Added nullability attributes to the API

MailKit/AccessRight.cs

@@ -200,7 +200,7 @@ public bool Equals (AccessRight other)
 		/// <param name="obj">The <see cref="System.Object"/> to compare with the current <see cref="MailKit.AccessRight"/>.</param>
 		/// <returns><see langword="true" /> if the specified <see cref="System.Object"/> is equal to the current <see cref="MailKit.AccessRight"/>;
 		/// otherwise, <see langword="false" />.</returns>
-		public override bool Equals (object obj)
+		public override bool Equals (object? obj)
 		{
 			return obj is AccessRight right && right.Right == Right;
 		}

MailKit/Annotation.cs

@@ -50,10 +50,10 @@ public class Annotation
 		/// </exception>
 		public Annotation (AnnotationEntry entry)
 		{
-			if (entry == null)
+			if (entry is null)
 				throw new ArgumentNullException (nameof (entry));
 
-			Properties = new Dictionary<AnnotationAttribute, string> ();
+			Properties = new Dictionary<AnnotationAttribute, string?> ();
 			Entry = entry;
 		}
 
@@ -75,7 +75,7 @@ public AnnotationEntry Entry {
 		/// Gets the annotation properties.
 		/// </remarks>
 		/// <value>The annotation properties.</value>
-		public Dictionary<AnnotationAttribute, string> Properties {
+		public Dictionary<AnnotationAttribute, string?> Properties {
 			get; private set;
 		}
 	}

MailKit/AnnotationAttribute.cs

@@ -181,7 +181,7 @@ public string Specifier {
 		/// <param name="other">The <see cref="MailKit.AnnotationAttribute"/> to compare with the current <see cref="MailKit.AnnotationAttribute"/>.</param>
 		/// <returns><see langword="true" /> if the specified <see cref="MailKit.AnnotationAttribute"/> is equal to the current
 		/// <see cref="MailKit.AnnotationAttribute"/>; otherwise, <see langword="false" />.</returns>
-		public bool Equals (AnnotationAttribute other)
+		public bool Equals (AnnotationAttribute? other)
 		{
 			return other?.Specifier == Specifier;
 		}
@@ -225,7 +225,7 @@ public bool Equals (AnnotationAttribute other)
 		/// <param name="obj">The <see cref="System.Object"/> to compare with the current <see cref="MailKit.AnnotationAttribute"/>.</param>
 		/// <returns><see langword="true" /> if the specified <see cref="System.Object"/> is equal to the current
 		/// <see cref="MailKit.AnnotationAttribute"/>; otherwise, <see langword="false" />.</returns>
-		public override bool Equals (object obj)
+		public override bool Equals (object? obj)
 		{
 			return obj is AnnotationAttribute attribute && attribute.Specifier == Specifier;
 		}

MailKit/AnnotationEntry.cs

@@ -172,8 +172,12 @@ static void ValidatePartSpecifier (string partSpecifier)
 				throw new ArgumentException ("Invalid part-specifier.", nameof (partSpecifier));
 		}
 
-		AnnotationEntry ()
+		AnnotationEntry (string? partSpecifier, string entry, string path, AnnotationScope scope)
 		{
+			PartSpecifier = partSpecifier;
+			Entry = entry;
+			Path = path;
+			Scope = scope;
 		}
 
 		/// <summary>
@@ -199,6 +203,7 @@ public AnnotationEntry (string path, AnnotationScope scope = AnnotationScope.Bot
 			case AnnotationScope.Shared: Entry = path + ".shared"; break;
 			default: Entry = path; break;
 			}
+
 			PartSpecifier = null;
 			Path = path;
 			Scope = scope;
@@ -233,6 +238,7 @@ public AnnotationEntry (string partSpecifier, string path, AnnotationScope scope
 			case AnnotationScope.Shared: Entry = string.Format ("/{0}{1}.shared", partSpecifier, path); break;
 			default: Entry = string.Format ("/{0}{1}", partSpecifier, path); break;
 			}
+
 			PartSpecifier = partSpecifier;
 			Path = path;
 			Scope = scope;
@@ -267,6 +273,7 @@ public AnnotationEntry (BodyPart part, string path, AnnotationScope scope = Anno
 			case AnnotationScope.Shared: Entry = string.Format ("/{0}{1}.shared", part.PartSpecifier, path); break;
 			default: Entry = string.Format ("/{0}{1}", part.PartSpecifier, path); break;
 			}
+
 			PartSpecifier = part.PartSpecifier;
 			Path = path;
 			Scope = scope;
@@ -290,7 +297,7 @@ public string Entry {
 		/// Gets the part-specifier component of the annotation entry.
 		/// </remarks>
 		/// <value>The part-specifier.</value>
-		public string PartSpecifier {
+		public string? PartSpecifier {
 			get; private set;
 		}
 
