How can I make my image control's imageurl dynamic depending on host?

Protected Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
    If Request.Url.Host.Contains("localhost") Then
        Image1.ImageUrl = "C:Usersfirstname.lastnameDocumentsVisual Studio 2008WebSitesecardsystemimagesECard Platform.jpg."


    End If

End Sub

Image1.ImageUrl = "~/images/Card Platform.jpg."