Can text be read and written to a text file?

I need to be able to have the C# code in my website store text characters from a string variable in a new “.txt” file like those created with Microsoft Notepad software without any formatting.  This file needs to be stored in a sub directory of where my web page files are stored in a hosting server.  I also need to be able to have my web page code read the text characters from the file so that they can be stored and retrieved from a string variable.  Is this possible?
 
Maurice