C# Wpf toolkit autocomplebox - how to get the selected item?

Question

I'm trying to access selected item from the wpf toolkit autoCompleBox (the one from codeplex) but i keep getting the null reference error.

I have really hit a brick wall with this!

here is my XAML:

     <my:AutoCompleteBox
     x:Name="autoTxtBoxProductCode"
     VerticalAlignment="Top" Height="28" Margin="112,10,0,0" Width="144"           
     Background="#FFEDF4AB"
     Populating="AutoBoxPopulateProductCode"
     ValueMemberPath="ProductCode"
     PreviewKeyUp="autoTxtBoxProductCode_PreviewKeyUp"
     HorizontalAlignment="Left" 
     IsTextCompletionEnabled="False"

      <my:AutoCompleteBox.ItemTemplate>
            <DataTemplate>
              <StackPanel Orientation="Horizontal">
                  <TextBlock Text="{Binding ProductID}" FontWeight="Bold" Foreground="Black" Width="25"/>
                  <TextBlock Text="{Binding ProductBrandCode}" FontWeight="Bold" Foreground="Black" Width="55"/>
                  <TextBlock Text="{Binding ProductCode}" Foreground="Black"/>
                </StackPanel>
              </DataTemplate>         
             </my:AutoCompleteBox.ItemTemplate>
        </my:AutoCompleteBox>

That's how i update the item source:

    private void AutoBoxPopulateProductCode(object sender, System.Windows.Controls.PopulatingEventArgs e)
    {
        // TextBox t = (TextBox)sender;

        autoTxtBoxProductCode.ItemsSource = Product.GetListOfProductCodesAndBrands(autoTxtBoxProductCode.Text.ToString());
        autoTxtBoxProductCode.PopulateComplete();
    }

What i'm trying to archive is when user hit enter I want to get the ProductID.

I have tried something like this:

   private void autoTxtBoxProductCode_PreviewKeyUp(object sender, KeyEventArgs e)
    {

        if (e.Key != Key.Enter)
        { return; }
        else
        {   
            Product prd = (Product)(autoTxtBoxProductCode.SelectedItem);
            MessageBox.Show(prd.ProductID.ToString());

        }

    }

but the above returns null reference error.

I must be missing some sort of binding but since WPF is new to me I can't figure out what needs to be changed.

Help would be much appreciated.

EDIT:

Just after posting this question I found the solution. All I needed to add was:

SelectedItem="{Binding ElementName=this,
               Path=ProductID,
               Mode=TwoWay,
               UpdateSourceTrigger=LostFocus}"

I hope it can help someone else with a similar problem.

Cheers,

Answer 1

Just after posting this question I found the solution. All I needed to add was:

SelectedItem="{Binding ElementName=this,
           Path=ProductID,
           Mode=TwoWay,
           UpdateSourceTrigger=LostFocus}"