I’ve been working on a personal project (more for learning than anything else) in C# where the user can perform a search and preview images as thumbnails on a button then select an image they want. I wanted images to start showing up as soon as the user began typing. The time it takes to shrink just 9 full sized photos to a thumbnail image is large enough that performing the search can become unbearable. Naturally I decided to solve the problem using threads, but ran into a brick wall when an exception was thrown – apparently, developers are unable to change form elements from different threads.

The exception had a link I followed that gave information on how to overcome this issue. While the article was not super easy to follow, I was able to manage. I noticed a lot of people posted questions on forums on how to overcome this error, so I got to thinking and came up with what I think is an easier alternative.

My basic setup is as follows:

1. The buttons are first created on the form.
2. A timer is started.
3. Threads are created that shrink images to thumbnail sizes for being displayed on the button.
4. A class ThreadedQ is created in which it stores a thread number, a reference to a button, a reference to the image to be shrinked, and a reference to Q (defined next)
5. The calling form has a variable, List Q, defined.
6. As threads complete, they push ThreadedQ objects onto Q.
7. Whenever the timer ticks, it checks Q for items; when one is found, it maps the newly created thumbnail to the button it references.
8. When all threads have completed, the timer stops.

While this setup may not be as good as what the original tutorial proposed, I think it may be easier for beginners to follow.