How to use Power BI Rest API without GUI authentication (redirect uri)

Below is the code for getting AccessToken by giving User credential, client Id (without AccessCode & Azure-Login UI).

using Newtonsoft.Json;
using System.IO;
using System.Text;

private async void SetAccessToken()
{
List<KeyValuePair<string, string>> vals = new List<KeyValuePair<string, string>>();
vals.Add(new KeyValuePair<string, string>("grant_type", "password"));
vals.Add(new KeyValuePair<string, string>("scope", "openid"));
vals.Add(new KeyValuePair<string, string>("resource", "https://analysis.windows.net/powerbi/api"));
vals.Add(new KeyValuePair<string, string>("client_id", ""));
vals.Add(new KeyValuePair<string, string>("client_secret", ""));
vals.Add(new KeyValuePair<string, string>("username", ""));
vals.Add(new KeyValuePair<string, string>("password", ""));
string TenantId = "";
string url = string.Format("https://login.windows.net/{0}/oauth2/token", TenantId);
HttpClient hc = new HttpClient();
HttpContent content = new FormUrlEncodedContent(vals);
HttpResponseMessage hrm = hc.PostAsync(url, content).Result;
string responseData = "";
if (hrm.IsSuccessStatusCode)
{
Stream data = await hrm.Content.ReadAsStreamAsync();
using (StreamReader reader = new StreamReader(data, Encoding.UTF8))
{
responseData = reader.ReadToEnd();
}
}
Token = JsonConvert.DeserializeObject<AccessToken>(responseData);
}

public class AccessToken
{
public string token_type;
public string scope { get; set; }
public string expires_in { get; set; }
public string expires_on { get; set; }
public string not_before { get; set; }
public string resource { get; set; }
public string access_token { get; set; }
public string refresh_token { get; set; }
public string id_token { get; set; }
}