The set_value() can't use with teyp="file"?(Solved)

[eluser]fell0206[/eluser]
Hello, I'm encountered a problem. When I followed the "user guide" of "file uploading class", I want value can be re-populating, so I add "set_value...", but it can't work, how can I fix it? Thank you!
My Code:
<input type="file" name="Image1" id="Image1" class="text-input medium-input" value="<?php echo set_value('Image1'); ?>" >