WPF ItemSource returns null

Question

I have a named class

public class testClass
{
    public testClass(string showCode, string urn)
    {
        ShowCode = showCode;
        URN = urn;
    }

    public string ShowCode { get; set; }
    public string URN { get; set; }
}

I create an ArrayList, add to the list and bind it to a wpf datagrid

ArrayList l = new ArrayList();
l.Add(new testClass("ose11", "7016463"));
this.grdTestData.ItemsSource = l;

This displays just what I want in the datagrid.

Now I want to get the datagrid's data back and iterate throught it

IEnumerable<testClass> t = this.grdTestData.ItemsSource as IEnumerable<testClass>;

..but 't' is null! !! this is the problem !!

This is the datagrid definition:

<DataGrid AutoGenerateColumns="False" HorizontalAlignment="Left" Margin="12,66,0,48" Name="grdTestData" Width="200" CanUserAddRows="True" >
    <DataGrid.Columns>
        <DataGridTextColumn Header="ShowCode" Binding="{Binding ShowCode}" />
        <DataGridTextColumn Header="URN"  Binding="{Binding Path=URN}" />
    </DataGrid.Columns>
</DataGrid>

Answer 1

The ItemsSource is not null, it's just that ArrayList does not implement IEnumerable<testClass>, and therefore the cast you perform returns null. If you use

var list = (IEnumerable<testClass>) datagrid.ItemsSource;

you will get an error saying that this cast is not valid.

If you use a List<testClass> instead of ArrayList for the source, the cast will be valid and not return null.

If you don't wish to use a generic collection, then cast it to ArrayList or IEnumerable (non-generic) instead, if you wish to have an interface.