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Scroll to Newly Added Item

This article shows how to scroll RadGridView to the newly added item.

You can achieve this by using the ScrollIntoViewAsync method and the CollectionChanged event of the control's Items collection. For the purpose, you can create a custom behavior and attach it to your RadGridView control.

Example 1: The custom behavior

public class ScrollToNewItemBehavior : Behavior<RadGridView> 
{ 
    private RadGridView GridView 
    { 
        get 
        { 
            return this.AssociatedObject as RadGridView; 
        } 
    } 
 
    protected override void OnAttached() 
    { 
        base.OnAttached(); 
        this.GridView.Items.CollectionChanged += OnCollectionChanged; 
    } 
 
    protected override void OnDetaching() 
    { 
        base.OnDetaching(); 
        this.GridView.Items.CollectionChanged -= OnCollectionChanged; 
    } 
 
    private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs args) 
    { 
        if (args.Action == NotifyCollectionChangedAction.Add) 
        { 
            this.GridView.ScrollIntoViewAsync(args.NewItems[0], this.GridView.Columns[0], null); 
        } 
    } 
} 
Public Class ScrollToNewItemBehavior 
    Inherits Behavior(Of RadGridView) 
 
    Private ReadOnly Property GridView() As RadGridView 
        Get 
            Return TryCast(Me.AssociatedObject, RadGridView) 
        End Get 
    End Property 
 
    Protected Overrides Sub OnAttached() 
        MyBase.OnAttached() 
        AddHandler GridView.Items.CollectionChanged, AddressOf OnCollectionChanged 
    End Sub 
 
    Protected Overrides Sub OnDetaching() 
        MyBase.OnDetaching() 
        RemoveHandler GridView.Items.CollectionChanged, AddressOf OnCollectionChanged 
    End Sub 
 
    Private Sub OnCollectionChanged(ByVal sender As Object, ByVal args As NotifyCollectionChangedEventArgs) 
        If args.Action = NotifyCollectionChangedAction.Add Then 
            Me.GridView.ScrollIntoViewAsync(args.NewItems(0), Me.GridView.Columns(0), Nothing) 
        End If 
    End Sub 
End Class 

Example 2 and Example 3 demonstrate how you can apply the new behavior to all RadGridView instances in your application by creating an attached property which you can then use in an implicit style.

Example 2: Defining the attached property

public class GridViewAttachedProperties 
{ 
    public static bool GetScrollToNewItem(DependencyObject obj) 
    { 
        return (bool)obj.GetValue(ScrollToNewItemProperty); 
    } 
 
    public static void SetScrollToNewItem(DependencyObject obj, bool value) 
    { 
        obj.SetValue(ScrollToNewItemProperty, value); 
    } 
 
    public static readonly DependencyProperty ScrollToNewItemProperty = 
        DependencyProperty.RegisterAttached("ScrollToNewItem", typeof(bool), typeof(GridViewAttachedProperties), new PropertyMetadata(false, OnScrollNewItemIntoViewChanged)); 
 
    private static void OnScrollNewItemIntoViewChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) 
    { 
        var gridView = d as RadGridView; 
        if (gridView != null) 
        { 
            var scrollToNewItem = GetScrollToNewItem(d); 
            var behaviors = Interaction.GetBehaviors(d); 
            var scrollToNewItemBehavior = behaviors.SingleOrDefault(x => x is ScrollToNewItemBehavior); 
 
            if (scrollToNewItemBehavior != null && !scrollToNewItem) 
            { 
                behaviors.Remove(scrollToNewItemBehavior); 
            } 
            else if (scrollToNewItemBehavior == null && scrollToNewItem) 
            { 
                scrollToNewItemBehavior = new ScrollToNewItemBehavior(); 
                behaviors.Add(scrollToNewItemBehavior); 
            } 
        } 
    } 
} 
Public Class GridViewAttachedProperties 
    Public Shared Function GetScrollToNewItem(ByVal obj As DependencyObject) As Boolean 
        Return CBool(obj.GetValue(ScrollToNewItemProperty)) 
    End Function 
 
    Public Shared Sub SetScrollToNewItem(ByVal obj As DependencyObject, ByVal value As Boolean) 
        obj.SetValue(ScrollToNewItemProperty, value) 
    End Sub 
 
    Public Shared ReadOnly ScrollToNewItemProperty As DependencyProperty = DependencyProperty.RegisterAttached("ScrollToNewItem", GetType(Boolean), GetType(GridViewAttachedProperties), New PropertyMetadata(False, AddressOf OnScrollNewItemIntoViewChanged)) 
 
    Private Shared Sub OnScrollNewItemIntoViewChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs) 
        Dim gridView = TryCast(d, RadGridView) 
        If gridView IsNot Nothing Then 
            Dim scrollToNewItem = GetScrollToNewItem(d) 
            Dim behaviors = Interaction.GetBehaviors(d) 
            Dim scrollToNewItemBehavior = behaviors.SingleOrDefault(Function(x) TypeOf x Is ScrollToNewItemBehavior) 
 
            If scrollToNewItemBehavior IsNot Nothing AndAlso Not scrollToNewItem Then 
                behaviors.Remove(scrollToNewItemBehavior) 
            ElseIf scrollToNewItemBehavior Is Nothing AndAlso scrollToNewItem Then 
                scrollToNewItemBehavior = New ScrollToNewItemBehavior() 
                behaviors.Add(scrollToNewItemBehavior) 
            End If 
        End If 
    End Sub 
End Class 

Example 3: Set the attached property in an implicit style

<Application.Resources> 
    <Style TargetType="telerik:RadGridView"> 
        <Setter Property="local:GridViewAttachedProperties.ScrollToNewItem" Value="True" /> 
    </Style> 
</Application.Resources> 

If you're using implicit styles, you should base your style on the RadGridViewStyle as explained in this article.

See Also

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