Draggable Form: Drag a Borderless Form by Clicking Anywhere on the Form

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Introduction

This is useful when you have a form without any border and you want to allow the user to drag it. This is a simple code and doesn't require any explanation at all. But I feel this will be helpful for at least some of you for your development. If you set the BorderStyle of a form to None, no title bar will be available for you to move the form. Here you can make use of this simple code to setup a base form and inherit all your form from this base form. After inheriting from this base form, you will be provided with two more properties in the Property Editor, Draggable (boolean) and ExcludeList (String). By setting the Draggable property to true, you are enabling the draggable feature of the form. You can pass a comma separated list of controls for which you don't want the draggable feature to be enabled. That is by default if Draggable=true, the form will be draggable by clicking anywhere on the form and any controls on the form. And naturally, you don't want the form draggable while a user clicks on a Button on it. So you can pass the name of the button to this list. E.g.: ExcludeList = "button1, button2, button3";.

FormBase.cs

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace DraggableForm
{    
    public class FormBase :Form
    {
        #region Declarations
        private bool drag = false;
        private Point start_point = new Point(0, 0);
        private bool draggable = true;
        private string exclude_list = "";

        /// <SUMMARY>
        /// Required designer variable.
        /// </SUMMARY>
        private System.ComponentModel.IContainer components = null;
        #endregion

        #region Constructor , Dispose

        public FormBase()
        {
            InitializeComponent();

        //
        //Adding Mouse Event Handlers for the Form
        //
        this.MouseDown += new MouseEventHandler(Form_MouseDown);
            this.MouseUp += new MouseEventHandler(Form_MouseUp);
            this.MouseMove += new MouseEventHandler(Form_MouseMove);
        }     

        /// <SUMMARY>
        /// Clean up any resources being used.
        /// </SUMMARY>
        /// true if managed resources should be disposed; otherwise, false.
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #endregion

        #region Windows Form Designer generated code

        /// <SUMMARY>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </SUMMARY>
        private void InitializeComponent()
        {
            // 
            // FormBase
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(369, 182);
            this.Name = "FormBase";
            this.Text = "AlerterForm";
        }

        #endregion

        #region Overriden Functions

        protected override void OnControlAdded(ControlEventArgs e)
        {
            //
            //Add Mouse Event Handlers for each control added into the form,
            //if Draggable property of the form is set to true and the control
            //name is not in the ExcludeList.Exclude list is the comma separated
            //list of the Controls for which you do not require the mouse handler 
            //to be added. For Example a button.  
            //
            if (this.Draggable && (this.ExcludeList.IndexOf(e.Control.Name) == -1))
            {
                e.Control.MouseDown += new MouseEventHandler(Form_MouseDown);
                e.Control.MouseUp += new MouseEventHandler(Form_MouseUp);
                e.Control.MouseMove += new MouseEventHandler(Form_MouseMove);
            }
            base.OnControlAdded(e);
        }

        #endregion

        #region Event Handlers

        void Form_MouseDown(object sender, MouseEventArgs e)
        {          
            //
            //On Mouse Down set the flag drag=true and 
            //Store the clicked point to the start_point variable
            //
            this.drag = true;            
            this.start_point = new Point(e.X, e.Y);
        }

        void Form_MouseUp(object sender, MouseEventArgs e)
        {
            //
            //Set the drag flag = false;
            //
            this.drag = false;
        }

        void Form_MouseMove(object sender, MouseEventArgs e)
        {
            //
            //If drag = true, drag the form
            //
            if (this.drag)
            {
                Point p1 = new Point(e.X, e.Y);
                Point p2 = this.PointToScreen(p1);
                Point p3 = new Point(p2.X - this.start_point.X, 
                                     p2.Y - this.start_point.Y);
                this.Location = p3;
            }
        }

        #endregion

        #region Properties

        public string ExcludeList
        {
            set
            {
                this.exclude_list = value;
            }
            get
            {
                return this.exclude_list.Trim();
            }
        }

        public bool Draggable
        {
            set
            {
                this.draggable = value;
            }
            get
            {
                return this.draggable;
            }
        }

        #endregion
    }
}

Now, you can simply inherit your form from the FormBase and voila, it'll be draggable. If you have any suggestions, please mail me. I love to have friends and that's the reason I am here. Happy coding!

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