How to catch multiple key in c#

Question

How can I catch the process that will be done when the user presses the Left-Up-Right-Down direction arrow keys respectively on the Windows Form Application respectively?

Answer 1

One way to do it would be to track them in the KeyUp and KeyDown events. In the sample below, you can just start with a blank form, and then double-click the form to create the Form_Load event. Then add the following private members and Form_Load code, which will set the size of the form and place a label on the form:

// Fields to track keys that are pressed
private bool keyUpPressed = false;
private bool keyDownPressed = false;
private bool keyLeftPressed = false;
private bool keyRightPressed = false;

// A control to display the keypress status
private Label displayLabel = new Label();

private void Form1_Load(object sender, EventArgs e)
{
    // Set the form size and hook up the KeyDown and KeyUp events
    this.Size = new Size {Height = 700, Width = 700};
    this.KeyDown += Form1_KeyDown;
    this.KeyUp += Form1_KeyUp;

    // Put our display label on the form
    displayLabel.Location = new Point {X = 0, Y = 0};
    displayLabel.Size = new Size {Height = 100, Width = 300};
    this.Controls.Add(displayLabel);

    DisplayKeyStatus();
}

Now we can add the code for the KeyDown and KeyUp events, where we simply check which key was pressed (or un-pressed), update our private fields if necessary, and then display the key status:

private void Form1_KeyUp(object sender, KeyEventArgs e)
{
    switch (e.KeyCode)
    {
        case Keys.Left:
            keyLeftPressed = false;
            break;
        case Keys.Up:
            keyUpPressed = false;
            break;
        case Keys.Right:
            keyRightPressed = false;
            break;
        case Keys.Down:
            keyDownPressed = false;
            break;
    }

    DisplayKeyStatus();
}

private void Form1_KeyDown(object sender, KeyEventArgs e)
{
    switch (e.KeyCode)
    {
        case Keys.Left:
            keyLeftPressed = true;
            break;
        case Keys.Up:
            keyUpPressed = true;
            break;
        case Keys.Right:
            keyRightPressed = true;
            break;
        case Keys.Down:
            keyDownPressed = true;
            break;
    }

    DisplayKeyStatus();
}

And finally, the method that will update our label control with the current status of the keys we're tracking:

private void DisplayKeyStatus()
{
    var message = new StringBuilder();
    message.AppendLine("Arrow keys pressed:");
    if (!(keyDownPressed || keyLeftPressed || keyRightPressed || keyUpPressed))
    {
        message.AppendLine(" - None");
    }
    else
    {
        if (keyLeftPressed) message.AppendLine(" - Left Arrow");
        if (keyUpPressed) message.AppendLine(" - Up Arrow");
        if (keyRightPressed) message.AppendLine(" - Right Arrow");
        if (keyDownPressed) message.AppendLine(" - Down Arrow");
    }

    displayLabel.Text = message.ToString();
}