我可以序列化C＃Type对象吗？

Question

我正在尝试按以下方式序列化Type对象：

Type myType = typeof (StringBuilder);
var serializer = new XmlSerializer(typeof(Type));
TextWriter writer = new StringWriter();
serializer.Serialize(writer, myType);

执行此操作时，对Serialize的调用会引发以下异常：

  

“不期望System.Text.StringBuilder类型。使用   XmlInclude或SoapInclude属性指定不是的类型   静静地知道。“

我有没有办法序列化Type对象？请注意，我不是要尝试序列化StringBuilder本身，而是序列化Type对象，其中包含有关StringBuilder类的元数据。

Answer 1

我不知道只能使用包含完全限定名称的字符串创建Type对象。要获取完全限定名称，可以使用以下命令：

string typeName = typeof (StringBuilder).FullName;

然后您可以根据需要保留此字符串，然后重建类型：

Type t = Type.GetType(typeName);

如果您需要创建该类型的实例，可以执行以下操作：

object o = Activator.CreateInstance(t);

如果检查o.GetType（）的值，它将是StringBuilder，正如您所期望的那样。

Answer 2

我遇到了同样的问题，我的解决方案是创建一个SerializableType类。它可以自由地转换为System.Type和从System.Type转换，但它序列化为字符串。您所要做的就是将变量声明为SerializableType，从那时起您可以将其称为System.Type。

这是班级：

// a version of System.Type that can be serialized
[DataContract]
public class SerializableType
{
    public Type type;

    // when serializing, store as a string
    [DataMember]
    string TypeString
    {
        get
        {
            if (type == null)
                return null;
            return type.FullName;
        }
        set
        {
            if (value == null)
                type = null;
            else
            {
                type = Type.GetType(value);
            }
        }
    }

    // constructors
    public SerializableType()
    {
        type = null;
    }
    public SerializableType(Type t)
    {
        type = t;
    }

    // allow SerializableType to implicitly be converted to and from System.Type
    static public implicit operator Type(SerializableType stype)
    {
        return stype.type;
    }
    static public implicit operator SerializableType(Type t)
    {
        return new SerializableType(t);
    }

    // overload the == and != operators
    public static bool operator ==(SerializableType a, SerializableType b)
    {
        // If both are null, or both are same instance, return true.
        if (System.Object.ReferenceEquals(a, b))
        {
            return true;
        }

        // If one is null, but not both, return false.
        if (((object)a == null) || ((object)b == null))
        {
            return false;
        }

        // Return true if the fields match:
        return a.type == b.type;
    }
    public static bool operator !=(SerializableType a, SerializableType b)
    {
        return !(a == b);
    }
    // we don't need to overload operators between SerializableType and System.Type because we already enabled them to implicitly convert

    public override int GetHashCode()
    {
        return type.GetHashCode();
    }

    // overload the .Equals method
    public override bool Equals(System.Object obj)
    {
        // If parameter is null return false.
        if (obj == null)
        {
            return false;
        }

        // If parameter cannot be cast to SerializableType return false.
        SerializableType p = obj as SerializableType;
        if ((System.Object)p == null)
        {
            return false;
        }

        // Return true if the fields match:
        return (type == p.type);
    }
    public bool Equals(SerializableType p)
    {
        // If parameter is null return false:
        if ((object)p == null)
        {
            return false;
        }

        // Return true if the fields match:
        return (type == p.type);
    }
}

以及使用示例：

[DataContract]
public class A
{

    ...

    [DataMember]
    private Dictionary<SerializableType, B> _bees;

    ...

    public B GetB(Type type)
    {
        return _bees[type];
    }

    ...

}

您也可以考虑使用AssemblyQualifiedName而不是Type.FullName - 请参阅@GreyCloud的评论

Answer 3

如果类型与调用在同一个程序集中，那么

Brian's回答很有效（就像GreyCloud在其中一条注释中指出的那样）。 因此，如果类型在另一个程序集中，则需要使用AssemblyQualifiedName，正如GreyCloud也指出的那样。

但是，由于AssemblyQualifiedName保存了版本，如果您的程序集的版本与您拥有该类型的字符串的版本不同，则它将无效。

在我的情况下，这是一个问题，我解决了这个问题：

string typeName = typeof (MyClass).FullName;

Type type = GetTypeFrom(typeName);

object myInstance = Activator.CreateInstance(type);

GetTypeFrom方法

private Type GetTypeFrom(string valueType)
    {
        var type = Type.GetType(valueType);
        if (type != null)
            return type;

        try
        {
            var assemblies = AppDomain.CurrentDomain.GetAssemblies();                

