c# - 如何在代码外部定义 AutoMapper 映射，即在 XML 文件中或使用不同的方法进行完全可配置的对象映射？

Question

编辑:最初我打算使用 AutoMapper 来实现我的目标，但我不得不了解到 AutoMapper 并非旨在以这种方式工作。它使您可以创建配置文件，但在我的情况下(完全可配置)我需要为每个参数组合一个配置文件，所以我想出了一种自己的方法，请参阅答案。

从 AutoMapper wiki 我学会了创建一个像

这样的简单映射

    Mapper.CreateMap<CalendarEvent, CalendarEventForm>().ForMember(dest => dest.Title, opt => opt.MapFrom(src => src.Title));
    Mapper.CreateMap<CalendarEvent, CalendarEventForm>().ForMember(dest => dest.EventDate, opt => opt.MapFrom(src => src.EventDate.Date));
    Mapper.CreateMap<CalendarEvent, CalendarEventForm>().ForMember(dest => dest.EventHour, opt => opt.MapFrom(src => src.EventDate.Hour));
    Mapper.CreateMap<CalendarEvent, CalendarEventForm>().ForMember(dest => dest.EventMinute, opt => opt.MapFrom(src => src.EventDate.Minute));

对于像这样的两个类

public class CalendarEvent
{
    public DateTime EventDate;
    public string Title;
}

public class CalendarEventForm
{
    public DateTime EventDate { get; set; }
    public int EventHour { get; set; }
    public int EventMinute { get; set; }
    public string Title { get; set; }
}

我现在想知道是否有可能在外部定义映射，即在 XML 文件中，例如

<ObjectMapping>
<mapping>
    <src>Title</src>
    <dest>Tile</dest>
</mapping>
<mapping>
    <src>EventDate.Date</src>
    <dest>EventDate</dest>
</mapping>
<mapping>
    <src>EventDate.Hour</src>
    <dest>EventHour</dest>
</mapping>
<mapping>
    <src>EventDate.Minute</src>
    <dest>EventMinute</dest>
</mapping>

并由此影响 map 的创建(XML 不是必需的，也可以是其他任何东西)。为简单起见，说类型没有问题，所以 src 和 dest 应该相同，否则失败是可以的。这背后的想法是在应该映射什么以及应该映射到哪里方面非常灵活。我正在考虑反射以根据其名称获取属性值，但这似乎行不通。我也不确定这是否有意义，或者我是否遗漏了一些重要的东西，因此非常感谢您的帮助和想法。

Answer 1

最后，我自己实现了原始需求，尽管我并不需要它(需求已更改)。我会在这里提供代码，以防有人需要它(或多或少作为概念证明，因为仍然可以做很多改进)或者对 XML 感兴趣，请记住，XML 容易出错，这种方法的关键组成部分，属性名称和类型必须完全匹配，否则它将无法工作，但是通过一个小的 GUI 来编辑文件，这应该是可以实现的(我的意思是不手动编辑文件)。

我使用了来自 here 的代码和 here并添加了类 PropertyMapping 来存储从 XML 读取的映射，还添加了类 Foo 和 Bar 来创建嵌套数据结构，以便复制到。

无论如何，这里是代码，也许它可以帮助某些人:

主要内容:

public class Program
{
    public static void Main(string[] args)
    {
        // Model
        var calendarEvent = new CalendarEvent
        {
            EventDate = new DateTime(2008, 12, 15, 20, 30, 0),
            Title = "Company Holiday Party"
        };

        MyObjectMapper mTut = new MyObjectMapper(@"SampleMappings.xml");

        Console.WriteLine(string.Format("Result MyMapper: {0}", Program.CompareObjects(calendarEvent, mTut.TestMyObjectMapperProjection(calendarEvent))));

        Console.ReadLine();
    }

    public static bool CompareObjects(CalendarEvent calendarEvent, CalendarEventForm form)
    {
        return calendarEvent.EventDate.Date.Equals(form.EventDate) &&
               calendarEvent.EventDate.Hour.Equals(form.EventHour) &&
               calendarEvent.EventDate.Minute.Equals(form.EventMinute) &&
               calendarEvent.Title.Equals(form.Title);
    }
}

