string tokenEndpoint = "https://<servername>/adfs/oauth2/token";
string clientId = "<clientid>";
string clientSecret = "<clientsecret>";
string scope = "https://localhost/exampleapi/readdata";

var client = new HttpClient();

// Obtain the token
var tokenResponse = await client.PostAsync(tokenEndpoint, new FormUrlEncodedContent(new[]
{
    new KeyValuePair<string, string>("client_id", clientId),
    new KeyValuePair<string, string>("client_secret", clientSecret),
    new KeyValuePair<string, string>("grant_type", "client_credentials"),
    new KeyValuePair<string, string>("scope", scope)
}));