JavaScriptSerializer Deserialize - how to change field names

Question

Summary  How do I map a field name in JSON data to a field name of a  Net object when using JavaScriptSerializer Deserialize    Longer version  I have the following JSON data coming to me from a server API  Not coded in  Net     user id  1234   detail level   low     I have the following C  object for it    Serializable  public class DataObject        XmlElement  user id        public int UserId   get  set          XmlElement  detail level        public DetailLevel DetailLevel   get  set        Where DetailLevel is an enum with  Low  as one of the values   This test fails    TestMethod  public void DataObjectSimpleParseTest         JavaScriptSerializer serializer   new JavaScriptSerializer        DataObject dataObject   serializer Deserialize lt DataObject gt  JsonData        Assert IsNotNull dataObject       Assert AreEqual DetailLevel Low  dataObject DetailLevel       Assert AreEqual 1234  dataObject UserId       And the last two asserts fail  since there is no data in those fields  If I change the JSON data to     userid  1234   detaillevel   low     Then it passes  But I can t change the server s behaviour  and I want the client classes to have well-named properties in the C  idiom  I can t use LINQ to JSON since I want it to work outside of Silverlight  It looks like the XmlElement tags are having no effect  I don t know where I got the idea they were relevant at all  they probably aren t   How do you do field name mapping in JavaScriptSerializer  Can it be done at all

User · Answer

My requirements included    must honor the dataContracts must deserialize dates in the format received in service must handle colelctions must target 3 5 must NOT add an external dependency  especially not Newtonsoft  I m creating a distributable package myself   must not be deserialized by hand   My solution in the end was to use SimpleJson https   github com facebook-csharp-sdk simple-json    Although you can install it via a nuget package  I included just that single SimpleJson cs file  with the MIT license  in my project and referenced it   I hope this helps someone

User · Answer

There is no standard support for renaming properties in JavaScriptSerializer however you can quite easily add your own   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 lt string  object gt  dictionary  Type type  JavaScriptSerializer serializer                List lt MemberInfo gt  members   new List lt MemberInfo gt             members AddRange type GetFields             members AddRange type GetProperties   Where p   gt  p CanRead  amp  amp  p CanWrite  amp  amp  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  amp  amp  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 lt string  object gt  kvp   dictionary FirstOrDefault x   gt  string Equals x Key  member Name  StringComparison InvariantCultureIgnoreCase                     if   kvp Equals default KeyValuePair lt string  object gt                                           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 lt string  object gt  Serialize object obj  JavaScriptSerializer serializer                Type type   obj GetType            List lt MemberInfo gt  members   new List lt MemberInfo gt             members AddRange type GetFields             members AddRange type GetProperties   Where p   gt  p CanRead  amp  amp  p CanWrite  amp  amp  p GetIndexParameters   Length    0             Dictionary lt string  object gt  values   new Dictionary lt string  object gt              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 lt Type gt  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            The DataObject class then becomes   public class DataObject        JsonProperty  user id        public int UserId   get  set          JsonProperty  detail level        public DetailLevel DetailLevel   get  set        I appreicate this might be a little late but thought other people wanting to use the JavaScriptSerializer rather than the DataContractJsonSerializer might appreciate it

User · Answer

Json NET will do what you want  disclaimer  I m the author of the package   It supports reading DataContract DataMember attributes as well as its own to change the property names  Also there is the StringEnumConverter class for serializing enum values as the name rather than the number

User · Answer

I have used the using Newtonsoft Json as below  Create an object    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          Now Call the below method to serialize to Json object as shown below    string sortColumn   JsonConvert SerializeObject worklistSortColumn

User · Answer

I took another try at it  using the DataContractJsonSerializer class  This solves it   The code looks like this   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        And the test is   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       The only drawback is that I had to change DetailLevel from an enum to a string - if you keep the enum type in place  the DataContractJsonSerializer expects to read a numeric value and fails  See DataContractJsonSerializer and Enums for further details    In my opinion this is quite poor  especially as JavaScriptSerializer handles it correctly  This is the exception that you get trying to parse a string into an enum   System Runtime Serialization SerializationException  There was an error deserializing the object of type DataObject  The value  low  cannot be parsed as the type  Int64   --- gt  System Xml XmlException  The value  low  cannot be parsed as the type  Int64   --- gt    System FormatException  Input string was not in a correct format   And marking up the enum like this does not change this behaviour    DataContract  public enum DetailLevel        EnumMember Value    low        Low              This also seems to work in Silverlight

