c# - 字典将字符串映射到属性

Question

我有一个类，我想根据一个字符串返回各种属性的值，我可以像这样定义一个属性:

    [FieldName("data_bus")]
    public string Databus
    {
        get { return _record.Databus; }
    }

所以我想要一本字典:

private static readonly IDictionary<string, Func<string>> PropertyMap;

这里初始化:

static MyClass()
    {
        PropertyMap = new Dictionary<string, Func<string>>();

        var myType = typeof(ArisingViewModel);

        foreach (var propertyInfo in myType.GetProperties(BindingFlags.Instance | BindingFlags.Public))
        {
            if (propertyInfo.GetGetMethod() != null)
            {
                var attr = propertyInfo.GetCustomAttribute<FieldNameAttribute>();

                if (attr == null)
                    continue;

                PropertyInfo info = propertyInfo;
                PropertyMap.Add(attr.FieldName, () => info.Name);
                // Not sure what I'm doing here.
            }
        }
    }

并以某种方式调用:

   public static object GetPropertyValue(object obj, string field)
    {

        Func<string> prop;
        PropertyMap.TryGetValue(field, out prop);
        // return 
    }

谁能告诉我如何设置它？我不确定我是否正确理解 Func 的工作原理。

Answer 1

您将需要更改您的字典定义，以便该函数将接受该类的一个实例

private static readonly IDictionary<string, Func<ArisingViewModel,string>> PropertyMap;

那么你需要你的静态初始化器是

static MyClass()
{
    PropertyMap = new Dictionary<string, Func<ArisingViewModel,string>>();

    var myType = typeof(ArisingViewModel);

    foreach (var propertyInfo in myType.GetProperties(BindingFlags.Instance | BindingFlags.Public))
    {
        if (propertyInfo.GetGetMethod() != null)
        {
            var attr = propertyInfo.GetCustomAttribute<FieldNameAttribute>();

            if (attr == null)
                continue;

            PropertyInfo info = propertyInfo;
            PropertyMap.Add(attr.FieldName, obj => (string)info.GetValue(obj,null));
        }
    }
}

public static object GetPropertyValue(ArisingViewModel obj, string field)
{
    Func<ArisingViewModel,string> prop;
    if (PropertyMap.TryGetValue(field, out prop)) {
       return prop(obj);
    }
    return null; //Return null if no match
  }

如果您愿意，您还可以使您的解决方案更通用一些。

public static MyClass<T> {

  private static readonly IDictionary<string, Func<T,string>> PropertyMap;


  static MyClass()
  {
    PropertyMap = new Dictionary<string, Func<T,string>>();

    var myType = typeof(T);

    foreach (var propertyInfo in myType.GetProperties(BindingFlags.Instance | BindingFlags.Public))
    {
        if (propertyInfo.GetGetMethod() != null)
        {
            var attr = propertyInfo.GetCustomAttribute<FieldNameAttribute>();

            if (attr == null)
                continue;

            PropertyInfo info = propertyInfo;
            PropertyMap.Add(attr.FieldName, obj => (string)info.GetValue(obj,null));
        }
    }
  }

  public static object GetPropertyValue(T obj, string field)
  {
    Func<ArisingViewModel,string> prop;
    if (PropertyMap.TryGetValue(field, out prop)) {
       return prop(obj);
    }
    return null; //Return null if no match
  }
}

编辑 - 并调用你会做的通用版本

var value = MyClass<ArisingViewModel>.GetPropertyValue(mymodel,"data_bus");