Trying to learn C#

What would be the equivalent of a vb6 Module in C# and how would the code below appear in C#.

strFileName = Dir("\\CAKPOSSERVER\C\POSiTrack\FTP\POS*.TXT")
What would be comparable to Open "\\CAKPOSSERVER\C\POSiTrack\FTP\" & strFileName for input as #1 in vb6
Line Input #1, textLineIn

I have several text files that I must iterate through and parse the text from each one using I suppose the substring function.

Thanks in advance!!

Jerry