Question

I thought I would post this here not so much as a question but to share with the community some code I wrote after not being able to find the answer here on StackOverflow. If someone would like to take a look at the code and improve it, that would be great, but not required. I have left out some code (try-catch blocks & error handling) to make it a little bit easier to consume the concept and code.

Answer 1

So, let’s start with the problem I needed to solve. I wanted to be able to allow someone to enter part or all of a city, state, zipcode combination and use Yahoo’s PlaceFinder API to figure out exactly where it was. Nothing fancy, just a simple way to resolve a city & state from a zip code or vice-versa.

This process involves:

1. Receiving the input (city/state/zip) server-side
2. Constructing a URL with the proper parameters (I wanted to receive the response in JSON format)
3. Making the HTTP GET request to the PlaceFinder service.
4. Consuming the JSON response in a way that would give me an object model in C# to easily work with the reponse data.

Let’s start with the namespaces you’ll want to import:

using System.Net; // for HttpWebRequest
using System.Text; // for utf8 encoding
using System.Web.Script.Serialization; // for json parsing
using System.IO; // for datastream

Next, let’s look at constructing the request:

string parameters = String.Empty;
UTF8Encoding utf8 = new UTF8Encoding(); // yahoo docs state utf-8 encoding
string unparsedLocation = "Beverly Hills, CA 90210"; // contrived example

parameters += "line2=" + Url.Encode(unparsedLocation); // yahoo docs say to url encode
parameters += "&flags=J"; // J = want the response formatted in json
parameters += "&appid=[your-app-id-here]"; // using your appID obtained from Yahoo
parameters = utf8.GetString(utf8.GetBytes(parameters));
WebRequest request = WebRequest.Create(@"http://where.yahooapis.com/geocode?" + parameters);
request.Method = "GET";

Next, we want to get the response and put it into an object model that makes it easy to work with:

WebResponse response = request.GetResponse();
// Check the status. If it's not OK then don't bother with trying to parse the result
if (((HttpWebResponse)response).StatusCode == HttpStatusCode.OK)
{
    // Get the stream containing content returned by the server.
    Stream dataStream = response.GetResponseStream();
    // Open the stream using a StreamReader.
    StreamReader reader = new StreamReader(dataStream);
    // Read the content.
    string responseFromServer = reader.ReadToEnd();

    JavaScriptSerializer jss = new JavaScriptSerializer();
    YahooResponse yr = jss.Deserialize<YahooResponse>(responseFromServer);

    // You may not want such strict checking; if not, remove the "NO ERROR" check
    if (yr.ResultSet.Error == 0 && yr.ResultSet.ErrorMessage.ToUpper() == "NO ERROR" && yr.ResultSet.Found > 0)
    {
        // inside here is where you can do whatever you need to.
        // ex. 1 - get the first result
        Result result = yr.ResultSet.results[0];

        // ex. 2 - loop through results
        foreach (Result r in yr.ResultSet.results)
        {
            // add values to a List<T> or something useful
        }
    }
}

// always do this as a matter of good practice
response.Close();

But wait, there’s one last important piece missing. What is a ‘YahooResponse‘ object? What does the class definition look like? Here is what I came up with:

namespace PlaceFinder
{
    public class YahooResponse
    {
        public ResultSet ResultSet { get; set; }
    }

    public class ResultSet
    {
        public string version { get; set; }
        public int Error { get; set; }
        public string ErrorMessage { get; set; }
        public string Locale { get; set; }
        public int Quality { get; set; }
        public int Found { get; set; }
        public Result[] results { get; set; }
    }

    public class Result
    {
        public int quality { get; set; }
        public string latitude { get; set; }
        public string longitude { get; set; }
        public string offsetlat { get; set; }
        public string offsetlon { get; set; }
        public int radius { get; set; }
        public string name { get; set; }
        public string line1 { get; set; }
        public string line2 { get; set; }
        public string line3 { get; set; }
        public string line4 { get; set; }
        public string house { get; set; }
        public string street { get; set; }
        public string xstreet { get; set; }
        public string unittype { get; set; }
        public string unit { get; set; }
        public string postal { get; set; }
        public string neighborhood { get; set; }
        public string city { get; set; }
        public string county { get; set; }
        public string state { get; set; }
        public string country { get; set; }
        public string countrycode { get; set; }
        public string statecode { get; set; }
        public string countycode { get; set; }
        public string uzip { get; set; }
        public string hash { get; set; }
        public long woeid { get; set; }
        public int woetype { get; set; }
    }
}

Read more about the PlaceFinder service here: http://developer.yahoo.com/geo/placefinder/guide/