USPS Rates Basic Example

Rates.cs

try
{
    using (var usps = new USPSRates(UseUSPSSandbox, USPSClientId, USPSClientSecret))
    {
        Dictionary<string, object> rates = usps.GetRates(FromZip, toZip, weightIn / 16); // weight in pounds
        foreach (var rate in (JArray)rates["rateOptions"])
        {
            ListItem li = new ListItem();
            string service = ((JArray)rate["rates"])[0]["productName"].ToString();
            if (service == "")
                continue;
            decimal amount = Convert.ToDecimal(rate["totalBasePrice"]);
            li.Text = "USPS " + service + " " + amount.ToString("c");
            li.Value = amount.ToString("c") + "^USPS " + service;
            if (ShipService.Items.FindByValue(li.Value) != null)
                continue;
            ShipService.Items.Add(li);
        }
    }
}
catch
{

}

USPSRates.cs

public class USPSRates : IDisposable
{
    private readonly HttpClient _client;

    public USPSRates(bool sandbox, string clientId, string clientSecret)
    {
        _client = new HttpClient
        {
            BaseAddress = new Uri(sandbox ? "https://apis-tem.usps.com/" : "https://apis.usps.com/")
        };
        _client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        var data = new { client_id = clientId, client_secret = clientSecret, grant_type = "client_credentials" };
        using (var content = new StringContent(JsonConvert.SerializeObject(data), Encoding.UTF8, "application/json"))
        {
            var resp = _client.PostAsync("oauth2/v3/token", content).GetAwaiter().GetResult();
            resp.EnsureSuccessStatusCode();
            var result = JsonConvert.DeserializeObject<Dictionary<string, object>>(resp.Content.ReadAsStringAsync().GetAwaiter().GetResult());
            _client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", result["access_token"].ToString());
        }
    }

    public Dictionary<string, object> GetRates(string originZip, string destinationZip, decimal weightInPounds)
    {
        var requestBody = new
        {
            originZIPCode = originZip,
            destinationZIPCode = destinationZip,
            weight = weightInPounds,
            mailClasses = new string[] { "PRIORITY_MAIL", "FIRST-CLASS_PACKAGE_SERVICE", "USPS_RETAIL_GROUND" },
            width = 0,
            length = 0,
            height = 0,
            priceType = "COMMERCIAL",
        };
        using (var content = new StringContent(JsonConvert.SerializeObject(requestBody), Encoding.UTF8, "application/json"))
        {
            var response = _client.PostAsync("prices/v3/total-rates/search", content).GetAwaiter().GetResult();
            response.EnsureSuccessStatusCode();
            var result = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
            return JsonConvert.DeserializeObject<Dictionary<string, object>>(result);
        }
    }

    public void Dispose()
    {
        _client.Dispose();
    }
}