code for to maintain relation between three comboboxs

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C#

sir,

we have three combo boxes when we insert new values to first combobox then that value can be stored in backend table1(id (identity) primarykey,name ) and also fill that value into combobox.if value can be stored in table it generate an id we use that id as reference to table2(id,name,table1id(ref)).the value we write in combox2 is stored in table2 with the id of first combobox selected index as ref to that text
for example like this

  table1
-----------
bid   bname
---------
1     a 
2     b 
3     c


table2
------- 
fid   fname     bid
----------------------
1     first     1
2     second    1
3     first     2
4     second    2
5     first     3
6     second    3

table3
-------
rid  rn0   fid
-----------------
1    101    1
2    102    1
3    201    2

please send c# code to do this