将dbcontext连接字符串传递给DALayer

Question

我的应用程序中有4层UI, DomainClass, Model(DBCntext), Repository。

在仓库我有一个抽象类，像这样:

 public abstract class GenericRepository<C, T> :
    IGenericRepository<T>
        where T : class
        where C : DbContext, new()
    {
        private C _entities = new C();
        public C Context
        {
            get { return _entities; }
            set { _entities = value; }
        }
        public virtual IQueryable<T> GetAll()
        {
            IQueryable<T> query = _entities.Set<T>();
            return query;
        }
        public IQueryable<T> FindBy(System.Linq.Expressions.Expression<Func<T, bool>> predicate)
        {
            IQueryable<T> query = _entities.Set<T>().Where(predicate);
            return query;
        }
        public virtual void Add(T entity)
        {
            _entities.Set<T>().Add(entity);
        }
        public virtual void Delete(T entity)
        {
            _entities.Set<T>().Remove(entity);
        }
        public virtual void Edit(T entity)
        {
            _entities.Entry(entity).State = System.Data.Entity.EntityState.Modified;
        }
        public virtual void Save()
        {
            _entities.SaveChanges();
        }
    }

我所有的实体都继承自这个类，像这样:

namespace Repository
{
    public class StationRepository : GenericRepository<ShirazRailWay.ShirazRailwayEntities, DomainClass.Station>
    {
    }
}

I UI我称它为repositories。如你所见:

  stationrepository objnew=new stationrepository();
  obnew.getall();

在UI层，我有一个连接字符串在app.config，你可以看到这里:

<connectionStrings>
    <add name="ShirazRailwayEntities" connectionString="metadata=res://*/RailWay.csdl|res://*/RailWay.ssdl|res://*/RailWay.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=****;initial catalog=DB-Metro;user id=sa;password=****;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />
  </connectionStrings>

但是我想给我的用户一个选项，有了这个选项，他们可以自己设置他们的connection string。所以我在UI层创建了一个表单，当用户尝试log in时，它会问他们连接字符串。我的问题是How can pass this connection string to my dbcontext ?

在我的model layer(dbcontext)我有这个:

public partial class ShirazRailwayEntities : DbContext
    {
        public ShirazRailwayEntities()
            : base("name=ShirazRailwayEntities")
        {
        }
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }
        public DbSet<Advertisement> Advertisements { get; set; }
        public DbSet<Line> Lines { get; set; }
        public DbSet<Log> Logs { get; set; }
        public DbSet<Path> Paths { get; set; }
        public DbSet<Sensor> Sensors { get; set; }
        public DbSet<Station> Stations { get; set; }
        public DbSet<Train> Trains { get; set; }
        public DbSet<User> Users { get; set; }
        public DbSet<TimeTable> TimeTables { get; set; }
        public DbSet<ConfigFont> ConfigFonts { get; set; }
        public DbSet<ArrivalTime> ArrivalTimes { get; set; }
        public DbSet<ConfigColor> ConfigColors { get; set; }
    }

Answer 1

添加另一个接受连接字符串的构造函数:

public partial class ShirazRailwayEntities : DbContext
{
    public ShirazRailwayEntities()
        : base(name: "ShirazRailwayEntities")
    {
    }
    public ShirazRailwayEntities(string connectionName)
        : base(name: connectionName)
    {
    }
}
var context = new ShirazRailwayEntities("whatever connection name you want");