Hi..
This may be what you need..

[Serializable]
public class DataSetToolItem:System.Drawing.Design.ToolboxItem
{
 public  DataSetToolItem(System.Runtime.Serialization.SerializationInfo
info, System.Runtime.Serialization.StreamingContext context)
 {
  base.Deserialize(info,context);
 }

 public DataSetToolItem()
 {
 }
 public DataSetToolItem(Type toolType):base(toolType)
 {
 }
 protected override IComponent[] CreateComponentsCore(IDesignerHost host)
 {
  MessageBox.Show("Create component");
  return null;
  // return base.CreateComponentsCore (host);
 }
}

/// <summary>
/// Summary description for TestT.
/// </summary>
[ToolboxItem(typeof( DataSetToolItem))]
public class TestT:IComponent
{
....
....
...