How do I serialize object properties to lower case using System.Text.Json?-CodePudding

I have an ASP.NET 5 MVC Core application controller with the below code inside:

using System.Text.Json;

public async Task<IActionResult> EstoAPICall() {
  ...
  EstoOst estoOst;
  var json = JsonSerializer.Serialize(estoOst);
  StringContent content = new(json, Encoding.UTF8, "application/json");
  using var response = await httpClient.PostAsync("https://example.com", content);
  ...
}

public class EstoOst {
  public decimal Amount { get; set; }
}

This causes an error as the API requires lower case amount in the JSON but .Serialize(...) is returning upper case Amount.

How can I fix this?

Switching to Json.NET, or changing the class property name to lowercase don't seem to be good solutions.

CodePudding user response：

If you really are looking for all lowercase property names and not camel-case property names e.g. FullName becomes fullname and not fullName, there's nothing built-in - you will have to create your own JsonNamingPolicy like so:

LowerCaseNamingPolicy.cs

public class LowerCaseNamingPolicy : JsonNamingPolicy
{
  public override string ConvertName(string name)
  {
      if (string.IsNullOrEmpty(name) || !char.IsUpper(name[0]))
          return name;

      return name.ToLower();
  }
}

Usage:

var options = new JsonSerializerOptions {
    PropertyNamingPolicy = new LowerCaseNamingPolicy(),
};

var json = JsonSerializer.Serialize(estoOst, options);

However, I think you're looking for camel-case naming, considering you mentioned Json.NET which also doesn't have a lowercase naming policy.

If so, set the JsonSerializerOptions.PropertyNamingPolicy property to JsonNamingPolicy.CamelCase to serialise property names into a camel-case format:

var options = new JsonSerializerOptions {
    PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
};

var json = JsonSerializer.Serialize(estoOst, options);

Here's a working demo to output & show the difference of output for both methods:

public class Program
{
  public static void Main()
  {
      var person = new Person
      {
          Age = 100,
          FullName = "Lorem Ipsum"
      };

      var camelCaseJsonSerializerOptions = new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase };
      var lowercaseJsonSerializerOptions = new JsonSerializerOptions { PropertyNamingPolicy = new LowerCaseNamingPolicy()};

      var camelCaseJson = JsonSerializer.Serialize(person, camelCaseJsonSerializerOptions);
      var lowercaseJson = JsonSerializer.Serialize(person, lowercaseJsonSerializerOptions);

      Console.WriteLine(camelCaseJson);
      Console.WriteLine(lowercaseJson);
  }
}

public class Person
{
  public string FullName { get; set; }
  public int Age { get; set; }
}

public class LowerCaseNamingPolicy : JsonNamingPolicy
{
  public override string ConvertName(string name)
  {
      if (string.IsNullOrEmpty(name) || !char.IsUpper(name[0]))
          return name;

      return name.ToLower();
  }
}

Output:

{"fullName":"Lorem Ipsum","age":100}
{"fullname":"Lorem Ipsum","age":100}