How to autoscroll to the bottom of datagrid in wpf

Question

I have DataGrid, which has got 2 modes, ListView and alleryView. When we select an item in GalleryView and switch to ListView the same item gets selected in list view too. But scroll does not scrolls down to the selected item automatically. How to make it work automatically?

XAML File

    <DataGrid ItemsSource="{Binding ListItems}" RowStyle="{StaticResource DataGridRowStyle}"
              AutoGenerateColumns="False" RowHeight="60" CanUserAddRows="False" 
              CanUserDeleteRows="False" CanUserResizeRows="False" AlternationCount="2"
              HorizontalGridLinesBrush="LightSteelBlue" VerticalGridLinesBrush="LightSteelBlue"
              SelectionMode="Single" SelectedItem="{Binding SelectedSearchItem}" 
              IsReadOnly="True" KeyboardNavigation.TabNavigation="Once" behaviors:DataGridBehavior.Autoscroll="{Binding Autoscroll}" >

CS File

     private void SetSelectedItemOnViewChange()
    {
        if (SelectedViewMode.ModeName == ViewModes[1].ModeName)
            GallerySearchResults.SelectedSearchItem = GallerySearchResults.GalleryItems.FirstOrDefault((x => x.IndexNo == SelectedRecordIndex));


        else if (SelectedViewMode.ModeName == ViewModes[0].ModeName)
        {

            ListSearchResults.SelectedSearchItem = ListSearchResults.ListItems.FirstOrDefault((x => x.IndexNum == SelectedRecordIndex));
            if (SelectedRecordIndex > 10)
                Autoscroll = true;
        }

    }

Behavior file:

     public static class DataGridBehavior
{
    public static readonly DependencyProperty AutoscrollProperty = DependencyProperty.RegisterAttached(
    "Autoscroll", typeof(bool), typeof(DataGridBehavior), new PropertyMetadata(default(bool), AutoscrollChangedCallback));

    private static readonly Dictionary<DataGrid, NotifyCollectionChangedEventHandler> handlersDict = new Dictionary<DataGrid, NotifyCollectionChangedEventHandler>();

    private static void AutoscrollChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
    {
        var dataGrid = dependencyObject as DataGrid;
        if (dataGrid == null)
        {
            throw new InvalidOperationException("Dependency object is not DataGrid.");
        }

        if ((bool)args.NewValue)
        {
            Subscribe(dataGrid);
            dataGrid.Unloaded += DataGridOnUnloaded;
            dataGrid.Loaded += DataGridOnLoaded;
        }
        else
        {
            Unsubscribe(dataGrid);
            dataGrid.Unloaded -= DataGridOnUnloaded;
            dataGrid.Loaded -= DataGridOnLoaded;
        }
    }

    private static void Subscribe(DataGrid dataGrid)
    {
        var handler = new NotifyCollectionChangedEventHandler((sender, eventArgs) => ScrollToEnd(dataGrid));
        handlersDict.Add(dataGrid, handler);
        ((INotifyCollectionChanged)dataGrid.Items).CollectionChanged += handler;
        ScrollToEnd(dataGrid);
    }

    private static void Unsubscribe(DataGrid dataGrid)
    {
        NotifyCollectionChangedEventHandler handler;
        handlersDict.TryGetValue(dataGrid, out handler);
        if (handler == null)
        {
            return;
        }
        ((INotifyCollectionChanged)dataGrid.Items).CollectionChanged -= handler;
        handlersDict.Remove(dataGrid);
    }

    private static void DataGridOnLoaded(object sender, RoutedEventArgs routedEventArgs)
    {
        var dataGrid = (DataGrid)sender;
        if (GetAutoscroll(dataGrid))
        {
            Subscribe(dataGrid);
        }
    }

    private static void DataGridOnUnloaded(object sender, RoutedEventArgs routedEventArgs)
    {
        var dataGrid = (DataGrid)sender;
        if (GetAutoscroll(dataGrid))
        {
            Unsubscribe(dataGrid);
        }
    }

