在C＃中讀取XML數據

Question

我一直在嘗試如何用XML制作數據庫。 我已成功寫入數據，如下所示：

<Employees>
    <Worker>
        <ID>1</ID>
        <FirstName>Ilan</FirstName>
        <LastName>Berlinbluv</LastName>
        <Salary>5000</Salary>
    </Worker>
</Employees>  

問題是當我嘗試使用以下代碼閱讀時：

    string writePath = Environment.ExpandEnvironmentVariables("%USERPROFILE%") + @"\Desktop";
    string writeFile = writePath + @"\Employees.xml";

    using (XmlReader read = XmlReader.Create(writeFile))
    {
        while (read.Read())
        {
            if (read.IsStartElement())
            {
                Console.WriteLine("DEBUG: read.Name = {0}", read.Name);
                Console.WriteLine("DEBUG: read.Value = {0}", read.Value);
                switch (read.Name)
                {
                    case "Employees":
                        Console.WriteLine("Start <Employees> master element");
                        break;
                    case "Employee":
                        Console.WriteLine("Start <Employee> element");
                        break;
                    case "Worker":
                        Console.WriteLine("Start <Worker> element");
                        break;
                    case "ID":
                        Console.WriteLine("Start reading <ID> element");
                        Console.WriteLine("Contains: " + read.Value.Trim());
                        break;
                    case "FirstName":
                        Console.WriteLine("Start reading <FirstName> element");
                        Console.WriteLine("Contains: " + read.Value.Trim());
                        break;
                    case "LastName":
                        Console.WriteLine("Start reading <LastName> element");
                        Console.WriteLine("Contains: " + read.Value.Trim());
                        break;
                    case "Salary":
                        Console.WriteLine("Start reading <Salary> element");
                        Console.WriteLine("Contains: " + read.Value.Trim());
                        break;
                }
            }
            Console.ReadKey();
        }
    }

每當它說Start reading <Salary> element然后Contains: ，它都不會正確讀取值，它不會顯示任何值，但應該有一個值：5000。這是語法錯誤，在我需要的地方像：

<ID>
1
</ID>  

我一直在做dotnetperls教程，但無濟於事。

Answer 1

不要嘗試編寫代碼來讀取XML文檔。 請使用內置的XML序列化程序。 http://msdn.microsoft.com/en-us/library/fa420a9y.aspx

Answer 2

You can read XML like: 
 XmlDocument doc = new XmlDocument();
 doc.Load(Server.MapPath("\\foldername\\" + "filename.xml"));
 XmlNode node = doc.SelectSingleNode("//Employees//Worker/Salary");
 Response.Write(node.InnerText.ToString());

 This way, you can get 5000 as Salary. 

Answer 3

您可以使用XSD工具來使用序列化程序。 首先創建一個XML模式，然后從XML模式創建一個類。 然后，您可以將XML直接讀取到對象：

        /// <summary>
    /// 
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="xml"></param>
    /// <exception cref="InvalidOperationException"></exception>
    /// <returns></returns>
    public static T Deserialize<T>(XmlNode xml)
    {
        // Assuming xml is an XML document containing a serialized object.
        XmlNodeReader reader = new XmlNodeReader(xml);

        // When we get the xml, it is usually a sub element that can have a different name, than the type name. Therefore look for the name
        XmlSerializer ser = new XmlSerializer(typeof(T));
        object obj = ser.Deserialize(reader);

        // Then you just need to cast obj into whatever type it is eg:
        return (T)obj;
    }
    /// <summary>
    /// Serializes without removing namespace and using the specified encoding
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="obj"></param>
    /// <param name="encoding"></param>
    /// <returns></returns>
    /// <exception cref="InvalidOperationException">When the object can not be serialized to xml</exception>
    public static XmlDocument Serialize<T>(T obj, Encoding encoding)
    {
        XmlSerializer ser = GetSerializer(obj.GetType());
        using (MemoryStream stream = new MemoryStream())
        using (XmlTextWriter writer = new XmlTextWriter(stream, encoding))
        {
            ser.Serialize(writer, obj);
            XmlDocument doc = new XmlDocument();
            writer.Flush();
            stream.Position = 0;
            doc.Load(stream);
            return doc;
        }
    }

您可能需要在創建類之前編輯XML模式，以確保類型正確。

Answer 4

獲得對XML文件的特定節點的訪問權限的最簡單方法是使用LINQ。

string writePath = Environment.ExpandEnvironmentVariables("%USERPROFILE%") + @"\Desktop";
string writeFile = writePath + @"\Employees.xml";

XDocument xmlDocument = XDocument.Load(writeFile)

然后，如果您想讀取Worker元素中的所有元素

var queryResult = from x in xmlDocument.Root.Element("Worker").Elements() select x;
foreach (var item in queryResult)
{
    Console.WriteLine(item.Value);
}

或者，如果您要分別處理所有Worker元素，則只需將查詢結果轉換為列表

var queryResult = (from x in xmlDocument.Root.Element("Worker").Elements() select x).ToList();
Console.WriteLine("Start reading <ID> element");
Console.WriteLine("Contains: " + queryResult[0]);

Console.WriteLine("Start reading <FirstName> element");
Console.WriteLine("Contains: " + queryResult[1]);

Console.WriteLine("Start reading <LastName> element");
Console.WriteLine("Contains: " + queryResult[2]);

Console.WriteLine("Start reading <Salary> element");
Console.WriteLine("Contains: " + queryResult[3]);

Answer 5

我發現在業務對象之間進行序列化時，使用XML總是更容易。

[Serializable]
public class Employees
{
    private List<Worker> _Workers;
    [XmlArray]
    public List<Worker> Workers
    {
        get { return _Workers; }
        set { _Workers = value; }
    }
}

[Serializable]
public class Worker
{
    public Int32 ID { get; set; }
    public String FirstName { get; set; }
    // etc.


    public void SerializeToXML(string outputFolderLocation)
    {
        try
        {
            if (!outputFolderLocation.EndsWith('\\'))
            {
                outputFolderLocation += "\\";
            }

            //Create our own namespaces for the output
            XmlSerializerNamespaces ns = new XmlSerializerNamespaces();

            //Add an empty namespace and empty value
            ns.Add("", "");

            XmlSerializer serializer = new XmlSerializer(typeof(Worker));
            string outpath = outputFolderLocation + "FileName-" + DateTime.Now.ToBinary().ToString() + ".xml";
            XmlTextWriter textWriter = new XmlTextWriter(outpath, Encoding.GetEncoding("ISO-8859-1"));
            serializer.Serialize(textWriter, this, ns);
            textWriter.Close();
        }
        catch (Exception ex)
        {
            throw new Exception("Error serializing to XML", ex);
        }
    }
}

您還可以通過設置XML屬性值而不是節點來整理XML。 為此，您可以將屬性更改為：

[XmlAttribute("ID-Value")]
public Int32 ID { get; set; }
// would serialise like this <worker ID-Value="1"></worker>

Answer 6

您需要使用read.InnerText而不是read.Value。

了解了所有這些工作原理后，建議您使用內置的XML處理功能。 您將省去很多麻煩。