Distributed Transactions :: NullException: value cannot be null. Parameter name: assemblyString

 
I have a layer in c# with the business objects that is an assembly file
But now in the web Site en i try to send a object i receive the error  
NullException: value cannot be null.  Parameter name: assemblyString 
--
Assembly files
Class Object()
{   Insert(object_to_insert)  }
Web Pages
... 
Object obj = new Object()
obj.Insert(object_to_insert)    <<--  where receive the error
 ...
 in the rest all works fine the web pages and the assembly pages connect fine one with the other
  
 
 What should i do?
AssemblyString what is this ??  
 
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in the web i find an example where they use
this in the business layer 
    [Transaction(System.EnterpriseServices.TransactionOptio ...