title: How do you in C# read a text file for a specific string, and if it doesnt exist write it
body: <p>I know how to read append and write with Streamreader/Steamwriter.  But I am having issues with getting my program to read the text file and check for a specific string of data.  If it doesnt exist write it at the end.  Any Ideas?  Im trying to do this to a specific file, via web page button using Server.MapPath.</p>