Dataset field DBNull -> int?

Question

SQLServer int field. Value sometimes null. DataAdapter fills dataset OK and can display data in DatagridView OK.

When trying to retrieve the data programmatically from the dataset the Dataset field retrieval code throws a StronglyTypedException error.

 [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
    public int curr_reading {
        get {
            try {
                return ((int)(this[this.tableHistory.curr_readingColumn]));
            }
            catch (global::System.InvalidCastException e) {
                throw new global::System.Data.StrongTypingException("The value for column \'curr_reading\' in table \'History\' is DBNull.", e);
            }

Got past this by checking for DBNull in the get accessor and returning null but... When the dataset structure is modified (Still developing) my changes (unsurprisingly) are gone.

What is the best way to handle this situation? It seems I am stuck with dealing with it at the dataset level. Is there some sort of attribute that can tell the auto code generator to leave the changes in place?

Answer 1

In the typed dataset designer there is the nullvalue property. By default its value is throw exception (hence your generated code) You can set it to the desired default value.. ie. 0. Then it will return 0 instead of an exception. (other code is generated)

VS2008 :This works directly in the dataset designer.

VS2005 : It only works for strings in the designer but you can directly edit the XSD an set the property msprop:nullValue="0"