Combobox column validation always return "Input is not in a correct format" when value is null

[Edward]

Situation:

The entity ppl_language has a few properties.  One of them would be the defLanguage, (represents another entity called defLanguage, not nullable).  The other is idLanguage which is the foreign key.  The grid is bound to ppl_languages, which is a ObservableCollection of ppl_language.

The items source of the combobox column is set in the data loaded event - it is binding to a ObservableCollection of DefLanguage

<telerik:RadGridView ItemsSource="{Binding ppl_languages}" Grid.Row="12" Grid.ColumnSpan="2" CanUserInsertRows="True" CanUserDeleteRows="true" ShowInsertRow="True"
                                                 AutoGenerateColumns="False" ShowGroupPanel="False" ShowGroupFooters="False" DataLoaded="gdvLanguage_DataLoaded" telerik:StyleManager.Theme="Windows7" >
                             <telerik:RadGridView.Columns>
                                 <telerik:GridViewComboBoxColumn Header="Language" DisplayMemberPath="desc1" SelectedValueMemberPath="idLanguage" DataMemberBinding="{Binding idLanguage}" />
                             </telerik:RadGridView.Columns>
                         </telerik:RadGridView>

The issue is since ppl_language. is not nullable, some item must be selected in the combobox.  However, when the combobox is empty it will only return the error message "input in not in a correct format".

Metadata for ppl_language

[Include]
            [Display(Name = "Language", Description = "Language")]
            [Association("ppl_language_defLanguage", "idLanguage ", "idLanguage ", IsForeignKey = true)]
            public defLanguage defLanguage { get; set; }

            [CustomValidation(typeof(PplLanguageValidator), "ValidateHasLanguage")]
            public int idLanguage { get; set; }

The custom validator should return the proper error message, but I put a break point in the custom validator and the code is only run AFTER I select something in the combobox - when nothing is selected the validator is not used at all and just return the incorrect format error.

[Maya]

Hello Edward,

Basically, this would be the expected behavior since the custom validation will be performed after editing is performed and that validation will be on row-level. In the case of GridViewComboBoxColumn, selecting an item from the combo box is the editing on its nature, the custom validator will not be activated.
   

Best wishes,
Maya
the Telerik team

[Edward]

I kind of get around that by using CellEditTemplate and put a combobox there.  Then I will bind the ItemsSource and SelectedItem property in the loaded event.  It is not perfect but this is better than the "incorrect format" which does not really make sense.