Concatenate text with bind on image source

I'm developing an client application for my asp.net website and i want to show some pictures on this client. On the browser, it returns the image path like this: "/Image/img.jpg", and it works fine. But on the WPF i can't show those images.

I'm using EF to return me a list of objects that have the image filename and i pass them to my listview wich have the ItemTemplate to bind the image. To display the image i tried the string format like this:

<Image Source="{Binding Photo, StringFormat='https://localhost:1234/Image/{0}'}"

It displays the correct path, but dont show any image.