System .__ ComObject不转换....为什么这个例外？

Question

I purpose, turn obj into byte array objects. But serialize method is error 

Dim obj As Object = Nothing
    昏暗数据As Byte（）
    obj = getDocument（pid）'getdocument（pid） - ＆gt;类型：Object，obj.value = System._Object     data = ObjectToByteArray（obj）

*****高级代码Form_Load *****

**Public Function ObjectToByteArray(obje As Object) As Byte()**    
Dim ms As New MemoryStream()    
Dim bf As New BinaryFormatter()    
bf.Serialize(ms, obje)              ******Exeption Error**
Return ms.ToArray()    
**End Function**

我的例外是：在程序集'mscorlib中键入'System._ComObject'，版本= 4.0.0.0 Culture = neutral，PublicKeyToken = b77a5c561934e089'未标记为可预订的