WPF ItemsSource Binding

bindingwpfwpfdatagrid

I have a Datagrid control in my WPF application and I am trying to bind that control to an ObservableCollection property in my Main Window's class. The property I'm trying to bind to is defined as:

private ObservableCollection<RequestResult> m_SentRequests = new ObservableCollection<RequestResult>();
public ObservableCollection<RequestResult> SentRequests { get { return m_SentRequests; } }

My datagrid is in a group by which has the datacontext set to the MainWindow:

<GroupBox Header="Results" Height="275" HorizontalAlignment="Stretch" Margin="0,305,0,0" Name="grpResults" VerticalAlignment="Top" Width="712" DataContext="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=my:MainWindow, AncestorLevel=1}}">
    <Grid>
        <DataGrid AutoGenerateColumns="False" Height="246" HorizontalAlignment="Stretch" Margin="6,6,6,0" Name="dgResults" VerticalAlignment="Top" ItemsSource="{Binding Path=SentRequests}" DataContext="{Binding}" IsSynchronizedWithCurrentItem="True" />
    </Grid>
</GroupBox>

The problem that I'm having is that in the properties window, after I select SentRequests as my ItemsSource, I still can't select the "Edit Property-Bound Columns" option. I get a "You must set ItemsSource before you can perform this action" dialog. I get the same error when selecting "Generate Columns" and "Remove Columns". It's as if I haven't set anything in the ItemsSource property for my Dialog.

I can set AutoGenerateColumns to true though and I see my data get bound though (however, not with the columns I want to show).

I'm very new to WPF and I'm just writing this as a quick test app for testing a windows service.

Any one know what I'm doing wrong here?

Best Answer

I don't believe you need the Path parameter within your itemSource. You should be able to just set the binding as ItemsSource={Binding SentRequests}

You can also bind to the grid item source in code for example if I create a dummy collection:

    public class People
{

    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Age { get; set; }
    public string address { get; set; }
    public string zip { get; set; }
}

and then populate it

this.AllPeople = new ObservableCollection<People>();


        private void FillData()
    {
        People p1 = new People();
        p1.FirstName = "John";
        p1.LastName = "Doe";
        p1.Age = "24";
        p1.address = "123 Main Street";
        p1.zip = "11111";

        People p2 = new People();
        p2.FirstName = "Jane";
        p2.LastName = "Smith";
        p2.Age = "36";
        p2.address = "456 Water Street";
        p2.zip = "22222";

        People p3 = new People();
        p3.FirstName = "Larry";
        p3.LastName = "Williams";
        p3.Age = "24";
        p3.address = "785 Water Street";
        p3.zip = "33333";

        this.AllPeople.Add(p1);
        this.AllPeople.Add(p2);
        this.AllPeople.Add(p3);
    }

I could then set the items source in the mainpage contsructor or method as:

this.gridviewname.ItemsSource = "AllPeople";

Related Solutions

C# – Binding a WPF ComboBox to a custom list

You set the DisplayMemberPath and the SelectedValuePath to "Name", so I assume that you have a class PhoneBookEntry with a public property Name.

Have you set the DataContext to your ConnectionViewModel object?

I copied you code and made some minor modifications, and it seems to work fine. I can set the viewmodels PhoneBookEnty property and the selected item in the combobox changes, and I can change the selected item in the combobox and the view models PhoneBookEntry property is set correctly.

Here is my XAML content:

<Window x:Class="WpfApplication6.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window1" Height="300" Width="300">
<Grid>
    <StackPanel>
        <Button Click="Button_Click">asdf</Button>
        <ComboBox ItemsSource="{Binding Path=PhonebookEntries}"
                  DisplayMemberPath="Name"
                  SelectedValuePath="Name"
                  SelectedValue="{Binding Path=PhonebookEntry}" />
    </StackPanel>
</Grid>
</Window>

And here is my code-behind:

namespace WpfApplication6
{

    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            ConnectionViewModel vm = new ConnectionViewModel();
            DataContext = vm;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            ((ConnectionViewModel)DataContext).PhonebookEntry = "test";
        }
    }

    public class PhoneBookEntry
    {
        public string Name { get; set; }

        public PhoneBookEntry(string name)
        {
            Name = name;
        }

        public override string ToString()
        {
            return Name;
        }
    }

    public class ConnectionViewModel : INotifyPropertyChanged
    {
        public ConnectionViewModel()
        {
            IList<PhoneBookEntry> list = new List<PhoneBookEntry>();
            list.Add(new PhoneBookEntry("test"));
            list.Add(new PhoneBookEntry("test2"));
            _phonebookEntries = new CollectionView(list);
        }

        private readonly CollectionView _phonebookEntries;
        private string _phonebookEntry;

        public CollectionView PhonebookEntries
        {
            get { return _phonebookEntries; }
        }

        public string PhonebookEntry
        {
            get { return _phonebookEntry; }
            set
            {
                if (_phonebookEntry == value) return;
                _phonebookEntry = value;
                OnPropertyChanged("PhonebookEntry");
            }
        }

        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

Edit: Geoffs second example does not seem to work, which seems a bit odd to me. If I change the PhonebookEntries property on the ConnectionViewModel to be of type ReadOnlyCollection, the TwoWay binding of the SelectedValue property on the combobox works fine.

Maybe there is an issue with the CollectionView? I noticed a warning in the output console:

System.Windows.Data Warning: 50 : Using CollectionView directly is not fully supported. The basic features work, although with some inefficiencies, but advanced features may encounter known bugs. Consider using a derived class to avoid these problems.

Edit2 (.NET 4.5): The content of the DropDownList can be based on ToString() and not of DisplayMemberPath, while DisplayMemberPath specifies the member for the selected and displayed item only.

WPF: How to debug binding errors

I was also going to recommend Bea Stollnitz's article but Jonathan Allen got his post in while I was still typing this one. I also recommend the links in this blog entry.

In this particular case you can see that somewhere a ListBoxItem has a FindAncestor binding to an ItemsControl that is failing. That tells you right away there is a ListBoxItem somewhere that is either:

Not in the visual tree, or
Not under an ItemsControl (a ListBox is an ItemsControl)

In addition, you know that someone, somewhere, is binding a ListBoxItem's VerticalContentAlignment property to FindAncestor.

Looking at the system themes (shipped with Expression Blend and also available through NET Reflector's BAMLViewer Add-in), we see this:

<Style x:Key="{x:Type ListBoxItem}">
  <Setter Property="VerticalContentAlignment"
          Value="{Binding Path=VerticalContentAlignment,RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}" />

This explains where the binding comes from. The next question is, how is a ListBoxItem being created that is not under a ListBox (or other ItemsControl)?

Some things to look for:

Are you constructing ListBoxItems in code anywhere?
Is there any ListBoxItem explicitly specified in your XAML?
Do you have any code that manually manipulates the items in ListBox?

Hopefully this will head you in the right direction.

Best Answer

Related Solutions

C# – Binding a WPF ComboBox to a custom list

WPF: How to debug binding errors

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