c＃檢索多個XML子節點

Question

我已經成功地將一個XElement鏈接到了我的程序中，盡管我嘗試使用的其他兩個沒有運氣；

IEnumerable查詢=來自doc.Descendants（“ Booking”）中的預訂

雖然我運氣不太好，但是將這些值放入列表框。

這是功能代碼：

    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問題或需要添加/更改的內容，請告訴我:)

非常感謝，10gez10

Answer 1

您有幾個問題：

1. 首先，您的數據元素不是booking元素的直接子元素，其中包含中間元素<Customer> ， <Holiday>和<TravelInfo> 。 因此，您需要做類似的事情

     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，幾個元素拼寫錯誤：

   • CheckOutTime應該是CheckoutTime
   • 飛行中餐應該是飛行中餐。
   • CarHire應該是CareHire（是的，“ CareHire”是XML中的內容。）

   因此，當您執行（例如） Element("In-FlightMeals").Value ， Element()返回null，因此您將獲得null引用異常，並且代碼將中止。

3. 第三，元素BookTo完全丟失，因此BookTo = holiday.Element("BookTo").Value生成空引用異常。

更一般而言，我不推薦這種編碼方法。 如果缺少任何XML元素，則查詢將引發異常，因為element.Element("name")將為null。 更糟糕的是，Visual Studio似乎沒有報告出現空引用的准確行號，而是給出了select new語句的行號。 而且（至少在我的版本中）也無法進入匿名類型的構造函數。 這使得調試幾乎不可能。

而是跳過中間匿名類型並以更直接的傳統方式執行操作：

            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.
            }