Invalid HTTP Post Request to Authentication Server

Question

I try to do a POST request to my authentication server which provides a JWT for me. But I don't get the values packed into the request. The code line 'var content = new FormUrlEncodedContent(values);' seems to have no effect. Does anybody know what I can try? My responseString in that case says that the grant-type parameter is missing:

"{\"error\":\"invalid_request\",\"error_description\":\"The mandatory 'grant_type' parameter is missing.\"}"

Here is my code:

private async void postAuthentication(LoginViewModel model)
        {
            var values = new Dictionary<string, string>
            {
               { "grant-type", "password" },
               { "username", model.Email },
               { "password", model.Password },
               { "scope", "openid" }
            };

            var content = new FormUrlEncodedContent(values); //alternative way to declare?

            var response = await client.PostAsync("http://localhost:5000/connect/token", content);

            var responseString = await response.Content.ReadAsStringAsync();
        }