How do I replace unknown characters in a string? Wildcard?

Question

I have a string .. let's say:

string MyString = "SELECT Stuff FROM Table WHERE Code = "Foo" AND DATE=20120101";

I want to replace 20120101 with a ? . But, the 20120101 string I search for won't always be the same. It will always start with a 2 , and always contain 8 characters. It may be 20121225, 20130510, etc.

Can I use wildcards somehow? As in:

string Fixed = MyString.Replace("2*******", "?");

What I'm looking for is this result:

MyString = "SELECT Stuff FROM Table WHERE Code = "Foo" AND DATE=?";

Answer 1

You can use RegEx:

Regex.Replace(input,@"DATE=""\d*""", "?");

However, if this is a SQL query, it would be better to use a parameterized query to avoid SQL injection attacks and so forth. It's the industry standard way of doing these kinds of things.

Answer 2

string Fixed = Regex.Replace( MyString, @"DATE=2\d{7}", "DATE=?" ); 

或者，使用正向后看

 Replace( MyString, @"(?<=DATE=)2\d{7}", "?" ); 

Answer 3

A regex that matches the entire string would probably be ideal for preventing SQL injection attacks. To accomplish this you will use the start of line ( ^ ) and end of line ( $ ) characters.

This will match something which is 5 or 6 digits long, and capture everything besides the first.

^([0-9])([0-9]{4,5})$

If you want to capture something that starts with 2, and is always 6 digits long; you could use 2 instead of the character class:

^(2)([0-9]{5})$

This technique will not allow you to use the replace method directly, you will need to extract the capture groups 1 and 2, replace all the characters in group 2 with ?, and then concatenate them. Something like:

matcher.group(1) + Regex.replace(m.group(2) , ".", "?")

Again, not carefully matching the entire string will result in SQL injection.

The input, (DELETE * FROM Users Where 1=1) 200000 , would match these regex, and be merrily inserted into your SQL query as: (DELETE * FROM Users Where 1=1) 2?????

Answer 4

You could use the Regex replace method:

    string oldstring = "20120101";
    string newstring = Regex.Replace(oldstring, @"^2[0-9]{7}", "?");

Answer 5

So is this what you are looking for?

string MyString = "SELECT Stuff FROM Table WHERE Code = {0} AND DATE={1}";

This will allow you to use the same string with whatever you want in {0} and {1} with something like:

String.Format(MyString, codeString, dateString);

You can reuse the query string with whichever parameters you'd like.