Question

不是重复的 Add objects to arraylist and read them 我可以访问数据并以json格式读取它们，但不能以orderItem.PO等格式读取它们。而且我的问题不是“如何阅读”。

我有一个List<xmlOrder>物品，其中包含订单信息及其物品。我可以访问以下列表：

    foreach (var order in items)
    {
       string query = "insert into Orders values ('" + order.PO + "','" + order.Name + "','" + order.Company + "','" + order.Address + "','" + order.City + "','" + order.State + "','" + order.ZipCode + "','" + order.Country + "','" + order.Phone + "','" + order.Date + "','" + order.ShippingMethod + "','" + order.Notes + "')";
       foreach (var orderItem in order.OrderItems)
       {
        query = "insert into OrderItem values ('" + orderItem.PO + "','" + orderItem.StockNumber + "','" + orderItem.Quantity + "','" + orderItem.UnitPrice + "')";
       //Console.WriteLine(orderItem.ToJson());
       }
    }

我可以访问order.PO，order.Name等，但是我收到了orderItem的错误，如下所示：

奇怪的是，当我检查orderItem.ToJson()时，得到的json很好，如：

{"PO":"009723","StockNumber":"0040","Quantity":5,"UnitPrice":16.445000}

这意味着我正在获取数据，但是为什么当我尝试访问诸如orderItem.PO之类的数据时却给我错误？

如果需要，我的班级结构如下：

public class xmlOrder
{

    public string PO { get; set; }
    public string Name { get; set; }
    public string Company { get; set; }
    public string Address { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string ZipCode { get; set; }
    public string Country { get; set; }
    public string Phone { get; set; }
    public string Date { get; set; }
    public string ShippingMethod { get; set; }
    public string Notes { get; set; }
    public ArrayList OrderItems { get; set; }

    public xmlOrder()
    {
        this.PO = string.Empty;
        this.Name = string.Empty;
        this.Company = string.Empty;
        this.Address = string.Empty;
        this.City = string.Empty;
        this.State = string.Empty;
        this.ZipCode = string.Empty;
        this.Country = string.Empty;
        this.Phone = string.Empty;
        this.Date = string.Empty;
        this.ShippingMethod = string.Empty;
        this.Notes = string.Empty;
        this.OrderItems = new ArrayList();
    }
}

public class xmlOrderItem
{
    public string PO { get; set; }
    public string StockNumber { get; set; }
    public int Quantity { get; set; }
    public decimal UnitPrice { get; set; }

    public xmlOrderItem()
    {
        this.PO = string.Empty;
        this.StockNumber = string.Empty;
        this.Quantity = 0;
        this.UnitPrice = decimal.Zero;
    }
}

Answer 1

您的items对象的类型是什么？您应该展示更多这种方法。如果类型为object，则应尝试使其成为一个具体对象。您还可以将object强制转换为您的类型：

foreach (var orderItem in order.OrderItems)
   {
      var item = orderItem as xmlOrderItem
      if (item == null)
        throw new NullReferenceException("orderItem is not an xmlOrderItem")
      query = "insert into OrderItem values ('" + item .PO + "','" + item .StockNumber + "','" + item .Quantity + "','" + item .UnitPrice + "')";
   //Console.WriteLine(orderItem.ToJson());
   }

公共类中的访问数组列表

1 个答案: