FileNotFoundException: Could not load file or assembly 'System.Configuration.ConfigurationManager,

Question

I am trying to connect to Oracle database from .NET Core 3.1 using ADO.NET, here's my code:

private OracleConnection GetOracleConnection()
{
    string conString = "Data Source=Q550.adr.XXXX.com;Persist Security,Info=True;User ID=XXXX;Password=CCC39";
    OracleConnection con = new OracleConnection(conString);
    return con;
}

but when this function executes following exception occured at line number 2

System.TypeInitializationException: 'The type initializer for 'OracleInternal.Common.ProviderConfig' threw an exception**

FileNotFoundException: Could not load file or assembly 'System.Configuration.ConfigurationManager, Version=4.0.2.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The system cannot find the file specified.

Can anyone tell me what's happening?

Carpospore

Try this : Go to project properties and uncheck prefer 32 bit. – Haematocryal

By any chance, do you refer the ConfigurationManager.ConnectionStrings or added ConfigurationManager in your namespace? In .net core, you need to include the System.Configuration as a package to use the ConfigurationManager object to access the AppSettings and ConnectionStrings. – Firth

alternatively , you can Install-Package System.Configuration.ConfigurationManager from nuget – Haematocryal

"prefer 32 bit" is unchecked (by default when creating the project) and doesn't solve the problem. Installing System.Configuration.ConfigurationManager as you suggest does it. – Belva

exactly same problem here when trying to connect to MySQL – Speakeasy

Installing the package doesn't help when deploying because the dll is not included in the build – Areola

Answer 1

You can Install System.Configuration.ConfigurationManager from Nuget

Install-Package System.Configuration.ConfigurationManager

This problem is a known issue as you can see here and the recommended solution is nuget package

https://github.com/pusher/pusher-websocket-dotnet/issues/34

Haematocryal

For MySQL I needed this ,and also System.Management, no idea why. – Speakeasy

Install-Package Oracle.ManagedDataAccess.Core instead System.Configuration.ConfigurationManager. It is deprecated – Elbowroom

Answer 2

I tried adding a reference to NuGet package System.Configuration.ConfigurationManager, but the latest version of this library (7.0) doesn't contain the ConfigurationManager anymore. So then it still doesn't compile. After a lot of seaching, I figured out I had to include version 4.5 of the NuGet package.

Workday

I just double check using dotPeek, the dll version 7.0.0.0 for .NETCoreApp v.6.0 indeed contains the class ConfigurationManager. – Parmenter

I tried 7.0, no good, downgraded to 4.5, success! Thanks! – Polymerism