Circular reference causing stack overflow with Automapper

Question

I\'m using Automapper to map my NHibernate proxy objects (DTO) to my CSLA business objects

I\'m using Fluent NHibernate to create the mappings - this is working fine

Answer 1

Since this is the #1 google search result, I think there might be some people, like me, coming here who don't get a stackoverflow exception, but find trouble when sending the object (via ASP.NET) to the client, and thus it being JSON serialized.

So I had the same structure in place, Invoices has multiple InvoiceLines, when I load an Invoice and use the Linq-to-SQL .Include(x => x.InvoiceLines) I get errors when I try to load the object from the Api because each InvoiceLine contains the same Invoice again.

To solve this, do the following in ASP.NET Core Startup class:

services.AddMvc().AddJsonOptions(o =>
{
    o.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
    o.SerializerSettings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;
    o.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.Objects;
    // ^^ IMPORTANT PART ^^
}).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

So include o.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.Objects; in your JsonConfiguration when adding MVC to your application.

JSON.Net is taking the extra step to setup each reference with an additional meta-property called “$id”. When JSON.Net encounters the same instance in another place in the object graph, it simply drops a reference to the original instance, instead of duplicating the data, and thus not causing circular reference issues!

Source: https://johnnycode.com/2012/04/10/serializing-circular-references-with-json-net-and-entity-framework/

So now I don't have to further edit my AutoMapper configuration.