Question

I have a lot of this type of logic in my code when using the SqlDataReader Is there a cleaner more generic way to handle this?

 if (reader["VisitingAddressId"] != DBNull.Value)
 {
     visitingAddress = new Address()
     {
         AddressId = Convert.ToInt64(reader["VisitingAddressId"]),
         Address1 = reader["VisitingAddress"].ToString(),
         AddressType = AddressType.VisitingAddress,
         PostalCode = reader["VisitingPostal"].ToString(),
         PostalDistrict = reader["VisitingPostalDistrict"].ToString()
      };
  }

 if (reader["PostalAddressId"] != DBNull.Value)
 {
     postalAddress = new Address()
     {
         AddressId = Convert.ToInt64(reader["PostalAddressId"]),
         Address1 = reader["PostalAddress"].ToString(),
         AddressType = AddressType.PostalAddress,
         PostalCode = reader["PostalPostal"].ToString(),
         PostalDistrict = reader["PostalPostalDistrict"].ToString()
      };
  }

Answer 1

在数据服务类别中,我有这些助手方法(如果能够使这两种方法都静态):

    public T CastDBValue<T>(object value)
    {
        return MapValue<T>(value);
    }   

    internal static T MapValue<T>(object value)
    {
        try
        {
            T result;
            result = value == DBNull.Value ? default(T) : (T)value;
            return result;
        }
        catch (InvalidCastException cex)
        {
            logger.ErrorFormat("Invalid cast while mapping db value  {0}  to type {1}. Error: {2}", value, typeof(T).Name, cex);
            throw new InvalidCastException(string.Format("Invalid cast while mapping db value  {0}  to type {1}. Error: {2}", value, typeof(T).Name, cex.Message));
        }
    }

之后,在你的绘图法中,你刚刚做到:

AddressId = dataService.CastDBValue<int>(reader["AddressId"]));
if (AddressId > 0) { ... }

Answer 2

You could use a micro-ORM like Dapper: http://code.google.com/p/dapper-dot-net/

多层绘图功能将消除所有锅炉板代码。

db.Query<Post,Address,Address,Post>("select * from Posts left join Address ... etc", 
 (post,vaddress,paddress) => 
  {
     post.VisitingAddress = vaddress; 
     post.PostalAddress = paddress; 
     return post; 
   });

Answer 3

你们指的是管理办公室,其中有许多。 NHibernate, 实体框架,甚至ADO.NET(你已经使用)支持关系数据集,但在这种情况下,通常必须使用或衍生出重型类别。

查阅。表格中的网络部分:

你们的要求是什么? 也许我们可以缩小这一差距。

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