C# – Error System.Data.OracleClient requires Oracle client software version 8.1.7 or greater when installs setup

I've run into this error dozens of times:

Cause

Security permissions were not properly set when the Oracle client was installed on Windows with NTFS. The result of this is that content of the ORACLE_HOME directory is not visible to Authenticated Users on the machine; this causes an error while the System.Data.OracleClient is communicating with the Oracle Connectivity software from ASP.NET using Authenticated User privileges.

Solution

To fix the problem you have to give the Authenticated Users group privilege to the Oracle Home directory.

• Log on to Windows as a user with Administrator privileges.
• Start Windows Explorer and navigate to the ORACLE_HOME folder.
• Choose properties on the ORACLE_HOME folder.
• Click the Security tab of the Properties window.
• Click on Authenticated Users item in the Name list.
• Un-check the Read and Execute box in the Permissions list under the Allow column.
• Re-check the Read and Execute box under the Allow column.
• Click the Advanced button and in the Permission Entries verify that Authenticated Users are listed with permission: Read & Execute, and Apply To: This folder, subfolders and files. If not, edit that line and make sure that Apply To drop-down box is set to This folder, subfolders and files. This should already be set properly but it is important that you verify it.
• Click the OK button until you close out all of the security properties windows. The cursor may present the hour glass for a few seconds as it applies the permissions you just changed to all subfolders and files.
• Reboot, to assure that the changes have taken effect.

Try your application again.

Perhaps not an answer to your specific question, but for the record it is for this kind of reasons that I always favor Oracle Instant Client :

• You don't have to install anything on the target machines (including dev boxes !). So no tricky manual setup and goat sacrificing.
• You can make sure that your application will run with the specific client you picked (version, x86/x64).
• You could even easily have multiple applications work with different client versions on the same computer.
• As a downside, it adds a significant weight to your application (~19Mb minimum), and you can't participate in distributed transactions.

If you still can switch, this is the way to go IMHO. Check What is the minimum client footprint required to connect C# to an Oracle database? for more information.