namespace Swan { using System; using System.IO; using System.Net.Mail; using System.Reflection; /// /// Extension methods. /// public static class SmtpExtensions { private static readonly BindingFlags PrivateInstanceFlags = BindingFlags.Instance | BindingFlags.NonPublic; /// /// The raw contents of this MailMessage as a MemoryStream. /// /// The caller. /// A MemoryStream with the raw contents of this MailMessage. public static MemoryStream ToMimeMessage(this MailMessage @this) { if (@this == null) throw new ArgumentNullException(nameof(@this)); var result = new MemoryStream(); var mailWriter = MimeMessageConstants.MailWriterConstructor.Invoke(new object[] { result }); MimeMessageConstants.SendMethod.Invoke( @this, PrivateInstanceFlags, null, MimeMessageConstants.IsRunningInDotNetFourPointFive ? new[] { mailWriter, true, true } : new[] { mailWriter, true }, null); result = new MemoryStream(result.ToArray()); MimeMessageConstants.CloseMethod.Invoke( mailWriter, PrivateInstanceFlags, null, Array.Empty(), null); result.Position = 0; return result; } internal static class MimeMessageConstants { #pragma warning disable DE0005 // API is deprecated public static readonly Type MailWriter = typeof(SmtpClient).Assembly.GetType("System.Net.Mail.MailWriter"); #pragma warning restore DE0005 // API is deprecated public static readonly ConstructorInfo MailWriterConstructor = MailWriter.GetConstructor(PrivateInstanceFlags, null, new[] { typeof(Stream) }, null); public static readonly MethodInfo CloseMethod = MailWriter.GetMethod("Close", PrivateInstanceFlags); public static readonly MethodInfo SendMethod = typeof(MailMessage).GetMethod("Send", PrivateInstanceFlags); public static readonly bool IsRunningInDotNetFourPointFive = SendMethod.GetParameters().Length == 3; } } }