简介：在使用JavaScriptSerializer.Deserialize时，如何将JSON数据中的字段名称映射到.Net对象的字段名称？
更长版本：我从服务器API（未在.Net中编码）向我发送以下JSON数据
{"user_id":1234, "detail_level":"low"}
我有以下C＃对象：
[Serializable]
public class DataObject
{
[XmlElement("user_id")]
public int UserId { get; set; }
[XmlElement("detail_level")]
public DetailLevel DetailLevel { get; set; }
}
其中DetailLevel是一个枚举，其中“低”作为其中一个值。
此测试失败：
[TestMethod]
public void DataObjectSimpleParseTest()
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
DataObject dataObject = serializer.Deserialize<DataObject>(JsonData);
Assert.IsNotNull(dataObject);
Assert.AreEqual(DetailLevel.Low, dataObject.DetailLevel);
Assert.AreEqual(1234, dataObject.UserId);
}
最后两个断言失败，因为这些字段中没有数据。如果我将JSON数据更改为
{"userid":1234, "detaillevel":"low"}
然后它通过。但我不能改变服务器的行为，我希望客户端类在C＃语言中具有良好命名的属性。我不能使用LINQ to JSON，因为我希望它在Silverlight之外工作。看起来XmlElement标签没有任何效果。我不知道我在哪里知道它们是相关的，它们可能不是。
你如何在JavaScriptSerializer中进行字段名称映射？它可以完成吗？
我再次尝试使用DataContractJsonSerializer课程。这解决了它：
代码如下所示：
using System.Runtime.Serialization;
[DataContract]
public class DataObject
{
[DataMember(Name = "user_id")]
public int UserId { get; set; }
[DataMember(Name = "detail_level")]
public string DetailLevel { get; set; }
}
测试是：
using System.Runtime.Serialization.Json;
[TestMethod]
public void DataObjectSimpleParseTest()
{
DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(DataObject));
MemoryStream ms = new MemoryStream(Encoding.Unicode.GetBytes(JsonData));
DataObject dataObject = serializer.ReadObject(ms) as DataObject;
Assert.IsNotNull(dataObject);
Assert.AreEqual("low", dataObject.DetailLevel);
Assert.AreEqual(1234, dataObject.UserId);
}
唯一的缺点是我必须将DetailLevel从枚举更改为字符串 - 如果保持枚举类型，DataContractJsonSerializer期望读取数值并失败。有关详细信息，请参阅DataContractJsonSerializer and Enums。
在我看来，这是非常差的，特别是当JavaScriptSerializer正确处理它时。这是您尝试将字符串解析为枚举的例外：
System.Runtime.Serialization.SerializationException: There was an error deserializing the object of type DataObject. The value 'low' cannot be parsed as the type 'Int64'. --->
System.Xml.XmlException: The value 'low' cannot be parsed as the type 'Int64'. --->
System.FormatException: Input string was not in a correct format
并且像这样标记枚举不会改变这种行为：
[DataContract]
public enum DetailLevel
{
[EnumMember(Value = "low")]
Low,
...
}
这似乎也适用于Silverlight。
通过创建自定义JavaScriptConverter，您可以将任何名称映射到任何属性。但它确实需要手工编码地图，这不太理想。
public class DataObjectJavaScriptConverter : JavaScriptConverter
{
private static readonly Type[] _supportedTypes = new[]
{
typeof( DataObject )
};
public override IEnumerable<Type> SupportedTypes
{
get { return _supportedTypes; }
}
public override object Deserialize( IDictionary<string, object> dictionary,
Type type,
JavaScriptSerializer serializer )
{
if( type == typeof( DataObject ) )
{
var obj = new DataObject();
if( dictionary.ContainsKey( "user_id" ) )
obj.UserId = serializer.ConvertToType<int>(
dictionary["user_id"] );
if( dictionary.ContainsKey( "detail_level" ) )
obj.DetailLevel = serializer.ConvertToType<DetailLevel>(
dictionary["detail_level"] );
return obj;
}
return null;
}
public override IDictionary<string, object> Serialize(
object obj,
JavaScriptSerializer serializer )
{
var dataObj = obj as DataObject;
if( dataObj != null )
{
return new Dictionary<string,object>
{
{"user_id", dataObj.UserId },
{"detail_level", dataObj.DetailLevel }
}
}
return new Dictionary<string, object>();
}
}
然后你可以这样反序列化：
var serializer = new JavaScriptSerializer();
serialzer.RegisterConverters( new[]{ new DataObjectJavaScriptConverter() } );
var dataObj = serializer.Deserialize<DataObject>( json );
Json.NET会做你想做的事（免责声明：我是该套餐的作者）。它支持读取DataContract / DataMember属性以及它自己的属性来更改属性名称。另外还有StringEnumConverter类，用于将枚举值序列化为名称而不是数字。
在JavaScriptSerializer中没有重命名属性的标准支持，但是您可以很容易地添加自己的：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.Script.Serialization;
using System.Reflection;
public class JsonConverter : JavaScriptConverter
{
public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
{
List<MemberInfo> members = new List<MemberInfo>();
members.AddRange(type.GetFields());
