MVC accessing external Web API using login credentials - asp.net-mvc

Question

In need of some help accessing an external Web API passing along credentials in order to access the methods available. I have included the code below that i use in order to attempt to access the Web API. However, i receive the following error every time i attempt to access it:
"The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel."
What am i missing or what am i doing wrong? I have been circling around this for a couple days and have tried a couple different techniques but continue to get the same error. Here is one technique that i used.
private static async Task<string> GetAPIToken(string userName, string password, string apiBaseUri)
{
try
{
using (var client = new HttpClient())
{
//setup client
client.BaseAddress = new Uri(apiBaseUri);
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
//setup login data
var formContent = new FormUrlEncodedContent(new[]
{
new KeyValuePair<string,string>("username",userName),
new KeyValuePair<string,string>("password",password),
});
//send request
HttpResponseMessage responseMessage = await client.PostAsync("Token", formContent);
//get access token from response body
var responseJson = await responseMessage.Content.ReadAsStringAsync();
var jobject = JObject.Parse(responseJson);
return jobject.GetValue("access_token").ToString();
}
}
catch (Exception ex)
{
return null;
}
}
Any help would be greatly appreciated.
Thanks

Answer 1

There is a little bit of a difference when using HTTPS vs HTTP. This question should give you the information you need to fix your problem.
Make Https call using HttpClient