如何更快地进行XML反序列化？

Question

我有以下代码

public static object XmlDeserialize(string xml, Type objType)
{
    StringReader stream = null;
    XmlTextReader reader = null;
    try
    {
        XmlSerializer serializer = new XmlSerializer(objType);
        stream = new StringReader(xml); // Read xml data
        reader = new XmlTextReader(stream);  // Create reader
        return serializer.Deserialize(reader);
    }
    finally
    {
        if(stream != null) stream.Close();
        if(reader != null) reader.Close();
    }
}

该对象本身是通过xsd.exe生成的,看起来像这样:

/// <remarks/>
[System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "2.0.50727.3038")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)]
[System.Xml.Serialization.XmlRootAttribute(Namespace="", IsNullable=false)]
public partial class MyObject {

    private DemographicsCriteriaStateStartAge[] startAgesField;

    private DemographicsCriteriaStateEndAge[] endAgesField;

    private DemographicsCriteriaStateFilter[] selectedFiltersField;

    /// <remarks/>
    [System.Xml.Serialization.XmlArrayItemAttribute("StartAge", IsNullable=false)]
    public DemographicsCriteriaStateStartAge[] StartAges {
        get {
            return this.startAgesField;
        }
        set {
            this.startAgesField = value;
        }
    }
    ...

该方法通常如下所示:

var obj = (MyObject) XmlDeserialize(someXmlString, typeof(MyObject));

以下代码行总是花费相当多的时间(与其他所有内容相比):

XmlSerializer serializer = new XmlSerializer(objType);

这里发生了什么,例如它是否在后台编译反序列化程序集？为什么性能问题？

我该怎么做才能改善这个性能问题？

Answer 1

是的,它在运行时动态生成序列化程序集.您可以在Visual Studio中更改此行为.转到项目属性和构建部分."生成序列化程序集"的设置将其设置为true.这将生成一个类似于YourProject.XmlSerialiser.dll编译时的文件,并将在运行时停止此瓶颈.

但是,需要注意的一个例外是此设置仅适用于代理类型(例如,Web服务代理等).要实际强制Visual Studio 2010为常规类型生成序列化程序集,必须弄乱项目文件(.csproj)并从Sgen调用中删除/ proxytypes 或生成构建后步骤以手动调用程序集上的sgen.exe .

Answer 2

尝试XmlSerializer在类级别缓存每种类型的实例，这样如果使用相同的类型，您就不必每次都重新创建它：

class Foo
{
    private static Dictionary<Type, XmlSerializer> xmls = new Dictionary<Type, XmlSerializer>();

    // ...

    public static object XmlDeserialize(string xml, Type objType)
    {
        StringReader stream = null;
        XmlTextReader reader = null;
        try
        {
            XmlSerializer serializer;
            if(xmls.Contains(objType)) {
                serializer = xmls[objType];
            }
            else {
                serializer = new XmlSerializer(objType);
                xmls[objType] = serializer;
            }           

            stream = new StringReader(xml); // Read xml data
            reader = new XmlTextReader(stream);  // Create reader
            return serializer.Deserialize(reader);
        }
        finally
        {
            if(stream != null) stream.Close();
            if(reader != null) reader.Close();
        }
    }
}