EF中自定义连接字符串

public partial class WeighingSettlementModelContainer : DbContext
    {
        //不使用的默认构造函数，即dbContext(string nameOrConection)
        //该构造函数只能读取数据库名或app.config文件中的conectionstring字符，
        //若连接字符串加密，则无法使用，且该字符串中必须有providerName属性；
        //故选择DbContext(DbConnection existingConnection, bool contextOwnsConnection)构造函数
        //如此能构造sqlConnetion类读取app.config文件中的conectionstring的加密字符串（该连接字符串中可以
        //省略providerName属性），并返回SqlConection
        public WeighingSettlementModelContainer()

            : base(Utility.Sql.Sqlhelper.sqlConnection(),true)
        {
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            //throw new UnintentionalCodeFirstException();
        }
    
        public virtual DbSet<WeighingSettlement> WeighingSettlementSet { get; set; }
        public virtual DbSet<Customer> CustomerSet { get; set; }
        public virtual DbSet<Scrap> ScrapSet { get; set; }
    }