C#

public string StripPunctuation(string source)
{
   // any chars you want to keep, put between the [] brakets.
   // i think the ^ has to remain where it is though.
   string pattern = "[^a-zA-Z ]";
 
   // use regular expressions.
   System.Text.RegularExpressions.Regex regex;
   regex = new System.Text.RegularExpressions.Regex(pattern);
   return regex.Replace(source, "");
}

string pattern = "[^a-zA-Z ]";
System.Text.RegularExpressions.Regex regex;
regex = new System.Text.RegularExpressions.Regex(pattern);
return regex.Replace(source, "");

Regex regex = new Regex("[^a-zA-z]");
regex.Replace(source, "");