An error occurred creating the configuration section handler for system.data: Column 'InvariantName'

[insandur]

An error occurred creating the configuration section handler for system.data: Column 'InvariantName' is constrained to be unique. Value 'MySql.Data.MySqlClient' is already present. (C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config line

[EZReinert]

In my case I upgraded v8.0.30 to v9.0.0 and found a duplicate entry in the machine.config file. 
Deleted the line that was related to old version.
Restarted machine.

Everything is working ok now.
Thanks.

[insandur]

An error occurred creating the configuration section handler for system.data: Column 'InvariantName' is constrained to be unique. Value 'MySql.Data.MySqlClient' is already present. (C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config line

[v-yohua-msft]

Hi, @insandur 

You can locate the machine.config file:
For 32-bit systems: C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config
For 64-bit systems: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config
Then open the machine.config file in a text editor with administrative privileges. Search for the MySql.Data.MySqlClient entry under the <DbProviderFactories> section. Try to Remove or comment out the duplicate entry. Ensure that only one entry for MySql.Data.MySqlClient exists. Save the file and restart your application or service.

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