How I can show null value in the response from a POST request?

Question

I have a POST: localhost:10411/api/channel -> to create channel with request body:

"cut": {
{
"title": "track 200-1",
"duration": "00:00:30",
"album": "album 200-1",
"logoUrl":null
},
{
"title": "track 200-2",
"duration": "00:00:30",
"album": "album 200-2",
"logoUrl": "this is a text"
},
{
"title": "track 200-3",
"duration": "00:00:30",
"album": "album 200-3",
}
}

I want when:

1. no logoUrl provided -> it will generate image;

2. logoUrl string provided -> use text in the response;

3. logoUrl null provided -> use null in the response;

However, the response I received is only statisfy the 1) and 2) condition. I cannot get the 3) working. Here is the response:

{
"title": "track 200-1",
"album": "album 200-1",
"url": "localhost:10411/api/logos/album%200-1" (I want here show url = null instead of showing auto generate logo)
},
{
"title": "track 200-2",
"album": "album 200-2",
"url": "this is a text" (showing string, worked as expected)
},
{
"title": "track 200-3",
"duration": "00:00:30",
"album": "album 200-3",
"url": "localhost:10411/api/logos/album%200-3" (showed auto generate logo when not specify logoUrl in the request body, worked as expected)
}

Here is my mapping and the function:

CreateMap<Cut, CutData>()
   .ForMember(
       dest => dest.Album,
       opt => opt.MapFrom(scr => GetAlbum(scr.Channel.BaseUrl, src.LogoUrl, src.Album)));

private Album GetAlbum(string baseUrl, string customUrl, string albumName)
{
  Album album = new Album(baseUrl, albumName);
  if(customUrl != null)
  {
    image.Url = customUrl;
  }

  return album;
}

You guys please help me how I can distinguish the case when I didn't specify logoUrl in the request body (logoUrl is totally absent.) ->it will generate auto logo which is working well now. The case when I specify logoUrl = null -> I want it show in the response null instead of showing auto logo. Thank you very much for your help. Sincerely appreacited!

Answer 1

Unfortunately you can't. When you send an object to an API. Any value not provided will be automatically become the default value - for a string that's null . Meaning:

{
   "title": "track 200-1",
   "duration": "00:00:30",
   "album": "album 200-1",
   "logoUrl":null
}

And

{
   "title": "track 200-2",
   "album": "album 200-2",
   "url": "this is a text" 
}

Are the same.

If you really want a third value you can put logoUrl: "" . That way you can say something like:

if (logoUrl == null) {/* Do Work */}
if (logoUrl.Length == 0) {/* Do Work */}
if (logoUrl.Length > 0) {/* Do Work */}