- Posted by Ian Suttle on January 6, 2008
- Filed under .NET 3.5 | ASP.Net | JSON | .Net Framework
Download the sample code for this post.
In October of 2007 The Gu wrote a ToJSON extension method using the JavaScriptSerializer class. Since that time the JavaScriptSerializer class has been marked obsolete in favor of DataContractJsonSerializer. In this post we’ll write an updated ToJSON method to satisfy every JSON extension method fantasy you have. Quick agenda… the goal is to take a .Net object and convert it in to JSON text which would likely be consumed be a remote client. Let’s start with the object to convert… an Address class.
using System.Runtime.Serialization;
...
[DataContract(Name = "Address", Namespace = "")]
public class PersonAddress
{
[DataMember(Name = "City", Order = 1)]
public string City { get; set; }
[DataMember(Name = "Country", Order = 2)]
public string Country { get; set; }
[DataMember(Name = "PostalCode", Order = 3)]
public string PostalCode { get; set; }
[DataMember(Name = "State", Order = 4)]
public string State { get; set; }
[DataMember(Name = "Street", Order = 5)]
public string Street { get; set; }
}
DataContract and DataMember attributes provide information to the serialization process of how to structure the data. It is possible to use the more familiar System.Serializable attribute however the output isn’t nearly as friendly. More on that later.
The constructor for DataContractJsonSerializer we’re using requires knowledge of the Type of object being serialized to JSON. For the purposes of this method we’re likely to not know which Type is to be serialized. Quite often it will be a custom type. We need our extension method to be more generic… I love .Net… Here’s the method suitable for such a task:
using System.IO;
using System.Runtime.Serialization.Json;
using System.Text;
...
public static string ToJSON<T>(this T obj)
{
MemoryStream stream = new MemoryStream();
try
{
//serialize data to a stream, then to a JSON string
DataContractJsonSerializer jsSerializer = new DataContractJsonSerializer(typeof(T));
jsSerializer.WriteObject(stream, obj);
return Encoding.UTF8.GetString(stream.ToArray());
}
finally
{
stream.Close();
stream.Dispose();
}
}
Be sure to reference System.Runtime.Serialization and System.ServiceModel.Web.
Let’s dissect a bit. DataContractJsonSerializer needs to know the object type. In our case it’s generic, so we’ll let typeof(T) figure it out for us. The serializer WriteObject method wants a stream to write the serialization output to for which we’re using a MemoryStream; an easy object for retrieving text from. And that’s what we do… convert the stream’s byte array into a string; our JSON string.
Let’s run this pup using the following code:
PersonAddress address = new PersonAddress();
address.City = "Newport Beach";
address.Country = "US";
address.PostalCode = "92626";
address.State = "CA";
address.Street = "123 Candyland Way";
string json = address.ToJSON();
Response.Write(json);
And the results:
{"City":"Newport Beach","Country":"US","PostalCode":"92626","State":"CA","Street":"123 Candyland Way"}
Earlier I mentioned if you used the [Serializable] attribute instead of the [DataContract] attribute your solution would compile and function however your results would come out a bit different. Here’s the output when using Serializable:
<{"<City>k__BackingField":"Newport Beach","<Country>k__BackingField":"US","<PostalCode>k__BackingField":"92626","<State>k__BackingField":"CA","<Street>k__BackingField":"123 Candyland Way"}>
As you can see this is far less friendly to work with from a JSON consumer perspective… Make it easier on yourself and stick with DataContract in this case.
I hope this helps in your JSON endeavors. Let me know if you have any questions of problems!
Download the sample code for this post.
