[EpicTTR]

In Visual C#.NET, I want to change the color of specific text when it is typed in to a rich text box.

For example, I might want to color the world "hi", so when the user is typing in the rich text box, if they type "hi" it would immediately change colors and the word "hi" would be a different color from all the other text in the rich text box.

How would I do that?

I've tried something like:

            richTextBox.Select(rtxtMain.Text.IndexOf("hi"), "hi".Length);
            richtextBox.SelectionColor = Color.Aqua;

Its error/warning free, but when I debug it and type in "hi" the program just crashes.

So, how would I change the color of specific words (but not that of other words) while a user is typing into a rich text box?

[EpicTTR]

Bump, please help me.

[EpicTTR]

    rtxtMain.Select(rtxtMain.Text.IndexOf("hi"), "hi".Length);
    rtxtMain.SelectionColor = Color.Aqua;
    rtxtMain.SelectionFont = new Font("Times New Roman", FontStyle.Bold);

That was the code I was told to use, however, I have some problems with it.

By the way. "rtxtMain" is the rich textbox.
Anyways, its error/warning free until I run my program, as soon as I try to type in the rich text box, the program crashes, highlighting this line of code:

    rtxtMain.Select(rtxtMain.Text.IndexOf("hi"), "hi".Length);

And saying:

Quote

InvalidArgument=Value of '-1' is not valid for 'start'.
Parameter name: start

So, what exactly is wrong, and how do I fix it?

[Martyr2]

You have to check the index before you can stick it into the select. What it is saying is that when you type it does a search for "hi" and if it doesn't find it (which it won't after you type just "h") it then returns -1 and that is not valid.

if (rtxtMain.Text.IndexOf("hi") > -1) {
   // Now do the select and color change
}

Make sure that the word is actually found in the text first before you attempt to select it and change its color. Makes sense right? If it is not found, you don't want to attempt to do a select.

[EpicTTR]

Martyr2, on 17 June 2011 - 10:20 PM, said:

You have to check the index before you can stick it into the select. What it is saying is that when you type it does a search for "hi" and if it doesn't find it (which it won't after you type just "h") it then returns -1 and that is not valid.

if (rtxtMain.Text.IndexOf("hi") > -1) {
   // Now do the select and color change
}

Make sure that the word is actually found in the text first before you attempt to select it and change its color. Makes sense right? If it is not found, you don't want to attempt to do a select.

Yeah, but now when I do that:

            if (rtxtMain.Text.IndexOf("hi") > -1)
            {
                rtxtMain.Select(rtxtMain.Text.IndexOf("hi"), "hi".Length);
                rtxtMain.SelectionColor = Color.BlueViolet

It just makes my typing sorta go crazy (cursor jumps around) and in the end it just deletes the word instead of coloring it...

How do I fix it?

Martyr2, on 17 June 2011 - 10:20 PM, said:

You have to check the index before you can stick it into the select. What it is saying is that when you type it does a search for "hi" and if it doesn't find it (which it won't after you type just "h") it then returns -1 and that is not valid.

if (rtxtMain.Text.IndexOf("hi") > -1) {
   // Now do the select and color change
}

Make sure that the word is actually found in the text first before you attempt to select it and change its color. Makes sense right? If it is not found, you don't want to attempt to do a select.

Yeah, but now when I do that:

            if (rtxtMain.Text.IndexOf("hi") > -1)
            {
                rtxtMain.Select(rtxtMain.Text.IndexOf("hi"), "hi".Length);
                rtxtMain.SelectionColor = Color.BlueViolet

It just makes my typing sorta go crazy (cursor jumps around) and in the end it just deletes the word instead of coloring it...

How do I fix it?

[Martyr2]

What event are you putting this into? A keypress or change event or something else? If you put it in a change event then the fact you are selecting and altering text through the program may kick off other change events and lead to crazy stuff.

[EpicTTR]

Martyr2, on 17 June 2011 - 10:43 PM, said:

What event are you putting this into? A keypress or change event or something else? If you put it in a change event then the fact you are selecting and altering text through the program may kick off other change events and lead to crazy stuff.

Well, my goal is to have it change as soon as the user types it in, so I put it in the change event for the box. Is there a better way to do it?

[EpicTTR]

Martyr2, on 17 June 2011 - 10:43 PM, said:

What event are you putting this into? A keypress or change event or something else? If you put it in a change event then the fact you are selecting and altering text through the program may kick off other change events and lead to crazy stuff.

I think the problem is, that I never deselect the word, so it replaces the word with a space (once I type in the space). So how do I deselect the word before that happens?

[Curtis Rutland]

Duplicate posts merged. Please do not open multiple threads for the same topics.

[Milto]

I've had this problem before, with colors and italics. Maybe there is an issue with the iteration through the rtBox in the search for "hi". I'm trying to figure this out myself. Will revisit.

As for having these actions done while typing, a keyPress(which I believe someone here mentioned already) event with these statements should be sufficient. You could also use a timer.

Good luck.