Changing KeyCode in OnKeyDown

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Guest

I have sub-classed the TextBox. In its OnKeyDown event I can intercept key
strokes, examine them, etc. When I get a certain keycode (e.g., 'A') I want
to change it to another unicode key from a different code page (e.g.,
"\u2801"). But the KeyCode, KeyData, and KeyValue properties of KeyEventArgs
are all only getters. They are read only and thus do not permit changing the
assigned KeyCode. My question is this: How do I change the KeyCode of the
KeyEvenetArgs to be a different key? I tired to call base.OnKeyDown() passing
a new instance of KeyEventArgs, but the constructor for KeyEventArgs() takes
an instance of Keys, and THAT constructor takes no argument. Even if I create
an instance of Keys, then I'm faced with the read only nature of KeyCode,
KeyData, etc. It seems to be a vicious circle. Any help would be appreciated.
 
The Keys required by KeyEventArgs is an enumerated type, you don't use
the constructor. For example, to simulate pressing Enter:
new KeyEventArgs(Keys.Enter)

I don't think you'll be able to do your code page translation with the
KeyEventArgs class.

Do you have to use OnKeyDown? Would OnKeyPress meet your needs?

protected override void OnKeyPress(KeyPressEventArgs e)
{
// perform your logic to get the key from another codepage
Char newChar = translateChar(e.KeyChar);
base.OnKeyPress (new KeyPressEventArgs(newChar));
}


Joshua Flanagan
http://flimflan.com/blog
 
Thanks, Joshua, for your suggestion. This does work as you say. One problem
remains, and that is that the cursor (or caret) does not advance past the
newly inserted character. Guess I'll now have to work on developing a custom
Caret class that I will control via code. Thanks again for your help.
 
Actually, on closer inspection, it does not work. I still had remnants of
code left in OnKeyDown and that was getting in the way. In OnKeyDown I can
call a method that accepts the character I want to display instead of the
character that was typed, and that method just concatenates that new char to
the existing chars already in the TextBox. Although this does work, the
cursor (as I mentioned) does not advance. But calling
base.OnKeyPress(newchar) does not render the new character. The typed
character is the one that shows up.
 
This worked for me

protected override void OnKeyPress(KeyPressEventArgs e) {
//translate your character - I use ToUpper just for an example
Char newChar = Char.ToUpper(e.KeyChar);
this.Text += newChar;
// set the caret to the end
this.SelectionStart = this.Text.Length;
// tell the rest of the event chain there is no further work to do
e.Handled = true;
// I'm not sure if this line is necessary. it works without it
base.OnKeyPress (new KeyPressEventArgs(newChar));
}
 
Thanks, Joshua. I will give it a try and report back. I have to go teach a
class right now. P.S. Enjoyed your web site.
 
Yep. Works good. Thanks again.

Joshua Flanagan said:
This worked for me

protected override void OnKeyPress(KeyPressEventArgs e) {
//translate your character - I use ToUpper just for an example
Char newChar = Char.ToUpper(e.KeyChar);
this.Text += newChar;
// set the caret to the end
this.SelectionStart = this.Text.Length;
// tell the rest of the event chain there is no further work to do
e.Handled = true;
// I'm not sure if this line is necessary. it works without it
base.OnKeyPress (new KeyPressEventArgs(newChar));
}
Click to expand...
 
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