    private static void ScrollToEnd(DataGrid datagrid)
    {
        if (datagrid.Items.Count == 0)
        {
            return;
        }
        datagrid.ScrollIntoView(datagrid.Items[datagrid.Items.Count - 1]);
    }

    public static void SetAutoscroll(DependencyObject element, bool value)
    {
        element.SetValue(AutoscrollProperty, value);
    }

    public static bool GetAutoscroll(DependencyObject element)
    {
        return (bool)element.GetValue(AutoscrollProperty);
    }
}

xaml.cs file

    public partial class ItemGridControl : UserControl
{
    public ItemGridControl()
    {
        InitializeComponent();

    }

}

These are the I am working with. But the changes are not getting reflected. Item is getting selected on switching but the scroll bar is not going to bottom. I want it to go to bottom of the page when item number ie., SelectedRecordIndex is greater than 10

You can scroll to `SelectedItem` using `dataGrid.ScrollIntoView(dataGrid.SelectedItem)` — Aakanksha, Oct 30 '19 at 06:10
Not possible because it is a ViewModel and datagrid object cannot be created there — user3422209, Oct 30 '19 at 06:24
Check this out, this might help you. https://stackoverflow.com/questions/18019425/scrollintoview-for-wpf-datagrid-mvvm — Arif Eqbal, Oct 30 '19 at 06:30
You want to scroll to the end or to the selected item of datagrid? — Aakanksha, Oct 30 '19 at 06:32
Have you tried keeping breakpoint in AutoscrollChangedCallback method in the behaviour? Is it getting called? — Aakanksha, Oct 30 '19 at 06:50
Then check if it executing the line `dataGrid.ScrollIntoView(dataGrid.Items[dataGrid.Items.Count - 1]);` and for the correct `DataGrid`. Change you binding for AutoScroll like `behaviors:DataGridBehavior.Autoscroll="{Binding Autoscroll, Mode=TwoWay}"` and make sure you are setting this `AutoScroll` property in your `ViewModel`. — Aakanksha, Oct 30 '19 at 08:11

score 0 · Answer 1 · answered Oct 30 '19 at 06:30

0

To scroll DataGrid to particular row (or column) you can use DataGrid.ScrollIntoView, which has two overloads:

ScrollIntoView(Object) - scrolls to specified item in datagrid view (i.e. row)

ScrollIntoView(Object, DataGridColumn) - scrolls to specified item and column

In your case you rather need first overload. In order oto scroll to last row you could use such code:

myDataGrid.ScrollIntoView(myDataGrid.Items[myDataGrid.Items.Count - 1]);

answered Oct 30 '19 at 06:30

Michał Turczyn

32,028
14
47
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This has to be written code behind.. Is there any method by using ViewModel? Because I don't want to write anything code behind means in xaml.cs file. It is just for initialization – user3422209 Oct 30 '19 at 06:37
@user3422209 It is code behind. How would put that code in XAML ?? – Michał Turczyn Oct 30 '19 at 06:40
Not in XAML... in the CS file... ViewModel.CS.. not in Xaml.cs – user3422209 Oct 30 '19 at 06:46
@user3422209 Sorry, but I don't understnad you. THIS IS C# code, NOT XAML. I don't understand where do you have problem. – Michał Turczyn Oct 30 '19 at 06:47
I have these file, XAML, XAML.CS and ViewModel.CS.. as mentioned in the question. Only contructor is called in xaml.cs.... In Viewmodel.cs we do the coding – user3422209 Oct 30 '19 at 06:58

score 0 · Answer 2 · answered Oct 30 '19 at 08:44

0

If you want to do it in the ViewModel you can use a Behaviour.

You can check it in: Scroll WPF ListBox to the SelectedItem set in code in a view model

There explains how to do it with a ListBox, it's the same with a DataGrid.

answered Oct 30 '19 at 08:44

Josep B.

587
1
6
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How to autoscroll to the bottom of datagrid in wpf

2 Answers2