diff --git a/shadowsocks-csharp/Encryption/MbedTLSEncryptor.cs b/shadowsocks-csharp/Encryption/MbedTLSEncryptor.cs
index 5d958a1a..033daf4c 100644
--- a/shadowsocks-csharp/Encryption/MbedTLSEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/MbedTLSEncryptor.cs
@@ -15,9 +15,6 @@ namespace Shadowsocks.Encryption
         private IntPtr _encryptCtx = IntPtr.Zero;
         private IntPtr _decryptCtx = IntPtr.Zero;
 
-        // instance based lock
-        private readonly object _Lock = new object();
-
         public MbedTLSEncryptor(string method, string password, bool onetimeauth, bool isudp)
             : base(method, password, onetimeauth, isudp)
         {
@@ -108,8 +105,12 @@ namespace Shadowsocks.Encryption
         }
 
         #region IDisposable
+
         private bool _disposed;
 
+        // instance based lock
+        private readonly object _lock = new object();
+
         public override void Dispose()
         {
             Dispose(true);
@@ -123,31 +124,32 @@ namespace Shadowsocks.Encryption
 
         protected virtual void Dispose(bool disposing)
         {
-            lock (_Lock)
+            lock (_lock)
             {
-                if (_disposed)
-                {
-                    return;
-                }
+                if (_disposed) return;
                 _disposed = true;
             }
 
             if (disposing)
             {
-                if (_encryptCtx != IntPtr.Zero)
-                {
-                    MbedTLS.cipher_free(_encryptCtx);
-                    Marshal.FreeHGlobal(_encryptCtx);
-                    _encryptCtx = IntPtr.Zero;
-                }
-                if (_decryptCtx != IntPtr.Zero)
-                {
-                    MbedTLS.cipher_free(_decryptCtx);
-                    Marshal.FreeHGlobal(_decryptCtx);
-                    _decryptCtx = IntPtr.Zero;
-                }
+                // free managed objects
+            }
+
+            // free unmanaged objects
+            if (_encryptCtx != IntPtr.Zero)
+            {
+                MbedTLS.cipher_free(_encryptCtx);
+                Marshal.FreeHGlobal(_encryptCtx);
+                _encryptCtx = IntPtr.Zero;
+            }
+            if (_decryptCtx != IntPtr.Zero)
+            {
+                MbedTLS.cipher_free(_decryptCtx);
+                Marshal.FreeHGlobal(_decryptCtx);
+                _decryptCtx = IntPtr.Zero;
             }
         }
+
         #endregion
     }
 }
diff --git a/shadowsocks-csharp/Util/ProcessManagement/Job.cs b/shadowsocks-csharp/Util/ProcessManagement/Job.cs
index 098a3470..02646064 100644
--- a/shadowsocks-csharp/Util/ProcessManagement/Job.cs
+++ b/shadowsocks-csharp/Util/ProcessManagement/Job.cs
@@ -24,7 +24,7 @@ namespace Shadowsocks.Util.ProcessManagement
         [return: MarshalAs(UnmanagedType.Bool)]
         private static extern bool CloseHandle(IntPtr hObject);
 
-        private IntPtr handle;
+        private IntPtr handle = IntPtr.Zero;
         private bool disposed;
 
         public Job()
@@ -70,19 +70,26 @@ namespace Shadowsocks.Util.ProcessManagement
 
         private void Dispose(bool disposing)
         {
-            if (disposed)
-                return;
+            if (disposed) return;
+            disposed = true;
 
             if (disposing) { }
 
             Close();
-            disposed = true;
         }
 
-        public void Close()
+        private void Close()
+        {
+            if (handle != IntPtr.Zero)
+            {
+                CloseHandle(handle);
+                handle = IntPtr.Zero;
+            }
+        }
+
+        ~Job()
         {
-            CloseHandle(handle);
-            handle = IntPtr.Zero;
+            Dispose(false);
         }
 
         public bool AddProcess(IntPtr processHandle)
diff --git a/shadowsocks-csharp/View/MenuViewController.cs b/shadowsocks-csharp/View/MenuViewController.cs
index ce63734d..41cd73db 100644
--- a/shadowsocks-csharp/View/MenuViewController.cs
+++ b/shadowsocks-csharp/View/MenuViewController.cs
@@ -501,12 +501,14 @@ namespace Shadowsocks.View
 
         void logForm_FormClosed(object sender, FormClosedEventArgs e)
         {
+            logForm.Dispose();
             logForm = null;
             Utils.ReleaseMemory(true);
         }
 
         void configForm_FormClosed(object sender, FormClosedEventArgs e)
         {
+            configForm.Dispose();
             configForm = null;
             Utils.ReleaseMemory(true);
             if (_isFirstRun)
@@ -519,12 +521,14 @@ namespace Shadowsocks.View
 
         void proxyForm_FormClosed(object sender, FormClosedEventArgs e)
         {
+            proxyForm.Dispose();
             proxyForm = null;
             Utils.ReleaseMemory(true);
         }
 
         void hotkeySettingsForm_FormClosed(object sender, FormClosedEventArgs e)
         {
+            hotkeySettingsForm.Dispose();
             hotkeySettingsForm = null;
             Utils.ReleaseMemory(true);
         }