c# - InvalidCastException when serializing and deserializing

Question

I have this code:

public byte[] SerializeToBlob()
{
    using (var buffer = new MemoryStream())
    {
        var formatter = new BinaryFormatter();
        formatter.Serialize(buffer, this);
        buffer.Position = 0;
        return buffer.ToArray();
    }
}

public static ActionData DeserializeFromBlob(byte[] state)
{
    using (var buffer = new MemoryStream(state))
    {
        var formatter = new BinaryFormatter();
        var result = formatter.Deserialize(buffer);
        return (ActionData) result;
    }
}

And am calling it as follows:

byte[] actionDataBlob = ad.SerializeToBlob();
var ad1 = ActionData.DeserializeFromBlob(actionDataBlob);

However, I get an InvalidCastException when it tries to cast the deserialized object to its type:

[A]ActionData cannot be cast to [B]ActionData. Type A originates from 'XXXX.XXXX.Auditing, Version=1.0.76.0, Culture=neutral, PublicKeyToken=null' in the context 'Default' at location 'C:UsersCraigAppDataLocalTempTemporary ASP.NET Files oot5d978e5bffc57fe1assemblydl32b1e5f8f102c846e_9506ca01XXXX.XXXX.Auditing.DLL'. Type B originates from 'XXXX.XXXX.Auditing, Version=1.0.76.0, Culture=neutral, PublicKeyToken=null' in the context 'LoadNeither' at location 'F:Visual Studio ProjectsXXXXXXXXXsourceXXXX.XXXX.SilverlightClient.WebinXXXX.XXXX.Auditing.dll'.

(XXXX.XXXX is there to obscure the client's name)

What gives?

I've now asked a related question here:

How should I serialize some simple auditing data for storing in a SQL table?

Answer 1

You have loaded the same assembly twice, in different loader contexts. E.g. you happened to load the XXX.Auditing with Assembly.LoadFrom() first, and then some other (or your) assembly loaded it normally. In fact, the binary deserializer could be the one who loaded the assembly a second time, though I wouldn't know why (no experience with ASP.NET).