学习

DataColumn newcol = new DataColumn("field3");

            newcol.Expression = "[field1] * [field2]";

            mydatatable.Columns.Add(newcol);

datagrid1.DataSource = mydatatable;

datagrid1.DataBind();

or

select 数量,价格,数量*价格 as 总价 from 你的表

然后DataGrid 绑定不就行啦......