.AddRoundRobinLoadBalancer() causes NotSupportedException in .net5.0

[antonpopov]

When using .AddRoundRobinLoadBalancer() for client side load balancing in .net5.0 upon sending a http request an exception is thrown: NotSupportedException: BinaryFormatter serialization and deserialization are disabled within this application. See https://aka.ms/binaryformatter for more information.

Steps to reproduce

Steps to reproduce the behavior:

1. Create an ASP.NET Core Web API project
2. Configure a named http client to use DiscoveryHttpClientHandler and add .AddRoundRobinLoadBalancer().

services.AddHttpClient("test")
        .AddRoundRobinLoadBalancer()
        .ConfigurePrimaryHttpMessageHandler(sp => new DiscoveryHttpClientHandler(sp.GetService<IDiscoveryClient>()))
        .AddTypedClient<ITestService, TestService>();

3. Make a request through the http client.

Environment:

• Steeltoe Version [3.0.1]
• .NET Version [.NET5.0]

[antonpopov]

I did some research on the issue and I believe here is the problem and it's caused by a breaking change in .NET 5.0.
Here is a temporary workaround for anyone who has the same issue:

<PropertyGroup>
  <TargetFramework>net5.0</TargetFramework>
  <!-- Warning: Setting the following switch is *NOT* recommended in web apps. -->
  <EnableUnsafeBinaryFormatterSerialization>true</EnableUnsafeBinaryFormatterSerialization>
</PropertyGroup>

N.B. As pointed in Microsoft's documentation this workaround is not recommended as a long term solution due to security reasons.

[TimHess]

Thanks for finding this @antonpopov