Errors occur in applications that combine transaction flow and remote calls after the July 2018 .NET Framework Security and Quality Rollups are installed

After you install the July 2018 .NET Framework Security and Quality Rollups that apply to .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, and 4.7.2 on Windows 7 Service Pack 1 (SP1), Windows Server 2008 R2 SP1, or Windows Server 2008 SP2, you notice errors in a .NET Framework application that meets the following criteria:

• The application uses instances of the System.Transaction.TransactionScope class in which transaction flow is enabled by passing TransactionScopeAsyncFlowOption.Enabled to the constructor.
• The application makes one or more remote calls while one of these transaction scopes is active. In this case, a remote call is any call that travels through a transparent proxy before it reaches the server object. Examples of remote calls include calls to other application domains and calls made through remoting channels, such as the client channels that are defined in the System.Runtime.Remoting.Channels namespaces.
• After the remote call, System.Transactions.Transaction.Current returns a null value instead of the value that was returned before the remote call.

To work around this issue, try any of the following methods:

• For each transaction scope that enables transaction flow, change the application to make sure that no remote calls occur anywhere in the code that runs while the transaction scope is active. When you determine whether a transaction scope contains any remote calls, consider the following guidelines:
  • A call to a static method is never a remote call.
  • For a call to an instance method on a target object, the call is remote only if the target object is a transparent proxy.
  • For a call to a constructor, the call is remote only if the constructed object is a transparent proxy.
  Note You can always use the System.Runtime.Remoting.RemotingServices.IsTransparentProxy method to check whether an object is a transparent proxy.
• Disable transaction flow by removing the TransactionScopeAsyncFlowOption.Enabled constructor argument. 

  Warning

  This workaround is likely to cause other errors if any "await" operations execute while the transaction scope is active.

• The Transaction.Current property is not automatically serialized to the remote call. It must be passed as a parameter. If the remote call does not pass the transaction as a parameter and does not make a callback to the client during the remote call, you can create the remote call inside a new TransactionScope object that uses the TransactionScopeOptions.Suppress option. Inside this suppress transaction scope, the Transaction.Current property has a null value.

We are aware of this issue and are currently working on a resolution.