Deserialize JSON with null Safety in C#

Question

A little bit of context:

I have a C# 8 project using a resource called Nullable Reference Types. When this feature is enabled in the project settings (csproj) compiler treats all class instances as unallowable unless they are declared explicitly unattainable.

For example:

string  str1 = null; // isso é inválido
string? str2 = null; // isso é válido

However I noticed that this feature exists only at compile time, if the type variable string is initialized by an external code, it can still receive the value null at runtime.

So I have my classes declared with non-avoidable properties, I will use any example here:

class User
{
    [JsonPropertyName("name")]
    public string Name { get; set; } = "";

    [JsonPropertyName("email")]
    public string Email { get; set; } = "";
}

In that class I hope the properties Name and Email are never null, but if I get one JSON in format {"name": null, "email": null}, and deserialize it in an instance of that class with the library System.Text.Json, i will have a user with name and email equal to null.

I would like to know what can be done to prevent this kind of behavior. Until then I thought to implement all getters and setters manually to prevent them from receiving null, in the following style:

class User
{
    private string name = "";
    [JsonPropertyName("name")]
    public string Name 
    { 
        get { return name; }
        set { name = value ?? ""; }
    }

    private string email = "";
    [JsonPropertyName("email")]
    public string Email
    {
        get { return email; }
        set { email = value ?? ""; }
    }
}

But this seems to me unnecessarily verbose and repetitive. I wonder if there is a more practical standard approach to this problem.

Answer 1

You have the settings to ignore values null as described in documentation:

Example:

var options = new JsonSerializerOptions
{
    IgnoreNullValues = true,
    WriteIndented = true
};
jsonString = JsonSerializer.Serialize(weatherForecast, options);

then in your class starts with some value and with this configuration will have the expected behavior.

_References:

• Exclude properties from serialization
• Delete all null value properties
• Jsonserializeroptions.Ignorenullvalues Property