Serialization of byte[]

[Stuart Harris]

Hi, I'm having problems with the bson serializer and properties of
type byte[]. It seems to try to calculate the size of each byte
individually. The following exception was thrown during serialization
of an object with a byte[] property (stack trace shortened):

System.ArgumentOutOfRangeException was unhandled by user code
Message=Specified argument was out of the range of valid values.
Parameter name: Type: System.Byte not recognized
Source=MongoDB
ParamName=Type: System.Byte not recognized
StackTrace:
at MongoDB.Bson.BsonWriter.TranslateToBsonType(Object obj) in D:
\Dev\mongodb-csharp\source\MongoDB\Bson\BsonWriter.cs:line 612
at MongoDB.Bson.BsonWriter.CalculateSize(Object obj) in D:\Dev
\mongodb-csharp\source\MongoDB\Bson\BsonWriter.cs:line 325
at MongoDB.Bson.BsonWriter.CalculateSizeObject(Object obj,
IEnumerable`1 propertys) in D:\Dev\mongodb-csharp\source\MongoDB\Bson
\BsonWriter.cs:line 485
at MongoDB.Bson.BsonWriter.CalculateSize(IEnumerable
enumerable) in D:\Dev\mongodb-csharp\source\MongoDB\Bson
\BsonWriter.cs:line 503
at MongoDB.Bson.BsonWriter.CalculateSize(Object obj) in D:\Dev
\mongodb-csharp\source\MongoDB\Bson\BsonWriter.cs:line 349
at MongoDB.Bson.BsonWriter.CalculateSizeObject(Object obj,
IEnumerable`1 propertys) in D:\Dev\mongodb-csharp\source\MongoDB\Bson
\BsonWriter.cs:line 485
at MongoDB.Bson.BsonWriter.CalculateSizeObject(Object obj) in D:
\Dev\mongodb-csharp\source\MongoDB\Bson\BsonWriter.cs:line 464
at MongoDB.Bson.BsonWriter.CalculateSize(Object obj) in D:\Dev
\mongodb-csharp\source\MongoDB\Bson\BsonWriter.cs:line 347
at MongoDB.Protocol.InsertMessage.ChunkMessage(BsonWriter
writer) in D:\Dev\mongodb-csharp\source\MongoDB\Protocol
\InsertMessage.cs:line 73
at MongoDB.Protocol.InsertMessage.Write(Stream stream) in D:\Dev
\mongodb-csharp\source\MongoDB\Protocol\InsertMessage.cs:line 56
at
MongoDB.Connections.Connection.SendMessageCore(IRequestMessage
message) in D:\Dev\mongodb-csharp\source\MongoDB\Connections
\Connection.cs:line 144
at MongoDB.Connections.Connection.SendMessage(IRequestMessage
message, String database) in D:\Dev\mongodb-csharp\source\MongoDB
\Connections\Connection.cs:line 128
at MongoDB.MongoCollection`1.Insert[TElement](IEnumerable`1
documents) in D:\Dev\mongodb-csharp\source\MongoDB
\MongoCollection_1.cs:line 333
at MongoDB.MongoCollection`1.Insert(Object document) in D:\Dev
\mongodb-csharp\source\MongoDB\MongoCollection_1.cs:line 283

So I thought that the following test would prove this:

public class ByteArrayObject
{
public byte[] A { get; set; }
}

[Test]
public void CanConvertByteArrayValue(){
var bytes = new byte[] { 1 };
var bson = Serialize(new Document("A", bytes));
var result = Deserialize<ByteArrayObject>(bson);

Assert.AreEqual(bytes, result.A);
}

But weirdly it succeeds on the serialization and fails on the de-
serialization with the following exception:

System.InvalidCastException : Unable to cast object of type
'MongoDB.Binary' to type 'System.Object[]'.
at
MongoDB.Configuration.Mapping.Model.CollectionMemberMap.SetValue(Object
instance, Object value) in CollectionMemberMap.cs: line 62
at
MongoDB.Serialization.Builders.ConcreteClassMapBuilder.AddProperty(String
name, Object value) in ConcreteClassMapBuilder.cs: line 33
at MongoDB.Serialization.BsonClassMapBuilder.EndProperty(Object
instance, String name, Object value) in BsonClassMapBuilder.cs: line
73
at MongoDB.Bson.BsonReader.ReadElement(Object instance) in
BsonReader.cs: line 119
at MongoDB.Bson.BsonReader.ReadElements(Object instance) in
BsonReader.cs: line 99
at MongoDB.Bson.BsonReader.ReadObject() in BsonReader.cs: line 76
at
MongoDB.UnitTests.Serialization.SerializationTestBase.Deserialize(String
base64) in SerializationTestBase.cs: line 23
at
MongoDB.UnitTests.Serialization.Builders.ValueConversionTests.CanConvertByteArrayValues()
in ValueConversionTests.cs: line 32

I hoped that I could find the problems and submit a patch, but it's
going to take me a while to get up to speed with the code. So in the
meantime, I'm posting this here in case someone gets there before me!

Cheers
Stu

[Steve Wagner]

This is because the BsonWriter writes byte[] as Binary(MongoDB-CSharp
type which maps to the coresponding BSON type) and so it also reads
that. The deserializer currently not convert it back while setting a
property.

You can make it work if you change you model to:

public class ByteArrayObject
{
public Binary A { get; set; }
}

The Binary type also supports direct conversion to and from byte[]. So

var bytes = new byte[100];
....
obj.A = bytes;

Should work.

I plan to add conversion to byte[] while setting the property soon.

-Steve

[Sam Corder]

Stu, would you mind filing a JIRA for this?

[Stuart Harris]

Great - that works. Thanks guys.

I recorded it in Jira (http://jira.mongodb.org/browse/CSHARP-46).

Cheers
Stu