How can access rest api using C#

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C#

REST

API

I have rest api url like this
https://example.com/ProductAPI/api/V1/getproduct.
This api has api_key,username and password.How can I access this api and getproduct details using c#.
The token which will get from another url
https://example.com/ProductAPI/ by passing username,password,client_key and generictype

What I have tried:

WebRequest request = WebRequest.Create(@"https://example.com/ProductAPI/api/V1/getproduct");

request.Method = "GET";
request.Headers.Add("api_key","5g13441f-6915-4a34-8a53-bcb4er88b554");
request.Headers["Authorization"] = "Basic" + Convert.ToBase64String(Encoding.Default.GetBytes("admin:123"));
request.ContentLength = 0;
request.ContentType = @"application/json; charset=utf-8";
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
string jsonResponse = string.Empty;
using (StreamReader sr = new StreamReader(response.GetResponseStream()))
{
jsonResponse = sr.ReadToEnd();
Console.WriteLine(jsonResponse);
Console.ReadLine();
}