Downloading a Web Page Programmatically - .NET Framework

public static void PostData(string localFile)
{
    var targetUrl = @"http://www.zip-codes.com/zip-code-radius-finder.asp";
    var parameters = "zipMilesLow=0&zipMilesHigh=50&zip1=30303";

    //--- Build the request object ---
    var request = System.Net.WebRequest.Create(targetUrl);
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    request.ContentLength = parameters.Length;

    //--- Add the parameters to the request ---
    var sw = new System.IO.StreamWriter(request.GetRequestStream());
    sw.Write(parameters);
    sw.Close();

    //--- Get the response object ---
    var response = request.GetResponse();
    var sr = new System.IO.StreamReader(response.GetResponseStream());
    System.IO.File.WriteAllText(localFile, sr.ReadToEnd());
}