How to Sum up two datatable same Column ?

Question

Dear Friends ,

                 I had a situation , Like i wanna to sum up two datatable same column...

            i shown the data and desired data .. If anybody Possible ..Guide  me 

Datatable :1
Sno	Agent Id	Amount
1	AG121	400
2	AG125	300
3	AG127	200
Datatable :2
Sno	Agent Id	Amount
1	AG121	100
2	AG125	200
3	AG127	100
4	AG129	400

My desired OutPut Is,

SNo     Agent Id             Amount 

1         AG121                 500

2         AG125                 500

3         AG127                 300

4         AG129                 400

 This what i am really want to do ...

Thanks in advance 

- KARTHIK