Joining Datasets using columns

Hi,

I am looking for a way of joining or merging two datasets together in VB.net.  
Essentially I have two separate datasets, which have been populated
with data from a CSV file. The example below gives an Idea of
structure of both datasets.

ds1
----

Code, Name, Spend
A45 5, tyyy, 0.56
B65 5, YUTYU, 0.78
H74 0, GFGHHG, 0.59

ds2
---
Code, Data1, Data2, Data3
A45 5, Data, Data, Data
B65 5, Data, Data, Data
H74 0, Data, Data, Data

What I am trying to do is join the two data sets together using in the Code
field (This is same as a vlookup in excel or a join in SQL).  This
would then produce another dataset with the merged datasets which I can then
export to another CSV file.

ds3
---
Code, Name, Spend, Data1, Data2, Data3
A45 5, tyyy, 0.56,  Data, Data, Data
B65 5, YUTYU, 0.78, Data, Data, Data
H74 0, GFGHHG, 0.59, Data, Data, Data

I have a SQL version but this is done in a store procedure. I really need
to do this using flat files (csv) outside of SQL in a standalone application.
Also with the number of records being over 100,000 I can not use excel.

Does anyone have any ideas?  Also if anyone can think of an alternative way of
doing this the please let me know!!

Thanks in advance!!