How to distinguish between clicks and double-clicks (Windows Forms .NET)

Typically, a single click initiates a user interface action and a double-click extends the action. For example, one click usually selects an item, and a double-click edits the selected item. However, the Windows Forms click events do not easily accommodate a scenario where a click and a double-click perform incompatible actions, because an action tied to the Click or MouseClick event is performed before the action tied to the DoubleClick or MouseDoubleClick event. This topic demonstrates two solutions to this problem.

One solution is to handle the double-click event and roll back the actions in the handling of the click event. In rare situations you may need to simulate click and double-click behavior by handling the MouseDown event and by using the DoubleClickTime and DoubleClickSize properties of the SystemInformation class. You measure the time between clicks and if a second click occurs before the value of DoubleClickTime is reached and the click is within a rectangle defined by DoubleClickSize, perform the double-click action; otherwise, perform the click action.

To roll back a click action

Ensure that the control you are working with has standard double-click behavior. If not, enable the control with the SetStyle method. Handle the double-click event and roll back the click action as well as the double-click action. The following code example demonstrates a how to create a custom button with double-click enabled, as well as how to roll back the click action in the double-click event handling code.

This code example uses a new button control that enables double-clicks:

C#

public partial class DoubleClickButton : Button
{
    public DoubleClickButton()
    {
        // Set the style so a double click event occurs.
        SetStyle(ControlStyles.StandardClick | ControlStyles.StandardDoubleClick, true);
    }
}

The following code demonstrates how a form changes the style of border based on a click or double-click of the new button control:

C#

public partial class Form1 : Form
{
    private FormBorderStyle _initialStyle;
    private bool _isDoubleClicking;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        _initialStyle = this.FormBorderStyle;

        var button1 = new DoubleClickButton();
        button1.Location = new Point(50, 50);
        button1.Size = new Size(200, 23);
        button1.Text = "Click or Double Click";
        button1.Click += Button1_Click;
        button1.DoubleClick += Button1_DoubleClick;

        Controls.Add(button1);
    }

    private void Button1_DoubleClick(object sender, EventArgs e)
    {
        // This flag prevents the click handler logic from running
        // A double click raises the click event twice.
        _isDoubleClicking = true;
        FormBorderStyle = _initialStyle;
    }

    private void Button1_Click(object sender, EventArgs e)
    {
        if (_isDoubleClicking)
            _isDoubleClicking = false;
        else
            FormBorderStyle = FormBorderStyle.FixedToolWindow;
    }
}

To distinguish between clicks

Handle the MouseDown event and determine the location and time span between clicks using the SystemInformation property and a Timer component. Perform the appropriate action depending on whether a click or double-click takes place. The following code example demonstrates how this can be done.

C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

namespace project
{
    public partial class Form2 : Form
    {
        private DateTime _lastClick;
        private bool _inDoubleClick;
        private Rectangle _doubleClickArea;
        private TimeSpan _doubleClickMaxTime;
        private Action _doubleClickAction;
        private Action _singleClickAction;
        private Timer _clickTimer;

        public Form2()
        {
            InitializeComponent();
            _doubleClickMaxTime = TimeSpan.FromMilliseconds(SystemInformation.DoubleClickTime);

            _clickTimer = new Timer();
            _clickTimer.Interval = SystemInformation.DoubleClickTime;
            _clickTimer.Tick += ClickTimer_Tick;

            _singleClickAction = () => MessageBox.Show("Single clicked");
            _doubleClickAction = () => MessageBox.Show("Double clicked");
        }

        private void Form2_MouseDown(object sender, MouseEventArgs e)
        {
            if (_inDoubleClick)
            {
                _inDoubleClick = false;

                TimeSpan length = DateTime.Now - _lastClick;

                // If double click is valid, respond
                if (_doubleClickArea.Contains(e.Location) && length < _doubleClickMaxTime)
                {
                    _clickTimer.Stop();
                    _doubleClickAction();
                }

                return;
            }

            // Double click was invalid, restart 
            _clickTimer.Stop();
            _clickTimer.Start();
            _lastClick = DateTime.Now;
            _inDoubleClick = true;
            _doubleClickArea = new Rectangle(e.Location - (SystemInformation.DoubleClickSize / 2), 
                                             SystemInformation.DoubleClickSize);
        }

        private void ClickTimer_Tick(object sender, EventArgs e)
        {
            // Clear double click watcher and timer
            _inDoubleClick = false;
            _clickTimer.Stop();

            _singleClickAction();
        }
    }
}

See also

• Overview of using the mouse (Windows Forms .NET)
• Using mouse events (Windows Forms .NET)
• Manage mouse pointers (Windows Forms .NET)
• How to simulate mouse events (Windows Forms .NET)
• Control.Click
• Control.MouseDown
• Control.SetStyle