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

Question

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.

The KeyPress event is not raised by noncharacter keys; however, the noncharacter keys do raise the KeyDown and KeyUp events.

https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.control.keypress

KeyPress is only fired by printable characters and is fired after the KeyDown event. Depending on the typing delay settings there can be multiple KeyDown and KeyPress events but only one KeyUp event.

KeyDown
KeyPress
KeyUp

KeyPress is a higher level of abstraction than KeyDown (and KeyUp). KeyDown and KeyUp are hardware related: the actual action of a key on the keyboard. KeyPress is more "I received a character from the keyboard".

Keydown is pressing the key without releasing it, Keypress is a complete press-and-release cycle.

Put another way, KeyDown + KeyUp = Keypress