractive user interface is more powerful instrument than skins or CSS. For example, user could feel free to change ribbon UI (like MS Office 2007) to standart button bar UI.