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Using USPS APIs in C#

Do you want to know how to use the USPS API in C#? We'll show you how, and share step-by-step examples with you. (You may also want to check out our video tutorial on how to use the USPS APIs in C#).

In this article, we'll discuss:

Creating a USPS Account

Before you can use the USPS APIs, you will need to register with the USPS to receive a USERID. This ID is used in the sample code below where "USERID" is mentioned.

Types of USPS APIs

  • There are three USPS APIs available:
    • Address Standardization: validates an address and returns the accepted standardized version of it with other helpful metadata.
    • Zipcode Lookup: a simplified version of the standardization API and returns the zipcode and zip+4 given an address.
    • City/State Lookup: returns the city and state associated with a specified zipcode.
  • You can only make up to 5 requests per API call.
  • XML is used for the Request and Response docs. (Bummer)

Code Examples

Note that these samples require a USERID (see Register above).

Address Standardization Sample Code


using System;
using System.Net;
using System.Xml.Linq;

namespace USPSApi_CLI {
    class USPSAddressStandardization {
        public static void Main() {

            XDocument requestDoc = new XDocument(
                new XElement("AddressValidateRequest",
                        new XAttribute("USERID", ""),
                    new XElement("Revision", "1"),
                    new XElement("Address",
                        new XAttribute("ID", "0"),
                        new XElement("Address1", "2335 S State"),
                        new XElement("Address2", "Suite 300"),
                        new XElement("City", "Provo"),
                        new XElement("State", "UT"),
                        new XElement("Zip5", "84604"),
                        new XElement("Zip4", "")
                    )
                )
            );

            try {
                var url = "http://production.shippingapis.com/ShippingAPI.dll?API=Verify&XML=" + requestDoc;
                Console.WriteLine(url);
                var client = new WebClient();
                var response = client.DownloadString(url);

                var xdoc = XDocument.Parse(response.ToString());
                Console.WriteLine(xdoc.ToString());
                foreach (XElement element in xdoc.Descendants("Address")) {
                    Console.WriteLine("-------------------------------");
                    Console.WriteLine("Address ID:           " + GetXMLAttribute(element, "ID"));
                    Console.WriteLine("Address1:             " + GetXMLElement(element, "Address1"));
                    Console.WriteLine("Address2:             " + GetXMLElement(element, "Address2"));
                    Console.WriteLine("City:                 " + GetXMLElement(element, "City"));
                    Console.WriteLine("State:                " + GetXMLElement(element, "State"));
                    Console.WriteLine("Zip5:                 " + GetXMLElement(element, "Zip5"));
                    Console.WriteLine("Zip4:                 " + GetXMLElement(element, "Zip4"));

                }

            }
            catch (WebException e) {
                Console.WriteLine(e.ToString());
            }

        }

        public static string GetXMLElement(XElement element, string name) {
            var el = element.Element(name);
            if (el != null) {
                return el.Value;
            }
            return "";
        }

        public static string GetXMLAttribute(XElement element, string name) {
            var el = element.Attribute(name);
            if (el != null) {
                return el.Value;
            }
            return "";
        }

    }
}
                    

Zipcode Lookup Sample Code


using System;
using System.Net;
using System.Xml.Linq;

namespace USPSApi_CLI {
    public class USPSApiZipCode {
        public static void Main() {
            XDocument requestDoc = new XDocument(
                new XElement("ZipCodeLookupRequest",
                             new XAttribute("USERID", ""),
                    new XElement("Revision", "1"),
                    new XElement("Address",
                                 new XAttribute("ID", "0"),
                                 new XElement("Address1", "2335 S State"),
                                 new XElement("Address2", "Suite 300"),
                                 new XElement("City", "Provo"),
                                 new XElement("State", "UT"),
                                 new XElement("Zip5", "84604"),
                                 new XElement("Zip4", "")
                                ),
                    new XElement("Address",
                                 new XAttribute("ID", "1"),
                                 new XElement("Address1", "1427 S 2340 E"),
                                 new XElement("Address2", ""),
                                 new XElement("City", "Spanish Fork"),
                                 new XElement("State", "UT"),
                                 new XElement("Zip5", "84660"),
                                 new XElement("Zip4", "")
                                )
                )
            );

