/// <summary>
/// Retrieves the article Header at the specified ordinal position.
/// </summary>
/// <param name="index">The ordinal position of the article to be retrieved.</param>
/// <returns>A byte array containing the article header.</returns>
/// <example>
/// <code>
/// C#
///
/// NntpClient nntp = new NntpClient();
///
/// nntp.Connect("news.myhost.com");
///
/// NewsGroup group = nntp.SelectGroup("mygroup");
/// //Retrieve the Header of the article at position 29 in this group.
/// byte[] header29 = group.RetrieveHeader(29);
/// //Retrieve last Header in this group.
/// byte[] Header = group.RetrieveHeader(group.LastHeader);
///
/// nntp.Disconnect();
///
/// VB.NET
///
/// Dim nntp As New NntpClient
///
/// nntp.Connect("news.myhost.com")
///
/// Dim group As NewsGroup = nntp.SelectGroup("mygroup")
/// 'Retrieve the Header of the article at position 29 in this group.
/// Dim header29() As Byte = group.RetrieveHeader(29)
/// 'Retrieve last Header in this group.
/// Dim header() As Byte = group.RetrieveHeader(group.LastHeader)
///
/// nntp.Disconnect()
///
/// JScript.NET
///
/// var nntp:NntpClient = new NntpClient();
///
/// nntp.Connect("news.myhost.com");
///
/// var group:NewsGroup = nntp.SelectGroup("mygroup");
/// //Retrieve the Header of the article at position 29 in this group.
/// var header29:byte[] = group.RetrieveHeader(29);
/// //Retrieve last Header in this group.
/// var header:byte[] = group.RetrieveHeader(group.LastHeader);
///
/// nntp.Disconnect();
/// </code>
/// </example>
public byte[] RetrieveHeader(int index)
{
_nntp.OnHeaderRetrieving(new HeaderRetrievingEventArgs(index));
byte[] buffer = _nntp.CommandMultiline("head " + index.ToString());
if (Encoding.ASCII.GetString(buffer, 0, buffer.Length).StartsWith("221"))
{
Pointer = index;
}
_nntp.OnHeaderRetrieved(new HeaderRetrievedEventArgs(buffer, index));
return(buffer);
}