public class CatalogContext : DbContext
...
public static List<Author> RawStoreCommand(string name)
        {
            List<Author> result = new List<Author>();
            var ctx = new CatalogContext();
            using (var conn = (EntityConnection)((IObjectContextAdapter)ctx).ObjectContext.Connection)
            {
                conn.Open();
                // Create an EntityCommand.
                using (EntityCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "GetAuthorByNickname";
                    cmd.CommandType = CommandType.StoredProcedure;
                    EntityParameter pName = new EntityParameter();
                    pName.ParameterName = "name";
                    pName.Value = name;
                    cmd.Parameters.Add(pName);
                    

                    // Execute the command.
                    using (EntityDataReader rdr = cmd.ExecuteReader()) //ХХХ
                    {
                        // Read the results returned by the stored procedure.
                        while (rdr.Read())
                        {
                            Author author = new Author();
                            author.Id = rdr.GetInt32(0);
                            author.Nickname = rdr.GetString(1);
                            author.Birthdate = rdr.GetDateTime(2);
                            author.ArticlesCount = rdr.GetInt32(3);
                            result.Add(author);
                        }
                    }
                    conn.Close();
                }
            }
            return result;
        }

public static List<Author> RawStoreCommand(string name)
        {
            List<Author> result = new List<Author>();
            var ctx = new CatalogContext();
            using (var conn = ctx.Database.Connection)
            {
                conn.Open();
                // Create an EntityCommand.
                using (DbCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = "GetAuthorByNickname";
                    cmd.CommandType = CommandType.StoredProcedure;
                    SqlParameter pName = new SqlParameter();
                    pName.ParameterName = "name";
                    pName.Value = name;
                    cmd.Parameters.Add(pName);
                    

                    // Execute the command.
                    using (DbDataReader rdr = cmd.ExecuteReader())
                    {
                        // Read the results returned by the stored procedure.
                        while (rdr.Read())
                        {
                            Author author = new Author();
                            author.Id = rdr.GetInt32(0);
                            author.Nickname = rdr.GetString(1);
                            author.Birthdate = rdr.GetDateTime(2);
                            author.ArticlesCount = rdr.GetInt32(3);
                            result.Add(author);
                        }
                    }
                    conn.Close();
                }
            }
            return result;
        }