User · Answer

Create a class inherited from JavaScriptConverter   You must then implement three things   Methods-   Serialize Deserialize   Property-   SupportedTypes   You can use  the JavaScriptConverter class when you need more control over the serialization and deserialization process   JavaScriptSerializer serializer   new JavaScriptSerializer    serializer RegisterConverters new JavaScriptConverter     new MyCustomConverter        DataObject dataObject   serializer Deserialize lt DataObject gt  JsonData     Here is a link for further information

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By creating a custom JavaScriptConverter you can map any name to any property  But it does require hand coding the map  which is less than ideal   public class DataObjectJavaScriptConverter   JavaScriptConverter       private static readonly Type    supportedTypes   new                 typeof  DataObject               public override IEnumerable lt Type gt  SupportedTypes                 get   return  supportedTypes                public override object Deserialize  IDictionary lt string  object gt  dictionary                                           Type type                                           JavaScriptSerializer serializer                 if  type    typeof  DataObject                           var obj   new DataObject                if  dictionary ContainsKey   user id                      obj UserId   serializer ConvertToType lt int gt                                               dictionary  user id                  if  dictionary ContainsKey   detail level                      obj DetailLevel   serializer ConvertToType lt DetailLevel gt                                              dictionary  detail level                   return obj                     return null             public override IDictionary lt string  object gt  Serialize               object obj               JavaScriptSerializer serializer                 var dataObj   obj as DataObject          if  dataObj    null                         return new Dictionary lt string object gt                                  user id   dataObj UserId                      detail level   dataObj DetailLevel                                   return new Dictionary lt string  object gt               Then you can deserialize like so   var serializer   new JavaScriptSerializer    serialzer RegisterConverters  new    new DataObjectJavaScriptConverter        var dataObj   serializer Deserialize lt DataObject gt   json

User · Answer

For those who don t want to go for Newtonsoft Json Net or DataContractJsonSerializer for some reason  I can t think of any       here is an implementation of JavaScriptConverter that supports DataContract and enum to string conversion -      public class DataContractJavaScriptConverter   JavaScriptConverter               private static readonly List lt Type gt   supportedTypes   new List lt Type gt              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 lt Type gt  SupportedTypes                       get   return  supportedTypes                       public override object Deserialize IDictionary lt string  object gt  dictionary  Type type  JavaScriptSerializer serializer                        if  Attribute IsDefined type  typeof DataContractAttribute                                  try                                       object instance   Activator CreateInstance type                        IEnumerable lt MemberInfo gt  members     IEnumerable lt MemberInfo gt  type GetFields                             Concat type GetProperties   Where property   gt  property CanWrite  amp  amp  property GetIndexParameters   Length    0                            Where  member    gt  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  amp  amp  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  amp  amp  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 lt string  object gt  Serialize object obj  JavaScriptSerializer serializer                        Dictionary lt string  object gt  dictionary   new Dictionary lt string  object gt                 if  obj    null  amp  amp  Attribute IsDefined obj GetType    typeof DataContractAttribute                                  Type type   obj GetType                    IEnumerable lt MemberInfo gt  members     IEnumerable lt MemberInfo gt  type GetFields                         Concat type GetProperties   Where property   gt  property CanRead  amp  amp  property GetIndexParameters   Length    0                        Where  member    gt  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  amp  amp  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  amp  amp  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                    Note  This DataContractJavaScriptConverter will only handle DataContract classes defined in the assembly where it is placed  If you want classes from separate assemblies  modify the  supportedTypes list accordingly in the static constructror    This can be used as follows -      JavaScriptSerializer serializer   new JavaScriptSerializer        serializer RegisterConverters new JavaScriptConverter     new DataContractJavaScriptConverter true          DataObject dataObject   serializer Deserialize lt DataObject gt  JsonData     The DataObject class would look like this -      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            Please note that this solution doesn t handle EmitDefaultValue and Order properties supported by DataMember attribute

[c#] JavaScriptSerializer.Deserialize - how to change field names

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