Problem

While upgrading a .NET customisation that interfaced with our client Dynamics 365 online environment (Version 9). I encountered the following error while attempting to fetch some records from our Dynamics 365 instance.

The same code had previously worked without issue in our Dynamics 365 Version 8 environment.

“Metadata contains a reference that cannot be resolved: ‘https://XXXX.api.crm6.dynamics.com/XRMServices/2011/Organization.svc?wsdl&sdkversion=9'.”

{“The underlying connection was closed: An unexpected error occurred on a send.”}

{“Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.”}

“The underlying connection was closed: An unexpected error occurred on a send.”

Error Screenshot

Solution

As per the below Microsoft article Dynamics 365 now requires TLS 1.2

https://support.microsoft.com/en-au/help/4051700

 

The solution is to either:

  • Use .NET framework version 4.6 which uses TLS 1.2 by default

or

  • Add the below line of code to your app (before making calls to Dynamics 365) to explicitly enable TLS 1.2
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11;

 

Shane Bartholomeusz