Identifying substrings in text

I have a large string in which I need to replace specific strings with other values. For example, within this string I might see the following characters: [[sub id=5]]

I am trying to replace those substrings with values, pulled from a table and based on the id. What would be the simplest way to accomplish this. My first thought was to loop through and examine each character and note their positions when they match the pattern. I would then have to identify the id. That would be fairly complicated, however, and there must be a better way. Any thoughts?

Take a look at the replace function

like DataMiser said use string.Replace()