Error: No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'

Question

I recently upgraded/updated Entity Framework in an old project from version 4 or 5 to version 6. Now I get this exception:

An exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll but was not handled in user code

Additional information: No Entity Framework provider found for the ADO.NET provider with invariant name 'System.Data.SqlClient'. Make sure the provider is registered in the 'entityFramework' section of the application config file. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information.

I googled the error and came across a couple of SO threads, but none of them contained a solution that works for me. This is what my App.config looks like:

<?xml version="1.0" encoding="utf-8"?> <configuration>   <configSections>     <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->     <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />   </configSections>   <entityFramework>     <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />     <providers>       <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />     </providers>   </entityFramework> </configuration> 

I already uninstalled Entity Framework from my project and re-installed it, deleted all the references to old EF files and re-installed, but nothing works for me. I keep getting this error.

Answer 1

I had this problem in a situation where I have a model project that has the references to both EntityFramework and the .SqlServer assemblies, and a separate UI project that uses ASP.NET MVC. I wanted to upgrade from EF 4.1 to 6.1. I actually had to do part of what was described here: http://robsneuron.blogspot.com/2013/11/entity-framework-upgrade-to-6.html. I want to emphasize that I did not add a reference to these projects to my UI project nor did I add the configuration to the UI project's web.config, as those steps would violate my separation of concerns.

What I did do was in my model project, I had to flip the "Copy Local" reference settings for EntityFramework.SqlServer (and the EntityFramework reference, to be safe) to "False" and save all, to get the project to put the <Private> node into the .csproj file, and then set it back to "True" and save again, so that True ends up as the final value.

I also had to add the hack line to my DbContext-derived class in its constructor to force the use of the assembly, even though the line does nothing. Both of these steps I learned from the blog post.

public MyContext : DbContext {     public MyContext() : base("name=MyContext")     {         // the terrible hack         var ensureDLLIsCopied =                  System.Data.Entity.SqlServer.SqlProviderServices.Instance;        } 

I want to thank the author of that blog that I referenced, as well as all the people that asked and answered the questions on SO, to try to help us get past this terrible bug.

Answer 2

Ok, this is pretty weird. I have a couple of projects: one is a UI project (an ASP.NET MVC project) and the others are projects for stuff like repositories. The repositories project had a reference to EF, but the UI project didn't (because it didn't need one, it just needed to reference the other projects). After I installed EF for the UI project as well, everything started working. This is why, it added this piece of code to my Web.config:

<entityFramework>   <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />   <providers>     <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />   </providers> </entityFramework>