If you want to roll your own, you can do something like
string[][] result;
string[] lines = content.Split('\n');
result = new string[lines.Length][];
for(int ri = 0; ri < lines.Length; ri++)
result[ri] = lines[ri].Split(',');
Be aware, though, that this does not implement the complete CSV standard. Handling quoted items, items with commas in etc is considerably trickier (which is why there are third party libraries available that do it for you).
I'm sure there is also a regex you could look up to do it. Regexes are typically quite inefficient, though (but if your tables are really 3×3 then that won't matter).