c# - MySQL connector 6.7.4 and Entity Framework 5 exceptions

Question

I downloaded MySQL Connector/Net 6.7.4 and MySQL for Visual Studio 1.0.2, and then followed these instructions to test it:

1. Create a connection to the existing MySQL database.
2. Create a console application.
3. Add the ADO.NET Entity Data Model from the existing database connection.
4. Add Code Generation Item EF 5.x DbContext Generator, replacing the .tt files.
5. Write some code that retrieved records from the database.

Running the application, I got this exception:

ConfigurationErrorsException: Failed to find or load the registered .Net Framework Data Provider.

Then I added references to the MySql.Data and MySql.Data.Entity libraries version 6.7.4.0 to my .NET 4.5 project. Now when I run the application, I get a different exception:

FileLoadException: Could not load file or assembly 'MySql.Data, Version=6.6.5.0,culture=neutral, PublicKeyToken=c5687fc88969c44d' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Note the version number, which is not the version of MySQL Connector that I have installed.

How do I get it working correctly?

Answer 1

The trick to solving this was:

1. Add references to the MySql.Data and MySql.Data.Entity libraries of the correct version (6.7.4.0 for .NET 4.5, in my case) to the project.
2. Edit machine.config with your editor run as administrator, and replace all occurences of MySQL version 6.6.5.0 by 6.7.4.0.

For the second step, note that there are multiple machine.config files, one for each framework version (3.0, 3.5, 4.0) and architecture (32-bit, 64-bit). Also note that the machine.config file for .NET 4.5 is in the .NET 4.0 folder. You can find the machine.config files in:

C:WindowsMicrosoft.NETFramework\Config

And:

C:WindowsMicrosoft.NETFramework64\Config

If there are no references to MySQL in the machine.config file, you might not have installed MySQL for Visual Studio. Either do that, or add the following to the app.config file of your project:

<system.data>
    <DbProviderFactories>
        <add name="MySQL Data Provider"
            invariant="MySql.Data.MySqlClient"
            description=".Net Framework Data Provider for MySQL"
            type="MySql.Data.MySqlClient.MySqlClientFactory, MySql.Data, Version=6.7.4.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />
    </DbProviderFactories>
</system.data>

Note however, that when you both install MySQL for Visual Studio and add the above snippet to your app.config file, then you'll get this exception:

ConfigurationErrorsException: Column 'InvariantName' is constrained to be unique. Value 'MySql.Data.MySqlClient' is already present.