Едно и също приложение, различни бази данни:Entity framework 6.X + MySQL + SQL Server

И така, окончателното решение е:

1. Създайте собствен наследник на DbConfiguration с блекджек и проститутки:

       public class MultipleDbConfiguration : DbConfiguration
       {
           #region Constructors 
   
           public MultipleDbConfiguration()
           {
               SetProviderServices(MySqlProviderInvariantName.ProviderName, new MySqlProviderServices());
           }
   
           #endregion Constructors
   
           #region Public methods 
   
           public static DbConnection GetMySqlConnection(string connectionString)
           {
               var connectionFactory = new MySqlConnectionFactory();
   
               return connectionFactory.CreateConnection(connectionString);
           }
   
           #endregion Public methods
       }   
   

2. Маркирайте Ms_SqlContext с MultipleDbConfiguration (и не правете нищо друго с този вид DbContext)

       [DbConfigurationType(typeof(MultipleDbConfiguration))]
       partial class Ms_SqlContext
       {
       }
   

3. Маркирайте Ms_SqlContext с MultipleDbConfiguration и коригирайте MY_SqlContext(string nameOrConnectionString) с извикване MultipleDbConfiguration.GetMySqlConnection(nameOrConnectionString)

       [DbConfigurationType(typeof(MultipleDbConfiguration))]
       partial class MY_SqlContext : DbContext
       {
                   public MY_SqlContext(string nameOrConnectionString) : base(MultipleDbConfiguration.GetMySqlConnection(nameOrConnectionString), true)
                   {}
       }
   

4. ТОВА Е!!!