HMRC Hello Application

namespace consoleapp1 
{ 
  public class response1 
  { 
    public string? access_token { get; set; } 
    public string? scope { get; set; } 
    public int expires_in { get; set; } 
    public string? token_type { get; set; } 
  } 

  class Program 
  { 
    private static readonly 
    System.Net.Http.HttpClient client = new System.Net.Http.HttpClient(); 

    //-------------------------------------------------------------------------------------- 
    static async 
    System.Threading.Tasks.Task 
    Main(string[] args) 
    { 
      var response = await Method_HelloApplication(); 
      System.Console.WriteLine(response); 
    } 
    //-------------------------------------------------------------------------------------- 
    private static async 
    System.Threading.Tasks.Task<string> 
    Method_GetAccessToken() 
    { 
      client.DefaultRequestHeaders.Accept.Clear(); 
      client.DefaultRequestHeaders.Accept.Add( 
          new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json")); 

      var parametersObject = new 
      { 
        client_id = "********", 
        client_secret = "********", 
        scope = "hello", 
        grant_type = "client_credentials", 
        redirect_uri = "https://localhost:8081" 
      }; 
      var parametersJSON = System.Text.Json.JsonSerializer.Serialize(parametersObject); 
      System.Net.Http.StringContent _httpCONTENT = new System.Net.Http.StringContent(parametersJSON.ToString(), System.Text.Encoding.UTF8, "application/json"); 
      System.Net.Http.HttpResponseMessage response = 
      await client.PostAsync("https://test-api.service.hmrc.gov.uk/oauth/token", _httpCONTENT); 

      string response_string = 
      await response.Content.ReadAsStringAsync(); 
      return response_string; 
    } 
    //-------------------------------------------------------------------------------------- 
    private static async 
    System.Threading.Tasks.Task<string> 
    Method_GetApplicationResponse(string AccessToken) 
    { 
      client.DefaultRequestHeaders.Accept.Clear(); 
      client.DefaultRequestHeaders.Accept.Add( 
          new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/vnd.hmrc.1.0+json")); 

      client.DefaultRequestHeaders.Authorization = 
          new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", AccessToken); 

      System.Net.Http.HttpResponseMessage response = 
      await client.GetAsync("https://test-api.service.hmrc.gov.uk/hello/application"); 

      string response_string = 
      await response.Content.ReadAsStringAsync(); 
      return response_string; 
    } 
    //-------------------------------------------------------------------------------------- 
    private static async 
    System.Threading.Tasks.Task<string> 
    Method_HelloApplication() 
    { 
      string _tokenResults = await Method_GetAccessToken(); 

      if (_tokenResults != null) 
      { 
        var responseObject = System.Text.Json.JsonSerializer.Deserialize<response1>(_tokenResults); 
        if (responseObject != null) 
        { 
          string _accessToken = responseObject.access_token ?? ""; 

          if (_accessToken != null) 
          { 
            string _getapplication = await Method_GetApplicationResponse(_accessToken); 

            if (_getapplication != null) 
            { 
              return _getapplication; 
            } 
          } 
        } 
      } 
      return ""; 
    } 
    //-------------------------------------------------------------------------------------- 
  } 
}