/git/AboutUs/Startup.cs(62,22): error CS1061: 
'IServiceCollection' does not contain a definition for 'AddEntityFramework' and no extension method 'AddEntityFramework' accepting a first argument of type 'IServiceCollection' could be found (are you missing a using directive or an assembly reference?)

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddEntityFramework()
        .AddSqlServer()
        .AddDbContext<EfDbContext>(options =>
        {
            options.UseSqlServer(Configuration["data:ConnectionString"]);
        });
}