As our policy is to keep our .NET applications on the latest LTS version, we started to upgrade our application portfolio to .NET 8. Changing the Target Framework Moniker and updating the ASP.NET Core NuGet packages was sufficient to get the upgrade done. However the upgrade also triggered some warnings and because we had ‘Treat warnings as errors’ enabled in Visual Studio, our applications refused to compile.
SYSLIB0051
The first warning we got was SYSLIB0051:
| Severity | Code | Description | Project | File | Line | Suppression State |
| Warning | SYSLIB0051 | 'Exception.Exception(SerializationInfo, StreamingContext)' is obsolete: 'This API supports obsolete formatter-based serialization. It should not be called or extended by application code.' | SOFACore | C:\source\repos\SOFACore\Configuration\ConfigurationException.cs | 20 | Active |
For every exception class we had a specific constructor that was only used for serialization purposes. As this constructor was intended to support remoting and remoting is not supported in .NET Core it doesn’t make sense to keep this constructor.
We got rid of this warning by removing all the serialization constructors for our Exception classes.
SYSLIB0049
A second (less frequent) warning we got SYSLIB0049:
| Severity | Code | Description | Project | File | Line | Suppression State |
| Warning | SYSLIB0049 | 'JsonSerializerOptions.AddContext<TContext>()' is obsolete: 'JsonSerializerOptions.AddContext is obsolete. To register a JsonSerializerContext, use either the TypeInfoResolver or TypeInfoResolverChain properties.' | eShopExample | C:\source\repos\SOFACore\Example\eShopExample\Startup.cs | 55 | Active |
In our code we use a custom JsonContext to configure how serialization should be handled by System.Text.Json:
The JsonSerializerOptions.AddContext<TContext>() method was introduced in .NET 6 as a means to associate JsonSerializerOptions instances with a specified JsonSerializerContext type. This method was superseded in .NET 7 with the introduction of contract customization and the TypeInfoResolver property.
As the JsonSerializerContext type implements the ITypeInfoResolver interface , we can easily get rid of this warn by updating our code like this:
In the code above the JsonContext class is our own implemented JsonSerializerContext: