Problems binding a DataGrid with an Observable Collection that receive null parameters in WPF

Question

I'm new programming with C# in WPF, and I have an error:

I've bind my WPF DataGRid with an Observable Collection that receive parameters from a DataBase. First, when the Observable Collection receive all the parameters from the Stored Procedure the APP function normally, but when I have a null parameter into my data source (StoredProcedure), so the Observable Collection receive a null parameter, the application crash, and it don´t start.... the page just remain in blank

How to fix that problem ?

First Here I show the class I used as a Dada Context to my Page

class ColeccionDeDatos : INotifyPropertyChanged
{
    private RegistroBLL regBll = new RegistroBLL();
    private DivisionBLL divBll = new DivisionBLL();
    private BrigadaBLL briBll = new BrigadaBLL();
    private BatallonBLL batBll = new BatallonBLL();
    private TropasBLL tropBll = new TropasBLL();
    private CompañiaBLL compBLL = new CompañiaBLL();
    private EstudioBLL estBll = new EstudioBLL();
    private RegistroFullBLL regFullBll = new RegistroFullBLL();


    private ObservableCollection<RegistroFullBO> coleccionFullRegistro = new ObservableCollection<RegistroFullBO>();
    public ObservableCollection<RegistroFullBO> ColeccionFullRegistro
    {
        get { return coleccionFullRegistro; }
        set { coleccionFullRegistro = value; }

    }

    private ObservableCollection<RegistroBO> coleccionRegistro = new ObservableCollection<RegistroBO>();
    public ObservableCollection<RegistroBO> ColeccionRegistro
    {
        get { return coleccionRegistro; }
        set { coleccionRegistro = value; }

    }

    private ObservableCollection<DivisionBO> coleccionDivision = new ObservableCollection<DivisionBO>();
    public ObservableCollection<DivisionBO> ColeccionDivision
    {
        get { return coleccionDivision; }
        set { coleccionDivision = value; }

    }

    private ObservableCollection<BrigadaBO> coleccionBrigada = new ObservableCollection<BrigadaBO>();
    public ObservableCollection<BrigadaBO> ColeccionBrigada
    {
        get { return coleccionBrigada; }
        set { coleccionBrigada = value; }
    }

    private ObservableCollection<BatallonBO> coleccionBatallon = new ObservableCollection<BatallonBO>();
    public ObservableCollection<BatallonBO> ColeccionBatallon
    {
        get { return coleccionBatallon; }
        set { coleccionBatallon = value; }
    }

    private ObservableCollection<TropasBO> coleccionTropas = new ObservableCollection<TropasBO>();
    public ObservableCollection<TropasBO> ColeccionTropas
    {
        get { return coleccionTropas; }
        set { coleccionTropas = value; }
    }

    private ObservableCollection<CompañiaBO> coleccionCompañia = new ObservableCollection<CompañiaBO>();
    public ObservableCollection<CompañiaBO> ColeccionCompañia
    {
        get { return coleccionCompañia; }
        set { coleccionCompañia = value; }
    }

    private ObservableCollection<EstudioBO> coleccionEstudio = new ObservableCollection<EstudioBO>();
    public ObservableCollection<EstudioBO> ColeccionEstudio
    {
        get { return coleccionEstudio; }
        set { coleccionEstudio = value; }
    }

    public ColeccionDeDatos() 
    {
        ColeccionRegistro = regBll.ObtenerFilasRegistro();
        ColeccionDivision = divBll.ObtenerFilasDivision();
        ColeccionBrigada = briBll.ObtenerFilasBrigada();
        ColeccionBatallon = batBll.ObtenerFilasBatallon();
        ColeccionTropas = tropBll.ObtenerFilasTropas();
        ColeccionCompañia = compBLL.ObtenerFilasCompañia();
        ColeccionEstudio = estBll.ObtenerFilasEstudio();
        ColeccionFullRegistro = regFullBll.ObtenerFilasRegistro();
    }

Then In the code behind of the page a asign an instance of this class as DataContext for the Page element.

private void Page_Loaded(object sender, RoutedEventArgs e)
    {
        try
        {
            PagRegistroName.DataContext = colData;

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message + "+++++++++++");
        }

    }

And for my Data Grid this one:

<DataGrid Name="dgRegistro" Margin="5" SelectionChanged="dgRegistro_SelectionChanged"
                            ItemsSource="{Binding Path=ColeccionFullRegistro}" AutoGenerateColumns="False">

In each cell template I used a combobox:

<DataGridTemplateColumn.CellEditingTemplate >
                        <DataTemplate>
                            <ComboBox x:Name="cmbDivision" Text="{Binding Path=Division, Mode=TwoWay}"     
                                      ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=Page, AncestorLevel=1},
                                      Path=DataContext.ColeccionDivision}"  DisplayMemberPath="Nom_division" SelectionChanged="cmbDivision_SelectionChanged" SelectedValuePath="Nom_division">
                            </ComboBox>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellEditingTemplate>

so it is function a well as I want

https://onedrive.live.com/redir?resid=B371651233630F9A!153&authkey=!ADzRW6OvvdMZiMI&v=3&ithint=photo%2c.png

which corresponds to the table in DataBase

BUT, when I put a NULL value directly in the DataBase

http://1drv.ms/RrN5qO

The App start but still in blank everytime, so something is wrong..

Any idea what is the problem ?

Answer 1

Filter like this:

if(MyProperty == null)
{ 
    MyProperty = string.Empty;
]