Does Server.MapPath Behaves Differently In Local Machine And Server Machine

I have had a real nightmare with Server.MapPath(). When I call Server.MapPath("~") in my application that is running in ASP.NET Development Server it returns root directory that ends in a back slash like f:projectsapp1, but I call it in published version, installed in IIS, it returns root directory without any back slash like c:inetpubwwwrootapp1.

string mainRoot = HttpContext.Current.Server.MapPath("~");
DirectoryInfo di = new DirectoryInfo(mainRoot);
//added to solve this problem with Server.MapPath
if (!mainRoot.EndsWith(@""))
mainRoot += @"";
FileInfo[] files = di.GetFiles("*.aspx");
foreach (FileInfo item in files)
{
string path = item.FullName.Replace(mainRoot, "~/").Replace(@"", "/");
//do more here
}