c# datatable

　　DataTable dt = new DataTable("cart");   //创建表dt.Columns.Add( new DataColumn("number", Type.GetType("System.String")));   //创建列
dt.Columns.Add( new DataColumn("qq", Type.GetType("System.String")));DataRow dr = dt.NewRow();   //创建行dr["number"]="123"        //行赋值
dr["qq"]="1x"dt.Rows.Add(dr);          //添加行DataColumn[] clos = new DataColumn[1];   //设置主键 
clos[0] = dt.Columns["number"];
dt.PrimaryKey = clos;dt.Rows.Count             //表行数
dt.Columns.Count          //表列数dtSource.Columns.Remove("qq");  //删除列DataRow dr = qtSource.Rows.Find(dt.Rows[i]["number"].ToString());  //查询行var num = qtSource.Select("number like 'xx%'");    //模糊查询 dt.Columns[0].ColumnName    //字段名

 重复判断

 var query = from d in dt.AsEnumerable()
                            group d by new {t1= d.Field<string>("file1") } into g
                            where g.Count() >1
                            select new
                            {
                                g.Key,
                            };
                var heavy = query.Select(o=>o.Key.t1).ToList();
                
                if (heavy.Count>0)
                {
                    resultMsg = string.Join(",", heavy.ToList()) + "有重复项目不能保存";
                }