using System.Net;

/// <summary>
/// Checks the file exists or not.
/// </summary>
/// <param name="url">The URL of the remote file.</param>
/// <returns>True : If the file exits, False if file not exists</returns>
private bool RemoteFileExists(string url)
{
    try
    {
        //Creating the HttpWebRequest
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        //Setting the Request method HEAD, you can also use GET too.
        request.Method = "HEAD";
        //Getting the Web Response.
        HttpWebResponse response = request.GetResponse() as HttpWebResponse;
        //Returns TURE if the Status code == 200
        return (response.StatusCode == HttpStatusCode.OK);
    }
    catch
    {
        //Any exception will returns false.
        return false;
    }
}