如何检查c#中动态匿名类型上是否存在属性？

Question

我有一个匿名类型对象,我从一个方法接收动态,我想检查该对象上存在的属性.

....
var settings = new {
                   Filename="temp.txt",
                   Size=10
}
...

function void Settings(dynamic settings) {
var exists = IsSettingExist(settings,"Filename")
}

我该如何实现IsSettingExist？

Answer 1

  public static bool IsPropertyExist(dynamic settings, string name)
  {
    if (settings is ExpandoObject)
      return ((IDictionary<string, object>)settings).ContainsKey(name);

    return settings.GetType().GetProperty(name) != null;
  }

  var settings = new {Filename = @"c:\temp\q.txt"};
  Console.WriteLine(IsPropertyExist(settings, "Filename"));
  Console.WriteLine(IsPropertyExist(settings, "Size"));

输出:

 True
 False

Answer 2

public static bool HasProperty(dynamic obj, string name)
{
    Type objType = obj.GetType();

    if (objType == typeof(ExpandoObject))
    {
        return ((IDictionary<string, object>)obj).ContainsKey(name);
    }

    return objType.GetProperty(name) != null;
}

Answer 3

如果你可以控制创建/传递设置对象,我建议使用ExpandoObject.

dynamic settings = new ExpandoObject();
settings.Filename = "asdf.txt";
settings.Size = 10;
...

function void Settings(dynamic settings)
{
    if ( ((IDictionary<string, object>)settings).ContainsKey("Filename") )
        .... do something ....
}

Answer 4

这适用于匿名类型ExpandoObject，Nancy.DynamicDictionary或其他任何可强制转换为IDictionary<string, object>。

    public static bool PropertyExists(dynamic obj, string name) {
        if (obj == null) return false;
        if (obj is IDictionary<string, object> dict) {
            return dict.ContainsKey(name);
        }
        return obj.GetType().GetProperty(name) != null;
    }

Answer 5

我遇到的动态是Newtonsoft.Json.Linq.JObject而不是IDictionary

我添加了额外的 if 并且它有效。

public static bool PropertyExists(dynamic obj, string name)
{
    if (obj == null) return false;

    else if (obj is IDictionary<string, object> dict)
    {
        return dict.ContainsKey(name);
    }

    else if (obj is Newtonsoft.Json.Linq.JObject jObject)
    {
        return jObject.ContainsKey(name);
    }

    else
    {
        return obj.GetType().GetProperty(name) != null;
    }
}

使用 switch 表达式编辑比以前更智能的解决方案

public static bool PropertyExists(dynamic obj, string name)
{
    if (obj == null) return false;
    return obj switch
    {
        IDictionary<string, object> dict => dict.ContainsKey(name),
        Newtonsoft.Json.Linq.JObject jObject => jObject.ContainsKey(name),
        _ => obj.GetType().GetProperty(name) != null
    };
}

Answer 6

如果有人需要处理来自 Json 的动态对象，我修改了 Seth Reno 答案来处理从 NewtonSoft.Json.JObjcet 反序列化的动态对象。

public static bool PropertyExists(dynamic obj, string name)
    {
        if (obj == null) return false;
        if (obj is ExpandoObject)
            return ((IDictionary<string, object>)obj).ContainsKey(name);
        if (obj is IDictionary<string, object> dict1)
            return dict1.ContainsKey(name);
        if (obj is IDictionary<string, JToken> dict2)
            return dict2.ContainsKey(name);
        return obj.GetType().GetProperty(name) != null;
    }

Answer 7

合并并修复 Serj-TM 和 user3359453 的答案，以便它可以与 ExpandoObject 和 DynamicJsonObject 一起使用。这对我有用。

public static bool HasPropertyExist(dynamic settings, string name)
{
    if (settings is System.Dynamic.ExpandoObject)
        return ((IDictionary<string, object>)settings).ContainsKey(name);

    if (settings is System.Web.Helpers.DynamicJsonObject)
    try
    {
        return settings[name] != null;
    }
    catch (KeyNotFoundException)
    {
        return false;
    }


    return settings.GetType().GetProperty(name) != null;
}