C# JSON Serialization of Dictionary into {key:value, ...} instead of {key:key, value:value, ...}

Is it possible to serialize a .Net Dictionary<Key,Value> into JSON with DataContractJsonSerializer that is of the format:

{
  key0:value0,
  key1:value1,
  ...
}

I use Dictionary <K,V>, because there is not predefined structure of the inputs.

I'm interesting just for DataContractJsonSerializer result! I've already found a "Surrogate" example, but there is an additional "data" in the output, and if the dictionary <K, String> is, the escaping is false too.

---

I've found the solution, what a needed! First of all, a serializable "dictionary" class: (Of course, this sample works just in one way, but I dont't need deserialization)

[Serializable]
public class MyJsonDictionary<K, V> : ISerializable {
	Dictionary<K, V> dict = new Dictionary<K, V>();
	
	public MyJsonDictionary() { }

	protected MyJsonDictionary( SerializationInfo info, StreamingContext context ) {
		throw new NotImplementedException();
	}

	public void GetObjectData( SerializationInfo info, StreamingContext context ) {
		foreach( K key in dict.Keys ) {
			info.AddValue( key.ToString(), dict[ key ] );
		}
	}

	public void Add( K key, V value ) {
		dict.Add( key, value );
	}
	
	public V this[ K index ] {
		set { dict[ index ] = value; }
		get { return dict[ index ]; }
	}
}

Usage:

public class MainClass {
	public static String Serialize( Object data ) {
		var serializer = new DataContractJsonSerializer( data.GetType() );
		var ms = new MemoryStream();
		serializer.WriteObject( ms, data );

		return Encoding.UTF8.GetString( ms.ToArray() );
	}

	public static void Main() {
		MyJsonDictionary<String, Object> result = new MyJsonDictionary<String, Object>();
		result["foo"] = "bar";
		result["Name"] = "John Doe";
		result["Age"] = 32;
		MyJsonDictionary<String, Object> address = new MyJsonDictionary<String, Object>();
		result["Address"] = address;
		address["Street"] = "30 Rockefeller Plaza";
		address["City"] = "New York City";
		address["State"] = "NY";

		Console.WriteLine( Serialize( result ) );

		Console.ReadLine();
	}
}

And the result:

{
      "foo":"bar",
      "Name":"John Doe",
      "Age":32,
      "Address":{
         "__type":"MyJsonDictionaryOfstringanyType:#Json_Dictionary_Test",
         "Street":"30 Rockefeller Plaza",
         "City":"New York City",
         "State":"NY"
      }
   }

Json.NET does this...

Dictionary<string, string> values = new Dictionary<string, string>();
values.Add("key1", "value1");
values.Add("key2", "value2");

string json = JsonConvert.SerializeObject(values);
// {
//   "key1": "value1",
//   "key2": "value2"
// }

More examples: Serializing Collections with Json.NET

use property UseSimpleDictionaryFormat on DataContractJsonSerializer and set it to true.

Does the job :)

I'm using out of the box MVC4 with this code (note the two parameters inside ToDictionary)

 var result = new JsonResult()
 {
     Data = new
     {
         partials = GetPartials(data.Partials).ToDictionary(x => x.Key, y=> y.Value)
     }
 };

I get what's expected:

{"partials":{"cartSummary":"\u003cb\u003eCART SUMMARY\u003c/b\u003e"}}

---

Important: WebAPI in MVC4 uses JSON.NET serialization out of the box, but the standard web JsonResult action result doesn't. Therefore I recommend using a custom ActionResult to force JSON.NET serialization. You can also get nice formatting

Here's a simple actionresult JsonNetResult

http://james.newtonking.com/archive/2008/10/16/asp-net-mvc-and-json-net.aspx

You'll see the difference (and can make sure you're using the right one) when serializing a date:

Microsoft way:

 {"wireTime":"\/Date(1355627201572)\/"}

JSON.NET way:

 {"wireTime":"2012-12-15T19:07:03.5247384-08:00"}

In .NET 5 and later, you can simply write:

using System;
using System.Collections.Generic;
					
public class Program
{
	public static void Main()
	{
		Dictionary<string, string> values = new();
        values.Add("key1", "value1");
        values.Add("key2", "value2");

        string json = System.Text.Json.JsonSerializer.Serialize(values);
		Console.WriteLine(json);
	}
}

to get {"key1":"value1","key2":"value2"}.

No external dependency is needed.

Unfortunately, this is not currently possible in the latest version of DataContractJsonSerializer. See: http://connect.microsoft.com/VisualStudio/feedback/details/558686/datacontractjsonserializer-should-serialize-dictionary-k-v-as-a-json-associative-array

The current suggested workaround is to use the JavaScriptSerializer as Mark suggested above.

Good luck!

The MyJsonDictionary class worked well for me EXCEPT that the resultant output is XML encoded - so "0" becomes "0030". I am currently stuck at .NET 3.5, as are many others, so many of the other solutions are not available to me. "Turns the pictures" upside down and realized I could never convince Microsoft to give me the format I wanted but...

string json = XmlConvert.DecodeName(xmlencodedJson);

TADA!

The result is what you would expect to see - regular human readable and non-XML encoded. Works in .NET 3.5.