How to replace lower case with upper case using regular Expression?

Question

I have the string a with full of lower case. I tried to use the following Expression to replace lower case with upper case but it does not work as I want. How can I turn the lower case into upper case in string a?

using System.Text.RegularExpressions;

string a = "pieter was a small boy";
a = Regex.Replace(a, @"\B[A-Z]", m => " " + m.ToString().ToUpper());

Answer 1

You have two problems here:

1. Your pattern needs to use \\b instead of \\B . See this question for more info.
2. Since your string is in lowercase and your pattern only matches uppercase ( [AZ] ) you need to use RegexOptions.IgnoreCase to make your code work.

---

string a = "pieter was a small boy";
var regex = new Regex(@"\b[A-Z]", RegexOptions.IgnoreCase);
a = regex.Replace(a, m=>m.ToString().ToUpper());

The output of the above code is:

Pieter Was A Small Boy

Answer 2

If you are trying to convert all the characters in the string to upper case then simply do string.ToUpper()

string upperCasea = a.ToUpper();

If you want to do a case insensitive replace then use Regex.Replace Method (String, String, MatchEvaluator, RegexOptions) :

a = Regex.Replace(a, 
                  @"\b[A-Z]", 
                  m => " " + m.ToString().ToUpper(), 
                  RegexOptions.IgnoreCase);

Answer 3

Using Regular Expression as you wanted,

a = Regex.Replace(a, @"\b[a-z]", m => m.ToString().ToUpper());

Source

Answer 4

Regex.Replace(inputStr, @"[^a-zA-Z0-9_\\]", "").ToUpperInvariant();

Answer 5

It works fine for you :

string a = "pieter was a small boy";
a = a.ToUpper();