序列化集合中的空值会在Protobuf V2.0.0668

Question

1。 NullReference对可空集合中的空值的异常。

[ProtoContract]
public class ProtoTest
{
    [ProtoMember(1)]
    public List<string> Collecton { get; set; }
}
static void Main(string[] args)
{
    ProtoTest test = new ProtoTest();
    test.Collecton = new List<string>();
    test.Collecton.Add("A");
    test.Collecton.Add(null);
    test.Collecton.Add("B");
    test.Collecton.Add(null);

    //This code works fine on Protobuf 1.0.0.282
    //But throws exception on Protobuf 2.0.0.668
    byte[] buffer = Serialize<ProtoTest>(test);
    ProtoTest converted = Deserialize<ProtoTest>(buffer);

    //In 1.0.0.282 converted.Collection is having 2 items excluded null values.
    //In 2.0.0.668 Serialization fails with NullReference exception.
    Console.Read();

}

2。尝试在侧引用类型集合

中的空值上创建默认实例

[ProtoContract]        
public abstract class NullableBase
{
    public NullableBase()
    {
    }

    [ProtoMember(1)]
    public int? Value { get; set; }            
}

[ProtoContract]
public class NullableChild:NullableBase
{
    [ProtoMember(2)]
    public string StrValue { get; set; }
}

[ProtoContract]
public class ProtoTest
{
    [ProtoMember(1)]
    public List<NullableBase> RefCollecton { get; set; }

}


static void Main(string[] args)
{
    var nullableBaseType=ProtoBuf.Meta.RuntimeTypeModel.Default.Add(typeof(NullableBase), true);
    nullableBaseType.AddSubType(100, typeof(NullableChild));
    ProtoTest test = new ProtoTest();

    test.RefCollecton = new List<NullableBase>();
    test.RefCollecton.Add(new NullableChild() { StrValue = "A" });
    test.RefCollecton.Add(new NullableChild() { StrValue = "B" });
    test.RefCollecton.Add(null);

    byte[] buffer = Serialize<ProtoTest>(test);
    //For null values on reference type Protobuf is trying to create default instance.
    //Here the type is NullBase and its an abstract class. Protobuf wont be able to create it and throwing exception.
    //Why Protobuf creates default instance for null values.
    ProtoTest converted = Deserialize<ProtoTest>(buffer);
    Console.Read();

}

我们使用的是Protobuf 1.0.0.282，它在序列化时排除了参考类型和可空集合的空值。但是在V 2.0.0.668中，它对于可空类型和引用类型的行为方式不同。对于可空类型，它会在序列化时对空值抛出NullReferenceException。但是对于引用类型，它被序列化并且在反序列化时尝试为空值创建默认实例。

为什么他们删除了这个功能？这有什么特别的原因吗？ 如果有任何好的理由，那么对于引用和可空类型集合它应该抛出nullreferenece异常吗？我们尝试过“SupportNull”https://code.google.com/p/protobuf-net/issues/detail?id=217的解决方案。