Handle multiple filename parameters (e.g. as passed by browsers through a Content-Disposition header when uploading content) such as "filename=foo.txt; filename*=UTF-8''foo.txt" (recommended by RFC 6266 Appendix D: http://tools.ietf.org/html/rfc6266#appendix-D)

rfc6266.diff

diff --git a/MimeKit/ContentDisposition.cs b/MimeKit/ContentDisposition.cs
index 4d5355a..69d80f3 100644
--- a/MimeKit/ContentDisposition.cs
+++ b/MimeKit/ContentDisposition.cs
@@ -411,7 +411,7 @@ namespace MimeKit {
 				return true;
 
 			ParameterList parameters;
-			if (!ParameterList.TryParse (options, text, ref index, endIndex, throwOnError, out parameters))
+			if (!ParameterList.TryParse (options, text, ref index, endIndex, throwOnError, true, out parameters))
 				return false;
 
 			disposition.Parameters = parameters;
diff --git a/MimeKit/ContentType.cs b/MimeKit/ContentType.cs
index d15f1ed..2bda133 100644
--- a/MimeKit/ContentType.cs
+++ b/MimeKit/ContentType.cs
@@ -439,7 +439,7 @@ namespace MimeKit {
 				return true;
 
 			ParameterList parameters;
-			if (!ParameterList.TryParse (options, text, ref index, endIndex, throwOnError, out parameters))
+			if (!ParameterList.TryParse (options, text, ref index, endIndex, throwOnError, false, out parameters))
 				return false;
 
 			contentType.Parameters = parameters;
diff --git a/MimeKit/ParameterList.cs b/MimeKit/ParameterList.cs
index a8b4e54..173dd92 100644
--- a/MimeKit/ParameterList.cs
+++ b/MimeKit/ParameterList.cs
@@ -710,7 +710,7 @@ namespace MimeKit {
 			return new string (output, 0, outLength);
 		}
 
-		internal static bool TryParse (ParserOptions options, byte[] text, ref int index, int endIndex, bool throwOnError, out ParameterList paramList)
+		internal static bool TryParse (ParserOptions options, byte[] text, ref int index, int endIndex, bool throwOnError, bool respectRfc6266, out ParameterList paramList)
 		{
 			var rfc2184 = new Dictionary<string, List<NameValuePair>> (icase);
 			var @params = new List<NameValuePair> ();
@@ -807,6 +807,17 @@ namespace MimeKit {
 					value = string.Empty;
 				}
 
+				// RFC6266 (appendix D) recommends including a filename* parameter with an encoding
+				// containing the encoded filename following an ASCII filename parameter for legacy
+				// browser compatibilty; MimeKit handles the parsing of the *=<ENCODING> parameters,
+				// but does not allow multiples with the same name; in this case remove the preivous
+				// one, which should be the ASCII one; a more thorough fix for this would be to
+				// more accurately differentiate parameters with the same name but different encodings
+				// inside TryParseNameValuePair.
+				int filenameIndex = -1;
+				if (respectRfc6266 && param.Name == "filename" && (filenameIndex = paramList.IndexOf ("filename")) >= 0)
+					paramList.RemoveAt (filenameIndex);
+
 				paramList.Add (new Parameter (param.Name, value));
 			}