If you search online there are over a dozen sites and blogs offering ways for developers to allow multiple file uploads on a site.
I have tried the top 10 most offered solutions, and the best one I have found is on CodeProject here.
The code solution offered above is based on another developers open source solution by fyneworks here. The CodeProject solution removes the excess code around the fyneworks code, allowing you to quickly, cleanly and easily integrate his code into your web page.
The CodeProject solution works in both asp.net webforms and MVC. Two valuable options not explained in the CodeProject introduction is the maxlength and accept attributes below.
<input type="file" class="multi" maxlength="2"/> <input type="file" class="multi" accept="gif|jpg"/>