protected override void OnClick()
{
ESRI.ArcGIS.esriSystem.UID uid = new ESRI.ArcGIS.esriSystem.UIDClass();
// this is from Config.esriaddinx (<DockableWindow id="Test_TestingAddin1_DockableWindow1" class="testbrowser+AddinImpl"...)
uid.Value = "Test_TestingAddin1_DockableWindow1";
ESRI.ArcGIS.Framework.IDockableWindow dw = ArcMap.DockableWindowManager.GetDockableWindow(uid);
if (!dw.IsVisible())
dw.Show(true);
}