C# – WPF, MVVM datagrid row binding

bindingcmvvmwpf

I am wandering if anyone could help me work out the binding issues I am having?

Snippets of Code:

<DataGrid AutoGenerateColumns="False" Grid.Column="1" Grid.Row="1" SelectionMode="Single" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" ItemsSource="{Binding PersonList}" CanUserSortColumns="True" SelectedItem="{Binding Path=SelectedPerson}" >
            <DataGrid.Columns>
                <DataGridTextColumn Header="FirstName" Width="100" Binding="{Binding FirstName}" />
                <DataGridTextColumn Header="LastName" Width="100" Binding="{Binding LastName}" />
                <DataGridTemplateColumn Width="140" Header="Operator">
                    <DataGridTemplateColumn.CellTemplate>
                            <DataTemplate>
                        <ComboBox ItemsSource="{Binding Path=OperatorList}" DisplayMemberPath="FullName" SelectedValue="{Binding Path=SelectedOperator}" />
                            </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn> 
                ...
</DataGrid>

Above is a snippet of code from the view:

Each person in the list is its own viewmodel that has the code snippet below:

CollectionView _operatorList;
public CollectionView DebtorAgentList { get { return _operatorList; } }

Model.Operator _selectedOperator;
public Model.Operator SelectedOperator
{...}

Now the problem I am having is that the SelectedValue binding isn't working and I can't work out why? But what makes it tricky or different (maybe) is that every row in the data grid has its own viewmodel , so in otherwords a datagrid of viewmodels. So what is happening is that FirstName and LastName and Combobox are all filled correctly but I can't seem to get the SelectedValue to bind?
P.S. It isnt because of some spell mistake, if there are spelling mistakes is because i renamed methods when I wrote the question etc.

Further Details:

The above Datagrid is part of a view that has its own viewmodel, this view model fills the datagrid above with a list of people, each person is a viewmodel in essence( well it isn't really a viewmodel but then again its more of a viewmodel than a plane model). It works the way I need it to until I try to bind the SelectedView attribute?

Could someone please tell me why that binding might not working?

Thanks In advance 😀

Best Answer

Use SelectedValuePath and then use 'SelectedValue' to select any item in the collection, see the following code :-

<ComboBox ItemsSource="{Binding Path=OperatorList}" DisplayMemberPath="FullName" SelectedValuePath="SelectedOperator" SelectedValue="{Binding SelectedOperator}" />

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.

C# – How to use RelativeSource Binding to create DataGrid binding to Model and ViewModel

Bind to the datacontext of the grid :

<DataGrid ItemsSource="{Binding ModelValues, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
      <DataGridTemplateColumn Header="myHeader" Width="200">
           <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                     <ComboBox DisplayMemberPath="Value" SelectedValuePath="Key" IsEnabled="False"
                          SelectedValue="{Binding myID, Mode=TwoWay}"
                          ItemsSource="{Binding Path=DataContext.myList, 
                          RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}" />
                </DataTemplate>
           </DataGridTemplateColumn.CellTemplate>
           <DataGridTemplateColumn.CellEditingTemplate>
                <DataTemplate>
                     <ComboBox DisplayMemberPath="Value" SelectedValuePath="Key" IsEnabled="False"
                          SelectedValue="{Binding myID, Mode=TwoWay}"
                          ItemsSource="{Binding Path=DataContext.myList, 
                          RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}" />
                </DataTemplate>
           </DataGridTemplateColumn.CellEditingTemplate>
      </DataGridTemplateColumn>
 </DataGrid>

Best Answer

Related Solutions

C# – Binding a WPF ComboBox to a custom list

C# – How to use RelativeSource Binding to create DataGrid binding to Model and ViewModel

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