System.ArgumentNullException: Value cannot be null.

Parameter name: replacement

at System.Text.RegularExpressions.Regex.Replace(String input, String replacement, Int32 count, Int32 startat)

at System.Text.RegularExpressions.Regex.Replace(String input, String replacement)

at System.Text.RegularExpressions.Regex.Replace(String input, String pattern, String replacement, RegexOptions options)

when run application in windows 7 ultimate its gives this error.