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alex-1337's avatar
alex-1337
Copper Contributor
Oct 10, 2022

Could not load file or assembly System.Data.SqlClient

Hello, I'm currently learning the ASP.NET Core-Web-API (.NET 6) system. I added a class-library (.NET Framework) (v4.8) as a DataAccessLayer to my project. There is a DAO class with a sql-query that...
ASP.NET Core
Web API
alex-1337's avatar
alex-1337
Copper Contributor
Oct 12, 2022

I found a solution, without knowing why this is a solution, for this problem.

 

I have two projects:

1. ASP.NET Core-Web-API (.NET 6)

2. Class-Library (.NET Framework) (Framework v4.8)

 

The connection to the database happens with Dapper and System.Data.SqlClient. Both are added to the references of the the Class-Library, but not added to the dependencies of the the Web-API. This should work, because the Class-Library should provide the SqlClient and Dapper, but it doesn't. It provides only Dapper to the Web-API. Idk why, but I needed to add the System.Data.SqlClient with NuGet to my Web-API dependencies too. I'll never use the SqlClient in my Web-API in furure. Currently it's a bug in the ASP.NET Core-Web-API in my opinion. I would be very grateful, if someone could explain this behaviour to me.

 

Regards

mBardos76's avatar
mBardos76
Copper Contributor
Jun 19, 2023

alex-1337 anyone stumbles on this, the System.Data.SqlClient.dll will be copied with the class library, if you add the following lines to your class library's app.config:
<entityFramework>
  ...
   <providers>
       <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
</entityFramework>

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