404 error with Server Control DLLs in IIS

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404 error with Server Control DLLs in IIS

How to copy Server Control DLLs to the GAC in Windows to prevent the “404 (File Not Found) error” in Microsoft IIS.


The 404 or Not Found error message is an HTTP response indicating that the server could not find what was requested. In many cases, this is because of an incorrectly formed URL, insufficient access rights to the file, a renamed file, or a deleted file on the server. When using the Barcode Streaming Server for IIS or the Barcode Server Controls, a “404 (File Not Found) error” may also be received if the Server Control DLL is not placed in the Global Assembly Cache (GAC). When this is the case, security in IIS will prevent the server from reading the DLL file and cause the error.

The latest versions of IIS may require the Server Control DLLs to be placed in the GAC in addition to the bin folder of the Virtual Directory. To place the DLLs in the Global Assembly Cache, follow these steps:

  1. Locate the Global Assembly Cache folder. On most systems, this is the C:\windows\assembly folder. If the assembly folder does not exist, use a registry-editing tool such as RegEdit and find the key HKLM\Software\Microsoft\Fusion\CacheLocation
  2. Copy the Server Control DLL to the Global Assembly Cache directory. This is best performed with two windows explorer windows; right-click on the file, drag it to the GAC of the other explorer window and choose Copy.
  3. Restart IIS.

For more information, refer to the Microsoft Global Assembly Cache Site.