When overridden in derived class, renders the field in a child control that lets its value be changed.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Typically, this method is used on the Edit form and New form.
With the default implementation, if IsValid is false, an error message is rendered. This is the value of ErrorMessage, unless it is a null reference (Nothing in Visual Basic), in which case a generic error message is rendered.Notes to inheritors
You must override this method to create the editable child control.