JavaScriptSerializer 可以排除具有 null/默认值的属性吗？

Question

我正在使用 JavaScriptSerializer 来序列化一些实体对象。

问题是，许多公共属性包含 null 或默认值。有没有办法让 JavaScriptSerializer 排除具有 null 或默认值的属性？

我希望生成的 JSON 不那么冗长。

Answer 1

仅供参考，如果您想采用更简单的解决方案，下面是我使用 JavaScriptConverter 实现和 JavaScriptSerializer 来完成此操作的方法：

private class NullPropertiesConverter: JavaScriptConverter {
 public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer) {
  throw new NotImplementedException();
 }

 public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer) {
  var jsonExample = new Dictionary<string, object >();
  foreach(var prop in obj.GetType().GetProperties()) {
   //check if decorated with ScriptIgnore attribute
   bool ignoreProp = prop.IsDefined(typeof(ScriptIgnoreAttribute), true);

   var value = prop.GetValue(obj, BindingFlags.Public, null, null, null);
   if (value != null && !ignoreProp)
    jsonExample.Add(prop.Name, value);
  }

  return jsonExample;
 }

 public override IEnumerable<Type> SupportedTypes {
  get {
   return GetType().Assembly.GetTypes();
  }
 }
}

然后使用它：

var serializer = new JavaScriptSerializer();
serializer.RegisterConverters(new JavaScriptConverter[] {
  new NullPropertiesConverter()
});
return serializer.Serialize(someObjectToSerialize);

Answer 2

对我有用的解决方案：

序列化的类和属性将装饰如下：

[DataContract]
public class MyDataClass
{
  [DataMember(Name = "LabelInJson", IsRequired = false)]
  public string MyProperty { get; set; }
}

IsRequired 是关键项。

实际的序列化可以使用 DataContractJsonSerializer 完成：

public static string Serialize<T>(T obj)
{
  string returnVal = "";
  try
  {
    DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
    using (MemoryStream ms = new MemoryStream())
    {
      serializer.WriteObject(ms, obj);
      returnVal = Encoding.Default.GetString(ms.ToArray());
    }
  }
  catch (Exception /*exception*/)
  {
    returnVal = "";
    //log error
  }
  return returnVal;
}

Answer 3

为了那些在 google 上找到此内容的人的利益，请注意，在使用 Newtonsoft.Json 进行序列化期间可以本机跳过空值

var json = JsonConvert.SerializeObject(
            objectToSerialize,
            new JsonSerializerSettings {NullValueHandling = NullValueHandling.Ignore});

Answer 4

您可以实现 JavaScriptConverter 并使用 JavaScriptSerializer的RegisterConverters方法。

Answer 5

Json.NET 具有自动排除空值或默认值的选项。

Answer 6

此代码是数字类型的块 null 和 default(0) 值

private class NullPropertiesConverter: JavaScriptConverter {
 public override object Deserialize(IDictionary < string, object > dictionary, Type type, JavaScriptSerializer serializer) {
  throw new NotImplementedException();
 }

 public override IDictionary < string, object > Serialize(object obj, JavaScriptSerializer serializer) {
  var jsonExample = new Dictionary < string,
   object > ();
  foreach(var prop in obj.GetType().GetProperties()) {
   //this object is nullable 
   var nullableobj = prop.PropertyType.IsGenericType && prop.PropertyType.GetGenericTypeDefinition() == typeof(Nullable < > );
   //check if decorated with ScriptIgnore attribute
   bool ignoreProp = prop.IsDefined(typeof(ScriptIgnoreAttribute), true);

   var value = prop.GetValue(obj, System.Reflection.BindingFlags.Public, null, null, null);
   int i;
   //Object is not nullable and value=0 , it is a default value for numeric types 
   if (!(nullableobj == false && value != null && (int.TryParse(value.ToString(), out i) ? i : 1) == 0) && value != null && !ignoreProp)
    jsonExample.Add(prop.Name, value);
  }

  return jsonExample;
 }

 public override IEnumerable < Type > SupportedTypes {
  get {
   return GetType().Assembly.GetTypes();
  }
 }
}

Answer 7

无需更改 DataContractSerializer

您可以使用 ScriptIgnoreAttribute

[1] http://msdn.microsoft.com/en-us/library/system.web.script.serialization.scriptignoreattribute.aspx