diff --git a/SerializableMailMessage/SerializableAttachment.cs b/SerializableMailMessage/SerializableAttachment.cs
index d8ac2bb..72608d5 100644
--- a/SerializableMailMessage/SerializableAttachment.cs
+++ b/SerializableMailMessage/SerializableAttachment.cs
@@ -11,23 +11,13 @@ public static implicit operator Attachment(SerializableAttachment attachment) {
 			if (attachment == null)
 				return null;
 			Attachment a = new Attachment(attachment.ContentStream, attachment.Name);
-
-			a.ContentStream.Position = 0;
-			a.ContentDisposition.CreationDate = attachment.ContentDisposition.CreationDate;
-			a.ContentDisposition.DispositionType = attachment.ContentDisposition.DispositionType;
-			a.ContentDisposition.FileName = attachment.ContentDisposition.FileName;
-			a.ContentDisposition.Inline = attachment.ContentDisposition.Inline;
-			a.ContentDisposition.ModificationDate = attachment.ContentDisposition.ModificationDate;
-			a.ContentDisposition.ReadDate = attachment.ContentDisposition.ReadDate;
-			a.ContentDisposition.Size = attachment.ContentDisposition.Size;
-			foreach (string k in attachment.ContentDisposition.Parameters.Keys)
-				a.ContentDisposition.Parameters.Add(k, attachment.ContentDisposition.Parameters[k]);
-
+			a.ContentStream.Position = 0;            
 			a.NameEncoding = attachment.NameEncoding;
 			a.Name = attachment.Name;
 			a.ContentId = attachment.ContentId;
 			a.ContentType = attachment.ContentType;
 			a.TransferEncoding = attachment.TransferEncoding;
+			attachment.ContentDisposition.CopyTo(a.ContentDisposition);
 			return a;
 		}
 
diff --git a/SerializableMailMessage/SerializableContentDisposition.cs b/SerializableMailMessage/SerializableContentDisposition.cs
index d64678b..34d695c 100644
--- a/SerializableMailMessage/SerializableContentDisposition.cs
+++ b/SerializableMailMessage/SerializableContentDisposition.cs
@@ -9,16 +9,7 @@ public static implicit operator ContentDisposition(SerializableContentDispositio
 			if (disposition == null)
 				return null;
 			ContentDisposition d = new ContentDisposition();
-
-			d.CreationDate = disposition.CreationDate;
-			d.DispositionType = disposition.DispositionType;
-			d.FileName = disposition.FileName;
-			d.Inline = disposition.Inline;
-			d.ModificationDate = disposition.ModificationDate;
-			foreach (string k in disposition.Parameters.Keys)
-				d.Parameters.Add(k, disposition.Parameters[k]);
-			d.ReadDate = disposition.ReadDate;
-			d.Size = disposition.Size;
+			disposition.CopyTo(d);
 			return d;
 		}
 
@@ -41,6 +32,24 @@ private SerializableContentDisposition(ContentDisposition disposition) {
 			Size = disposition.Size;
 		}
 
+		public void CopyTo(ContentDisposition disposition) {
+			if (disposition == null)
+				return;
+
+			disposition.Inline = Inline;
+			disposition.DispositionType = DispositionType;
+			disposition.FileName = FileName;
+			disposition.CreationDate = CreationDate;
+			disposition.ModificationDate = ModificationDate;
+			disposition.ReadDate = ReadDate;
+			if (Size != -1L) 
+				disposition.Size = Size;
+
+			foreach (string k in Parameters.Keys)
+				if (disposition.Parameters.ContainsKey(k) == false)
+					disposition.Parameters.Add(k, Parameters[k]);
+		}
+
 		public DateTime CreationDate { get; set; }
 		public string DispositionType { get; set; }
 		public string FileName { get; set; }