Reorder Columns in RadVirtualGrid

Environment

Product Version	Product	Author
2019.3.917	RadVirtualGrid for WinForms	Desislava Yordanova

Description

RadVirtualGrid loads data on demand providing the respective cell's value (even for the header cells) via the CellValueNeeded event. Reordering the columns can be achieved by forcing an update and applying a new order for the columns from the external source that is used for the data to be loaded in the grid.

Solution

This tutorial demonstrates a sample approach how to use the standard OLE drag and drop functionality and simulate columns reordering in RadVirtualGrid.

DataTable data;
List<string> visibleColumns = new List<string>();

public RadForm1()
{
    InitializeComponent();

    this.data = GetTable();
    for (int i = 0; i < 10; i++)
    {
        string name = "Column " + i;
        this.visibleColumns.Add(name);
    }

    this.radVirtualGrid1.AllowDrop = true;

    this.radVirtualGrid1.MouseDown += radVirtualGrid1_MouseDown;
    this.radVirtualGrid1.MouseMove += radVirtualGrid1_MouseMove;
    this.radVirtualGrid1.DragEnter += radVirtualGrid1_DragEnter;
    this.radVirtualGrid1.DragDrop += radVirtualGrid1_DragDrop;
    this.radVirtualGrid1.MouseUp += radVirtualGrid1_MouseUp;

    this.radVirtualGrid1.CellValueNeeded += RadVirtualGrid1_CellValueNeeded;
    this.radVirtualGrid1.RowCount = data.Rows.Count;
    this.radVirtualGrid1.ColumnCount = data.Columns.Count;
}

private void radVirtualGrid1_DragEnter(object sender, DragEventArgs e)
{
    e.Effect = DragDropEffects.Move;
}

private void radVirtualGrid1_MouseUp(object sender, MouseEventArgs e)
{
    this.mouseDownPosition = Point.Empty;
}

private void radVirtualGrid1_DragDrop(object sender, DragEventArgs e)
{
    VirtualGridHeaderCellElement source = e.Data.GetData(typeof(VirtualGridHeaderCellElement)) as VirtualGridHeaderCellElement;
    Point mousePosition = this.radVirtualGrid1.VirtualGridElement.ElementTree.Control.PointToClient(Control.MousePosition);
    VirtualGridHeaderCellElement target = this.radVirtualGrid1.ElementTree.GetElementAtPoint(mousePosition) as VirtualGridHeaderCellElement;
    if (target != null)
    {
        int s = visibleColumns.IndexOf(source.Text);
        int t = visibleColumns.IndexOf(target.Text);

        visibleColumns.RemoveAt(s);
        visibleColumns.Insert(t, source.Text);

        foreach (VirtualGridRowElement rowElement in
            this.radVirtualGrid1.VirtualGridElement.TableElement.GetDescendants(delegate(RadElement x) { return x is VirtualGridRowElement; },
                TreeTraversalMode.BreadthFirst))
        {
            rowElement.CellContainer.Children.Clear();
        }
    }
}

private void radVirtualGrid1_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Left)
    {
        RadVirtualGrid grid = (RadVirtualGrid)sender;
        VirtualGridHeaderCellElement cell = grid.ElementTree.GetElementAtPoint(e.Location) as VirtualGridHeaderCellElement;
        if (cell != null)
        {
            if (this.ShouldBeginDrag(this.mouseDownPosition, e.Location))
            {
                if (cell != null)
                {
                    this.isDragging = true;
                    grid.DoDragDrop(cell, DragDropEffects.Move);
                }
            }
        }
    }
}

private Point mouseDownPosition;
private bool isDragging;

private void radVirtualGrid1_MouseDown(object sender, MouseEventArgs e)
{
    this.mouseDownPosition = e.Location;
}

private bool ShouldBeginDrag(Point current, Point capture)
{
    Size dragSize = SystemInformation.DragSize;
    Rectangle dragRect = new Rectangle(capture.X - dragSize.Width / 2,
        capture.Y - dragSize.Height / 2, dragSize.Width, dragSize.Height);
    return !dragRect.Contains(current);
}

private void RadVirtualGrid1_CellValueNeeded(object sender, Telerik.WinControls.UI.VirtualGridCellValueNeededEventArgs e)
{
    if (e.ColumnIndex < 0 || e.ColumnIndex >= radVirtualGrid1.ColumnCount)
        return;

    if (e.RowIndex == RadVirtualGrid.HeaderRowIndex)
    {
        e.Value = data.Columns[this.visibleColumns[e.ColumnIndex]];
    }

    if (e.RowIndex < 0)
    {
        return;
    }

    var row = data.Rows[e.RowIndex];
    e.Value = row[this.visibleColumns[e.ColumnIndex]];
}

static DataTable GetTable()
{
    DataTable table = new DataTable();
    for (int i = 0; i < 10; i++)
    {
        table.Columns.Add("Column " + i, typeof(int));
    }

    for (int i = 0; i < 100; i++)
    {
        table.Rows.Add(new object[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 });
    }

    return table;
}

Private data As DataTable
Private visibleColumns As List(Of String) = New List(Of String)()

