Unexpected red border (validation error) on DataGrid when selecting blank row

Question

When I select (by clicking or by keyboard) blank row on my DataGrid (when I want to add new row), unexpected validation error occurs (but with no exception) - the border of

Answer 1

To get the reason, when you click the new row of DataGrid in Debug mode, please see the debug window. There are first exception messages which will give you the idea why your problem is occurred.

Yes, the problem is from type casting. You need to modify the type of SelectedItem to object type as below.

public class ManageModulesVM : BaseVM  // Implements INotifyPropertyChanged
{
    // ...

    public object SelectedConfigFile
    {
        get { return selectedModule == null ? null : selectedModule.SelectedConfigFile; }
        set
        {
            if (value != null)
            {
                selectedModule.SelectedConfigFile = value;
            }
            OnPropertyChanged(() => SelectedConfigFile);
            OnPropertyChanged(() => Parameters);
        }
    }

    // ...
}