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PODeserialize unknown type with protobuf-net
 

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    <p>I have 2 networked apps that should send serialized protobuf-net messages to each other. I can serialize the objects and send them, however, <b>I cannot figure out how to deserialize the received bytes</b>.</p> <p>I tried to deserialize with this and it failed with a NullReferenceException.</p> <pre><code>// Where "ms" is a memorystream containing the serialized // byte array from the network. Messages.BaseMessage message = ProtoBuf.Serializer.Deserialize&lt;Messages.BaseMessage&gt;(ms); </code></pre> <p>I am passing a header before the serialized bytes that contains message type ID, which I can use in a giant switch statement to return the expected sublcass Type. With the block below, I receive the error: System.Reflection.TargetInvocationException ---> System.NullReferenceException.</p> <pre><code>//Where "ms" is a memorystream and "messageType" is a //Uint16. Type t = Messages.Helper.GetMessageType(messageType); System.Reflection.MethodInfo method = typeof(ProtoBuf.Serializer).GetMethod("Deserialize").MakeGenericMethod(t); message = method.Invoke(null, new object[] { ms }) as Messages.BaseMessage; </code></pre> <p>Here's the function I use to send a message over the network:</p> <pre><code>internal void Send(Messages.BaseMessage message){ using (System.IO.MemoryStream ms = new System.IO.MemoryStream()){ ProtoBuf.Serializer.Serialize(ms, message); byte[] messageTypeAndLength = new byte[4]; Buffer.BlockCopy(BitConverter.GetBytes(message.messageType), 0, messageTypeAndLength, 0, 2); Buffer.BlockCopy(BitConverter.GetBytes((UInt16)ms.Length), 0, messageTypeAndLength, 2, 2); this.networkStream.Write(messageTypeAndLength); this.networkStream.Write(ms.ToArray()); } } </code></pre> <p>This the class, with base class, I'm serializing:</p> <pre><code>[Serializable, ProtoContract, ProtoInclude(50, typeof(BeginRequest))] abstract internal class BaseMessage { [ProtoMember(1)] abstract public UInt16 messageType { get; } } [Serializable, ProtoContract] internal class BeginRequest : BaseMessage { [ProtoMember(1)] public override UInt16 messageType { get { return 1; } } } </code></pre> <p><hr> <b>Fixed</b> using Marc Gravell's suggestion. I removed the ProtoMember attribute from the readonly properties. Also switched to using SerializeWithLengthPrefix. Here's what I have now:</p> <pre><code>[Serializable, ProtoContract, ProtoInclude(50, typeof(BeginRequest))] abstract internal class BaseMessage { abstract public UInt16 messageType { get; } } [Serializable, ProtoContract] internal class BeginRequest : BaseMessage { public override UInt16 messageType { get { return 1; } } } </code></pre> <p>To receive an object:</p> <pre><code>//where "this.Ssl" is an SslStream. BaseMessage message = ProtoBuf.Serializer.DeserializeWithLengthPrefix&lt;BaseMessage&gt;( this.Ssl, ProtoBuf.PrefixStyle.Base128); </code></pre> <p>To send an object:</p> <pre><code>//where "this.Ssl" is an SslStream and "message" can be anything that // inherits from BaseMessage. ProtoBuf.Serializer.SerializeWithLengthPrefix&lt;BaseMessage&gt;( this.Ssl, message, ProtoBuf.PrefixStyle.Base128); </code></pre>
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    1. USNick VanderPyle
    1. USNick VanderPyle
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    1. COI forgot to mention, I'm serializing in .NET 3.5 on Windows and deserializing in Mono 2.2 and am using the appropriate protobuf-net dlls on each platform.
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      1. USNick VanderPyle
    2. COI'll be back to read this and post an answer in about half an hour... gotta run at the moment, sorry. BTW - the next release has non-generic wrappers built in - still on my laptop at the moment, though.
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      1. USMarc Gravell
    3. CObtw - I'm working on merging my local copy, so I can commit the changes to make this easier. I have one outstanding test-fail, but that covers new code, so I'm content to commit it (marked as ignored) if it helps.
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