In a GridDropDownColumn I can't override this method as it doesn't exist. All I could do is call GetTextFromInnerList and if the returned value is an empty string, I know that the value does not exist and I could manage that.
I can I deal with the following:
I have a databound grid. Some DropdownColumns reference a lookup list, e.g. Colors:
Now my databound datasource for the column contains "Blue", hence blue is selected. So far so good. Now someone changes the naming of colors and I have "BlueXXX" instead of Blue in my values for the dropdown column. The databound value for the column remains at Blue.
The dropdown column now only displays an empty string instead of the value from the database: "Blue" (even though "Blue" doesn't exist anymore in the datasource).
How can I e.g. Display the value "Blue" when in View mode and in Edit mode return an error - or don't allow to save the custom value "Blue" as it is not a valid selection anymore (BlueXXX would be valid now).