members.AddRange(type.GetProperties().Where(p => p.CanRead && p.CanWrite && p.GetIndexParameters().Length == 0));
object obj = Activator.CreateInstance(type);
foreach (MemberInfo member in members)
{
JsonPropertyAttribute jsonProperty = (JsonPropertyAttribute)Attribute.GetCustomAttribute(member, typeof(JsonPropertyAttribute));
if (jsonProperty != null && dictionary.ContainsKey(jsonProperty.Name))
{
SetMemberValue(serializer, member, obj, dictionary[jsonProperty.Name]);
}
else if (dictionary.ContainsKey(member.Name))
{
SetMemberValue(serializer, member, obj, dictionary[member.Name]);
}
else
{
KeyValuePair<string, object> kvp = dictionary.FirstOrDefault(x => string.Equals(x.Key, member.Name, StringComparison.InvariantCultureIgnoreCase));
if (!kvp.Equals(default(KeyValuePair<string, object>)))
{
SetMemberValue(serializer, member, obj, kvp.Value);
}
}
}
return obj;
}
private void SetMemberValue(JavaScriptSerializer serializer, MemberInfo member, object obj, object value)
{
if (member is PropertyInfo)
{
PropertyInfo property = (PropertyInfo)member;
property.SetValue(obj, serializer.ConvertToType(value, property.PropertyType), null);
}
else if (member is FieldInfo)
{
FieldInfo field = (FieldInfo)member;
field.SetValue(obj, serializer.ConvertToType(value, field.FieldType));
}
}
public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
{
Type type = obj.GetType();
List<MemberInfo> members = new List<MemberInfo>();
members.AddRange(type.GetFields());
members.AddRange(type.GetProperties().Where(p => p.CanRead && p.CanWrite && p.GetIndexParameters().Length == 0));
Dictionary<string, object> values = new Dictionary<string, object>();
foreach (MemberInfo member in members)
{
JsonPropertyAttribute jsonProperty = (JsonPropertyAttribute)Attribute.GetCustomAttribute(member, typeof(JsonPropertyAttribute));
if (jsonProperty != null)
{
values[jsonProperty.Name] = GetMemberValue(member, obj);
}
else
{
values[member.Name] = GetMemberValue(member, obj);
}
}
return values;
}
private object GetMemberValue(MemberInfo member, object obj)
{
if (member is PropertyInfo)
{
PropertyInfo property = (PropertyInfo)member;
return property.GetValue(obj, null);
}
else if (member is FieldInfo)
{
FieldInfo field = (FieldInfo)member;
return field.GetValue(obj);
}
return null;
}
public override IEnumerable<Type> SupportedTypes
{
get
{
return new[] { typeof(DataObject) };
}
}
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class JsonPropertyAttribute : Attribute
{
public JsonPropertyAttribute(string name)
{
Name = name;
}
public string Name
{
get;
set;
}
}
然后DataObject类成为：
public class DataObject
{
[JsonProperty("user_id")]
public int UserId { get; set; }
[JsonProperty("detail_level")]
public DetailLevel DetailLevel { get; set; }
}
我认为这可能有点晚，但认为其他人想要使用JavaScriptSerializer而不是DataContractJsonSerializer可能会欣赏它。
创建一个继承自JavaScriptConverter的类。然后你必须实现三件事：
方法-
属性-
当您需要对序列化和反序列化过程进行更多控制时，可以使用JavaScriptConverter类。
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.RegisterConverters(new JavaScriptConverter[] { new MyCustomConverter() });
DataObject dataObject = serializer.Deserialize<DataObject>(JsonData);
我使用了如下的Newtonsoft.Json。创建一个对象：
public class WorklistSortColumn
{
[JsonProperty(PropertyName = "field")]
public string Field { get; set; }
[JsonProperty(PropertyName = "dir")]
public string Direction { get; set; }
[JsonIgnore]
public string SortOrder { get; set; }
}
现在调用以下方法序列化为Json对象，如下所示。
string sortColumn = JsonConvert.SerializeObject(worklistSortColumn);
对于那些因某些原因不想去Newtonsoft Json.Net或DataContractJsonSerializer的人（我想不出任何:)），这里是JavaScriptConverter的实现，支持DataContract和enum到string转换 -
public class DataContractJavaScriptConverter : JavaScriptConverter
{
private static readonly List<Type> _supportedTypes = new List<Type>();
static DataContractJavaScriptConverter()
{
foreach (Type type in Assembly.GetExecutingAssembly().DefinedTypes)
{
if (Attribute.IsDefined(type, typeof(DataContractAttribute)))
{
_supportedTypes.Add(type);
}
}
}
private bool ConvertEnumToString = false;
public DataContractJavaScriptConverter() : this(false)
{
}
public DataContractJavaScriptConverter(bool convertEnumToString)
