仅在Json.Net中的反序列化时忽略空值

Question

When I have the following model:

public class Customer
{
    public Customer()
    {
        FirstName = string.Empty;
        LastName = string.Empty;
    }

    [JsonProperty(NullValueHandling=NullValueHandling.Ignore)]
    public string FirstName {get;set;}

    [JsonProperty(NullValueHandling=NullValueHandling.Ignore)]
    public string LastName {get;set;}
}

And that works great for when I'm posting data:

// {
//    firstName: null,
//    lastName: null
// }

public int Post([FromBody]Customer customer)
{
    var firstName = customer.FirstName; //  <-- value is ""
}

The problem with this is that if the developer forgets in this system to initialize the data, then the response structure will leave it out:

public Customer
{
    FirstName = "";
}

// {
//    firstName: ''
// }

Basically, I don't want the values to be null but I also don't want to require the user to add an optional parameter in the request. I can't use [Require] because it doesn't satisfy that second part.

How it is set up now the onus is on the developer to initialize the property or else it will be omitted. Is there a way to accomplish this so that it only ignores for deserialization and not serialization?

Answer 1

If I might rephrase your question, you appear to be asking, How can I have a property of a type that always has a default, non-null value even when set to null when deserializing JSON or when uninitialized in application code? If this rephrasing is correct, this can be handled by the type itself by using explicit rather than automatic properties:

public class Customer
{
    string firstName = "";
    string lastName = "";

    public Customer() { }

    public string FirstName { get { return firstName; } set { firstName = value ?? ""; } }

    public string LastName { get { return lastName; } set { lastName = value ?? ""; } }
}

FirstName and LastName are now guaranteed to be non-null no matter how the Customer class is constructed.