Azure Functions – Json: Self referencing loop detected for property


Whilst developing a Rest API using Azure functions I got the error below.

 Newtonsoft.Json: Self referencing loop detected for property 'task' with type 'System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[System.Collections.Generic.IEnumerable`1[Feature.Order.Domain.TravelCard.OrderedTravelCard],Feature.Order.Domain.TravelCard.OrderedTravelCardRepository+<Get>d__4]'. Path 'stateMachine.<>t__builder'

As we had created a lot of new models and called a number of external API’s, which had a bad habit of changing their models without notification. I assumed incorrectly that one of the swagger files for the API’s was not correct.

But after much investigation I could not detect any issue with the data returned from the external API’s and the models match correctly their definitions.

Eventually I found out what the issue was, can you see what is wrong with the following code?


See the image above that a Task<…> is returned from the OrderedTravelCardRepository.Get() function.

I had forgotten to await the asynchronous call of the function, see the fixed code below.

Simple when you know how, simply awful when you don’t!

I hope this blog post helps others avoid the time I wasted on this issue.

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