What the hell could be wrong

                absolutepath = absolutepath == null ? ("/" + folders[i] + "/") : absolutepath + folders[i] + "/";

outputs the folder[i] text just fine but leaves out the leading "/" 

by setting absolutepath = to something you are erasing the previous values

try

absolutepath += absolutepath == null ? ("/" + folders[i] + "/") : absolutepath + folders[i] + "/";

or

absolutepath = absolutepath + absolutepath == null ? ("/" + folders[i] + "/") : absolutepath + folders[i] + "/";

or

if(absolutepath == null)
  absolutepath = ("/" + folders[i] + "/");
else
  absolutepath += folders[i] + "/";

 Are you sure that absolutepath is null?  If it is equal to string.Empty then the else path will be taken and it would look like it went down the first path but missed the /.

huenemeca is right... not knowing what your absolutepath represents makes it kinda obtuse.

if its a string type, look for this:

if(absolutepath == string.empty) { }

Seems should be absolutepath = (absolutepath == null || absolutepath.Trim() == "") ? ("/" + folders[i] + "/") : absolutepath + folders[i] + "/";

dba123:

What the hell could be wrong

Not using the appropriate methods and being to fond of one-liners perhaps? ;-) Try something like this:

if (String.IsNullOrEmpty(absolutePath))
{
  absolutePath = "/";
}
absolutePath = VirtualPathUtility.AppendTrailingSlash(absolutePath + folders[i]);

What about this?

absolutepath = ( absolutepath ?? "/" ) + folders[i] + "/";

Sorry not works when absolute path is empty string, the best and safest I think is 

che3358:

Seems should be absolutepath = (absolutepath == null || absolutepath.Trim() == "") ? ("/" + folders[i] + "/") : absolutepath + folders[i] + "/";