Merging 2 datasets in 1 new dataset

<b></b>i thanks for reading the thread, i am using C#.
I have 2 datasets,& i have to merge them in the 1st one dataset like as

lets say <b>TABLE A</b> has columns name
ID      LoanID Firstname  lastname
1         1       abc       xhs
2         2       ali       naeem
3         3       khan      rock
4         4       sami      rock1
5         5       sameer    rock2
6         6       khan1     rock3
<b>TABLE B</b>  has columns name
OrgID  LoanID  Created BY
1         2       abc1
2         2       ali1
3         4      khan21
4         6       sami21
5         6       sameer213
6         6       khan1213
Now the destination <b>TABLE A</b> (if LoanID in the TAbleB then) <b>TABLE C would have column value otherwise no value</b>
ID  LoanID Firstname     lastname      OrgID  LoanID  CreatedBY
1         1       abc       xhs
2         2       ali       naeem
3         2       ali       naeem       2      2       abc1
4         2       ali       naeem       2      2       ali1
5         3       khan      rock
6         4       sami      rock1
7         4       sami      rock1       3      4      khan21
8         5       sameer    rock2
now total four rows for loanid=6 and so on