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Rows Reordering in Master-Detail Hierarchy

Consider the case you have a bound RadGridView with master-detail hierarchical data. This article demonstrates how to utilize the RadGridViewDragDropService and implement rows reordering.

Figure 1: Rows reordering in Master-Detail hierarchy

rows-reordering-in-master-detail-hierarchy 001

There are several main steps that need to be followed:

  1. Register a custom GridDataRowBehavior which starts the RadGridViewDragDropService when you click with the left mouse button over a child row.

  2. Override the OnMouseDownLeft method of the GridDataRowBehavior and start the service.

  3. Handle the RadDragDropService.PreviewDragStart event in order to indicate that RadGridView can start the drag operation. In the RadDragDropService.PreviewDragOver event you can control on what targets the row being dragged can be dropped on. In the PreviewDragDrop event you can perform the actual reordering of the data bound records. Note that it is important to update the ParentId field of the affected child record. Thus, you will indicate the new parent record to which the dragged record belongs.

BindingList<Level0> parentRecords = new BindingList<Level0>();
BindingList<Level1> childRecords = new BindingList<Level1>(); 
GridViewRowInfo draggedRow = null;

public RadForm1()
{
    InitializeComponent();

    FillData();

    radGridView1.DataSource = parentRecords;
    radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;

    GridViewTemplate template = new GridViewTemplate();
    template.DataSource = childRecords;
    template.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
    radGridView1.MasterTemplate.Templates.Add(template);

    GridViewRelation relation = new GridViewRelation(radGridView1.MasterTemplate);
    relation.ChildTemplate = template;
    relation.RelationName = "ParentChild";
    relation.ParentColumnNames.Add("Id");
    relation.ChildColumnNames.Add("ParentId");
    radGridView1.Relations.Add(relation);
    radGridView1.UseScrollbarsInHierarchy = true;
    this.radGridView1.AllowRowReorder = true;

    //handle drag and drop events for the grid through the DragDrop service
    RadDragDropService svc = this.radGridView1.GridViewElement.GetService<RadDragDropService>();
    svc.PreviewDragStart += svc_PreviewDragStart;
    svc.PreviewDragDrop += svc_PreviewDragDrop;
    svc.PreviewDragOver += svc_PreviewDragOver;

    //register the custom row selection behavior
    var gridBehavior = this.radGridView1.GridBehavior as BaseGridBehavior;
    gridBehavior.UnregisterBehavior(typeof(GridViewDataRowInfo));
    gridBehavior.RegisterBehavior(typeof(GridViewDataRowInfo), new RowSelectionGridBehavior());
}

private void svc_PreviewDragStart(object sender, PreviewDragStartEventArgs e)
{  
    GridDataRowElement draggedRowElement = e.DragInstance as GridDataRowElement;
    if (draggedRowElement != null && draggedRowElement.RowInfo != null)
    {
        e.CanStart = true;
        draggedRow = draggedRowElement.RowInfo;
    }
    else
    {
        e.CanStart = false;
    }
}

private void svc_PreviewDragOver(object sender, RadDragOverEventArgs e)
{
    if (e.DragInstance is GridDataRowElement)
    {
        e.CanDrop = e.HitTarget is GridDataRowElement || e.HitTarget is GridNewRowElement ||
                    e.HitTarget is GridTableElement ||
                    e.HitTarget is GridSummaryRowElement;
    }
}

private void svc_PreviewDragDrop(object sender, RadDropEventArgs e)
{
    var rowElement = e.DragInstance as GridDataRowElement;
    if (rowElement == null)
    {
        return;
    }
    e.Handled = true;

    var dropTarget = e.HitTarget as GridDataRowElement;
    var targetGrid = dropTarget.ElementTree.Control as RadGridView;
    if (targetGrid == null)
    {
        return;
    } 
    var dragGrid = draggedRow.ViewTemplate.MasterTemplate.Owner;
    if (targetGrid == dragGrid && dropTarget.RowInfo.HierarchyLevel == 1 && draggedRow.HierarchyLevel == 1)
    {
        e.Handled = true;
        Level1 draggedItem = draggedRow.DataBoundItem as Level1;  
        int targetIndex = childRecords.IndexOf(dropTarget.RowInfo.DataBoundItem as Level1);
        Level1 newItem = new Level1(draggedItem.Id, (int)((GridViewHierarchyRowInfo)dropTarget.RowInfo.Parent).Cells["Id"].Value, draggedItem.Name);
        GridViewRowInfo targetDataRow = dropTarget.RowInfo;

        targetGrid.BeginUpdate();
        childRecords.Remove(draggedItem);
        childRecords.Insert(targetIndex, newItem);
        targetGrid.EndUpdate();
        targetGrid.CurrentRow = targetDataRow;
    } 
}