            try {
                var url = "http://production.shippingapis.com/ShippingAPI.dll?API=ZipCodeLookup&XML=" + requestDoc;
                Console.WriteLine(url);
                var client = new WebClient();
                var response = client.DownloadString(url);

                var xdoc = XDocument.Parse(response.ToString());
                Console.WriteLine(xdoc.ToString());

                foreach (XElement element in xdoc.Descendants("Address")) {
                    Console.WriteLine("-------------------------------");
                    Console.WriteLine("Address ID:           " + GetXMLAttribute(element, "ID"));
                    Console.WriteLine("Address1:             " + GetXMLElement(element, "Address1"));
                    Console.WriteLine("Address2:             " + GetXMLElement(element, "Address2"));
                    Console.WriteLine("City:                 " + GetXMLElement(element, "City"));
                    Console.WriteLine("State:                " + GetXMLElement(element, "State"));
                    Console.WriteLine("Zip5:                 " + GetXMLElement(element, "Zip5"));
                    Console.WriteLine("Zip4:                 " + GetXMLElement(element, "Zip4"));
                    Console.WriteLine("Urbanization:         " + GetXMLElement(element, "Urbanization"));
                }
            }
            catch (WebException e) {
                Console.WriteLine(e.ToString());
            }
        }

        public static string GetXMLElement(XElement element, string name) {
            var el = element.Element(name);
            if (el != null) {
                return el.Value;
            }
            return "";
        }

        public static string GetXMLAttribute(XElement element, string name) {
            var el = element.Attribute(name);
            if (el != null) {
                return el.Value;
            }
            return "";
        }
    }
}
                    

City/State Lookup Sample Code


using System;
using System.Net;
using System.Xml.Linq;

namespace USPSApi_CLI {
    public class USPSApiCityStateLookup {
        public static void Main() {
            XDocument requestDoc = new XDocument(
                new XElement("CityStateLookupRequest",
                             new XAttribute("USERID", ""),
                    new XElement("Revision", "1"),
                    new XElement("ZipCode",
                                 new XAttribute("ID", "0"),
                                 new XElement("Zip5", "84414")
                                ),
                    new XElement("ZipCode",
                                 new XAttribute("ID", "1"),
                                 new XElement("Zip5", "84660")
                                )
                )
            );

            try {
                var url = "http://production.shippingapis.com/ShippingAPI.dll?API=CityStateLookup&XML=" + requestDoc;
                Console.WriteLine(url);
                var client = new WebClient();
                var response = client.DownloadString(url);

                var xdoc = XDocument.Parse(response.ToString());
                Console.WriteLine(xdoc.ToString());

                foreach (XElement element in xdoc.Descendants("ZipCode")) {
                    Console.WriteLine("-------------------------------");
                    Console.WriteLine("ZipCode ID:           " + GetXMLAttribute(element, "ID"));
                    Console.WriteLine("City:                 " + GetXMLElement(element, "City"));
                    Console.WriteLine("State:                " + GetXMLElement(element, "State"));
                    Console.WriteLine("Zip5:                 " + GetXMLElement(element, "Zip5"));
                }
            }
            catch (WebException e) {
                Console.WriteLine(e.ToString());
            }
        }

        public static string GetXMLElement(XElement element, string name) {
            var el = element.Element(name);
            if (el != null) {
                return el.Value;
            }
            return "";
        }

        public static string GetXMLAttribute(XElement element, string name) {
            var el = element.Attribute(name);
            if (el != null) {
                return el.Value;
            }
            return "";
        }
    }
}
                    

Alternative Address Validation APIs

We know what you're thinking. Why would SmartyStreets assist me in using an API that isn't theirs?

The answer is simple - we care. We want you to get your job done, and if you really want to use the USPS API, then hopefully this article will help you.

However, we think that once you see how much easier the SmartyStreets .NET SDK is to use, you will want to use it instead of the USPS APIs. And, if you do, you'll get excellent customer service in the process. And of course we won't even mention that SmartyStreet APIs are blazingly fast!

Take a moment and compare the sample code above with the SmartyStreets .NET SDK sample code.

When you compare the USPS API experience with the SmartyStreets API experience, you'll see that SmartyStreets wins, every time. From the easy-to-use JSON response, to the stellar support, and the faster response times, and the fact that you can make up to 100 requests per API call to SmartyStreets APIs, SmartyStreets wins everytime.

Try SmartyStreets for yourself with a free demo account. You'll be glad that you did.

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