How do I serialize a C anonymous type to a JSON string

Question

I m attempting to use the following code to serialize an anonymous type to JSON   var serializer   new DataContractJsonSerializer thing GetType     var ms   new MemoryStream    serializer WriteObject ms  thing   var json   Encoding Default GetString ms ToArray        However  I get the following exception when this is executed      Type     lt  f  AnonymousType1 3 System Int32 System Int32 System Object       cannot be serialized  Consider marking   it with the DataContractAttribute   attribute  and marking all of its   members you want serialized with the   DataMemberAttribute attribute   See   the Microsoft  NET Framework   documentation for other supported   types    I can t apply attributes to an anonymous type  as far as I know    Is there another way to do this serialization or am I missing something

User · Accepted Answer

Try the JavaScriptSerializer instead of the DataContractJsonSerializer  JavaScriptSerializer serializer   new JavaScriptSerializer    var output   serializer Serialize your anon object

User · Answer

For those checking this around the year 2020  Microsoft s System Text Json namespace is the new king in town  In terms of performance  it is the best as far as I can tell  var model   new Model       Name    quot Test Name quot       Age   5     string json   JsonSerializer Serialize model    As some others have mentioned  NewtonSoft Json is a very nice library as well

User · Answer

public static class JsonSerializer       public static string Serialize lt T gt  this T data                try                       DataContractJsonSerializer serializer   new DataContractJsonSerializer typeof T                var stream   new MemoryStream                serializer WriteObject stream  data               string jsonData   Encoding UTF8 GetString stream ToArray    0   int stream Length               stream Close                return jsonData                    catch                       return                         public static T Deserialize lt T gt  this string jsonData                try                       DataContractJsonSerializer slzr   new DataContractJsonSerializer typeof T                var stream   new MemoryStream Encoding UTF8 GetBytes jsonData                T data    T slzr ReadObject stream               stream Close                return data                    catch                       return default T

User · Answer

Please note this is from 2008  Today I would argue that the serializer should be built in and that you can probably use swagger   attributes to inform consumers about your endpoint and return data     Iwould argue that you shouldn t be serializing an anonymous type   I know the temptation here  you want to quickly generate some throw-away types that are just going to be used in a loosely type environment aka Javascript in the browser   Still  I would create an actual type and decorate it as Serializable   Then you can strongly type your web methods   While this doesn t matter one iota for Javascript  it does add some self-documentation to the method   Any reasonably experienced programmer will be able to look at the function signature and say   Oh  this is type Foo   I know how that should look in JSON    Having said that  you might try JSON Net to do the serialization   I have no idea if it will work

User · Answer

Please note this is from 2008  Today I would argue that the serializer should be built in and that you can probably use swagger   attributes to inform consumers about your endpoint and return data     Iwould argue that you shouldn t be serializing an anonymous type   I know the temptation here  you want to quickly generate some throw-away types that are just going to be used in a loosely type environment aka Javascript in the browser   Still  I would create an actual type and decorate it as Serializable   Then you can strongly type your web methods   While this doesn t matter one iota for Javascript  it does add some self-documentation to the method   Any reasonably experienced programmer will be able to look at the function signature and say   Oh  this is type Foo   I know how that should look in JSON    Having said that  you might try JSON Net to do the serialization   I have no idea if it will work

User · Answer

As others have mentioned  Newtonsoft JSON NET is a good option   Here is a specific example for simple JSON serialization   return JsonConvert SerializeObject      new              DataElement1         SomethingElse           I have found it to be a very flexible  versatile library

User · Answer

Assuming you are using this for a web service  you can just apply the following attribute to the class    System Web Script Services ScriptService    Then the following attribute to each method that should return Json    ScriptMethod ResponseFormat   ResponseFormat Json     And set the return type for the methods to be  object

User · Answer

Assuming you are using this for a web service  you can just apply the following attribute to the class    System Web Script Services ScriptService    Then the following attribute to each method that should return Json    ScriptMethod ResponseFormat   ResponseFormat Json     And set the return type for the methods to be  object

User · Answer

Assuming you are using this for a web service  you can just apply the following attribute to the class    System Web Script Services ScriptService    Then the following attribute to each method that should return Json    ScriptMethod ResponseFormat   ResponseFormat Json     And set the return type for the methods to be  object

User · Answer

The fastest way I found was this   var obj   new  Id   thing Id  Name   thing Name  Age   30   JavaScriptSerializer serializer   new JavaScriptSerializer    string json   serializer Serialize obj     Namespace  System Web Script Serialization JavaScriptSerializer