映射器实现:

public class MyObjectMapper
{
    private List<PropertyMapping> myMappings = new List<PropertyMapping>();

    public MyObjectMapper(string xmlFile)
    {
        this.myMappings = GenerateMappingObjectsFromXml(xmlFile);
    }

    /*
     * Actual mapping; iterate over internal mappings and copy each source value to destination value (types have to be the same)
     */ 
    public CalendarEventForm TestMyObjectMapperProjection(CalendarEvent calendarEvent)
    {
        CalendarEventForm calendarEventForm = new CalendarEventForm();

        foreach (PropertyMapping propertyMapping in myMappings)
        {
            object originalValue = GetPropValue(calendarEvent,propertyMapping.FromPropertyName);

            SetPropValue(propertyMapping.ToPropertyName, calendarEventForm, originalValue);
        }

        return calendarEventForm;
    }
    /*
     * Get the property value from the source object
     */ 
    private object GetPropValue(object obj, String compoundProperty)
    {
        foreach (String part in compoundProperty.Split('.'))
        {
            if (obj == null) { return null; }

            Type type = obj.GetType();
            PropertyInfo info = type.GetProperty(part);
            if (info == null) { return null; }

            obj = info.GetValue(obj, null);
        }
        return obj;
    }
    /*
     * Set property in the destination object, create new empty objects if needed in case of nested structure
     */ 
    public void SetPropValue(string compoundProperty, object target, object value)
    {
        string[] bits = compoundProperty.Split('.');
        for (int i = 0; i < bits.Length - 1; i++)
        {
            PropertyInfo propertyToGet = target.GetType().GetProperty(bits[i]);

            propertyToGet.SetValue(target, Activator.CreateInstance(propertyToGet.PropertyType));

            target = propertyToGet.GetValue(target, null);               
        }
        PropertyInfo propertyToSet = target.GetType().GetProperty(bits.Last());
        propertyToSet.SetValue(target, value, null);
    }              

    /*
     * Read XML file from the provided file path an create internal mapping objects
     */ 
    private List<PropertyMapping> GenerateMappingObjectsFromXml(string xmlFile)
    {
        XElement definedMappings = XElement.Load(xmlFile);
        List<PropertyMapping> mappings = new List<PropertyMapping>();

        foreach (XElement singleMappingElement in definedMappings.Elements("mapping"))
        {
            mappings.Add(new PropertyMapping(singleMappingElement.Element("src").Value, singleMappingElement.Element("dest").Value));
        }

        return mappings;
    } 
}

我的模型类:

public class CalendarEvent
{
    public DateTime EventDate { get; set; }
    public string Title { get; set; }
}

public class CalendarEventForm
{
    public DateTime EventDate { get; set; }
    public int EventHour { get; set; }
    public int EventMinute { get; set; }
    public string Title { get; set; }
    public Foo Foo { get; set; }
}

public class Foo
{
    public Bar Bar { get; set; }

}

public class Bar
{
    public DateTime InternalDate { get; set; }

}

内部映射表示:

public class PropertyMapping
{
    public string FromPropertyName;
    public string ToPropertyName;

    public PropertyMapping(string fromPropertyName, string toPropertyName)
    {
        this.FromPropertyName = fromPropertyName;
        this.ToPropertyName = toPropertyName;
    }
}

示例 XML 配置:

<?xml version="1.0" encoding="utf-8" ?>
    <ObjectMapping>
      <mapping>
        <src>Title</src>
        <dest>Title</dest>
       </mapping>
      <mapping>
        <src>EventDate.Date</src>
        <dest>EventDate</dest>
      </mapping>
      <mapping>
        <src>EventDate.Hour</src>
        <dest>EventHour</dest>
      </mapping>
      <mapping>
        <src>EventDate.Minute</src>
        <dest>EventMinute</dest>
      </mapping>
      <mapping>
        <src>EventDate</src>
        <dest>Foo.Bar.InternalDate</dest>
      </mapping>
     </ObjectMapping>