I had an interesting question earlier today which I thought was worth sharing. One of my coworkers was trying to use the code sample from my Programmatically Flushing FTP Logs blog, and he was getting the following error:

Unhandled Exception: System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
   at Microsoft.Web.Administration.Interop.IAppHostMethodInstance.Execute()
   at Sample.Main() in c:\Projects\FtpTests\Program.cs:line 25

I knew that the code sample in my blog worked perfectly when I originally wrote it, so I figured that my coworker must be doing something wrong. (And every developer has said "It works on my computer..." at one time or other.) But I decided to give him the benefit of the doubt, so I copied the source code from my blog into a new Visual Studio project and I ran it.

Much to my surprise, I saw the same error that my coworker was seeing if I didn't step the code through with a debugger.

When I stepped through the code in a debugger, I saw the following error message:

At this point I was thinking, "What the heck? I know this code was working before..." I started to wonder if we had released a breaking change to the FTP service sometime during the past two years, but then it suddenly dawned on me: I hadn't started the FTP service on my computer.

[Duh.]

That was the source of the problem: I usually have the FTP service configured for manual startup on my development computers, but the FTP methods to start and stop FTP sites and flush the FTP logs do not work when the FTP service is not running. Once both of us started the FTP service on each of our systems the problem went away.

I hope this helps. ;-]