How to change Symbol Number to Upper Case... in the "richTextBox.Lines" array?
<p>How to change to Upper Case SymbolNumber... in the "richTextBox.Lines" array?
I have a problem with "ToUpper()", because it is working only with the "String" data, but I need change the case to upper by number of the symbol.</p>

<p>For example...
I have a text...
"qwerty \n
 asdfgh \n
 zxcvbn"
...in the "richTextBox.Text", and I need to change case of symbol #3 in each line (e, d, c) to Upper.</p>
