1) FileOpen is the old non-.Net way of doing things and StreamReader is the correct way ;)
2)
Dim sr as new System.IO.StreamReader("C:\test.txt")
dim line as string
line = sr.ReadLine()
dim vals() as string = line.split(",")
3)
Dim swr as new System.IO.StreamWriter("C:\test.txt")
dim line as string
dim vals() as string = {"test","data","Only"}
line = line.join(vals,",")
sw.WriteLine(line)
4) bit more difficult but most data types have methods to support conversion i.e.
integer.Parse will parse a string into an integer
Long.ToString will convert to a string etc.