Using Regex.Replace

Say you want to get the username from a fully qualified username such as MyDomain\AUser

Most developers would turn to SubString and LastIndexOf functions .. for example

string userName = @"MyDomain\AUser";
string result = userName.SubString(userName.LastIndexOf(@"\"));

Instead of using these functions you should consider the use of Regex.Replace(). Here's how you'd do it:

string userName = @"MyDomain\AUser";
string result = Regex.Replace(userName, @".*\\(.*?)$", "$1");

You can see from the example above that the Replace method is matching on the string and just returning the first Group. (.*?) is represented in the replace expression by $1

As I'm sure you can imagine, the possibilities here are endless... example

string userName = @"MyDomain\AUser";
string result = Regex.Replace(userName, @".*\\(.*?)$", "Welcome back $1. Nice to see you again");
 

I hope you find uses for Regex.Replace in your applications.