如何使用Django上传文件

I'm trying to write form to upload a file with Django. The admin form works just fine, but the problem is that after I click submit on my form, the form loses the file that I selected (filename disappears and 'No file chosen' appears next to 'Choose File' button), and the view won't validate the form because the file is missing. My form/view/file handler look just like the I'm trying to write form to upload a file with