Calculate and display the value in a textbox

Question

i have a table with the name salary

EmpId Salary
----- ------
121   2000
122   2000
123   5000
124   4000
131   2000
132   6000
133   1000
134   1000
125   1000
126   20000

this is my table,
what i wanna do is calculate all the salary of the employe and display it in my text box as a total,how can i achieve it.