Resizing the Header Row in RadGridView for WinForms

Environment

Product Version	Product	Author
2024.2.514	RadGridView for WinForms	Dinko Krastev

Description

By default, the header row of the RadGridView is not resizable. This article explains how to resize the header row using custom code.

Solution

To implement this functionality we can use mouse events. We can subscribe to MouseDown, MouseMove, and MouseUp events of the RadGridView.

1. Attach the mouse event handlers to radGridView1:

• C#

this.radGridView1.MouseDown += RadGridView1_MouseDown;
this.radGridView1.MouseMove += RadGridView1_MouseMove;
this.radGridView1.MouseUp += RadGridView1_MouseUp;

1. In the MouseDown event handler, we can determine if the mouse is over the header row and prepare for resizing:

• C#

private void RadGridView1_MouseDown(object? sender, MouseEventArgs e)
{
    GridCellElement cellUnderMouse = this.radGridView1.ElementTree.GetElementAtPoint<GridCellElement>(e.Location);
    if (cellUnderMouse != null && cellUnderMouse is GridTableHeaderCellElement)
    {
        rowElement = this.radGridView1.ElementTree.GetElementAtPoint<GridRowElement>(e.Location);
        rowToResizeInitialHeight = this.rowElement.Size.Height;
        headerCell = cellUnderMouse;
        isMouseLeftButtonHold = true;
        mouseDownLocation = e.Location;
        this.radGridView1.GridViewElement.ElementTree.Control.Cursor = Cursors.SizeNS;
    }
}

1. In the MouseMove event handler, we can resize the row if the mouse is being dragged:

• C#

private void RadGridView1_MouseMove(object? sender, MouseEventArgs e)
{
    if (isMouseLeftButtonHold)
    {
        this.ResizeRow(e.Location);
    }
}

protected virtual void ResizeRow(System.Drawing.Point currentLocation)
{
    int delta = currentLocation.Y - this.mouseDownLocation.Y;
    GridViewRowInfo rowToResizeInfo = this.headerCell.RowInfo;
    int height = this.rowToResizeInitialHeight + delta;
    if (rowToResizeInfo != null && height >= rowToResizeInfo.MinHeight)
    {
        rowToResizeInfo.Height = height;
    }
}

1. In the MouseUp event handler, we can stop the custom resizing logic from executing:

• C#

private void RadGridView1_MouseUp(object? sender, MouseEventArgs e)
{
    isMouseLeftButtonHold = false;
    this.radGridView1.GridViewElement.ElementTree.Control.Cursor = (this.radGridView1.GridViewElement.GridBehavior as BaseGridBehavior).OriginalCursor;
}

Notes

• This logic is executed when the user clicks on the header cell. Clicking on other cells may trigger sorting and interfere with the resizing logic.
• This is a custom solution. While it works in a sample application, it may not be compatible with all scenarios and built-in functionalities of the control.