Aspnetcore: Object reference not set to an instance of an object.

[abhishekgoenka]

I am getting the following error after including Newtonsoft.Json(version 11.0.2) package

Uncaught Error: Newtonsoft.Json.JsonSerializationException: Error setting value to 'TargetId' on 'BlazorApp1.Message'. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at System.Linq.Expressions.Interpreter.LightLambda.MakeRunDelegateCtor (System.Type delegateType) <0x1d7f658 + 0x00308> in :0
at System.Linq.Expressions.Interpreter.LightLambda.GetRunDelegateCtor (System.Type delegateType) <0x1d78e70 + 0x00048> in :0
at System.Linq.Expressions.Interpreter.LightLambda.MakeDelegate (System.Type delegateType) <0x1d78ce8 + 0x0000e> in :0
at System.Linq.Expressions.Interpreter.LightDelegateCreator.CreateDelegate (System.Runtime.CompilerServices.IStrongBox[] closure) <0x1d783c0 + 0x00024> in :0
at System.Linq.Expressions.Interpreter.LightDelegateCreator.CreateDelegate () <0x1d78250 + 0x0000a> in :0
at System.Linq.Expressions.LambdaExpression.Compile (System.Boolean preferInterpretation) <0x205a910 + 0x00018> in :0
at System.Linq.Expressions.LambdaExpression.Compile () <0x205a8d8 + 0x0000a> in :0

[danroth27]

Yes, this is a known issue (https://github.com/aspnet/Blazor/issues/370) that we hope will be resolved with the next Mono update (#831)

[wdupree]

Has this issue been addressed with 0.4.0? I'm having an issue with trying to serialize and deserialize using Newtonsoft (originally in 0.3.0, then updated this morning to 0.4.0) with a simple class (it errors on an int in the object). I didn't want to open another duplicate.

[danroth27]

There are some reports from folks that this might actually be an issue with how Blazor trims out unused IL. @kiyote do you want to share the linker config you were using to get Json.NET working here?

[wdupree]

Thanks @danroth27, hopefully that would help - what's a linker config and how does it help change how serialization happens?

[danroth27]

@abhishekgoenka Could you please try out your scenario with this linker config and see if it resolves your issue?

[abhishekgoenka]

@danroth27 I am using this linker. Will the same linker config work?

[danroth27]

Blazor runs the mono linker by default as part of each build. You just need to configure it to not link out System.Linq.Expressions.* so that compiled expressions work. See https://gist.github.com/Suchiman/a5e65f40c353120c9cf7f6a631ded28b

[abhishekgoenka]

It works with linker.xml file.

[wjulianpineda]

it work also for AutoMapper @danroth27 thanks.