I have a grid that when populated may or may not have null values for a column that is a string.
If the data returned is already null everything works fine. If the string column had data and I step into the column and delete all the data I get a message stating that there is a Data Error - Unable to update the data value: Object of type 'System.DBNull' cannot be converted to type 'System.String'.
How can I allow a column to go back to a null value once it contained data?
It sounds to me like your data source doesn't accept DBNull, only an empty string. If that's the case, you can fix this by setting the Nullable property on the column.
I am not sure that may be it, but I am not certain where to verify this information. I can manually set the records on the data source to null without a problem. I am using a bindingsource and its datasource is a class inherited from a BindingList
I also tried checking the Nullable property on the column but it did not make any difference.
This is happening when I step out of the row that I deleted the string from and before the OnUpdateRecord event.