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Draggable WinForms Controls

, 8 Apr 2011
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Extension method to make any WinForms control to be draggable at runtime
Sometimes, you need to make the control draggable during runtime. It can be a form with FormBorderStyle property set to None, or any other situation.
I want to propose a simple extension method that allows you to make this possible.
using System;
using System.Collections.Generic;
using System.Windows.Forms;
namespace DraggableControls
{
    public static class ControlExtension
    {
        // TKey is control to drag, TValue is a flag used while dragging
        private static Dictionary<Control, bool> draggables = 
                   new Dictionary<Control, bool>();
        private static System.Drawing.Size mouseOffset;
 
        /// <summary>
        /// Enabling/disabling dragging for control
        /// </summary>
        public static void Draggable(this Control control, bool Enable)
        {
            if (Enable)
            {
                // enable drag feature
                if (draggables.ContainsKey(control))
                {   // return if control is already draggable
                    return;
                }
                // 'false' - initial state is 'not dragging'
                draggables.Add(control, false);
 
                // assign required event handlersnnn
                control.MouseDown += new MouseEventHandler(control_MouseDown);
                control.MouseUp += new MouseEventHandler(control_MouseUp);
                control.MouseMove += new MouseEventHandler(control_MouseMove);
            }
            else
            {
                // disable drag feature
                if (!draggables.ContainsKey(control))
                {  // return if control is not draggable
                    return;
                }
                // remove event handlers
                control.MouseDown -= control_MouseDown;
                control.MouseUp -= control_MouseUp;
                control.MouseMove -= control_MouseMove;
                draggables.Remove(control);
            }
        }
        static void control_MouseDown(object sender, MouseEventArgs e)
        {
            mouseOffset = new System.Drawing.Size(e.Location);
            // turning on dragging
            draggables[(Control)sender] = true;
        }
        static void control_MouseUp(object sender, MouseEventArgs e)
        {
            // turning off dragging
            draggables[(Control)sender] = false;
        }
        static void control_MouseMove(object sender, MouseEventArgs e)
        {
            // only if dragging is turned on
            if (draggables[(Control)sender] == true)
            {
                // calculations of control's new position
                System.Drawing.Point newLocationOffset = e.Location - mouseOffset;
                ((Control)sender).Left += newLocationOffset.X;
                ((Control)sender).Top += newLocationOffset.Y;
            }
        }
    }
}
 
It's pretty simple to use this code. To make control draggable, you just need to write one line of code:
AnyControl.Draggable(true);
and to disable this feature:
AnyControl.Draggable(false);
For example, if your Form contains two checkboxes named checkBox_DragForm and checkBox_DragButton with CheckedChanged event handlers assigned, and button with name btnTest, you may use the following code to enable/disable drag feature on Form (represented by this) or/and button:
 
private void checkBox_DragForm_CheckedChanged(object sender, EventArgs e)
{
    this.Draggable(checkBox_DragForm.Checked);
}
private void checkBox_DragButton_CheckedChanged(object sender, EventArgs e)
{
    btnTest.Draggable(checkBox_DragButton.Checked);
}
 
The code sample is here (VS2010 solution).
Hope this would be helpful.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

InTRUEdeR
Software Developer DevelopEx
Ukraine Ukraine
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Comments and Discussions

 
GeneralMy vote of 5 PinmemberKeyi Zhang12-Jul-13 23:12 
GeneralMy vote of 5 PinmemberHorseman270323-Jan-13 22:18 
AnswerRe: My vote of 5 PinmemberInTRUEdeR23-Jan-13 23:55 
GeneralMy vote of 5 PinmemberLeszekCode27025-Oct-12 21:24 
GeneralMy vote of 5 Pinmembertruongvu_12324-Jun-12 23:20 
GeneralReason for my vote of 5 easy to use PinmemberCalvinWang18-Dec-11 23:17 
GeneralReason for my vote of 5 Very nice. Thanks Pinmemberzenwalker198518-Dec-11 23:15 
GeneralReason for my vote of 5 Excellent!! thank you very much..it... Pinmemberjawed.ace27-Jun-11 23:01 
GeneralReason for my vote of 5 Nice one..thanks!! Pinmemberjawed.ace25-Jun-11 21:23 
GeneralRe: thanks for your vote! PinmemberInTRUEdeR26-Jun-11 4:02 
Generalwow! I like it Pinmemberzhanghaocol1-May-11 22:44 
GeneralReason for my vote of 5 Nice and usefull snippet PinmemberDotNetMastermind12-Apr-11 0:15 
GeneralReason for my vote of 5 Simple, like it. PinmemberKim Togo11-Apr-11 22:16 
GeneralReason for my vote of 5 Cool! Wish I needed to use this some... PinmemberIGood11-Apr-11 13:54 
GeneralMy vote 5 This was really nice. PinmemberJAxelsson10-Apr-11 21:35 
GeneralReason for my vote of 5 Nice PinmemberHiMik200310-Apr-11 20:57 
GeneralReason for my vote of 5 Elegant and simple. Nice. PinmemberChris Trelawny-Ross8-Apr-11 7:32 

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