WCF can't serialize cyclic references

Question

I have a database with a lots of relationships between Tables and a Silverlight client that connects to my server with WCF service on ASP.Net side.

First i used LINQ to SQL as a robust mapper tables to object and in a WebMethod that returns a List<Foo> of my Database's object(suppose GetFoo()). The Foo has lots of relationships with other objects that each of that have lots of realaships too,(this means , there is a PK and FK between tables).also i use Microsoft Service Trace Viewr for track my service

When i call GetFoo() , WCF returns this error:

Object graph for type 'X.Y.Z' contains cycles and cannot be serialized if reference tracking is disabled

I searched this error and find this great post but that is not working properly and i see same error too.

Answer 1

I know this is an old question now, but did you try decorating the classes generated by your DBML with [DataContract(IsReference=True)]?

I had the same problem in 2010 and had to resort to some fairly extreme measures to get it to work on client and service sides, but recently went back through it with VS2013/.NET 4.5 and had much less pain, as documented here (with EF v6 RC 1 POCO objects): http://sanderstechnology.com/2013/more-with-the-entity-framework-v6-rc1/12423/

Answer 2

A bit late this. But if anyone are using linqtosql and have this problem you can simply just open the tables in your dbml class. Right click next to a table and click properties. HEre there is a property named Serialization Mode.. Set it to Unidirectional

The error will be gone

Answer 3

Various options:

• remove the cyclic dependencies from your model; this might be tricky for a generated model that has lots of existing code built against it, but is worth a try; however, you typically want to not serialize the parent, which is exactly what LINQ-to-SQL wants you to keep (it'll let you drop the children property, but that is what you usually want to serialize)
• enable cyclic references; it looks like you've tried this without success; did you enable it at both ends, though? Actually I wouldn't be surprised if Silverlight doesn't like this extension (it has limited extension support)
• use a separate (flat) DTO model for data transfer purposes
• try using NetDataContractSerializer; I can't remember if this is supported in Silverlight, and I must admit I'm not its biggest fan, but it might be a pragmatic fix here

I'd vote firmly in the "DTO model" category; simply, having a separate model means you are less likely to run into tangles whenever you tweak the DB - and you are in complete control over it.