@@ -327,7 +334,7 @@ public AnnotationScope Scope {
 		/// <param name="other">The <see cref="MailKit.AnnotationEntry"/> to compare with the current <see cref="MailKit.AnnotationEntry"/>.</param>
 		/// <returns><see langword="true" /> if the specified <see cref="MailKit.AnnotationEntry"/> is equal to the current
 		/// <see cref="MailKit.AnnotationEntry"/>; otherwise, <see langword="false" />.</returns>
-		public bool Equals (AnnotationEntry other)
+		public bool Equals (AnnotationEntry? other)
 		{
 			return other?.Entry == Entry;
 		}
@@ -371,7 +378,7 @@ public bool Equals (AnnotationEntry other)
 		/// <param name="obj">The <see cref="System.Object"/> to compare with the current <see cref="MailKit.AnnotationEntry"/>.</param>
 		/// <returns><see langword="true" /> if the specified <see cref="System.Object"/> is equal to the current
 		/// <see cref="MailKit.AnnotationEntry"/>; otherwise, <see langword="false" />.</returns>
-		public override bool Equals (object obj)
+		public override bool Equals (object? obj)
 		{
 			return obj is AnnotationEntry entry && entry.Entry == Entry;
 		}
@@ -427,7 +434,7 @@ public static AnnotationEntry Parse (string entry)
 
 			var scope = AnnotationScope.Both;
 			int startIndex = 0, endIndex;
-			string partSpecifier = null;
+			string? partSpecifier = null;
 			var component = 0;
 			var pc = entry[0];
 			string path;
@@ -497,12 +504,7 @@ public static AnnotationEntry Parse (string entry)
 
 			path = entry.Substring (startIndex, endIndex - startIndex);
 
-			return new AnnotationEntry {
-				PartSpecifier = partSpecifier,
-				Entry = entry,
-				Path = path,
-				Scope = scope
-			};
+			return new AnnotationEntry (partSpecifier, entry, path, scope);
 		}
 
 		internal static AnnotationEntry Create (string entry)

MailKit/AnnotationsChangedEventArgs.cs

@@ -38,17 +38,6 @@ namespace MailKit {
 	/// </remarks>
 	public class AnnotationsChangedEventArgs : MessageEventArgs
 	{
-		/// <summary>
-		/// Initializes a new instance of the <see cref="MailKit.AnnotationsChangedEventArgs"/> class.
-		/// </summary>
-		/// <remarks>
-		/// Creates a new <see cref="AnnotationsChangedEventArgs"/>.
-		/// </remarks>
-		/// <param name="index">The message index.</param>
-		internal AnnotationsChangedEventArgs (int index) : base (index)
-		{
-		}
-
 		/// <summary>
 		/// Initializes a new instance of the <see cref="T:MailKit.AnnotationsChangedEventArgs"/> class.
 		/// </summary>

MailKit/AppendRequest.cs

@@ -165,7 +165,7 @@ public MessageFlags Flags {
 		/// Gets or sets the keywords that should be set on the message.
 		/// </remarks>
 		/// <value>The keywords.</value>
-		public ISet<string> Keywords {
+		public ISet<string>? Keywords {
 			get; set;
 		}
 
@@ -192,7 +192,7 @@ public DateTimeOffset? InternalDate {
 		/// </note>
 		/// </remarks>
 		/// <value>The list of annotations.</value>
-		public IList<Annotation> Annotations {
+		public IList<Annotation>? Annotations {
 			get; set;
 		}
 
@@ -203,7 +203,7 @@ public IList<Annotation> Annotations {
 		/// Gets or sets the transfer progress reporting mechanism.
 		/// </remarks>
 		/// <value>The transfer progress mechanism.</value>
-		public ITransferProgress TransferProgress {
+		public ITransferProgress? TransferProgress {
 			get; set;
 		}
 	}