AxSymbologyControl怎么更新Symbol

我用代码修改了选择符号的背景颜色，但是AxSymbologyControl控件中的符号颜色并没有更新
 
                    ISymbologyStyleClass pSymbologyStyleClass  = this.SymbologyControl.GetStyleClass(this.SymbologyControl.StyleClass);
                    IStyleGalleryItem pStylGalleryItem = pSymbologyStyleClass.GetSelectedItem();
                    ISymbol symbol = pStylGalleryItem.Item as ISymbol;
                    pSymbolEditor.EditSymbol(ref symbol, this.SymbologyControl.hWnd);
                    pStylGalleryItem.Item = symbol;