public class RowSelectionGridBehavior : GridDataRowBehavior
{
    protected override bool OnMouseDownLeft(MouseEventArgs e)
    {
        GridDataRowElement row = this.GetRowAtPoint(e.Location) as GridDataRowElement;
        if (row != null)
        {
            RadGridViewDragDropService svc = this.GridViewElement.GetService<RadGridViewDragDropService>();
            svc.AllowAutoScrollColumnsWhileDragging = true;
            svc.AllowAutoScrollRowsWhileDragging = true;
            svc.Start(row);
        }
        return base.OnMouseDownLeft(e);
    }
}

private void FillData()
{
    int cnt = 0;
    for (int i = 0; i < 10; i++)
    {
        parentRecords.Add(new Level0(i, "Parent" + i));

        for (int j = 0; j < 5; j++)
        {
            childRecords.Add(new Level1(cnt, i, "Child " + cnt));
            cnt++;
        }
    }
}

public class Level0 : System.ComponentModel.INotifyPropertyChanged
{
    public Level0(int id, string title)
    {
        this.Id = id;
        this.Title = title;
    }

    public int Id
    {
        get
        {
            return this._id;
        }
        set
        {
            this._id = value;
            OnPropertyChanged("Id");
        }
    }

    public string Title
    {
        get
        {
            return this._title;
        }
        set
        {
            this._title = value;
            OnPropertyChanged("Title");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    private int _id;
    private string _title;
}

public class Level1 : System.ComponentModel.INotifyPropertyChanged
{
    public Level1(int id, int parentId, string name)
    {
        this.Id = id;
        this.ParentId = parentId;
        this.Name = name;
    }

    public int Id
    {
        get
        {
            return this._id;
        }
        set
        {
            this._id = value;
            OnPropertyChanged("Id");
        }
    }

    public int ParentId
    {
        get
        {
            return this._parentId;
        }
        set
        {
            this._parentId = value;
            OnPropertyChanged("ParentId");
        }
    }

    public string Name
    {
        get
        {
            return this._name;
        }
        set
        {
            this._name = value;
            OnPropertyChanged("Name");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    private int _id;
    private int _parentId;
    private string _name;
}


Private parentRecords As BindingList(Of Level0) = New BindingList(Of Level0)()
Private childRecords As BindingList(Of Level1) = New BindingList(Of Level1)()
Private draggedRow As GridViewRowInfo = Nothing

Public Sub New()
    InitializeComponent()
    FillData()
    RadGridView1.DataSource = parentRecords
    RadGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill
    Dim template As GridViewTemplate = New GridViewTemplate()
    template.DataSource = childRecords
    template.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill
    RadGridView1.MasterTemplate.Templates.Add(template)
    Dim relation As GridViewRelation = New GridViewRelation(RadGridView1.MasterTemplate)
    relation.ChildTemplate = template
    relation.RelationName = "ParentChild"
    relation.ParentColumnNames.Add("Id")
    relation.ChildColumnNames.Add("ParentId")
    RadGridView1.Relations.Add(relation)
    RadGridView1.UseScrollbarsInHierarchy = True
    Me.RadGridView1.AllowRowReorder = True
    Dim svc As RadDragDropService = Me.RadGridView1.GridViewElement.GetService(Of RadDragDropService)()
    AddHandler svc.PreviewDragStart, AddressOf svc_PreviewDragStart
    AddHandler svc.PreviewDragDrop, AddressOf svc_PreviewDragDrop
    AddHandler svc.PreviewDragOver, AddressOf svc_PreviewDragOver
    Dim gridBehavior = TryCast(Me.RadGridView1.GridBehavior, BaseGridBehavior)
    gridBehavior.UnregisterBehavior(GetType(GridViewDataRowInfo))
    gridBehavior.RegisterBehavior(GetType(GridViewDataRowInfo), New RowSelectionGridBehavior())
End Sub

Private Sub svc_PreviewDragStart(ByVal sender As Object, ByVal e As PreviewDragStartEventArgs)
    Dim draggedRowElement As GridDataRowElement = TryCast(e.DragInstance, GridDataRowElement)

    If draggedRowElement IsNot Nothing AndAlso draggedRowElement.RowInfo IsNot Nothing Then
        e.CanStart = True
        draggedRow = draggedRowElement.RowInfo
    Else
        e.CanStart = False
    End If
End Sub

Private Sub svc_PreviewDragOver(ByVal sender As Object, ByVal e As RadDragOverEventArgs)
    If TypeOf e.DragInstance Is GridDataRowElement Then
        e.CanDrop = TypeOf e.HitTarget Is GridDataRowElement OrElse TypeOf e.HitTarget Is GridNewRowElement OrElse
            TypeOf e.HitTarget Is GridTableElement OrElse TypeOf e.HitTarget Is GridSummaryRowElement
    End If
End Sub

