How to serialize properties to lower case using System.Text.Json.JsonSerializer-CodePudding

ASP.NET 5 MVC Core application controller consumes json API using

  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 returns error response because caller requires lower case amount but Serialize method returns upper case Amount.

How to fix this ? Switching to Newtosoft or changing class property name to lowercase seems to be not 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}