Dispatcher.BeginInvoke
applies to .NET 5.0 and other versions, you can see the applied table in part Applies to
at the bottom of the document.
BeginInvoke/EndInvoke delegate calls
are not supported in .NET Core.
The APM (using IAsyncResult and BeginInvoke) is no longer the preferred method of making asynchronous calls. And the implementation of async delegates depends on remoting features not present in .NET Core, so BeginInvoke and EndInvoke delegate calls are not supported in .NET Core. You can refer to Microsoft .Net Blog Migrating Delegate.BeginInvoke Calls for .NET Core for more details. If I misunderstand your question, please point out and give me more detailed info to analyze.