We tried connecting the Optimizely Forms to submit to a Leads database in D365.

If all of the form fields are mapping to D365 simple fields such as Single-line of text (text, email, phone, URL) or Option sets, the form submits successfully.

However, if we map a form element to a Lookup field, the form submit throws the following error:

A 'PrimitiveValue' node with non-null value was found when trying to read the value of the property '<field_name>'; 
however, a 'StartArray' node, a 'StartObject' node, or a 'PrimitiveValue' node with null value was expected.

Full stack trace here:

System.Exception: Unable to save entity for connector: Client-Test, EntityType: lead
       ---> Microsoft.PowerPlatform.Dataverse.Client.Utils.DataverseOperationException: Error identified in Payload provided by the user for Entity :'leads', For more information on this error please follow this help link https://go.microsoft.com/fwlink/?linkid=2195293  ---->  InnerException : Microsoft.OData.ODataException: A 'PrimitiveValue' node with non-null value was found when trying to read the value of the property 'custom_program'; however, a 'StartArray' node, a 'StartObject' node, or a 'PrimitiveValue' node with null value was expected.
       ---> Microsoft.Rest.HttpOperationException: Operation returned an invalid status code 'BadRequest'
         at Microsoft.PowerPlatform.Dataverse.Client.ConnectionService.ExecuteHttpRequestAsync(String uri, HttpMethod method, String body, Dictionary`2 customHeaders, CancellationToken cancellationToken, DataverseTraceLogger logSink, Nullable`1 requestTrackingId, String contentType, Nullable`1 sessionTrackingId, Boolean suppressDebugMessage, HttpClient providedHttpClient)
         at Microsoft.PowerPlatform.Dataverse.Client.ServiceClient.Command_WebExecuteAsync(String queryString, String body, HttpMethod method, Dictionary`2 customHeaders, String contentType, String errorStringCheck, Guid requestTrackingId)
         --- End of inner exception stack trace ---
         at Microsoft.PowerPlatform.Dataverse.Client.ServiceClient.Create(Entity entity)
         at Episerver.Marketing.Connector.MSDynamics.Services.MSDynamicsService.SaveEntity(Guid instanceId, String entityname, Dictionary`2 fields)
         at Episerver.Marketing.Connector.MSDynamics.MSDynamicsConnector.CreateEntity(ConnectorDataSource dataSource, Dictionary`2 entityFields)
         at Episerver.Marketing.Connector.Framework.MarketingConnectorManager.SaveEntity(IMarketingConnector connector, SaveEntityCriteria saveEntityCriteria, Dictionary`2 entityData)
         at Episerver.Marketing.Connector.Forms.Repositories.FormsRepository.PushDataToConnector(IMarketingConnector currentConnector, ConnectorDataSource currentDatasource, Dictionary`2 entityData, Int64 submissionTargetId)

The problem was due to the special handling required for saving values of Lookup fields in D365.

Instead of just this:

entity[fieldName] = value;

Lookup field values has to be set using `EntityReference` specifying the name of the parent lookup object

entity[fieldName] = new EntityReference(lookupEntityName, value);

The D365 SDK used in the connector can also be used to check the type of field, e.g. LookupAttributeMetadata, and the target lookup entity name.

In all honesty, we found a fix for this issue by replacing the implementation of `IMSDynamicsService.SaveEntity()` method.

However, I think this should be fixed on the package level moving forward.