Added IMailFolder.CanOpen property

MailKit/IMailFolder.cs

@@ -225,6 +225,15 @@ public interface IMailFolder : IEnumerable<MimeMessage>
 		/// <value><see langword="true" /> if the folder is currently open; otherwise, <see langword="false" />.</value>
 		bool IsOpen { get; }
 
+		/// <summary>
+		/// Get whether or not the folder can be opened.
+		/// </summary>
+		/// <remarks>
+		/// Gets whether or not the folder can be opened.
+		/// </remarks>
+		/// <value><see langword="true" /> if the folder can be opened; otherwise, <see langword="false" />.</value>
+		bool CanOpen { get; }
+
 		/// <summary>
 		/// Get whether or not the folder exists.
 		/// </summary>

MailKit/MailFolder.cs

@@ -296,6 +296,17 @@ public abstract bool IsOpen {
 			get;
 		}
 
+		/// <summary>
+		/// Get whether or not the folder can be opened.
+		/// </summary>
+		/// <remarks>
+		/// Gets whether or not the folder can be opened.
+		/// </remarks>
+		/// <value><see langword="true" /> if the folder can be opened; otherwise, <see langword="false" />.</value>
+		public bool CanOpen {
+			get { return (Attributes & (FolderAttributes.NoSelect | FolderAttributes.NonExistent)) == 0; }
+		}
+
 		/// <summary>
 		/// Get a value indicating whether the folder exists.
 		/// </summary>

UnitTests/Net/Imap/ImapFolderTests.cs

@@ -1711,6 +1711,7 @@ public void TestCreateRenameDelete ()
 				sublevel1.Closed += (o, e) => { sub1Closed++; };
 				sublevel2.Closed += (o, e) => { sub2Closed++; };
 
+				Assert.That (sublevel1.CanOpen, Is.True, "SubLevel1 can be opened");
 				sublevel1.Open (FolderAccess.ReadWrite);
 				sublevel1.Rename (toplevel2, "SubLevel1");
 
@@ -1722,6 +1723,7 @@ public void TestCreateRenameDelete ()
 				Assert.That (top1Deleted, Is.EqualTo (1), "TopLevel1 should have received a Deleted event");
 				Assert.That (toplevel1.Exists, Is.False, "TopLevel1.Exists");
 
+				Assert.That (sublevel2.CanOpen, Is.True, "SubLevel2 can be opened");
 				sublevel2.Open (FolderAccess.ReadWrite);
 				toplevel2.Rename (personal, "TopLevel");
 
@@ -1786,6 +1788,7 @@ public async Task TestCreateRenameDeleteAsync ()
 				sublevel1.Closed += (o, e) => { sub1Closed++; };
 				sublevel2.Closed += (o, e) => { sub2Closed++; };
 
+				Assert.That (sublevel1.CanOpen, Is.True, "SubLevel1 can be opened");
 				await sublevel1.OpenAsync (FolderAccess.ReadWrite);
 				await sublevel1.RenameAsync (toplevel2, "SubLevel1");
 
@@ -1797,6 +1800,7 @@ public async Task TestCreateRenameDeleteAsync ()
 				Assert.That (top1Deleted, Is.EqualTo (1), "TopLevel1 should have received a Deleted event");
 				Assert.That (toplevel1.Exists, Is.False, "TopLevel1.Exists");
 
+				Assert.That (sublevel2.CanOpen, Is.True, "SubLevel2 can be opened");
 				await sublevel2.OpenAsync (FolderAccess.ReadWrite);
 				await toplevel2.RenameAsync (personal, "TopLevel");