I am using NET 6 Web Api.

I would like to process objects with the same identifier sequentially, whilst in parallel to different identifiers.

To illustrate the issue, given my object is as follows:

class Data{ public int Id {get;set;} public string o {get;set}} 

So with a list as follows:

var l = new List<Data>(){
    new Data() { Id = 1, o = "xxxxxx"},
    new Data() { Id = 1, o = "yyyyyy"},
    new Data() { Id = 12, o = "aaaaaaa"},
    new Data() { Id = 12, o = "ccccccc"},
    new Data() { Id = 97, o = "mmmmmmm"}
}

I would expect 3 “queues” in parallel. One processing Id=1, another Id=12 and another Id=97.

I have been using Channel<Data> to foreach(var x in channel.Reader.ReadAllAsync(cancelationTken)) the data to process in a BackgroundService. But this leads to one long queue, which then processes everything sequentically.

I am looking for pointers on how I might go about implementing such a requirement. Parallel.ForEach came to mind – where it would group those with the same Id and put them in the same thread, but I am not sure if this grouping functionality is available yet.