Yahoo Weather API C# Example

YWSample.cs

// Yahoo Weather API C# Sample Code
// Code sample offered under the terms of the CC0 Public Domain designation. See https://creativecommons.org/publicdomain/zero/1.0/legalcode/ for terms.
// Author: Eugene Plotnikov


using System;
using System.Net;
using System.Security.Cryptography;
using System.Text;

class YWSample {

 const string cURL              = "https://weather-ydn-yql.media.yahoo.com/forecastrss";
 const string cAppID            = "test-app-id";
 const string cConsumerKey      = "your-consumer-key";
 const string cConsumerSecret   = "your-consumer-secret";
 const string cOAuthVersion     = "1.0";
 const string cOAuthSignMethod  = "HMAC-SHA1";
 const string cWeatherID        = "woeid=727232";  // Amsterdam, The Netherlands
 const string cUnitID           = "u=c";           // Metric units
 const string cFormat           = "xml";

 static string _get_timestamp () {
  TimeSpan lTS = DateTime.UtcNow - new DateTime ( 1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc );
  return Convert.ToInt64 ( lTS.TotalSeconds ).ToString ();
 }  // end _get_timestamp

 static string _get_nonce () {
  return Convert.ToBase64String (
   new ASCIIEncoding ().GetBytes (
    DateTime.Now.Ticks.ToString ()
   )
  );
 }  // end _get_nonce
 
 // NOTE: whenever the value of a parameter is changed, say cUnitID "u=c" => "location=sunnyvale,ca"
 // The order in lSign needs to be updated, i.e. re-sort lSign
 // Please don't simply change value of any parameter without re-sorting.
 static string _get_auth () {
  string retVal;
  string lNonce = _get_nonce     ();
  string lTimes = _get_timestamp ();
  string lCKey  = string.Concat ( cConsumerSecret, "&" );
  string lSign  = string.Format (  // note the sort order !!!
   "format={0}&"                 +
   "oauth_consumer_key={1}&"     +
   "oauth_nonce={2}&"            +
   "oauth_signature_method={3}&" +
   "oauth_timestamp={4}&"        +
   "oauth_version={5}&"          +
   "{6}&{7}",
   cFormat,
   cConsumerKey,
   lNonce,
   cOAuthSignMethod,
   lTimes,
   cOAuthVersion,
   cUnitID,
   cWeatherID
  );
  
  lSign = string.Concat (
   "GET&", Uri.EscapeDataString ( cURL ), "&", Uri.EscapeDataString ( lSign )
  );
  
  using (   var lHasher = new HMACSHA1 (  Encoding.ASCII.GetBytes( lCKey )  )   ) {
   lSign = Convert.ToBase64String (
    lHasher.ComputeHash (  Encoding.ASCII.GetBytes ( lSign )  )
   );
  }  // end using
  
  return "OAuth "                     +
         "oauth_consumer_key=\""     + cConsumerKey     + "\", " +
         "oauth_nonce=\""            + lNonce           + "\", " +
         "oauth_timestamp=\""        + lTimes           + "\", " +
         "oauth_signature_method=\"" + cOAuthSignMethod + "\", " +
         "oauth_signature=\""        + lSign            + "\", " +
         "oauth_version=\""          + cOAuthVersion    + "\"";
          
 }  // end _get_auth

 public static void Main ( string[] args ) {

  const string lURL = cURL + "?" + cWeatherID + "&" + cUnitID +"&format=" + cFormat;
  
  var lClt = new WebClient ();
  
  lClt.Headers.Set (  "Content-Type",  "application/" + cFormat );
  lClt.Headers.Add (  "X-Yahoo-App-Id",  cAppID                   );
  lClt.Headers.Add (  "Authorization", _get_auth ()             );

  Console.WriteLine( "Downloading Yahoo weather report . . ." );
  
  byte[] lDataBuffer = lClt.DownloadData ( lURL );
  
  string lOut = Encoding.ASCII.GetString ( lDataBuffer );
  
  Console.WriteLine ( lOut );

  Console.Write ( "Press any key to continue . . . " );
  Console.ReadKey ( true );

 }  // end Main
 
}  // end YWSample

how to download weather data by ZIP and LatLong?

retVal is not used here
So we do not need it.
You may update from my fork