/// <summary>
/// Load specified file and return instance
/// </summary>
/// <param name="filename"></param>
/// <returns></returns>
public static LoadedDocument Load(string filename)
{
ParameterizedThreadStart threadStart = ThreadLoader.Load;
iAsyncResult = threadStart.BeginInvoke(filename, null, null);
//do other things
threadStart.EndInvoke(iAsyncResult);
return(Document);
}