Use the RenderBeginTag override of the RenderBeginTag(String) method, if the markup element is not one of the HtmlTextWriterTag enumeration values.
To generate a markup element by using the RenderBeginTag method, first call the AddAttribute and the AddStyleAttribute methods, as necessary, to specify any element attributes or style attributes that are to appear in the opening tag of the element. After generating the inner markup, call the RenderEndTag method to generate the closing tag.
The following code example shows how to call the RenderBeginTag method in a custom control to render the opening tag of a non-standard MyTag element. The code example then calls the Write method to render inner markup, and then calls the RenderEndTag method to close the element.