How can I create and append to a tab-delimited file in C#?
Here is a fast and very easy to use library that allows you to specify the delimiter. It is hosted on CodeProjects. This gives a matrix like access to your delimited file (e.g. a 2 dimensional array).
CsvReader
IMHO, tab separated value files are some of the easiest to work with. Some applications (like Excel) will sometimes wrap values in quotes, but for the most part you can read TSV files by splitting rows on the tab character (and possibly checking for the first and last character being a quote). Writing them then, is even simpler - write a tab ("\t") between every field and a newline at the end of the row (or use a command that takes care of the newline for you, like writeline).
Here's quite a nice (free) utility for working with delimited files in .NET http://www.filehelpers.com/