{
ConvertEnumToString = convertEnumToString;
}
public override IEnumerable<Type> SupportedTypes
{
get { return _supportedTypes; }
}
public override object Deserialize(IDictionary<string, object> dictionary, Type type, JavaScriptSerializer serializer)
{
if (Attribute.IsDefined(type, typeof(DataContractAttribute)))
{
try
{
object instance = Activator.CreateInstance(type);
IEnumerable<MemberInfo> members = ((IEnumerable<MemberInfo>)type.GetFields())
.Concat(type.GetProperties().Where(property => property.CanWrite && property.GetIndexParameters().Length == 0))
.Where((member) => Attribute.IsDefined(member, typeof(DataMemberAttribute)));
foreach (MemberInfo member in members)
{
DataMemberAttribute attribute = (DataMemberAttribute)Attribute.GetCustomAttribute(member, typeof(DataMemberAttribute));
object value;
if (dictionary.TryGetValue(attribute.Name, out value) == false)
{
if (attribute.IsRequired)
{
throw new SerializationException(String.Format("Required DataMember with name {0} not found", attribute.Name));
}
continue;
}
if (member.MemberType == MemberTypes.Field)
{
FieldInfo field = (FieldInfo)member;
object fieldValue;
if (ConvertEnumToString && field.FieldType.IsEnum)
{
fieldValue = Enum.Parse(field.FieldType, value.ToString());
}
else
{
fieldValue = serializer.ConvertToType(value, field.FieldType);
}
field.SetValue(instance, fieldValue);
}
else if (member.MemberType == MemberTypes.Property)
{
PropertyInfo property = (PropertyInfo)member;
object propertyValue;
if (ConvertEnumToString && property.PropertyType.IsEnum)
{
propertyValue = Enum.Parse(property.PropertyType, value.ToString());
}
else
{
propertyValue = serializer.ConvertToType(value, property.PropertyType);
}
property.SetValue(instance, propertyValue);
}
}
return instance;
}
catch (Exception)
{
return null;
}
}
return null;
}
public override IDictionary<string, object> Serialize(object obj, JavaScriptSerializer serializer)
{
Dictionary<string, object> dictionary = new Dictionary<string, object>();
if (obj != null && Attribute.IsDefined(obj.GetType(), typeof(DataContractAttribute)))
{
Type type = obj.GetType();
IEnumerable<MemberInfo> members = ((IEnumerable<MemberInfo>)type.GetFields())
.Concat(type.GetProperties().Where(property => property.CanRead && property.GetIndexParameters().Length == 0))
.Where((member) => Attribute.IsDefined(member, typeof(DataMemberAttribute)));
foreach (MemberInfo member in members)
{
DataMemberAttribute attribute = (DataMemberAttribute)Attribute.GetCustomAttribute(member, typeof(DataMemberAttribute));
object value;
if (member.MemberType == MemberTypes.Field)
{
FieldInfo field = (FieldInfo)member;
if (ConvertEnumToString && field.FieldType.IsEnum)
{
value = field.GetValue(obj).ToString();
}
else
{
value = field.GetValue(obj);
}
}
else if (member.MemberType == MemberTypes.Property)
{
PropertyInfo property = (PropertyInfo)member;
if (ConvertEnumToString && property.PropertyType.IsEnum)
{
value = property.GetValue(obj).ToString();
}
else
{
value = property.GetValue(obj);
}
}
else
{
continue;
}
if (dictionary.ContainsKey(attribute.Name))
{
throw new SerializationException(String.Format("More than one DataMember found with name {0}", attribute.Name));
}
dictionary[attribute.Name] = value;
}
}
return dictionary;
}
}
注意：这个DataContractJavaScriptConverter只会处理放置它的程序集中定义的DataContract类。如果需要来自单独程序集的类，请在静态构造函数中相应地修改_supportedTypes列表。
这可以用如下 -
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.RegisterConverters(new JavaScriptConverter[] { new DataContractJavaScriptConverter(true) });
DataObject dataObject = serializer.Deserialize<DataObject>(JsonData);
DataObject类看起来像这样 -
using System.Runtime.Serialization;
[DataContract]
public class DataObject
{
[DataMember(Name = "user_id")]
public int UserId { get; set; }
[DataMember(Name = "detail_level")]
public string DetailLevel { get; set; }
}
请注意，此解决方案不处理EmitDefaultValue属性支持的Order和DataMember属性。
我的要求包括：
我的解决方案最终是使用SimpleJson（https://github.com/facebook-csharp-sdk/simple-json）。
虽然您可以通过nuget包安装它，但我在项目中只包含了一个SimpleJson.cs文件（带有MIT许可证）并引用了它。
我希望这可以帮助别人。