Difference Between the Keydown Event, Keypress Event and Keyup Event in Visual Studio

Difference between the KeyDown Event, KeyPress Event and KeyUp Event in Visual Studio

• KeyDown: happens when the person presses a key (when the keyboard first detects a finger on a key, this happens when the key is pressed down).

• KeyPress: happens when a key is pressed and then released.

• KeyUp: happens when the key is released

You are right that all of these events occur when a key is pressed and then released, in the order I described above.

What's the difference between KeyDown and KeyPress in .NET?

There is apparently a lot of misunderstanding about this!

The only practical difference between KeyDown and KeyPress is that KeyPress relays the character resulting from a keypress, and is only called if there is one.

In other words, if you press A on your keyboard, you'll get this sequence of events:

1. KeyDown: KeyCode=Keys.A, KeyData=Keys.A, Modifiers=Keys.None
2. KeyPress: KeyChar='a'
3. KeyUp: KeyCode=Keys.A

But if you press Shift+A, you'll get:

1. KeyDown: KeyCode=Keys.ShiftKey, KeyData=Keys.ShiftKey, Shift, Modifiers=Keys.Shift
2. KeyDown: KeyCode=Keys.A, KeyData=Keys.A | Keys.Shift, Modifiers=Keys.Shift
3. KeyPress: KeyChar='A'
4. KeyUp: KeyCode=Keys.A
5. KeyUp: KeyCode=Keys.ShiftKey

If you hold down the keys for a while, you'll get something like:

1. KeyDown: KeyCode=Keys.ShiftKey, KeyData=Keys.ShiftKey, Shift, Modifiers=Keys.Shift
2. KeyDown: KeyCode=Keys.ShiftKey, KeyData=Keys.ShiftKey, Shift, Modifiers=Keys.Shift
3. KeyDown: KeyCode=Keys.ShiftKey, KeyData=Keys.ShiftKey, Shift, Modifiers=Keys.Shift
4. KeyDown: KeyCode=Keys.ShiftKey, KeyData=Keys.ShiftKey, Shift, Modifiers=Keys.Shift
5. KeyDown: KeyCode=Keys.ShiftKey, KeyData=Keys.ShiftKey, Shift, Modifiers=Keys.Shift
6. KeyDown: KeyCode=Keys.A, KeyData=Keys.A | Keys.Shift, Modifiers=Keys.Shift
7. KeyPress: KeyChar='A'
8. KeyDown: KeyCode=Keys.A, KeyData=Keys.A | Keys.Shift, Modifiers=Keys.Shift
9. KeyPress: KeyChar='A'
10. KeyDown: KeyCode=Keys.A, KeyData=Keys.A | Keys.Shift, Modifiers=Keys.Shift
11. KeyPress: KeyChar='A'
12. KeyDown: KeyCode=Keys.A, KeyData=Keys.A | Keys.Shift, Modifiers=Keys.Shift
13. KeyPress: KeyChar='A'
14. KeyDown: KeyCode=Keys.A, KeyData=Keys.A | Keys.Shift, Modifiers=Keys.Shift
15. KeyPress: KeyChar='A'
16. KeyUp: KeyCode=Keys.A
17. KeyUp: KeyCode=Keys.ShiftKey

Notice that KeyPress occurs in between KeyDown and KeyUp, not after KeyUp, as many of the other answers have stated, that KeyPress is not called when a character isn't generated, and that KeyDown is repeated while the key is held down, also contrary to many of the other answers.

Examples of keys that do not directly result in calls to KeyPress:

• Shift, Ctrl, Alt
• F1 through F12
• Arrow keys

Examples of keys that do result in calls to KeyPress:

• A through Z, 0 through 9, etc.
• Spacebar
• Tab (KeyChar='\t', ASCII 9)
• Enter (KeyChar='\r', ASCII 13)
• Esc (KeyChar='\x1b', ASCII 27)
• Backspace (KeyChar='\b', ASCII 8)

For the curious, KeyDown roughly correlates to WM_KEYDOWN, KeyPress to WM_CHAR, and KeyUp to WM_KEYUP. WM_KEYDOWN can be called fewer than the the number of key repeats, but it sends a repeat count, which, IIRC, WinForms uses to generate exactly one KeyDown per repeat.

KeyDown event in a Form

You can override ProcessCmdKey to handle key presses on the form level.

See this question for more details and examples:
Hotkey (not global) in Windows Forms .NET

Why DateTimePicker won't trigger keyDown and KeyPress events with the tab key?

The Tab key is used for navigation. Moving the focus from one control to another. So your KeyDown event handler can never see it, the keystroke is intercepted and used before that. You could subscribe the PreviewKeyDown event and set the e.IsInputKey = true as a workaround, check the MSDN sample code in the linked article for code.

But it is the wrong event to use anyway, you'd still want this to work when the user changes focus with the mouse instead of the keyboard. So use the Enter event instead.

Do beware that both approaches have the same problem, the focus might already be on the month part from previous usage of the control so now your code will incorrectly move it to the year part. And you can't find out what part has the focus, that is up a creek without a good paddle. A very ugly workaround for that is to change the Format property, and back, that forces the control to re-create the control window and that always resets the focus. Use BeginInvoke() to run that code. Perhaps more constructively, consider to just not display the day if you are only interested in month+year, CustomFormat property.

Sample code that implements the focus hack:

Private Sub DateTimePicker1_Enter(sender As Object, e As EventArgs) Handles DateTimePicker1.Enter
    Me.BeginInvoke(
        New Action(Sub()
                       '' Hack to reset focus
                       DateTimePicker1.Format = DateTimePickerFormat.Long
                       DateTimePicker1.Format = DateTimePickerFormat.Short
                       DateTimePicker1.Focus()
                       SendKeys.Send("{Right}")
                   End Sub))
End Sub

Difference between the KeyDown Event, KeyPress Event and KeyUp Event in Visual Studio

• KeyDown: happens when the person presses a key (when the keyboard first detects a finger on a key, this happens when the key is pressed down).

• KeyPress: happens when a key is pressed and then released.

• KeyUp: happens when the key is released

You are right that all of these events occur when a key is pressed and then released, in the order I described above.

Double result when using keypress

You don't need to append keychar in your result.Text (Assuming result is your TextBox item) as you have written in line result.Text += e.KeyChar.ToString();. That's the line which is doubling your input.

Remove it and it'll work as expected.

---

Related Topics