Get Component’s Parent Form

[It is important to understand that the ISite technique below only works at design time. Because ContainerControl is public and gets assigned a value VisualStudio will write initialization code that sets it at run-time. Site is set at run-time, but you can’t get ContainerControl from it]

Here’s an article that describes how to do it for a non-visual component.

Basically you need to add a property ContainerControl to your component:

public ContainerControl ContainerControl
{
  get { return _containerControl; }
  set { _containerControl = value; }
}
private ContainerControl _containerControl = null;

and override the Site property:

public override ISite Site
{
  get { return base.Site; }
  set
  {
    base.Site = value;
    if (value == null)
    {
      return;
    }

    IDesignerHost host = value.GetService(
        typeof(IDesignerHost)) as IDesignerHost;
    if (host != null)
    {
        IComponent componentHost = host.RootComponent;
        if (componentHost is ContainerControl)
        {
            ContainerControl = componentHost as ContainerControl;
        }
    }
  }
}

If you do this, the ContainerControl will be initialized to reference the containing form by the designer. The linked article explains it in more detail.

A good way to see how to do things is to look at the implementation of Types in the .NET Framework that have behaviour similar to what you want with a tool such as Lutz Reflector. In this case, System.Windows.Forms.ErrorProvider is a good example to look at: a Component that needs to know its containing Form.