how can i get multiple columns value from dropdown list ?

i have a tabe (Employee) which have 4 coloumns (empID,Name,Age,salary).
now i have filled data in dropdownlist. datatext field is Name and datavaluefield is  EmpID.
Now i have disposed dataset object ds.
now hw cn i get salary of selected employee from dropdownlist without interecting with database. i dont wnt to fire any query again to database. i wnt to take infromation abt salary from table that is bind with dropdown list


        ddlEmployee.DataSource = ds.table[0];
        ddlEmployee.DataTextField = "Name";
        ddlEmployee.DataValueField = "EmpID";
        ddlEmployee.DataBind();
        ddlEmployee.Items.Insert(0, "select");



pls help me

Thank you