public bool Authorize(string username, string password)
{
    bool result = false;
    this.username = username;
    this.password = password;
 
    using (WebClient client = new WebClient())
    {
        // Send the requeset with username and password
        client.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
        string response = client.UploadString(
            "https://www.google.com/youtube/accounts/ClientLogin",
            string.Format("Email={0}&Passwd={1}&service=youtube&source=TrailsintheSand.YouTube.Library",
                username, password));
 
        // The response is plain text containing:
        // Auth=<authorization code>
        string[] split = response.Split('\n');
        foreach (string s in split)
        {
            string[] nvsplit = s.Split('=');
            if (nvsplit.Length == 2)
            {
                if (nvsplit[0] == "Auth")
                {
                    authCode = nvsplit[1];
                    result = true;
                }
            }
        }
    }
 
    return result;
}

public bool Upload(string title, string description, Catagory catagory,
              string keywords, string videoFileName, out string error)
{
    bool result = false;
    error = null;
 
    // Build byte arrays for the header file and footer
    byte[] header = Encoding.UTF8.GetBytes(GetHeader(title, description, catagory, keywords, videoFileName));
    byte[] file = File.ReadAllBytes(videoFileName);
    byte[] footer = Encoding.UTF8.GetBytes(lineTerm + boundary + "--");
 
    // Combine the byte arrays into one big byte array
    byte[] data = new byte[header.Length + file.Length + footer.Length];
    Array.Copy(header, 0, data, 0, header.Length);
    Array.Copy(file, 0, data, header.Length, file.Length);
    Array.Copy(footer, 0, data, header.Length + file.Length, footer.Length);
 
    // Using a HttpWebRequest here because it allows us to control the timeout
    HttpWebRequest req = (HttpWebRequest)WebRequest
        .Create(string.Format("http://uploads.gdata.youtube.com/feeds/api/users/{0}/uploads",
                username));
    req.Method = "POST";
    req.ContentType = string.Format("multipart/related; boundary={0};", boundaryheader);
    req.ContentLength = data.Length;
    req.Timeout = timeout;
    req.Headers.Add("Authorization", "GoogleLogin auth=" + authCode);
    req.Headers.Add("X-GData-Client", clientCode); // supposed to be optional
    req.Headers.Add("X-GData-Key", devCode);
    req.Headers.Add("Slug", Path.GetFileName(videoFileName));
 
    using (Stream postStream = req.GetRequestStream())
    {
        // Send the data to the server
        postStream.WriteTimeout = timeout;
        postStream.Write(data, 0, data.Length);
        postStream.Close();
 
        try
        {
            // Get the response back from the server
            WebResponse webResponse = req.GetResponse();
            using (Stream responseStream = webResponse.GetResponseStream())
            {
                using (StreamReader reader = new StreamReader(responseStream))
                {
                    // Should check the response here
                    reader.Close();
                    result = true;
                }
 
                responseStream.Close();
            }
 
            webResponse.Close();
        }
        catch (WebException ex)
        {
            // Got a bad response
            using (StreamReader sr = new StreamReader(ex.Response.GetResponseStream()))
            {
                error = sr.ReadToEnd();
            }
        }
    }
 
    return result;
}

private string GetHeader(string title, string description, Catagory catagory,
                         string keywords, string videoFileName)
{
    StringBuilder xml = new StringBuilder();
    xml.Append(boundary + lineTerm + "Content-Type: application/atom+xml; charset=UTF-8" + lineTerm + lineTerm);
    xml.Append("<?xml version=\"1.0\"?><entry xmlns=\"http://www.w3.org/2005/Atom\" ");
    xml.Append("xmlns:media=\"http://search.yahoo.com/mrss/\" xmlns:yt=\"http://gdata.youtube.com/schemas/2007\">");
    xml.AppendFormat("<media:group><media:title type=\"plain\">{0}</media:title>", title);
    xml.AppendFormat("<media:description type=\"plain\">{0}</media:description>", description);
    xml.AppendFormat("<media:category scheme=\"http://gdata.youtube.com/schemas/2007/categories.cat\">{0}</media:category>", catagory);
    xml.AppendFormat("<media:keywords>{0}</media:keywords>", keywords);
    xml.Append("</media:group></entry>" + lineTerm);
    xml.Append(boundary + lineTerm + "Content-Type: video/*" + lineTerm + "Content-Transfer-Encoding: binary" + lineTerm + lineTerm);
    return xml.ToString();
}

Trails.YouTube youTube = new Trails.YouTube();
Console.WriteLine("Authorizing...");
if(youTube.Authorize("youtube username", "youtube password"))
{
    Console.WriteLine("Authorized");
    Console.WriteLine("Uploading...");
    string error;
    if (youTube.Upload("Test Video", "This is a test", YouTube.Catagory.Howto, "test", @"c:\test.mp4", out error))
    {
        Console.WriteLine("Upload complete");
    }
    else
    {
        Console.WriteLine("Upload failed: {0}", error);
    }
}
else
{
    Console.WriteLine("Authorization failed");
}