C# – Unable to use Log4Net with .net Framework 4

The .NET Assembly loader:

• is unable to find 1.2.0.203
• but did find a 1.2.0.200

This assembly does not match what was requested and therefore you get this error.

In simple words, it can't find the assembly that was referenced. Make sure it can find the right assembly by putting it in the GAC or in the application path. Also see https://docs.microsoft.com/archive/blogs/junfeng/the-located-assemblys-manifest-definition-with-name-xxx-dll-does-not-match-the-assembly-reference.

I am having the same issues with VS 2012. I am not sure how to fix it but after spending quite a bit of time on it here is what I see is happening.

1. Over all your/my system is at mysql.data.dll version 6.9.9.0. I am not able to downgrade this to 6.9.8.0 When I do I create other version problems with mysql.data.dll that seem to be unresolveable with my knowledge level.

2. I chased down all 6.9.8.0 versions of the DLL and removed them, ensuring that there was a 6.9.9 version in its place. Once I have done this I am not able to add a data connection to a MySQL Database. When I try I get the error An error occurred that is normally caused by not having Visual Studio properly installed. In addition non of the previously defined data connections work.

3. Not having MYSQL-connector-net-6.9.9 installed gives an error of "Cannot obtain provider factory for data provider named MySql.Data.MySqlClient" and you don't even get to the error described above by the OP.

   4. I have tried various connector-net versions and this does not fix the problem.

I have no references to 6.9.8.0 in any of my projects but clearly for some reason VS needs it to create the data connections.

Update:

I removed MySQL, then went through and deleted all mysql*.dll and all config files. I then used the MySQL Installer 5.7.14 found at http://dev.mysql.com/downloads/installer/

The installer still installed the mysql.data.dll version 6.9.8.0 and it still causes the error.

Update: The problem is with MySQL Connector / Net. It is using version 6.9.9.0 of the DLL and everything else is using 6.9.8.0 Go to your community installer and uninstall connector / net. Then go to https://downloads.mysql.com/archives/c-net/ and get version 6.9.8 of the connector / net. Install this and everything should be fine. It has worked on my system.