Invert the case of a mixed case string (can I use regex?)

Posted on 2006-06-26
Last Modified: 2008-01-09

I have a string that contains a mixed bag of upper and lowercase letters.

I need to invert these (upper to lower, lower to upper) so my question is do I have to iterate through each letter and swap it or can I use a smaller, cleaner method (perhaps using a regex expression??).

Many thanks.

Question by:JAMES
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LVL 10

Expert Comment

ID: 16983403
i gess you will have to iterate thrtough each char, because there is no method to invert the case of the letters in string
LVL 13

Accepted Solution

devsolns earned 500 total points
ID: 16983434
Put this in a method or what have you,

                string text = "SoMe CaMEL cAse TEXT.";
                char[] textarray = text.ToCharArray();
                for(int i = 0; i < textarray.Length; i++)
                    if((int)textarray[i] >= 65 && (int)textarray[i] <= 90)
                        textarray[i] = (char)((int)textarray[i] + 32);
                    else if ((int)textarray[i] >= 97 && (int)textarray[i] <= 122)
                        textarray[i] = (char)((int)textarray[i] - 32);
                string newText = new string(textarray);

Expert Comment

ID: 16983458
Regular Expression is basically to model the condition or pattern and use that RegEx to check the input and decide if that satisfies the pattern or condition you want it to.

If you dont want to compare string in turn, You can Consider the use of BitMasking going to the Byte Level.
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Author Comment

ID: 16983516
OK - accepting there is no regex expression and no intrinsic method Dev's method works great - thank you!

Many thanks for your help dk but I am sure you will understand if i give the points to Dev for a such a detailed answer.


Expert Comment

ID: 16983526
     string s="ABcdEFgh";
                  char []c=s.ToCharArray();                  
                int c1=0;
                        else if(char.IsUpper(c[c1]))
                  s=new string(c);
LVL 13

Expert Comment

ID: 16983922
pradeepsudharsan & everyone,

my implementation of the method runs on average 60% faster than pradeepsudharsan version using the IsLower & IsUpper methods.

Test using 1 million iterations of a couple hundred length string.

-my version
1296 ms
1268 ms
1353 ms

avg:1305 milliseconds

-version using ToUpper & ToLower
2181 ms
2165 ms
2152 ms

avg:2166  milliseconds
LVL 13

Expert Comment

ID: 16983930
Kinda suprised by the diff in speed.

Author Comment

ID: 16983942
Thanks for the test results.

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