ASP.NET Web API partial response Json serialization

Question

I am implementing a Web API that supports partial response.

/api/users?fields=id,name,age

Given the class User

[JsonObject(MemberSerialization.OptIn)]
public partial class User
{
  [JsonProperty]
  public int id { get; set; }

  [JsonProperty]
  public string firstname { get; set; }

  [JsonProperty]
  public string lastname { get; set; }

  [JsonProperty]
  public string name { get { return firstname + " " + lastname; } }

  [JsonProperty]
  public int age { get; set; }
}

The Json formatter works great when serializing the all properties, but I can't manage to modify it at runtime to tell it to ignore some of the properties, depending on the query parameter "fields".

I am working with JsonMediaTypeFormatter.

I have followed http://tostring.it/2012/07/18/customize-json-result-in-web-api/ in order to customize the formatter, but I can't find any example on how to force the formatter to ignore some properties.

Answer 1

Create your own IContractResolver to tell JSON.NET which properties need to be serialized. There's an example in official documentation you can take draw inspiration from.

Answer 2

Just to add to the responses already here; I found a nuget package that does this for you

WebApi.PartialResponse

Git hub source code:
https://github.com/dotarj/PartialResponse

It essentially wraps the formatter discussed above, so that you only have to configure it like this:

GlobalConfiguration.Configuration.Formatters.Clear();
GlobalConfiguration.Configuration.Formatters.Add(new PartialJsonMediaTypeFormatter() { IgnoreCase = true });

Then, you can specify ?fields=<whatever> in your request, and it will return the model with only those fields specified.