使用正则表达式查找正则表达式中的正则表达式点

In an asp.net application, I need to validate user input against a configurable regular expression. I have a list of such regular expressions in a db, and it is user configurable, not fixed. My problem is that in these regexps, the dot is intented to match not any character, but any 'reasonable' character (reasonable in that context: letters, digits and some other ascii character). So the validation process is carried on in 2 stepsIn an asp.net application, I need to validate u