C#

string test = "A";

test = string.Format("{0}", (char)(test[0] + 1));

string oldStr = "Hello";
string newStr = "";
char[] hold = oldStr.ToCharArray();
for (int i = 0; i < hold.Length; i++)
{
    newStr += (char)(hold[i] + 1);
}
MessageBox.Show(oldStr + Environment.NewLine + newStr);

private string IncString(string s)
        {
            if (String.IsNullOrEmpty(s)) return "A";
            if (s[s.Length - 1] == 'Z')
            {
                if (s.Length == 1) return "AA";
                else return IncString(s.Substring(0, s.Length - 1)) + "A";
            }
            else
            {
                if (s.Length == 1) return IncChar(s[0]).ToString();
                else return s.Substring(0, s.Length - 1) + IncChar(s[s.Length - 1]).ToString();
            }
        }

        private char IncChar(char c)
        {
            return (char)((int)c + 1);
        }

Mark Nischalke wrote:

You should use DialogResult

if( MessaseBox.Show() == DialogResult.Yes )

Nader Elshehabi wrote:

You can inherit your own custom MessageBox from that class, or make your own form to simulate the MessageBox you want to display