Private Sub svc_PreviewDragDrop(ByVal sender As Object, ByVal e As RadDropEventArgs)
    Dim rowElement = TryCast(e.DragInstance, GridDataRowElement)

    If rowElement Is Nothing Then
        Return
    End If

    e.Handled = True
    Dim dropTarget = TryCast(e.HitTarget, GridDataRowElement)
    Dim targetGrid = TryCast(dropTarget.ElementTree.Control, RadGridView)

    If targetGrid Is Nothing Then
        Return
    End If

    Dim dragGrid = draggedRow.ViewTemplate.MasterTemplate.Owner

    If targetGrid.Equals(dragGrid) AndAlso dropTarget.RowInfo.HierarchyLevel = 1 AndAlso draggedRow.HierarchyLevel = 1 Then
        e.Handled = True
        Dim draggedItem As Level1 = TryCast(draggedRow.DataBoundItem, Level1)
        Dim targetIndex As Integer = childRecords.IndexOf(TryCast(dropTarget.RowInfo.DataBoundItem, Level1))
        Dim newItem As Level1 = New Level1(draggedItem.Id, CInt((CType(dropTarget.RowInfo.Parent, GridViewHierarchyRowInfo)).Cells("Id").Value), draggedItem.Name)
        Dim targetDataRow As GridViewRowInfo = dropTarget.RowInfo
        targetGrid.BeginUpdate()
        childRecords.Remove(draggedItem)
        childRecords.Insert(targetIndex, newItem)
        targetGrid.EndUpdate()
        targetGrid.CurrentRow = targetDataRow
    End If
End Sub

Public Class RowSelectionGridBehavior
    Inherits GridDataRowBehavior

    Protected Overrides Function OnMouseDownLeft(ByVal e As MouseEventArgs) As Boolean
        Dim row As GridDataRowElement = TryCast(Me.GetRowAtPoint(e.Location), GridDataRowElement)

        If row IsNot Nothing Then
            Dim svc As RadGridViewDragDropService = Me.GridViewElement.GetService(Of RadGridViewDragDropService)()
            svc.AllowAutoScrollColumnsWhileDragging = True
            svc.AllowAutoScrollRowsWhileDragging = True
            svc.Start(row)
        End If

        Return MyBase.OnMouseDownLeft(e)
    End Function
End Class

Private Sub FillData()
    Dim cnt As Integer = 0

    For i As Integer = 0 To 10 - 1
        parentRecords.Add(New Level0(i, "Parent" & i))

        For j As Integer = 0 To 5 - 1
            childRecords.Add(New Level1(cnt, i, "Child " & cnt))
            cnt += 1
        Next
    Next
End Sub

Public Class Level0
    Implements System.ComponentModel.INotifyPropertyChanged

    Public Sub New(ByVal id As Integer, ByVal title As String)
        Me.Id = id
        Me.Title = title
    End Sub

    Public Property Id As Integer
        Get
            Return Me._id
        End Get
        Set(ByVal value As Integer)
            Me._id = value
            OnPropertyChanged("Id")
        End Set
    End Property

    Public Property Title As String
        Get
            Return Me._title
        End Get
        Set(ByVal value As String)
            Me._title = value
            OnPropertyChanged("Title")
        End Set
    End Property

    Public Event PropertyChanged As PropertyChangedEventHandler
    Private Event INotifyPropertyChanged_PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub

    Private _id As Integer
    Private _title As String
End Class

Public Class Level1
    Implements System.ComponentModel.INotifyPropertyChanged

    Public Sub New(ByVal id As Integer, ByVal parentId As Integer, ByVal name As String)
        Me.Id = id
        Me.ParentId = parentId
        Me.Name = name
    End Sub

    Public Property Id As Integer
        Get
            Return Me._id
        End Get
        Set(ByVal value As Integer)
            Me._id = value
            OnPropertyChanged("Id")
        End Set
    End Property

    Public Property ParentId As Integer
        Get
            Return Me._parentId
        End Get
        Set(ByVal value As Integer)
            Me._parentId = value
            OnPropertyChanged("ParentId")
        End Set
    End Property

    Public Property Name As String
        Get
            Return Me._name
        End Get
        Set(ByVal value As String)
            Me._name = value
            OnPropertyChanged("Name")
        End Set
    End Property

    Public Event PropertyChanged As PropertyChangedEventHandler
    Private Event INotifyPropertyChanged_PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub

    Private _id As Integer
    Private _parentId As Integer
    Private _name As String
End Class

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