@nicholasdgoodman you are right about older frameworks, updating to .Net standard 2.1 if I remember correctly will drop the classic .NET framework out of the window. But stackalloc should be available in 2.0 and in the worse case if it isn’t, it should be possible to use ConcurrentBag to store heap arrays of 50 elements for uniqueness validation in arrayed Send() replacing dictionary. I use ConcurrentBag to store protobuf object instances for market data in this app. I put a link at the bottom with example of making object pool with it.
With regards to IMessage instances, I Reset() them after Send accepts them on a wire and reuse them on next Send. Acknowledgements come with a correlation tag set to my internal objects, so I don’t need IMessage instance beyond return of Send call.
Regarding the P/Invoke, this one is interesting, If I had pointers from the message instances and a session pointer I could call solClient_session_sendMultipleMsg directly and still use most of C# lib. Do you have an example or an idea if this is possible without modifying the library to expose those internal IntPtr? The last time I did trickery like that was a decade ago and it involved reflection.
Create an object pool by using a ConcurrentBag - .NET | Microsoft Learn