The BasicDesignerLoader.Initialize method is called the first time BasicDesignerLoader.BeginLoad(IDesignerLoaderHost) is invoked. You can add any services necessary to the designer loader host at this time. The base implementation adds services that System.ComponentModel.Design.Serialization.BasicDesignerLoader provides, so after calling the base implementation you may replace existing services. You must remove any custom services you add here by overriding BasicDesignerLoader.Dispose.