SourceGrid with Columns Drag and Swap – a grid all C# for .NET 2.0

Last night I discovery SourceGrid is not stopped on .NET 1.1, Davide Icardi version, but it’s maintained by dariusdamalakas (I don’t know if he’s the same guy, I think no), however is a great grid, but there was something missing really important for my project, lucky for me it’s quite simple to do, I need a columns drag and reorder or drag and swap reordering functionality.

First attempt [at the end failed] was to build a Controller for dragging headers, and it was working, but I cannot find a nice way to call column Swap and redraw header under mouse without changing more code that I was think it was a good code.
If I write too much code to do simple task, there’s a voice in me that tell me I’m wrong on what I’ve done.

So, trashed all tests, I prefer to keep original code “as is” and inherit original object:

* override OnMouseDown and save dragged column header
* override OnMouseMove to set destination column header by moving pointer
* override OnMouseUp to set final destination column header
* override OnPaint to redraw destination column header by moving pointer with a nice veil of transparent white

here a snapshot of result:

and here is the code:

using System;
using System.Drawing;

namespace SourceGrid_ColumnDragNSwap
{
    public class SourceGrid_ColumnDragNSwap:SourceGrid.DataGrid
    {
        int draggingColumn = -1;
        int targetColumn = -1;
        protected override void OnMouseDown(System.Windows.Forms.MouseEventArgs e)
        {
            base.OnMouseDown(e);

            draggingColumn = -1;
            if (e.Button == System.Windows.Forms.MouseButtons.Left)
                if (this.MouseCellPosition.Row == 0) // header
                    draggingColumn = this.MouseCellPosition.Column;
        }

        protected override void OnMouseMove(System.Windows.Forms.MouseEventArgs e)
        {
            base.OnMouseMove(e);
            if (draggingColumn != -1)
            {
                int newTargetColumn = this.PositionAtPoint(e.Location).Column;
                if (targetColumn != newTargetColumn)
                {
                    targetColumn = newTargetColumn;
                    // Invalidate to redraw all header cells
                    if (targetColumn != -1) this.InvalidateRange(new SourceGrid.Range(0, 0, 0, this.Columns.Count - 1));
                }
            }
        }

        protected override void OnMouseUp(System.Windows.Forms.MouseEventArgs e)
        {
            base.OnMouseUp(e);

            if (draggingColumn != -1)
            {
                targetColumn = this.PositionAtPoint(e.Location).Column;
                if (targetColumn != -1)
                {
                    //Swap Columns
                    if (targetColumn != draggingColumn) this.Columns.Swap(targetColumn, draggingColumn);
                    targetColumn = -1;
                }
                draggingColumn = -1;
            }
        }

        private Brush whiteVeilBrush = new SolidBrush(Color.FromArgb(150, Color.White));
        private Rectangle cellVeilRectangle = new Rectangle();
        protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
        {
            base.OnPaint(e);
            //Paint over target header cell a white veil
            if (draggingColumn != -1 && targetColumn != -1 && draggingColumn != targetColumn)
            {
                Rectangle currentCellRectangle = this.PositionToRectangle(new SourceGrid.Position(0, targetColumn));
                cellVeilRectangle.X = currentCellRectangle.X;
                cellVeilRectangle.Y = currentCellRectangle.Y;
                cellVeilRectangle.Width = currentCellRectangle.Width - 2;
                cellVeilRectangle.Height = currentCellRectangle.Height - 1;
                e.Graphics.FillRectangle(whiteVeilBrush, cellVeilRectangle);
            }
        }
    }
}

My source with test project is here