StreamReader and a 2d array

First off, I wouldn't necessaryliy use a StreamReader - I'd be more likely to use File.ReadAllLines instead: it reads to an array of strings, with a single line per string.
The second thing I'd do is not use a fixed size array (if only because there are six elements in your text file at the moment...)- instead I would use a List which could hold two elements, since it would appear that you want to store the data. There is a class which would do it nicely: KeyValuePair.
So:

string[] lines = File.ReadAllLines("FnNam.txt");
List<KeyValuePair<string, string>> list = new List<KeyValuePair<string, string>>();
foreach (string line in lines)
    {
    ...
    }

The next thing to do is to look at each line of text and break it into the part before and the part after the comma. Fortunately, .NET has a helper method for that: string.Split. Use it to split the line into two halves based on the comma:

string[] parts = line.Split(',');

Then you can save the two parts in your list for later:

if (parts.Length == 2)
    {
    list.Add(new KeyValuePair<string,string>(parts[0], parts[1]);
    }

In addition you can see it the "df" part exists at the same time.