Method 'ExecuteAsync' in type 'System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy' does not have an implementation

Question

I am newer about using Code First in c#. After I enabled Migration in my project and launch my site, I get an Error:

Method 'ExecuteAsync' in type 'System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy' from assembly 'EntityFramework.SqlServer, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' does not have an implementation.

I have defined the context class as below.

namespace MyOA.Migration.Contexts
{
    public class OADBContext : DbContext
    {
        public OADBContext() { }
    }
}

and I tried to create the DB in Global.asax as below.

protected void Application_Start()
{
    // Forces initialization of database on model changes.
    using (var context = new Migration.Contexts.OADBContext())
    {
        context.Database.Initialize(force: true);
    }    
}

I tried to search the reason but got no idea. Any suggestions? Thanks in advance.

Answer 1

If you check the .NET version of the two asseblies:

• EntityFramework (v4.5)
• EntityFramework.SqlServer (v4.0)

You will see that EntityFramework.SqlServer has v4.0 .NET dependency, but EntityFramework uses v4.5. That is the root of the issue. I use dotpeek tool for checking the assembly version (there are other options from stack overflow to check .net vestion of an assembly).

Note: and really when you decompile EntityFramework.SqlServer.dll using jetBrains reflector tool you will find that there is no ExecuteAsync method.

What we have to do to fix the issue is to use nuget.exe (from visual studio or from stand alone nuget executable: please find "latest nuget.exe"). And run it from command line:

cd "[path to your nuget.exe]"
nuget Install EntityFramework

A set of EF 6 assemblis will be downloaded. Use the EntityFramework and EntityFramework.SqlServer from .net v4.5 folder.