保存设置时没有保存OrderedDictionary

Question

在我的应用程序中，我实现了几个Controls，以不同的方式浏览数据。在每个控件中，我都会显示一个TreeView，以允许用户从一个文件夹转到另一个文件夹。

我希望我的控件以一种通用的方式“记住”最后一棵选定的树(我的意思是，如果将来我添加了另一个控件，我不想做太多的调整)。因此，我在设置中添加了一个OrderedDictionary。我使用控件的类型名称作为键，节点的路径作为值。

由于无法为该词典设置默认值，所以我使用了以下技巧：

Settings.cs：

public OrderedDictionary Paths
{
    get
    {
        return LastsPaths ?? (LastsPaths = new OrderedDictionary());
    }
    set
    {
        this["LastsPaths"] = value;
    }
}

Settings.Designer.cs：

[global::System.Configuration.UserScopedSettingAttribute()]
[global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
public global::System.Collections.Specialized.OrderedDictionary LastsPaths {
    get {
        return ((global::System.Collections.Specialized.OrderedDictionary)(this["LastsPaths"]));
    }
    set {
        this["LastsPaths"] = value;
    }
}

每次添加/更新值时，Save文件时间戳都会更改，但内容保持不变：

<setting name="LastsPaths" serializeAs="Xml">
    <value />
</setting>

它不适用于：

• 调试模式下的App；
• App在释放模式下；
• 安装了应用程序。

我怎么才能解决这个问题？

Answer 1

似乎是OrderedDictionary (和一般的通用字典) 不能序列化XML。。

您可以将它包装在另一个手动序列化的类中。这样，您就不会直接将字典公开给XML序列化程序。为了实现这一点，您必须实现IXmlSerializable。

Answer 2

这可能就足以让你开始了。这继承了在保存调用期间需要的IXMLSerializable。

[XmlRoot("PreviouslyVisitedPaths")]
public class PreviouslySelectedPaths : OrderedDictionary, IXmlSerializable
{

    #region Implementation of IXmlSerializable

    /// <summary>
    /// This method is reserved and should not be used. When implementing the IXmlSerializable interface, you should return null (Nothing in Visual Basic) from this method, and instead, if specifying a custom schema is required, apply the <see cref="T:System.Xml.Serialization.XmlSchemaProviderAttribute"/> to the class.
    /// </summary>
    /// <returns>
    /// An <see cref="T:System.Xml.Schema.XmlSchema"/> that describes the XML representation of the object that is produced by the <see cref="M:System.Xml.Serialization.IXmlSerializable.WriteXml(System.Xml.XmlWriter)"/> method and consumed by the <see cref="M:System.Xml.Serialization.IXmlSerializable.ReadXml(System.Xml.XmlReader)"/> method.
    /// </returns>
    public XmlSchema GetSchema()
    {
        return null;
    }

    /// <summary>
    /// Generates an object from its XML representation.
    /// </summary>
    /// <param name="reader">The <see cref="T:System.Xml.XmlReader"/> stream from which the object is deserialized. </param>
    public void ReadXml(XmlReader reader)
    {
        var keySerializer = new XmlSerializer(typeof(object));
        var valueSerializer = new XmlSerializer(typeof(object));

        var wasEmpty = reader.IsEmptyElement;
        reader.Read();

        if(wasEmpty)
        {
            return;
        }

        while(reader.NodeType != XmlNodeType.EndElement)
        {
            reader.ReadStartElement("item");

            reader.ReadStartElement("key");
            var key = keySerializer.Deserialize(reader);
            reader.ReadEndElement();

            reader.ReadStartElement("value");
            var value = valueSerializer.Deserialize(reader);
            reader.ReadEndElement();

            Add(key, value);

            reader.ReadEndElement();
            reader.MoveToContent();
        }
        reader.ReadEndElement();
    }

    /// <summary>
    /// Converts an object into its XML representation.
    /// </summary>
    /// <param name="writer">The <see cref="T:System.Xml.XmlWriter"/> stream to which the object is serialized. </param>
    public void WriteXml(XmlWriter writer)
    {
        var keySerializer = new XmlSerializer(typeof(object));
        var valueSerializer = new XmlSerializer(typeof(object));

        foreach(var key in Keys)
        {
            writer.WriteStartElement("item");

            writer.WriteStartElement("key");
            keySerializer.Serialize(writer, key);
            writer.WriteEndElement();

            writer.WriteStartElement("value");
            var value = this[key];
            valueSerializer.Serialize(writer, value);
            writer.WriteEndElement();

            writer.WriteEndElement();
        }

        #endregion
    }
}

然后将代码更改为：

public PreviouslySelectedPaths Paths
{
    get
    {
        return LastsPaths ?? (LastsPaths = new PreviouslySelectedPaths());
    }
    set
    {
        this["LastsPaths"] = value;
    }
}

您还需要使LastsPaths类型为PreviouslySelectedPaths。

这仅仅是为了开始您的工作，您可能需要为IXMLSerializable方法设置一个星期，并为GetSchema()填写逻辑。