Could not load type 'ServiceStack.UseSystemJson'

ServiceStack
1

I updated from ServiceStack 8.0.0 to 8.0.1 and my application now throws an exception:

System.TypeLoadException: Could not load type 'ServiceStack.UseSystemJson' from assembly 'ServiceStack.Interfaces, Version=6.0.0.0, Culture=neutral, PublicKeyToken=null'.
   at ServiceStack.AppHostBase..ctor(String serviceName, Assembly[] assembliesWithServices)
   at Server.ConfigurationNs.AppHost..ctor() in C:\XXX\code\src\Server\ConfigurationNs\Configure.AppHost.cs:line 47
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions)

Any ideas why 6.0.0.0 is shown above?

2

Do you have a mix of .NET 6 and .NET 8 projects?

UseSystemJson is only available in .NET 8 builds, so something must referencing .NET 6 dlls.

3

Everything should be NET 8, but I will double-check. Thank you.

4

All projects have TargetFramework as Net8.0

5

.NET 8.0 projects should be referencing the net8.0 .dll’s, but you have something referencing the 6.0.0 version of ServiceStack.Interfaces.

Can you check that all package references to ServiceStack.Interfaces reference 8.* version, i.e:

<PackageReference Include="ServiceStack.Interfaces" Version="8.*" />

Something must still be referencing the older 6.* version, try doing a clean rebuild, deleting bin/ and obj/ folders then doing a full restore if you believe that all projects (including any client projects) are referencing only 8.* packages.

6

It is strange, because all ServiceStack package references in the projects are equivalent to below:

<PackageReference Include="ServiceStack.Interfaces" Version="8.0.1" />

Previously, when all ServiceStack package references were 8.0.0 and there were no issues running the applications.

The ServiceStack packages fetched from feedz.

7

You can try downloading the pre-release packages on MyGet incase feedz is returning stale packages:

https://docs.servicestack.net/myget

8

I repeated the clearing of the nuget packages and I no longer have the error.

For reference, nuget commands documented here:

Thank you for your support.

1 Like
9

I have had to revert back to ServiceStack 8.0.0, because the 8.0.1 version caused the following error:

System.NotSupportedException: Could not resolve type 'Comment'
   at ServiceStack.GenerateCrudServices.ThrowCouldNotResolveType(String name) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack.Server/GenerateCrudServices.cs:line 319
   at ServiceStack.GenerateCrudServices.CreateOrGetType(ModuleBuilder dynModule, String typeName, List`1 metadataTypes, Dictionary`2 existingMetaTypesMap, Dictionary`2 generatedTypes) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack.Server/GenerateCrudServices.cs:line 314
   at ServiceStack.GenerateCrudServices.CreateOrGetType(ModuleBuilder dynModule, MetadataType metaType, List`1 metadataTypes, Dictionary`2 existingMetaTypesMap, Dictionary`2 generatedTypes) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack.Server/GenerateCrudServices.cs:line 508
   at ServiceStack.GenerateCrudServices.GenerateMissingServices(AutoQueryFeature feature, HashSet`1 requestTypes) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack.Server/GenerateCrudServices.cs:line 271
   at ServiceStack.AutoQueryFeature.AfterConfigure(IServiceCollection services) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack.Server/AutoQueryFeature.cs:line 191
   at ServiceStack.ServiceStackServicesOptions.ConfigurePlugins(IServiceCollection services) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack/AppHostBase.Options.cs:line 39
   at ServiceStack.ServiceStackHost.LoadPluginsInternal(IPlugin[] plugins) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack/ServiceStackHost.cs:line 1700
   at ServiceStack.ServiceStackHost.OnAfterInit() in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack/ServiceStackHost.cs:line 1226
   at ServiceStack.ServiceStackHost.Init() in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack/ServiceStackHost.cs:line 323
   at ServiceStack.NetCoreAppHostExtensions.UseServiceStack(IApplicationBuilder app, AppHostBase appHost, Action`1 configure) in /home/runner/work/ServiceStack/ServiceStack/ServiceStack/src/ServiceStack/AppHostBase.NetCore.cs:line 730
   at Program.<Main>$(String[] args) in C:\XXX\code\src\Server\Program.cs:line 43

Reverting the version removed the error.

10

We’ve had to refactor all ServiceStack Plugins to support our latest .NET 8 integration features. Sounds like the new behavior introduced this issue, which unfortunately we wont be able to identify and resolve without a repro.

If you have time to create a stand-alone repro I can look at fixing it before next release.