Via Virtual Earth

Taking the search server side RSS

This article is written for an old version of the Virtual Earth platform. While still available for reference purposes, it is unlikely to work if implemented.

This article introduces a technique to bypass the security issue introduced by accessing a cross domain data source as introduced in the Finding section of Part 2 of Creating Your First Virtual Earth Web Page.

By moving the work of doing the search to your web server you can access the search functionality and return the result to your site.

In order to do this you will need to write some server side functionality. This article will demonstrate doing this with ASP.NET.

The final outcome can be viewed here.

The full code listing can be viewed here.

Using the System.Net.HttpWebRequest object in ASP.NET server code will allow you to post a request to the search page on the Virtual Earth site. To get started let�s create the HttpWebRequest object.

private HttpWebRequest CreateSearchRequest()
{
  HttpWebRequest searchRequest = (HttpWebRequest) WebRequest.Create("http://207.46.159.133/search.ashx");
  searchRequest.Method = "POST";
  searchRequest.ServicePoint.Expect100Continue = false;
  searchRequest.ContentType = "application/x-www-form-urlencoded";
  return searchRequest;
}

Then you will need to build the search parameters to pass to the Virtual Earth search page.

private string BuildSearchParams(string place)
{
  string a="";
  string b=place;
  string c="0.0";
  string d="0.0";
  string e="0.0";
  string f="0.0";
  string g="";
  string i="";
  int r=0;
  string searchParams = "a="+a+"&b="+b+"&c="+c+"&d="+d+"&e="+e+"&f="+f+"&g="+g+"&i="+i+"&r="+r;
  return searchParams;
}

In order to get the results from the search that was posted you will need to use the HttpWebResponse object. From this object you can read the results from a stream and decode them into a string.

private string GetSearchResults(HttpWebRequest searchRequest)
{
  string results = string.Empty;
  HttpWebResponse searchResponse = (HttpWebResponse)searchRequest.GetResponse();
  
  Stream receiveStream = searchResponse.GetResponseStream();
  
  System.Text.Encoding encode = System.Text.Encoding.GetEncoding("utf-8");
  
  StreamReader readStream = new StreamReader(receiveStream, encode);
  
  Char[] read = new Char[256];
  
  // Reads 256 characters at a time.
  int count = readStream.Read(read, 0, 256);
  while (count > 0)
  {
    String str = new String(read, 0, count);
    results += str;
    count = readStream.Read(read, 0, 256);
  }
  
  searchResponse.Close();
  
  return results;
}

These methods can now be pulled together by a method that does the actual search.

private string Search(string place)
{
  string results = string.Empty;
  
  HttpWebRequest searchRequest = CreateSearchRequest();
  
  string searchParams = BuildSearchParams(place);
  System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
  byte[] bytes = encoding.GetBytes(searchParams);
  
  searchRequest.ContentLength = bytes.Length;
  
  Stream requestStream = searchRequest.GetRequestStream();
  requestStream.Write(bytes, 0, bytes.Length);
  requestStream.Close();
  
  try
  {
    results = GetSearchResults(searchRequest);
  }
  catch(Exception ex)
  {
    Console.Out.WriteLine(ex.Message);
  }
  
  return results;
}

You now have a function that will call out to the virtual Earth search and return the results in a string object. You can use this in your own search page by calling the Search method from your Page.Load event handler

private void Page_Load(object sender, System.EventArgs e)
{
  if(Request["place"] != null)
  {
    Response.Clear();
    Response.Write(Search(Request["place"]));
  }
}

An example of this page is hosted at http://www.viavirtualearth.com/MyVirtualEarth/Search.aspx

You can test the search by adding a request parameter.

For example try http://www.viavirtualearth.com/MyVirtualEarth/Search.aspx?place=Portland, OR

You will see this returns Jscript that you can execute on your page. To use this you will need to eval this script. This is done in the third sample page.

var xmlhttp=false;

function DoFind()
{
  try
  {
    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
  }
  catch (e)
  {
    try
    {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch (E)
    {
      xmlhttp = false;
    }
  }
  
  if (!xmlhttp && typeof XMLHttpRequest!='undefined')
  {
    xmlhttp = new XMLHttpRequest();
  }
  
  xmlhttp.onreadystatechange=searchHandler;
  
  var where = document.getElementById("WhereText").value;
  
  xmlhttp.open("GET","search.aspx?place="+where,true);
  xmlhttp.send(null);
}

function searchHandler()
{
  if (xmlhttp.readyState==4)
  {
    eval(xmlhttp.responseText); 
  }
}