JsonExtensions

A collection of extension for .NET System.Text.Json

SingleOrArrayJsonConverter

A JsonConverter that deserializes both a single JSON object and a JSON array as a C# array.

• With the default JsonConverter

public sealed class Example
{
  [JsonConverter(typeof(SingleOrArrayJsonConverter))]
  public string[]? Array { get; set; }
}

const string jsonSingle = """{"Array": "single"}""";
var deserializedSingle = JsonSerializer.Deserialize<Example>(jsonSingle);
Console.WriteLine($"{deserializedSingle.Array.Length}: {deserializedSingle.Array[0]}");
// Output: "1: single"

const string jsonArray = """{"Array": ["first", "second"]}""";
var deserializedArray = JsonSerializer.Deserialize<Example>(jsonArray);
Console.WriteLine($"{deserializedArray.Array.Length}: {deserializedArray.Array[0]}, {deserializedArray.Array[1]}");
// Output: "2: first, second"

• With a custom JsonConverter

public sealed class Person
{
  public string FirstName { get; }
  public string LastName { get; }

  public Person(string firstName, string lastName)
  {
    FirstName = firstName;
    LastName = lastName;
  }
}

// Converts a Person object into a "${FirstName} ${LastName}" string
public sealed class PersonJsonConverter : JsonConverter<string>
{
  public override string? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
  {
    var personConverter = (JsonConverter<Person>)options.GetConverter(typeof(Person));

    Person? person = personConverter.Read(ref reader, typeof(Person), options);

    return person != null ? $"{person.FirstName} {person.LastName}" : null;
  }

  public override void Write(Utf8JsonWriter writer, string value, JsonSerializerOptions options)
  {
    var personConverter = (JsonConverter<Person>)options.GetConverter(typeof(Person));

    var split = value.Split(' ');
    var firstName = split[0];
    var lastName = split[1];
    var person = new Person(firstName, lastName);

    personConverter.Write(writer, person, options);
  }
}

public sealed class Example
{
  [JsonConverter(typeof(SingleOrArrayJsonConverter<PersonJsonConverter>))]
  public string[]? Array { get; set; }
}

const string jsonSingle = """{"Array": {"FirstName": "John", "LastName": "Smith"}}""";
var deserializedSingle = JsonSerializer.Deserialize<Example>(json);
Console.WriteLine($"{deserializedSingle.Array.Length}: {deserializedSingle.Array[0]}");
// Output: "1: John Smith"

const string jsonArray = """{"Array": [{"FirstName": "John", "LastName": "Smith"}, {"FirstName": "John", "LastName": "Doe"}]}""";
var deserializedArray = JsonSerializer.Deserialize<Example>(json);
Console.WriteLine($"{deserializedArray.Array.Length}: {deserializedArray.Array[0]}, {deserializedArray.Array[1]}");
// Output: "2: John Smith, John Doe"

JsonMultiNameModifier

A JsonPropertyNames attribute and JsonMultiNameModifier that allows mapping of multiple JSON keys to one C# property.

• Allowing duplicate keys

public sealed class User
{
  [JsonPropertyNames("UserName", "User", "Name")]
  public string UserName { get; set; }
}

JsonSerializerOptions jsonOptions = new()
{
  TypeInfoResolver = new DefaultJsonTypeInfoResolver()
  {
    Modifiers = { Modifiers.JsonMultiNameModifier }
  }
}

const string json1 = """{"UserName": "JohnSmith1"}""";
const string json2 = """{"User": "JohnSmith2"}""";
const string json3 = """{"Name": "JohnSmith3"}""";
var deserialized = JsonSerializer.Deserialize<User>(json1, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith1"
deserialized = JsonSerializer.Deserialize<User>(json2, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith2"
deserialized = JsonSerializer.Deserialize<User>(json3, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith3"

string json = """{"UserName": "JohnSmith1", "User": "JohnSmith2", "Name": "JohnSmith3"}""";
deserialized = JsonSerializer.Deserialize<User>(json, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith3"

json = JsonSerializer.Serialize(deserialized, jsonOptions);
Console.WriteLine(json);
// Output: '{"UserName":"JohnSmith3"}'

• Disallowing duplicate keys

public sealed class User
{
  [JsonPropertyNames(throwOnDuplicate: true, "UserName", "User", "Name")]
  public string UserName { get; set; }
}

JsonSerializerOptions jsonOptions = new()
{
  TypeInfoResolver = new DefaultJsonTypeInfoResolver()
  {
    Modifiers = { Modifiers.JsonMultiNameModifier }
  }
}

const string json1 = """{"UserName": "JohnSmith1"}""";
const string json2 = """{"User": "JohnSmith2"}""";
const string json3 = """{"Name": "JohnSmith3"}""";
var deserialized = JsonSerializer.Deserialize<User>(json1, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith1"
deserialized = JsonSerializer.Deserialize<User>(json2, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith2"
deserialized = JsonSerializer.Deserialize<User>(json3, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith3"

try {
  const string json = """{"UserName": "JohnSmith1", "User": "JohnSmith2", "Name": "JohnSmith3"}""";
  deserialized = JsonSerializer.Deserialize<User>(json, jsonOptions);
  Console.WriteLine(deserialized.UserName);
} catch (JsonException) {
  Console.WriteLine("Deserialize failed");
}
// Output: "Deserialize failed"

• Different serialization key

public sealed class User
{
  [JsonPropertyNames(serializationName: "NickName", "UserName", "User", "Name")]
  public string UserName { get; set; }
}

JsonSerializerOptions jsonOptions = new()
{
  TypeInfoResolver = new DefaultJsonTypeInfoResolver()
  {
    Modifiers = { Modifiers.JsonMultiNameModifier }
  }
}

string json = """{"UserName": "JohnSmith"}""";
var deserialized = JsonSerializer.Deserialize<User>(json, jsonOptions);
Console.WriteLine(deserialized.UserName);
// Output: "JohnSmith"

json = JsonSerializer.Serialize(deserialized, jsonOptions);
Console.WriteLine(json);
// Output: '{"NickName":"JohnSmith"}'

MIT License

Copyright (c) 2023 Guiorgy

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.