c# 检索多个 XML 子节点

Question

我已经成功地将单个 XElement 链接到我的程序中，尽管我已经尝试使用其他两个，但我没有任何运气；

IEnumerable 查询 = 来自 doc.Descendants("Booking") 中的预订

虽然我没有太多运气将值放入列表框中。

函数代码如下：

    private void btnimport_Click(object sender, EventArgs e)
    {
        OpenFileDialog open = new OpenFileDialog();
        open.CheckFileExists = true;
        open.InitialDirectory = "@C:\\";
        open.Filter = "XML Files (*.xml)|*.xml|All Files(*.*)|*.*";
        open.Multiselect = false;

        if (open.ShowDialog() == DialogResult.OK)
        {
            try
            {
                XDocument doc = XDocument.Load(open.FileName);

                //Grabs the customer elements
                var query = from booking in doc.Descendants("Booking")
                select new
                {
                    //Customer Elements
                    CustomerId = booking.Element("CustomerId").Value,
                    Title = booking.Element("Title").Value,
                    Firstname = booking.Element("FirstName").Value,
                    Lastname = booking.Element("LastName").Value,
                    DateofBirth = booking.Element("DateofBirth").Value,
                    Email = booking.Element("Email").Value,
                    HouseNo = booking.Element("HouseNo").Value,
                    Street = booking.Element("Street").Value,
                    Postcode = booking.Element("Postcode").Value,
                    Town = booking.Element("Town").Value,
                    County = booking.Element("County").Value,
                    ContactNo = booking.Element("ContactNo").Value,

                    //Holiday Elements
                    HolidayId = booking.Element("HolidayId").Value,
                    HotelName = booking.Element("HotelName").Value,
                    Location = booking.Element("Location").Value,
                    BookFrom = booking.Element("BookFrom").Value,
                    BookTo = booking.Element("BookTo").Value,
                    CheckInTime = booking.Element("CheckInTime").Value,
                    CheckOutTime = booking.Element("CheckOutTime").Value,
                    NoOfRoomsBooked = booking.Element("NoOfRoomsBooked").Value,
                    RoomType = booking.Element("RoomType").Value,
                    RoomServices = booking.Element("RoomServices").Value,
                    Parking = booking.Element("Parking").Value,
                    Pet = booking.Element("Pet").Value,

                    //TravelInfo Elements
                    TravelInfoId = booking.Element("TravelInfoId").Value,
                    TravellingFrom = booking.Element("TravellingFrom").Value,
                    Destination = booking.Element("Destination").Value,
                    Fare = booking.Element("Fare").Value,
                    TravelInsurance = booking.Element("TravelInsurance").Value,
                    InFlightMeals = booking.Element("In-FlightMeals").Value,
                    LuggageAllowance = booking.Element("LuggageAllowance").Value,
                    ExtraLuggage = booking.Element("ExtraLuggage").Value,
                    CarHire = booking.Element("CarHire").Value,
                    ReturnTransfer = booking.Element("ReturnTransfer").Value,
                };

                //Inputs all of the values in bookings
                foreach (var booking in query)
                {
                    //Customer values
                    txtCustomerId.Text = txtCustomerId.Text + booking.CustomerId;
                    txttitle.Text = txttitle.Text + booking.Title;
                    txtfname.Text = txtfname.Text + booking.Firstname;
                    txtlname.Text = txtlname.Text + booking.Lastname;
                    txtdob.Text = txtdob.Text + booking.DateofBirth;
                    txtemail.Text = txtemail.Text + booking.Email;
                    txthouseno.Text = txthouseno.Text + booking.HouseNo;
                    txtstreet.Text = txtstreet.Text + booking.Street;
                    txtpostcode.Text = txtpostcode.Text + booking.Postcode;
                    txttown.Text = txttown.Text + booking.Town;
                    txtcounty.Text = txtcounty.Text + booking.County;
                    txtcontactno.Text = txtcontactno.Text + booking.ContactNo;

