Image Control Not Displaying An Image?

I am trying to display an image from "C:emp". Here's the code:

string root = "C: emp";
string[] files = Directory.GetFiles(root);
foreach (string f in files)
{
if (Path.GetFileName(f).Contains(user.WorkEmail))
img1.ImageUrl = root + Path.GetFileName(f);
}
}

If an image is not found, I get a thumbnail with a red "X" - fine, as expected.If an image is found, I get a thumbnail but no image gets loaded/displayed. When I right click the thumbnail and go 'Properties' it shows the correct filename.