Public Sub New()
    InitializeComponent()
    Me.data = GetTable()

    For i As Integer = 0 To 10 - 1
        Dim name As String = "Column " & i
        Me.visibleColumns.Add(name)
    Next

    Me.RadVirtualGrid1.AllowDrop = True
    AddHandler Me.RadVirtualGrid1.MouseDown, AddressOf radVirtualGrid1_MouseDown
    AddHandler Me.RadVirtualGrid1.MouseMove, AddressOf radVirtualGrid1_MouseMove
    AddHandler Me.RadVirtualGrid1.DragEnter, AddressOf radVirtualGrid1_DragEnter
    AddHandler Me.RadVirtualGrid1.DragDrop, AddressOf radVirtualGrid1_DragDrop
    AddHandler Me.RadVirtualGrid1.MouseUp, AddressOf radVirtualGrid1_MouseUp
    AddHandler Me.RadVirtualGrid1.CellValueNeeded, AddressOf RadVirtualGrid1_CellValueNeeded
    Me.RadVirtualGrid1.RowCount = data.Rows.Count
    Me.RadVirtualGrid1.ColumnCount = data.Columns.Count
End Sub

Private Sub radVirtualGrid1_DragEnter(ByVal sender As Object, ByVal e As DragEventArgs)
    e.Effect = DragDropEffects.Move
End Sub

Private Sub radVirtualGrid1_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs)
    Me.mouseDownPosition = Point.Empty
End Sub

Private Sub radVirtualGrid1_DragDrop(ByVal sender As Object, ByVal e As DragEventArgs)
    Dim source As VirtualGridHeaderCellElement = TryCast(e.Data.GetData(GetType(VirtualGridHeaderCellElement)), VirtualGridHeaderCellElement)
    Dim mousePosition As Point = Me.RadVirtualGrid1.VirtualGridElement.ElementTree.Control.PointToClient(Control.MousePosition)
    Dim target As VirtualGridHeaderCellElement = TryCast(Me.RadVirtualGrid1.ElementTree.GetElementAtPoint(mousePosition), VirtualGridHeaderCellElement)

    If target IsNot Nothing Then
        Dim s As Integer = visibleColumns.IndexOf(source.Text)
        Dim t As Integer = visibleColumns.IndexOf(target.Text)
        visibleColumns.RemoveAt(s)
        visibleColumns.Insert(t, source.Text)

        For Each rowElement As VirtualGridRowElement In Me.RadVirtualGrid1.VirtualGridElement.TableElement.GetDescendants(Function(x As RadElement) _
                                                                        TypeOf x Is VirtualGridRowElement, TreeTraversalMode.BreadthFirst)
            rowElement.CellContainer.Children.Clear()
        Next
    End If
End Sub

Private Sub radVirtualGrid1_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs)
    If e.Button = System.Windows.Forms.MouseButtons.Left Then
        Dim grid As RadVirtualGrid = CType(sender, RadVirtualGrid)
        Dim cell As VirtualGridHeaderCellElement = TryCast(grid.ElementTree.GetElementAtPoint(e.Location), VirtualGridHeaderCellElement)

        If cell IsNot Nothing Then

            If Me.ShouldBeginDrag(Me.mouseDownPosition, e.Location) Then

                If cell IsNot Nothing Then
                    Me.isDragging = True
                    grid.DoDragDrop(cell, DragDropEffects.Move)
                End If
            End If
        End If
    End If
End Sub

Private mouseDownPosition As Point
Private isDragging As Boolean

Private Sub radVirtualGrid1_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs)
    Me.mouseDownPosition = e.Location
End Sub

Private Function ShouldBeginDrag(ByVal current As Point, ByVal capture As Point) As Boolean
    Dim dragSize As Size = SystemInformation.DragSize
    Dim dragRect As Rectangle = New Rectangle(capture.X - dragSize.Width / 2, capture.Y - dragSize.Height / 2, dragSize.Width, dragSize.Height)
    Return Not dragRect.Contains(current)
End Function

Private Sub RadVirtualGrid1_CellValueNeeded(ByVal sender As Object, ByVal e As Telerik.WinControls.UI.VirtualGridCellValueNeededEventArgs)
    If e.ColumnIndex < 0 OrElse e.ColumnIndex >= RadVirtualGrid1.ColumnCount Then Return

    If e.RowIndex = RadVirtualGrid.HeaderRowIndex Then
        e.Value = data.Columns(Me.visibleColumns(e.ColumnIndex))
    End If

    If e.RowIndex < 0 Then
        Return
    End If

    Dim row = data.Rows(e.RowIndex)
    e.Value = row(Me.visibleColumns(e.ColumnIndex))
End Sub

Private Shared Function GetTable() As DataTable
    Dim table As DataTable = New DataTable()

    For i As Integer = 0 To 10 - 1
        table.Columns.Add("Column " & i, GetType(Integer))
    Next

    For i As Integer = 0 To 100 - 1
        table.Rows.Add(New Object() {0, 1, 2, 3, 4, 5, 6, 7, 8, 9})
    Next

    Return table
End Function