Escape Special Character in Regex

You can use .NET's built in Regex.Escape for this. Copied from Microsoft's example:

string pattern = Regex.Escape("[") + "(.*?)]"; 
string input = "The animal [what kind?] was visible [by whom?] from the window.";

MatchCollection matches = Regex.Matches(input, pattern);
int commentNumber = 0;
Console.WriteLine("{0} produces the following matches:", pattern);
foreach (Match match in matches)
   Console.WriteLine("   {0}: {1}", ++commentNumber, match.Value);  

// This example displays the following output: 
//       \[(.*?)] produces the following matches: 
//          1: [what kind?] 
//          2: [by whom?]

you can use Regex.Escape for the user's input