In a past blog post I wrote about a surprising change I encountered during the migration of a .NET Core 2.2 application to .NET Core 3.0. I have just migrated that same application to .NET 5 and guess what, I stumbled across another “tiny difference with big consequences”.

The situation: I have a WPF desktop client that communicates with an ASP.NET Core server that in turn communicates with a small TypeScript browser application. I use Web API for accessing files and meta data, and SignalR to call remote functions.

After the migration I ran the application and things were working fine – until a certain point, where I received the following exception in a call of SignalR’s HubConnection.InvokeCoreAsync() (actual function name replaced with “doSomething”):

Microsoft.AspNetCore.SignalR.HubException
   HResult=0x80131500
   Message=Failed to invoke 'doSomething' due to an error on the server.
   Source=System.Private.CoreLib

#signalr #dotnet #aspdotnet core #dotnet core #dotnet core 3.1 #dotnet 5