how to replace a character in a string for one instance

[Bob West]

Hi I'm trying to change a strings character for one instance only
Ex

 
string hexNum1 = "F00D";
 

How do I just change the second to last 0 only with out changing the other zero?

[GaryTexmo]

I don't know that you can with the built in functions. That said, it should be fairly easy for you to write your own.

The methods you'll be interested in are:

string.IndexOf
string.SubString
string.Replace

You can use these to find the occurrences of a particular string, slice it up, replace what you want to replace, then rebuild it. I'm also going to point out that if you care about efficiency, you might want to look at the StringBuilder class. The reason for this is that C# strings are immutable... when you change one, you're actually creating an entirely new string. A StringBuilder can be modified, then return the complete string result at the end with the ToString method.

Something to think about... give it a try and let us know if you need a hand working through the problem :)