因为Datatable默认字段类型都是字符串，解决方案:
DataTable.Columns.Add( "iPersonOrderSort ",System.Type.GetType( "System.Int32 "));
DataTable.Columns[ "iPersonOrderSort "].Expression = "Convert(iPersonOrder, 'System.Int32 ') ";
DataView dv = DataTable.DefaultView;
dv.Sort = "iPersonOrderSort ";