Record cound from datagridview , or datadet

Question

can some one post a sample code up where in you can get a record count in the datagridview

from a speacify item under a column or a row.


for example

id         a           b          c

--------------------------------
1   |      f      |       t     |   u
     |             |             |
2   |     f       |      w    |    t


How can i find f is populated under column a.   
this is the record count im trying to do

3       r              e           r