Silverlight combobox DisplayMemberPath?

11-04-2009 12:08 PM |

 Hi, trying something that should be relatively simple, but isn't working for me. Trying to bind a combobox to a list of objects and set a DisplayMemberPath to display the correct element while binding to the whole object. The following code doesn't kick out any errors and appears to bind 4 items to the source, but doesn't actually display the specified property.

 [EDIT - for some reason the code window removed my <CCType> specification off the list. Actual list is  public List<CCType> _types;]

 XAML:

                         <ComboBox x:Name="comboCardType" Height="16" Margin="1,0,150,0" Style="{StaticResource ComboBoxGreen}" VerticalAlignment="Center" Grid.Column="1" Grid.Row="2" />

CS:

 public partial class PaymentProcessing : Page
    {
        private decimal _cost;
        private int _count;
        private BillTo_Object _bill;
        private Card_Object _card;
        public List _types;


        public struct CCType
        {
            public string ID;
            public string DisplayString;
        }

        public PaymentProcessing()
        {
            InitializeComponent();
        }

        // Executes when the user navigates to this page.
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            _types = new List();
            _types.Add(new CCType() { ID = "001", DisplayString = "Visa" });
            _types.Add(new CCType() { ID = "002", DisplayString = "MasterCard" });
            _types.Add(new CCType() { ID = "003", DisplayString = "American Express" });
            _types.Add(new CCType() { ID = "004", DisplayString = "Discover" });

            comboCardType.ItemsSource = _types;
            comboCardType.DisplayMemberPath = "DisplayString";

...

Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:11 PM |

Have you tried moving your DisplayMemberPath into your XAML to see if it works?

Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:21 PM |

 No dice, behaves in the same fashion.... also tried (with same results):

•   moving DisplayMemberPath assignment in front of itemsource assignment
•  changing from itemssource to datacontext
• setting a datatemplate in the combobox with a textblock bound to DisplayString (w/o DisplayMemberPath set, with it set causes crash)
  

Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:23 PM |

Have you tried moving the Types initialisation into the Constructor, and then assign the ItemsSource in your OnNavigatedTo method?

Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:27 PM |

Ardman:

Have you tried moving the Types initialisation into the Constructor, and then assign the ItemsSource in your OnNavigatedTo method?

 Just gave it a shot, same result... ItemSource has correct values in it, but the control isn't rendering the DisplayMemberPath.

 Incidentally, targeting Silverlight 3 in case that matters.

Re: Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:29 PM |

Add to your XAML:

SelectedItem="{Binding DisplayString, Mode=TwoWay}"

Re: Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:34 PM |

Ardman:

Add to your XAML:

SelectedItem="{Binding DisplayString, Mode=TwoWay}"

 Again, same result, also tried setting DisplayMemberPath in same fashion. Current code:

                        <ComboBox x:Name="comboCardType" DisplayMemberPath="{Binding DisplayString, Mode=TwoWay}" Height="16" Margin="1,0,150,0" Style="{StaticResource ComboBoxGreen}" VerticalAlignment="Center" Grid.Column="1" Grid.Row="2" />

  public partial class PaymentProcessing : Page
    {
        private decimal _cost;
        private int _count;
        private BillTo_Object _bill;
        private Card_Object _card;
        public List<CCType> _types;


        public struct CCType
        {
            public string ID;
            public string DisplayString;
        }

        public PaymentProcessing()
        {
            _types = new List<CCType>();
            _types.Add(new CCType() { ID = "001", DisplayString = "Visa" });
            _types.Add(new CCType() { ID = "002", DisplayString = "MasterCard" });
            _types.Add(new CCType() { ID = "003", DisplayString = "American Express" });
            _types.Add(new CCType() { ID = "004", DisplayString = "Discover" });
            InitializeComponent();
        }

        // Executes when the user navigates to this page.
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {

            comboCardType.DisplayMemberPath = "DisplayString";
            comboCardType.ItemsSource = _types;

Re: Re: Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:35 PM |

You've assigned DisplayMemberPath and not SelectedItem.  DisplayMemberPath needs to stay as "DisplayString" whilst you need to add SelectedItem="{Binding DisplayString, Mode=TwoWay}"

Re: Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 12:38 PM |

 Yep, was just trying both... new XAML (w/codebehind assignment of DisplayMemberPath commented out)

 [EDIT - and, sad to say, same result with this]

                        <ComboBox x:Name="comboCardType" DisplayMemberPath="DisplayString" SelectedItem="{Binding DisplayString, Mode=TwoWay}" Height="16" Margin="1,0,150,0" Style="{StaticResource ComboBoxGreen}" VerticalAlignment="Center" Grid.Column="1" Grid.Row="2">
 

Re: Re: Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 1:55 PM |

 Can you put all of the Type instantiation and the ItemsSource assignment into your constructor to see if that helps?

Re: Re: Re: Re: Silverlight combobox DisplayMemberPath?

11-04-2009 2:03 PM |

Ardman:

 Can you put all of the Type instantiation and the ItemsSource assignment into your constructor to see if that helps?

 Gave it a shot, no difference.  The key here seems to be around the binding to a complex object/setting the DisplayMemberPath... I'm binding other Comboboxes in the OnNavigatedTo event to lists of simple strings without any problem.