The problem

An object (with a private MethodInfo field) serialized with version 1.0 of an assembly won't be deserialized with the version 1.1 of that assembly (a SerializationException will be thrown because required method has not been found).

What's changed?

I found that in .NET 4.5 the serialization mechanism of a MemberInfo via MemberInfoSerializationHolder has been changed. In the past (up to .NET 4.0) the serialized data was the method signature (obtained with a simple MethodInfo.ToString()). According to comments in the .NET source code they added a second signature obtained via SerializationToString() because:

m_signature stores the ToString() representation of the member which is sometimes ambiguous. Mulitple overloads of the same methods or properties can identical ToString(). m_signature2 stores the SerializationToString() representation which should be unique for each member. It is only written and used by post 4.0 CLR versions.

For what I can see the MemberInfoSerializationHolder.GetRealObject() uses this (simplified) code to resolve the method (from .NET source code):

for (int i = 0; i < methods.Length; i++)
{ 
    if (m_signature2 != null) // SerializationToString() signature
    {
        if (((RuntimeMethodInfo)methods[i]).SerializationToString().Equals(m_signature2))
        { 
            methodInfo = methods[i];
            break; 
        } 
    }
    else 
    {
        if (methods[i].ToString().Equals(m_signature))
        { 
            methodInfo = methods[i];
            break; 
        }
    }
}

if (methodInfo == null)
    throw new SerializationException(...);

In this case the deserialization fails because the m_signature2 signature can't be found because assembly name contains version information then String.Equals() wo