反序列化 - 指定默認值，以空值參數

Question

我的類定義如下

public class HotelRoomResponse 
{ 
    public string rateCode { get; set; } 
    public string rateDescription { get; set; } 
    public RoomType RoomType { get; set; } 
    public string supplierType { get; set; } 
    public int propertyId { get; set; } 
    public BedTypes BedTypes { get; set; } 
    public string smokingPreferences { get; set; } 
    public int rateOccupancyPerRoom { get; set; } 
    public int quotedOccupancy { get; set; } 
    public int minGuestAge { get; set; } 
    public RateInfos RateInfos { get; set; } 
    public ValueAdds ValueAdds { get; set; } 
    public string deepLink { get; set; } 
    public RoomImages RoomImages { get; set; } 
} 


public class ValueAdd 
{ 
    [JsonProperty(PropertyName = "@id")] 
    public string id { get; set; } 
    public string description { get; set; } 
} 

public class ValueAdds 
{ 
    private string valueaddsize="0"; 
    [JsonProperty(PropertyName = "size")] 
    [DefaultValue("0")] 
    public string size 
    { 
     get 
     { 
      return !string.IsNullOrEmpty(valueaddsize) 
         ? valueaddsize 
         : ((DefaultValueAttribute) 
          (TypeDescriptor.GetProperties(this)["size"].Attributes[ 
           typeof(DefaultValueAttribute)])).Value.ToString(); 
     } 
     set { valueaddsize = value; } 
    } 
    [JsonConverter(typeof(ObjectToArrayConverter<ValueAdd>))] 
    public List<ValueAdd> ValueAdd { get; set; } 
} 


public class RoomImage 
{ 
    //// private string useurl = "~/no-picture-available.jpg"; 
    // [DefaultValue("~/no-picture-available.jpg")] 
    // public string url { get; set; } 

    private string useurl="~/no-picture-available.jpg"; 
    [DefaultValue("~/no-picture-available.jpg")] 
    public string url 
    { 
     get 
     { 
      return !string.IsNullOrWhiteSpace(useurl) 
         ? useurl 
         : ((DefaultValueAttribute) 
          (TypeDescriptor.GetProperties(this)["url"].Attributes[ 
           typeof(DefaultValueAttribute)])).Value.ToString(); 
     } 
     set { useurl = value; } 
    } 
} 

public class RoomImages 
{ 
    public string size { get; set; } 
    public RoomImage RoomImage { get; set; } 
} 

而在反序列化過程中的幾個參數，每次丟失即幾家酒店會產生RoomImages和ValueAdds和幾個酒店不會。

我的問題是反序列化過程後，而不是發送空值，我嘗試設置默認值，但這些值不會反映後反序列化。如何將默認值設置爲RoomImages值爲「無圖像網址」，ValueAdds爲「無增值」？

Answer 1

Json.Net將忽略json中不存在的屬性，但我認爲你在談論case-2（下面）。然後使用NullValueHandling枚舉就足夠了。

//Case 1 (Json doesn't contain the property) 
var image = JsonConvert.DeserializeObject<RoomImage>("{}"); 
Console.WriteLine(image.Url); //<-- ~/no-picture-available.jpg 

//Case 2 (Property is explicitly set to null) 
var settings = new JsonSerializerSettings() {NullValueHandling = NullValueHandling.Ignore }; 
image = JsonConvert.DeserializeObject<RoomImage>("{\"Url\":null}", settings); 
Console.WriteLine(image.Url); //<-- ~/no-picture-available.jpg 

---

public class RoomImage 
{ 
    string _url = "~/no-picture-available.jpg"; 
    public string Url { get { return _url; } set { _url = value; } } 
}