Out of proc COM sluggishness

I'm presently working on a side-by-side application (C#, WinForms) that injects messages int开发者_开发技巧o an application via COM.

This application uses multiple foreach statements, polling entity metrics from the application that accepts COM. A ListBox is used to list each entity, and when a user selects one from this list, a thread is created and executed, calling a method that retrieves the required data.

When a user selects a different entity from the list, the running thread is aborted and a new thread is created for the newly selected entity.

I've spent a day looking into my threading and memory usage, and have come to a conclusion that everything is fine. Never is there more than 6 threads running concurrently (all unique for executing different members), and via the Windows task manager, my application never peaks >10 CPU%, 29M MEM.

The only thing coming to mind is that the COM object you are using is designed to run in a single threaded apartment (STA). If that is the case then it will not matter how many threads you start; they will all eventually get serialized when calling into this COM object. And if your machine has multiple cores then you will definitely see less than 100% usage. 10% seems awfully low though. I would not be surprised to see something around 25% which would basically represent one pegged core of a quad core system, but the 10% figure might require another explanation. If your code or the COM object itself is waiting for IO operations to complete that might explain more of the low throughput.

In WinForms you can do SuspendLayout() and ResumeLayout(). If you are inserting a lot of items (or in general doing a lot of screen updates) you would first call SuspectLayout() then do all of your updates and then ResumeLayout().

You don't mention what's slow, so it's very difficult to say anything with certainty. However, since you say that you insert items into a listbox, I'll make a complete guess and ask how many items is that each time? It can be very slow to insert a lot of items into a list box.

If that's the case, you could speed it up by instead of listing each entity in one listbox, only list a set of categories there and then when the user selects a category you'll populate another listbox with the entities related to that category.