sending json and files to Azure Function

I am trying to upload files to an Azure Function, but I also need a JSON object to add addition context and I am struggling.

I am not sure if its the restClient in vs code that the issue or if its the Azure function not being happy;

POST http://localhost:7071/api/upload
Content-Type: application/json; multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW

------WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="files"; filename="2020-04-29.png"
Content-Type: image/png

< C:\Users\enend\OneDrive\Pictures\Screenshots\2020-04-29.png
------WebKitFormBoundary7MA4YWxkTrZu0gW--

private async Task<UploadCommand?> GetCommandAsync(HttpRequestData httpRequest)
        {
            try
            {
                var command =  await httpRequest.ReadFromJsonAsync<UploadCommand>();

                if(command == null) return null;

                var parser = await MultipartFormDataParser.ParseAsync(httpRequest.Body);
                
                command.Files = parser.Files.ToList();

                return command;
            }
            catch(Exception ex)
            {
                _log.LogError(ex.ToString());
                return null;
            }
        }
    }

public class UploadCommand
    {
        [JsonPropertyName("files")]
        public IEnumerable<FilePart> Files {get;set;} = new List<FilePart>();
        [JsonPropertyName("culture")]
        public string? Culture { get; set; }
        [JsonPropertyName("status")]
        public string? Status { get; set; }
        [JsonPropertyName("accessType")]
        public string? AccessType { get; set; } 
        [JsonPropertyName("folders")]
        public IEnumerable<Folder>? Folders { get; set; }
        [JsonPropertyName("fileTypes")]
        public IEnumerable<string>? FileTypes { get; set; }
        [JsonPropertyName("allowOverrides")]
        public bool AllowOverride { get; set; }
    }

the above code works, but I can't figure away to add JSON to it, so my function accepts it (I can send JSON separately but not together).

Any thoughts would be appreciated.

You need to define your content-type at the root of the message with multipart/form-data and each unique part will define the content-type thereafter

POST "https://yourdomain.com/upload" HTTP/1.1
Authorization: ''
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW

----WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name='image'; filename:"test_file.png"
Content-Type: image/png
Content-Length: <number>

<test_file data in bytes>

----WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name='filename'
Content-Type: application/json
Content-Length: <number>

{
    "image": "<filename>",
    "countryCode": "US"
}
----WebKitFormBoundary7MA4YWxkTrZu0gW--