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How to: Distinguish Between Clicks and Double-Clicks

Typically, a single click initiates a user interface (UI) 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.

    using System;
    using System.ComponentModel;
    using System.Drawing;
    using System.Text;
    using System.Windows.Forms;
    
    namespace MouseRollBackSingleClick
    {
        public class Form1 : Form
        {
            private DoubleClickButton button1;
            private FormBorderStyle initialStyle;
           
            public Form1()
            {
                initialStyle = this.FormBorderStyle;
                this.ClientSize = new System.Drawing.Size(292, 266);
                button1 = new DoubleClickButton();
                button1.Location = new Point (40,40);
                button1.Click += new EventHandler(button1_Click);
                button1.AutoSize = true;
                this.AllowDrop = true;
                button1.Text = "Click or Double Click";
                button1.DoubleClick += new EventHandler(button1_DoubleClick);
                this.Controls.Add(button1);
               
            }
    
            
            // Handle the double click event.
            void button1_DoubleClick(object sender, EventArgs e)
            {
                // Change the border style back to the initial style.
                this.FormBorderStyle = initialStyle;
                MessageBox.Show("Rolled back single click change.");
            }
    
            // Handle the click event.
            void button1_Click(object sender, EventArgs e)
            {
                this.FormBorderStyle = FormBorderStyle.FixedToolWindow;
            }
    
            [STAThread]
            static void Main()
            {
                Application.EnableVisualStyles();
                Application.Run(new Form1());
            }
    
            
        }
        public class DoubleClickButton : Button
        {
            public DoubleClickButton() : base()
            {
                // Set the style so a double click event occurs.
                SetStyle(ControlStyles.StandardClick | 
                    ControlStyles.StandardDoubleClick, true);
            }
        }
    }
    
    

To distinguish between clicks in the MouseDown event

  • Handle the MouseDown event and determine the location and time span between clicks using the appropriate SystemInformation properties 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.

    using System;
    using System.Drawing;
    using System.Windows.Forms;
    
    namespace SingleVersusDoubleClick
    {
        class Form1 : Form
        {
            private Rectangle hitTestRectangle = new Rectangle();
            private Rectangle doubleClickRectangle = new Rectangle();
            private TextBox textBox1 = new TextBox();
            private Timer doubleClickTimer = new Timer();
            private ProgressBar doubleClickBar = new ProgressBar();
            private Label label1 = new Label();
            private Label label2 = new Label();
            private bool isFirstClick = true;
            private bool isDoubleClick = false;
            private int milliseconds = 0;
    
            [STAThread]
            public static void Main()
            {
                Application.EnableVisualStyles();
                Application.Run(new Form1());
            }
    
            public Form1()
            {
                label1.Location = new Point(30, 5);
                label1.Size = new Size(100, 15);
                label1.Text = "Hit test rectangle:";
    
                label2.Location = new Point(30, 70);
                label2.Size = new Size(100, 15);
                label2.Text = "Double click timer:";
    
                hitTestRectangle.Location = new Point(30, 20);
                hitTestRectangle.Size = new Size(100, 40);
    
                doubleClickTimer.Interval = 100;
                doubleClickTimer.Tick +=
                    new EventHandler(doubleClickTimer_Tick);
    
                doubleClickBar.Location = new Point(30, 85);
                doubleClickBar.Minimum = 0;
                doubleClickBar.Maximum = SystemInformation.DoubleClickTime;
    
                textBox1.Location = new Point(30, 120);
                textBox1.Size = new Size(200, 100);
                textBox1.AutoSize = false;
                textBox1.Multiline = true;
    
                this.Paint += new PaintEventHandler(Form1_Paint);
                this.MouseDown += new MouseEventHandler(Form1_MouseDown);
                this.Controls.AddRange(new Control[] { doubleClickBar, textBox1, 
                    label1, label2 });
            }
    
            // Detect a valid single click or double click.
            void Form1_MouseDown(object sender, MouseEventArgs e)
            {
                // Verify that the mouse click is in the main hit
                // test rectangle.
                if (!hitTestRectangle.Contains(e.Location))
                {
                    return;
                }
    
                // This is the first mouse click.
                if (isFirstClick)
                {
                    isFirstClick = false;
    
                    // Determine the location and size of the double click 
                    // rectangle area to draw around the cursor point.
                    doubleClickRectangle = new Rectangle(
                        e.X - (SystemInformation.DoubleClickSize.Width / 2),
                        e.Y - (SystemInformation.DoubleClickSize.Height / 2),
                        SystemInformation.DoubleClickSize.Width,
                        SystemInformation.DoubleClickSize.Height);
                    Invalidate();
    
                    // Start the double click timer.
                    doubleClickTimer.Start();
                }
    
                // This is the second mouse click.
                else
                {
                    // Verify that the mouse click is within the double click
                    // rectangle and is within the system-defined double 
                    // click period.
                    if (doubleClickRectangle.Contains(e.Location) &&
                        milliseconds < SystemInformation.DoubleClickTime)
                    {
                        isDoubleClick = true;
                    }
                }
            }
    
            void doubleClickTimer_Tick(object sender, EventArgs e)
            {
                milliseconds += 100;
                doubleClickBar.Increment(100);
    
                // The timer has reached the double click time limit.
                if (milliseconds >= SystemInformation.DoubleClickTime)
                {
                    doubleClickTimer.Stop();
    
                    if (isDoubleClick)
                    {
                        textBox1.AppendText("Perform double click action");
                        textBox1.AppendText(Environment.NewLine);
                    }
                    else
                    {
                        textBox1.AppendText("Perform single click action");
                        textBox1.AppendText(Environment.NewLine);
                    }
    
                    // Allow the MouseDown event handler to process clicks again.
                    isFirstClick = true;
                    isDoubleClick = false;
                    milliseconds = 0;
                    doubleClickBar.Value = 0;
                }
            }
    
            // Paint the hit test and double click rectangles.
            void Form1_Paint(object sender, PaintEventArgs e)
            {
                // Draw the border of the main hit test rectangle.
                e.Graphics.DrawRectangle(Pens.Black, hitTestRectangle);
    
                // Fill in the double click rectangle.
                e.Graphics.FillRectangle(Brushes.Blue, doubleClickRectangle);
            }
        }
    }
    
    

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