Datatable中对某列求和

C# code   方法一. object sumObject = DataTable.Compute("sum(Qty)", "TRUE"); 其中Qty的类型为Int整型 方法二. double ColumnSum(DataTable dt, string ColumnName) {     double d = 0 ;     foreach (DataRow row in dt.Rows)     {         d += double .Parse(row[ColumnName].ToString());     }     return d; } 方法三. DataTable dt=this.GridView1.Datasouce as DataTable; string Sum = dt.Compute("sum(jine)", "true").ToString();