XML 反序列化 IEnumerable class 时出错

Question

我正在尝试将 HistoryRoot class 序列化和反序列化为这种 XML 格式：

<?xml version="1.0"?>
<HistoryRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Files>
    <HistoryItem d="2015-06-21T17:40:42" s="file:///D:\cars.txt" />
  </Files>
  <Folders>
    <HistoryItem d="2015-06-21T17:40:42" s="D:\fc\Cars" />
  </Folders>
</HistoryRoot>

这是 HistoryRoot、HistoryList 和 HistoryItem class:

[Serializable]
public class HistoryRoot
{
    public HistoryList
    Files = new HistoryList
    {
        sl = new SortedList<DateTime, string>(),
        list = new List<HistoryItem>(),
        max = 500,
        c = program.M.qFile
    },
    Folders = new HistoryList
    {
        sl = new SortedList<DateTime, string>(),
        list = new List<HistoryItem>(),
        max = 100,
        c = program.M.qFolder
    },
}

[Serializable]
public class HistoryList : IEnumerable
{
    [XmlIgnore]
    public List<HistoryItem> list;

    [XmlIgnore]
    public SortedList<DateTime, string> sl;

    [XmlIgnore]
    public int max;

    [XmlIgnore]
    public ComboBox c;

    public IEnumerator GetEnumerator()
    {
        if (list == null) list = new List<HistoryItem>();
        return list.GetEnumerator();
    }
}

public struct HistoryItem
{
    [XmlAttribute("d")]
    public DateTime D;

    [XmlAttribute("s")]
    public string S;
}

这是我收到错误的地方：

using (FileStream fs = new FileStream("filepath.xml", FileMode.Open))
    {
        XmlSerializer serializer = new XmlSerializer(typeof(HistoryRoot));
        HistoryRoot h = (HistoryRoot)serializer.Deserialize(fs);
    }

"There was an error reflecting type 'History.HistoryRoot'." System.Exception {System.InvalidOperationException}
我该如何解决这个错误？谢谢！

Answer 1

为了使用 XmlSerializer, your class must have an Add method. From the documentation 序列化或反序列化实现 IEnumerable 的 class:

The XmlSerializer gives special treatment to classes that implement IEnumerable or ICollection. A class that implements IEnumerable must implement a public Add method that takes a single parameter. The Add method's parameter must be of the same type as is returned from the Current property on the value returned from GetEnumerator, or one of that type's bases.

即使你从不反序列化而只序列化，你也必须有这个方法，因为XmlSerializer同时为序列化和反序列化生成运行次代码。

该方法实际上并不需要 work 才能使序列化成功，它只需要 present:

    public void Add(object obj)
    {
        throw new NotImplementedException();
    }

（当然，要de序列化成功，必须实现该方法。）

Answer 2

虽然 sbc 的回答是正确的并且我接受了，但我现在将 HistoryList class 更改为这样更容易：

public class HistoryList : List<HistoryItem> //   <-- Add List<HistoryItem>
{    
    [XmlIgnore]
    public SortedList<DateTime, string> sl;

    [XmlIgnore]
    public int max;

    [XmlIgnore]
    public ComboBox c;
}

然后将HistoryRoot改为：

[Serializable]
public class HistoryRoot
{
    public HistoryList
    Files = new HistoryList
    {
        sl = new SortedList<DateTime, string>(),
        //list = new List<HistoryItem>(),   <-- Remove this line
        max = 500,
        c = program.M.qFile
    },
    Folders = new HistoryList
    {
        sl = new SortedList<DateTime, string>(),
        //list = new List<HistoryItem>(),   <-- Remove this line
        max = 100,
        c = program.M.qFolder
    },
}

XML 反序列化 IEnumerable class 时出错

Error with XML deserialization an IEnumerable class

c#

xml

xml-serialization

xml-deserialization