Fix possible nullable path (breaking change from previouse checking)

Fix disconnect logic to avoid ObjectDisposed exception

Renci.SshClient/Renci.SshNet.Tests/SftpClientTests/ListDirectoryTest.cs

@@ -98,6 +98,27 @@ namespace Renci.SshNet.Tests.SftpClientTests
             }
         }
 
+        [TestMethod]
+        [TestCategory("Sftp")]
+        public void Test_Sftp_ListDirectory_Empty()
+        {
+            using (var sftp = new SftpClient(Resources.HOST, Resources.USERNAME, Resources.PASSWORD))
+            {
+                sftp.Connect();
+
+                var files = sftp.ListDirectory(string.Empty);
+
+                Assert.IsTrue(files.Count() > 0);
+
+                foreach (var file in files)
+                {
+                    Debug.WriteLine(file.FullName);
+                }
+
+                sftp.Disconnect();
+            }
+        }
+
         [TestMethod]
         [TestCategory("Sftp")]
         public void Test_Sftp_ListDirectory_HugeDirectory()

Renci.SshClient/Renci.SshNet/BaseClient.cs

@@ -111,6 +111,9 @@ namespace Renci.SshNet
         /// </summary>
         public void Disconnect()
         {
+            if (!this.IsConnected)
+                return;
+
             this.OnDisconnecting();
 
             this.Dispose();

Renci.SshClient/Renci.SshNet/Session.cs

@@ -141,12 +141,14 @@ namespace Renci.SshNet
             }
         }
 
+        private bool _isDisconnectMessageSent;
+
         private uint _nextChannelNumber;
         /// <summary>
         /// Gets the next channel number.
         /// </summary>
         /// <value>The next channel number.</value>
-        public uint NextChannelNumber
+        internal uint NextChannelNumber
         {
             get
             {
@@ -805,13 +807,15 @@ namespace Renci.SshNet
 
         private void SendDisconnect(DisconnectReason reasonCode, string message)
         {
+            //  If disconnect message was sent already dont send it again
+            if (this._isDisconnectMessageSent)
+                return;
+
             var disconnectMessage = new DisconnectMessage(reasonCode, message);
 
             this.SendMessage(disconnectMessage);
 
-            //  Handle disconnect message as if it was sent by the server
-            //  TODO:   Review this code and may be handle it separately
-            this.HandleMessage(disconnectMessage);
+            this._isDisconnectMessageSent = true;
         }
 
         /// <summary>
@@ -1583,12 +1587,11 @@ namespace Renci.SshNet
             {
                 this.ErrorOccured(this, new ErrorEventArgs(exp));
             }
-            var disconnectReason = DisconnectReason.ByApplication;
 
-            if (connectionException != null)
-                disconnectReason = connectionException.DisconnectReason;
-
-            this.SendDisconnect(disconnectReason, exp.ToString());
+            if (connectionException != null && connectionException.DisconnectReason != DisconnectReason.ConnectionLost)
+            {
+                this.SendDisconnect(connectionException.DisconnectReason, exp.ToString());
+            }
         }
 
         #region IDisposable Members
@@ -1622,26 +1625,11 @@ namespace Renci.SshNet
 
                     if (this._socket != null)
                     {
-                        lock (this._socket)
-                        {
-                            //  TODO:   Not sure if it makes sense to do locking in Dispose but just want to check it for now as possible reason, need to remove later.
+                        //  If socket still open try to send disconnect message to the server
+                        this.SendDisconnect(DisconnectReason.ByApplication, "Connection terminated by the client.");
 
-                            if (this._socket != null)
-                            {
-                                try
-                                {
-                                    //  If socket still open try to send disconnect message to the server
-                                    this.SendMessage(new DisconnectMessage(DisconnectReason.ByApplication, "Connection terminated by the client."));
-                                }
-                                catch (Exception)
-                                {
-                                    //  Do nothing as this is not required to send disconnect message correctly.
-                                }
-
-                                this._socket.Dispose();
-                                this._socket = null;
-                            }
-                        }
+                        this._socket.Dispose();
+                        this._socket = null;
                     }
 
                     if (this._messageListener != null)

Renci.SshClient/Renci.SshNet/Sftp/ListDirectoryCommand.cs

@@ -47,7 +47,7 @@ namespace Renci.SshNet.Sftp
             base.OnName(files);
 
             var seperator = "/";
-            if (this._path[this._path.Length - 1] == '/')
+            if (!string.IsNullOrEmpty(this._path) && this._path[this._path.Length - 1] == '/')
                 seperator = string.Empty;
 
             var sftpFiles = from f in files

Renci.SshClient/Renci.SshNet/Sftp/SftpSession.cs

@@ -113,7 +113,7 @@ namespace Renci.SshNet.Sftp
         {
             var fullPath = path;
 
-            if (path[0] != '/' && this.WorkingDirectory != null)
+            if (!string.IsNullOrEmpty(path) && path[0] != '/' && this.WorkingDirectory != null)
             {
                 if (this.WorkingDirectory[this.WorkingDirectory.Length - 1] == '/')
                 {