                    //Holiday Values
                    txtHolidayId.Text = txtHolidayId.Text + booking.HolidayId;
                    txthname.Text = txthname.Text + booking.HotelName;
                    txtl.Text = txtl.Text + booking.Location;
                    txtbf.Text = txtbf.Text + booking.BookFrom;
                    txtbt.Text = txtbt.Text + booking.BookTo;
                    txtcit.Text = txtcit.Text + booking.CheckInTime;
                    txtcot.Text = txtcot.Text + booking.CheckOutTime;
                    txtnorb.Text = txtnorb.Text + booking.NoOfRoomsBooked;
                    txtrt.Text = txtrt.Text + booking.RoomType;
                    txtrs.Text = txtrs.Text + booking.RoomServices;
                    txtpark.Text = txtpark.Text + booking.Parking;
                    txtpet.Text = txtpet.Text + booking.Pet;

                    //TravelInfo Values
                    txtTravelInfoId.Text = txtTravelInfoId.Text + booking.TravelInfoId;
                    txttf.Text = txttf.Text + booking.TravellingFrom;
                    txtd.Text = txtd.Text + booking.Destination;
                    txtf.Text = txtf.Text + booking.Fare;
                    txtti.Text = txtti.Text + booking.TravelInsurance;
                    txtifi.Text = txtifi.Text + booking.InFlightMeals;
                    txtla.Text = txtla.Text + booking.LuggageAllowance;
                    txtel.Text = txtel.Text + booking.ExtraLuggage;
                    txtch.Text = txtch.Text + booking.CarHire;
                    txtrtrans.Text = txtrtrans.Text + booking.ReturnTransfer;
                }

                MessageBox.Show("XML has been imported");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }

如果有人知道我哪里出了问题或者我需要添加/更改什么，请告诉我:)

非常感谢， 10gez10

Answer 1

你有几个问题：

1. 首先，您的数据元素不是booking 元素的直接子元素，还有中间元素<Customer>、<Holiday> 和<TravelInfo>。因此你需要做类似的事情

           var query = from booking in doc.Descendants("Booking")
                       let customer = booking.Element("Customer")
                       let holiday = booking.Element("Holiday")
                       let travelInfo = booking.Element("TravelInfo")
                       select new
                       {
                           //Customer Elements
                           CustomerId = customer.Element("CustomerId").Value,
                           Title = customer.Element("Title").Value,
                           HolidayId = holiday.Element("HolidayId").Value,
                           TravelInfoId = travelInfo.Element("TravelInfoId").Value,
                       }
   

2. 其次，有几个元素拼写错误：

   • CheckOutTime 应该是 CheckoutTime
   • In-FlightMeals 应该是 InFlightMeals。
   • CarHire 应该是 CareHire（是的，“CareHire”就是 XML 中的内容。）

   因此，当您执行（例如）Element("In-FlightMeals").Value 时，Element() 将返回 null，因此您会收到 null 引用异常并且您的代码被中止。

3. 第三，元素BookTo完全缺失，所以BookTo = holiday.Element("BookTo").Value产生空引用异常。

更一般地说，我不推荐这种编码方法。如果缺少任何 XML 元素，您的查询将引发异常，因为 element.Element("name") 将为空。更糟糕的是，Visual Studio 似乎没有报告发生空引用的准确行号，而是给出了 select new 语句的行号。而且（至少在我的版本中），也无法进入匿名类型的构造函数。这使得调试几乎不可能。

相反，跳过中间匿名类型并以更直接、更传统的方式做事：

            foreach (var booking in doc.Descendants("Booking"))
            {
                var customer = booking.Element("Customer");
                var holiday = booking.Element("Holiday");
                var travelInfo = booking.Element("TravelInfo");

                XElement element;

                if (customer != null)
                {
                    if ((element = customer.Element("CustomerId")) != null)
                        txtCustomerId.Text = txtCustomerId.Text + element.Value;
                }
                // And so on.
            }