7

在我的应用程序中，我必须使用 ExpandoObject 才能在运行时创建/删除属性；但是，我必须将函数的返回 ExpandoObject 映射到相应的对象/类。所以我想出了一个可以完成这项工作但有3个问题的小型映射器：

  1. 它不会像预期的那样递归地映射 ExpandoObject 的内部对象。
  2. 当我尝试将 int 简单地映射到 Nullable 时，它​​会引发类型不匹配，因为我找不到检测和正确转换它的方法。
  3. 无法映射字段public string Property;。

代码：

我- 实施：

public static class Mapper<T> where T : class
{
    #region Properties

    private static readonly Dictionary<string, PropertyInfo> PropertyMap;

    #endregion

    #region Ctor

    static Mapper() { PropertyMap = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance).ToDictionary(p => p.Name.ToLower(), p => p); }

    #endregion

    #region Methods

    public static void Map(ExpandoObject source, T destination)
    {
        if (source == null)
            throw new ArgumentNullException("source");
        if (destination == null)
            throw new ArgumentNullException("destination");

        foreach (var kv in source)
        {
            PropertyInfo p;
            if (PropertyMap.TryGetValue(kv.Key.ToLower(), out p))
            {
                Type propType = p.PropertyType;
                if (kv.Value == null)
                {
                    if (!propType.IsByRef && propType.Name != "Nullable`1")
                    {
                        throw new ArgumentException("not nullable");
                    }
                }
                else if (kv.Value.GetType() != propType)
                {
                    throw new ArgumentException("type mismatch");
                }
                p.SetValue(destination, kv.Value, null);
            }
        }
    }

    #endregion
}

二：用法：

public static void Main()
{
    Class c = new Class();
    dynamic o = new ExpandoObject();
    o.Name = "Carl";
    o.Level = 7;
    o.Inner = new InnerClass
              {
                      Name = "Inner Carl",
                      Level = 10
              };

    Mapper<Class>.Map(o, c);

    Console.Read();
}

internal class Class
{
    public string Name { get; set; }
    public int? Level { get; set; }
    public InnerClass Inner { get; set; }
    public string Property;
}

internal class InnerClass
{
    public string Name { get; set; }
    public int? Level { get; set; }
}
4

1 回答 1

6

3-如果属性的格式是这样public string Property;的，则获取属性不会得到它。

哦，那不是属性，那是字段。如果您也想考虑字段。

static Mapper()
{
    PropertyMap = typeof(T).GetProperties(BindingFlags.Public |
                                              BindingFlags.NonPublic |
                                              BindingFlags.Instance)
                                              .ToDictionary(p => p.Name.ToLower(), p => p);

    FieldMap = typeof(T).GetFields(BindingFlags.Public |
                                                BindingFlags.NonPublic |
                                                BindingFlags.Instance)
                                                .ToDictionary(f => f.Name.ToLower(), f => f);
}

2-当我尝试将 int 简单地映射到 Nullable 时，它​​会引发类型不匹配，因为我找不到检测和正确转换它的方法。

为什么要检查Nullable类型，让反射弄清楚。如果值是有效的，它将被分配。

public static void Map(ExpandoObject source, T destination)
{
    if (source == null)
        throw new ArgumentNullException("source");
    if (destination == null)
        throw new ArgumentNullException("destination");

    foreach (var kv in source)
    {
        PropertyInfo p;
        if (PropertyMap.TryGetValue(kv.Key.ToLower(), out p))
        {
            p.SetValue(destination, kv.Value, null);
        }
        else
        {
            FieldInfo f;
            if (FieldMap.TryGetValue(kv.Key.ToLower(), out f))
            {
                f.SetValue(destination, kv.Value);
            }
        }
    }
}

1 - 它不会按照假设递归地映射 ExpandoObject 的内部对象。

似乎InnerClass至少对你有用。

Class c = new Class();
dynamic o = new ExpandoObject();
o.Name = "Carl";
o.Level = 7;
o.Inner = new InnerClass
{
    Name = "Inner Carl",
    Level = 10
};

o.Property = "my Property value"; // dont forget to set this

Mapper<Class>.Map(o, c);

编辑：根据您的评论，我创建了两个重载方法MergeProperty。您可以为字段编写类似的重载方法。

public static void MergeProperty(PropertyInfo pi, ExpandoObject source, object target)
{
    Type propType = pi.PropertyType;

    // dont recurse for value type, Nullable<T> and strings
    if (propType.IsValueType || propType == typeof(string))
    {
        var sourceVal = source.First(kvp => kvp.Key == pi.Name).Value;
        if(sourceVal != null)
            pi.SetValue(target, sourceVal, null);
    }
    else // recursively map inner class properties
    {
        var props = propType.GetProperties(BindingFlags.Public |
                                                  BindingFlags.NonPublic |
                                                  BindingFlags.Instance);

        foreach (var p in props)
        {
            var sourcePropValue = source.First(kvp => kvp.Key == pi.Name).Value;
            var targetPropValue = pi.GetValue(target, null);

            if (sourcePropValue != null)
            {
                if (targetPropValue == null) // replace
                {
                    pi.SetValue(target, source.First(kvp => kvp.Key == pi.Name).Value, null);
                }
                else
                {
                    MergeProperty(p, sourcePropValue, targetPropValue);
                }
            }
        }

    }
}

public static void MergeProperty(PropertyInfo pi, object source, object target)
{
    Type propType = pi.PropertyType;
    PropertyInfo sourcePi = source.GetType().GetProperty(pi.Name);

    // dont recurse for value type, Nullable<T> and strings
    if (propType.IsValueType || propType == typeof(string)) 
    {
        var sourceVal = sourcePi.GetValue(source, null);
        if(sourceVal != null)
            pi.SetValue(target, sourceVal, null);
    }
    else // recursively map inner class properties
    {
        var props = propType.GetProperties(BindingFlags.Public |
                                                  BindingFlags.NonPublic |
                                                  BindingFlags.Instance);

        foreach (var p in props)
        {
            var sourcePropValue = sourcePi.GetValue(source, null);
            var targetPropValue = pi.GetValue(target, null);

            if (sourcePropValue != null)
            {
                if (targetPropValue == null) // replace
                {
                    pi.SetValue(target, sourcePi.GetValue(source, null), null);
                }
                else
                {
                    MergeProperty(p, sourcePropValue, targetPropValue);
                }
            }
        }

    }
}

您可以通过这种方式使用这些方法：

public static void Map(ExpandoObject source, T destination)
{
    if (source == null)
        throw new ArgumentNullException("source");
    if (destination == null)
        throw new ArgumentNullException("destination");

    foreach (var kv in source)
    {
        PropertyInfo p;
        if (PropertyMap.TryGetValue(kv.Key.ToLower(), out p))
        {
            MergeProperty(p, source, destination);
        }
        else
        {
            // do similar merge for fields
        }
    }
}
于 2013-10-22T23:27:34.180 回答