            //To speed things up, we check first in the already loaded assemblies.
            foreach (var assembly in assemblies)
            {
                type = assembly.GetType(valueType);
                if (type != null)
                    break;
            }
            if (type != null)
                return type;

            var loadedAssemblies = assemblies.ToList();

            foreach (var loadedAssembly in assemblies)
            {
                foreach (AssemblyName referencedAssemblyName in loadedAssembly.GetReferencedAssemblies())
                {
                    var found = loadedAssemblies.All(x => x.GetName() != referencedAssemblyName);

                    if (!found)
                    {
                        try
                        {
                            var referencedAssembly = Assembly.Load(referencedAssemblyName);
                            type = referencedAssembly.GetType(valueType);
                            if (type != null)
                                break;
                            loadedAssemblies.Add(referencedAssembly);
                        }
                        catch
                        {
                            //We will ignore this, because the Type might still be in one of the other Assemblies.
                        }
                    }
                }
            }                
        }
        catch(Exception exception)
        {
            //throw my custom exception    
        }

        if (type == null)
        {
            //throw my custom exception.
        }

        return type;
    }

如果有人需要，我会张贴此内容。

Answer 4

根据System.Type [1]的MSDN文档，您应该能够序列化System.Type对象。但是，由于错误明确指向System.Text.StringBuilder，这可能是导致序列化错误的类。

[1]类型类（系统） - http://msdn.microsoft.com/en-us/library/system.type.aspx

Answer 5

只是看看它的定义，它没有标记为Serializable。如果您确实需要将此数据序列化，则可能必须将其转换为标记为此类的自定义类。

public abstract class Type : System.Reflection.MemberInfo
    Member of System

Summary:
Represents type declarations: class types, interface types, array types, value types, enumeration types, type parameters, generic type definitions, and open or closed constructed generic types.

Attributes:
[System.Runtime.InteropServices.ClassInterfaceAttribute(0),
System.Runtime.InteropServices.ComDefaultInterfaceAttribute(System.Runtime.InteropServices._Type),
System.Runtime.InteropServices.ComVisibleAttribute(true)]

Answer 6

我遇到了这个问题，试图在.net standard 2.0中进行二进制序列化。我最终使用自定义的SurrogateSelector和SerializationBinder解决了这个问题。

TypeSerializationBinder是必需的，因为框架在解决System.RuntimeType之前无法解决SurrogateSelector。我不太明白为什么在此步骤之前必须先解析类型...

代码如下：

// Serializes and deserializes System.Type
public class TypeSerializationSurrogate : ISerializationSurrogate {
    public void GetObjectData(object obj, SerializationInfo info, StreamingContext context) {
        info.AddValue(nameof(Type.FullName), (obj as Type).FullName);
    }

    public object SetObjectData(object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector) {
        return Type.GetType(info.GetString(nameof(Type.FullName)));
    }
}

// Just a stub, doesn't need an implementation
public class TypeStub : Type { ... }

// Binds "System.RuntimeType" to our TypeStub
public class TypeSerializationBinder : SerializationBinder {
    public override Type BindToType(string assemblyName, string typeName) {
        if(typeName == "System.RuntimeType") {
            return typeof(TypeStub);
        }
        return Type.GetType($"{typeName}, {assemblyName}");
    }
}

// Selected out TypeSerializationSurrogate when [de]serializing Type
public class TypeSurrogateSelector : ISurrogateSelector {
    public virtual void ChainSelector(ISurrogateSelector selector) => throw new NotSupportedException();

    public virtual ISurrogateSelector GetNextSelector() => throw new NotSupportedException();

    public virtual ISerializationSurrogate GetSurrogate(Type type, StreamingContext context, out ISurrogateSelector selector) {
        if(typeof(Type).IsAssignableFrom(type)) {
            selector = this;
            return new TypeSerializationSurrogate();
        }
        selector = null;
        return null;
    }
}

用法示例：

byte[] bytes
var serializeFormatter = new BinaryFormatter() {
    SurrogateSelector = new TypeSurrogateSelector()
}
using (var stream = new MemoryStream()) {
    serializeFormatter.Serialize(stream, typeof(string));
    bytes = stream.ToArray();
}

var deserializeFormatter = new BinaryFormatter() {
    SurrogateSelector = new TypeSurrogateSelector(),
    Binder = new TypeDeserializationBinder()
}
using (var stream = new MemoryStream(bytes)) {
    type = (Type)deserializeFormatter .Deserialize(stream);
    Assert.Equal(typeof(string), type);
}