C# Clean String Input

You can use the CleanInput method defined in this example to strip potentially harmful characters that have been entered into a text field that accepts user input. In this case, CleanInput strips out all non-alphanumeric characters except periods (.), at symbols (@), and hyphens (-), and returns the remaining string.

using System;
using System.Text.RegularExpressions;

public class Example
{
    protected static string CleanInput (string strIn)
		{
		// Replace invalid characters with empty strings.
		try
			{
			return System.Text.RegularExpressions.Regex.Replace(strIn, @"[^w.@ -]", "",
								 RegexOptions.None, TimeSpan.FromSeconds(1.5));
			}
		// If we timeout when replacing invalid characters,
		// we should return Empty.
		catch (System.Text.RegularExpressions.RegexMatchTimeoutException)
			{
			return String.Empty;
			}
		}
}

Reference: http://msdn.microsoft.com/en-us/library/844skk0h(v=vs.110).aspx