如何使用仅使用XAML数据绑定的DataGrid获取行选择

Question

I have the following DataGrid definition

 <DataGrid
    VirtualizingPanel.VirtualizationMode="Recycling"
    CanUserAddRows="False"
    CanUserDeleteRows="False"
    SelectionMode="Single"
    ItemsSource="{Binding 
        ToolPath.ToolPath, 
        Mode=OneWay,
        Converter={StaticResource indexedConverter}}" 
    AutoGenerateColumns="False" 
    SelectedIndex="{Binding SelectedIndex, Mode=TwoWay}">

I'm using MVVM and have a view model with a SelectedIndex property implementing INPC. I've used snoop to verify that the SelectedIndex on the DataGrid changes when it does in the view model. However the row of the grid is not selected or highlighted when I do so.

As you can see the row is not highlighted but I think I can detect that the little 3 pixel wide widget to the left of the row is a darker blue.

Is there a XAML only way via databinding ( without writing code behind ) to get row selection working?

Answer 1

Can't seem to figure out a way from XAML. With much hacking and reading posts the best I can come up with is.

<DataGrid
    x:Name="ToolPathGridView"
    VirtualizingPanel.VirtualizationMode="Recycling"
    CanUserAddRows="False"
    SelectionUnit="FullRow"
    CanUserDeleteRows="False"
    SelectionMode="Single"
    Loaded="ToolPathGridView_Loaded"
    ItemsSource="{Binding 
        ToolPath.ToolPath, 
        Mode=OneWay,
        Converter={StaticResource indexedConverter}}" 
    AutoGenerateColumns="False" 
    SelectedIndex="{Binding SelectedIndex, Mode=TwoWay}">

and

private void ToolPathGridView_Loaded( object sender, RoutedEventArgs e )
{
    ToolPathGridView.ItemContainerGenerator.StatusChanged += new EventHandler(ItemContainerGenerator_StatusChanged);
}
 void ItemContainerGenerator_StatusChanged( object sender, EventArgs e )
{
    if ( ToolPathGridView.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated )
    {
        int i = 0;
        if ( ViewModel!=null )
        {
            i = ViewModel.SelectedIndex;
        }
        ToolPathGridView.SelectedIndex = 0;
        DataGridRow r = ToolPathGridView.ItemContainerGenerator.ContainerFromIndex(0) as DataGridRow;
        if ( r != null )
        {
            r.IsSelected = false;
            r.IsSelected = true;
        }
    }
}

so what is happening here. The trick seems to be that you have to wait till the datagrid has built it's internal container model. When that is done you can pick off a row and mark it as selected. If you try to do this too early there are no rows.

This really should be a property of the grid itself.

Answer 2

Working example using MVVM light from NuGet .

You can write the index in the lower textbox to see it changing on the DataGrid.

MainWindow.xaml

<Window
    x:Class="Test_DataGridSelectedIndexItem.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:testDataGridSelectedIndexItem="clr-namespace:Test_DataGridSelectedIndexItem"
    Title="MainWindow"
    Height="350"
    Width="525"
    >
    <Window.DataContext>
        <testDataGridSelectedIndexItem:MainViewModel />
    </Window.DataContext>

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height=".9*"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <DataGrid
            Grid.Row="0"
            ItemsSource="{Binding Items}"
            SelectedItem="{Binding Selected, Mode=TwoWay}"
            SelectedIndex="{Binding SelectedIndex, Mode=TwoWay}"
            />

        <TextBlock
            Grid.Row="1"
            Text="{Binding Selected}"
            />

        <TextBlock
            Grid.Row="2"
            Text="{Binding SelectedIndex}"
            />

        <TextBox
            Grid.Row="3"
            Text="{Binding SelectedIndex, Mode=TwoWay}"
            />
    </Grid>
</Window>

MainViewModel.cs

using System.Collections.ObjectModel;
using GalaSoft.MvvmLight;

namespace Test_DataGridSelectedIndexItem
{
    public class MainViewModel : ViewModelBase
    {
        private ItemViewMode selected;
        private int selectedIndex;

        public MainViewModel()
        {
            this.Items = new ObservableCollection<ItemViewMode>()
                         {
                             new ItemViewMode("Item1"),
                             new ItemViewMode("Item2"),
                             new ItemViewMode("Item3"),
                         };
        }

        public ObservableCollection<ItemViewMode> Items { get; private set; }

        public ItemViewMode Selected
        {
            get
            {
                return this.selected;
            }
            set
            {
                this.selected = value;
                this.RaisePropertyChanged(() => this.Selected);
            }
        }

        public int SelectedIndex
        {
            get
            {
                return this.selectedIndex;
            }
            set
            {
                this.selectedIndex = value;
                this.RaisePropertyChanged(() => this.SelectedIndex);
            }
        }
    }
}

ItemViewModel.cs

using GalaSoft.MvvmLight;

namespace Test_DataGridSelectedIndexItem
{
    public class ItemViewModel : ViewModelBase
    {
        private string text;

        public ItemViewModel() : this(string.Empty)
        {
        }

        public ItemViewModel(string text)
        {
            this.text = text;
        }

        public string Text
        {
            get
            {
                return this.text;
            }
            set
            {
                this.text = value;
                this.RaisePropertyChanged(() => this.Text);
            }
        }

        public override string ToString()
        {
            return this.text;
        }
    }
}