User · Answer

Please note this is from 2008  Today I would argue that the serializer should be built in and that you can probably use swagger   attributes to inform consumers about your endpoint and return data     Iwould argue that you shouldn t be serializing an anonymous type   I know the temptation here  you want to quickly generate some throw-away types that are just going to be used in a loosely type environment aka Javascript in the browser   Still  I would create an actual type and decorate it as Serializable   Then you can strongly type your web methods   While this doesn t matter one iota for Javascript  it does add some self-documentation to the method   Any reasonably experienced programmer will be able to look at the function signature and say   Oh  this is type Foo   I know how that should look in JSON    Having said that  you might try JSON Net to do the serialization   I have no idea if it will work

User · Answer

You can try my ServiceStack JsonSerializer it s the fastest  NET JSON serializer at the moment  It supports serializing DataContract s  Any POCO Type  Interfaces  Late-bound objects including anonymous types  etc   Basic Example  var customer   new Customer   Name  Joe Bloggs   Age 31    var json   customer ToJson    var fromJson   json FromJson lt Customer gt        Note  Only use Microsofts JavaScriptSerializer if performance is not important to you as I ve had to leave it out of my benchmarks since its up to 40x-100x slower than the other JSON serializers

User · Answer

public static class JsonSerializer       public static string Serialize lt T gt  this T data                try                       DataContractJsonSerializer serializer   new DataContractJsonSerializer typeof T                var stream   new MemoryStream                serializer WriteObject stream  data               string jsonData   Encoding UTF8 GetString stream ToArray    0   int stream Length               stream Close                return jsonData                    catch                       return                         public static T Deserialize lt T gt  this string jsonData                try                       DataContractJsonSerializer slzr   new DataContractJsonSerializer typeof T                var stream   new MemoryStream Encoding UTF8 GetBytes jsonData                T data    T slzr ReadObject stream               stream Close                return data                    catch                       return default T

User · Answer

Assuming you are using this for a web service  you can just apply the following attribute to the class    System Web Script Services ScriptService    Then the following attribute to each method that should return Json    ScriptMethod ResponseFormat   ResponseFormat Json     And set the return type for the methods to be  object

User · Answer

You could use Newtonsoft Json   var warningJSON   JsonConvert SerializeObject new                   warningMessage    You have been warned

User · Answer

Please note this is from 2008  Today I would argue that the serializer should be built in and that you can probably use swagger   attributes to inform consumers about your endpoint and return data     Iwould argue that you shouldn t be serializing an anonymous type   I know the temptation here  you want to quickly generate some throw-away types that are just going to be used in a loosely type environment aka Javascript in the browser   Still  I would create an actual type and decorate it as Serializable   Then you can strongly type your web methods   While this doesn t matter one iota for Javascript  it does add some self-documentation to the method   Any reasonably experienced programmer will be able to look at the function signature and say   Oh  this is type Foo   I know how that should look in JSON    Having said that  you might try JSON Net to do the serialization   I have no idea if it will work

User · Answer

As others have mentioned  Newtonsoft JSON NET is a good option   Here is a specific example for simple JSON serialization   return JsonConvert SerializeObject      new              DataElement1         SomethingElse           I have found it to be a very flexible  versatile library

User · Answer

You could use Newtonsoft Json   var warningJSON   JsonConvert SerializeObject new                   warningMessage    You have been warned

User · Answer

You can try my ServiceStack JsonSerializer it s the fastest  NET JSON serializer at the moment  It supports serializing DataContract s  Any POCO Type  Interfaces  Late-bound objects including anonymous types  etc   Basic Example  var customer   new Customer   Name  Joe Bloggs   Age 31    var json   customer ToJson    var fromJson   json FromJson lt Customer gt        Note  Only use Microsofts JavaScriptSerializer if performance is not important to you as I ve had to leave it out of my benchmarks since its up to 40x-100x slower than the other JSON serializers

User · Answer

The fastest way I found was this   var obj   new  Id   thing Id  Name   thing Name  Age   30   JavaScriptSerializer serializer   new JavaScriptSerializer    string json   serializer Serialize obj     Namespace  System Web Script Serialization JavaScriptSerializer

User · Answer

For those checking this around the year 2020  Microsoft s System Text Json namespace is the new king in town  In terms of performance  it is the best as far as I can tell  var model   new Model       Name    quot Test Name quot       Age   5     string json   JsonSerializer Serialize model    As some others have mentioned  NewtonSoft Json is a very nice library as well

[c#] How do I serialize a C# anonymous type to a JSON string?

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