C＃ - 的IDataReader使用泛型对象映射 [英] C# - IDataReader to Object mapping using generics

问题描述

我如何映射DataReader对象为一类，目的是通过使用泛型？

How can I map a DataReader object into a class object by using generics?

例如，我需要做到以下几点：

For example I need to do the following:

public class Mapper<T>
    {
        public static List<T> MapObject(IDataReader dr)
        {
            List<T> objects = new List<T>();

            while (dr.Read())
            {
                //Mapping goes here...
            }

            return objects;
        }
    }

后来我需要调用这个类，方法如下所示：

And later I need to call this class-method like the following:

IDataReder dataReader = DBUtil.Fetchdata("SELECT * FROM Book");

List<Book> bookList = Mapper<Book>.MapObject(dataReder);

foreach (Book b in bookList)
{
     Console.WriteLine(b.ID + ", " + b.BookName);
}

需要注意的是，映射器 - 类应该能够映射由T. psented任何类型的再$ P $的目标

Note that, the Mapper - class should be able to map object of any type represented by T.

推荐答案

我用 ValueInjecter 了解这种

我在做这样的：

 while (dr.Read())
  {
      var o = new User();
      o.InjectFrom<DataReaderInjection>(dr);
      yield return o;
  }

您会需要这个ValueInjection这个工作：

you gonna need this ValueInjection for this to work:

public class DataReaderInjection : KnownSourceValueInjection<IDataReader>
    {
        protected override void Inject(IDataReader source, object target, PropertyDescriptorCollection targetProps)
        {
            for (var i = 0; i < source.FieldCount; i++)
            {
                var activeTarget = targetProps.GetByName(source.GetName(i), true);
                if (activeTarget == null) continue;

                var value = source.GetValue(i);
                if (value == DBNull.Value) continue;

                activeTarget.SetValue(target, value);
            }
        }
    }

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