Configuring the JSON Serializer

Follow Along

To follow along committing your changes to this course, you'll need to fork the aspnet-fitness-frog-spa repo. Then you can clone, commit, and push your changes to your fork like this:

git clone <your-fork>
cd aspnet-fitness-frog-spa
git checkout tags/v3.3 -b configuring-the-json-serializer

Configuring Json.NET to Ignore Model Properties

Fortunately, the Json.NET framework provides a convenient way to tell the serializer to ignore a property. To get started with this change, we need to add the Json.NET framework—using the NuGet package manager—to the shared class library.

Go ahead and stop the app if it's running. Then use the NuGet package manager to add the Json.NET framework (v6.0.4) to the shared class library. We're installing an older version of the Json.NET framework, because that's the version that was installed when we installed the Web API framework.

After the package has finished installing, open the Activity.cs file located in the "Models" folder.

And add the JsonIgnore attribute to the Entries property.

[JsonIgnore]
public IList<Entry> Entries { get; set; }

Now, let's retest by pressing F5 to start debugging. Using Postman again, make a GET request against the "/api/entries" endpoint. In Visual Studio, let's remove any breakpoints and press F5 to continue execution.

And back in Postman, we can see a much slimmed down version of our JSON entries data!

Reducing Response Data Payloads Using DTOs

Our current response data payload contains more data than it needs to. As we saw above, we can decorate the Activity Entries property with a JsonIgnore attribute in order to instruct the JSON serializer to not serialize that property.

We could also leverage data transfer objects—or DTOs—to refine or shape the response data. If we had an EntryListDto class that looked like this:

public class EntryListDto
{
    public int Id { get; set; }
    public DateTime Date { get; set; }
    public string ActivityName { get; set; }
    public decimal Duration { get; set; }
    public string IntensityName { get; set; }
}

We could use like this in our EntriesController's Get method:

public IHttpActionResult Get()
{
    var entries = _entriesRepository.GetList();
    var entryDtos = entries.Select(e => new EntryListDto()
    {
        Id = e.Id,
        Date = e.Date,
        ActivityName = e.Activity.Name,
        Duration = e.Duration,
        IntensityName = e.Intensity.ToString()
    }).ToList();

    return Ok(entryDtos);
}

We'll also see an example later in this section of using DTOs to prevent users from under-posting data.

Additional Learning

• Json.NET ContractResolver
• Entity Framework Resources
  • Loading Related Data and Eager Loading
  • Another Example of Automatic Relationship Fix-up