Check .NET Framework version on startup

shadowsocks-csharp/Data/cn.txt

@@ -130,6 +130,7 @@ System Proxy On: =系统代理已启用：
 Running: Port {0}=正在运行：端口 {0}
 Unexpected error, shadowsocks will exit. Please report to=非预期错误，Shadowsocks将退出。请提交此错误到
 Unsupported operating system, use Windows Vista at least.=不支持的操作系统版本，最低需求为Windows Vista。
+Unsupported .NET Framework, please update to 4.6.2 or later.=当前 .NET Framework 版本过低，请升级至4.6.2或更新版本。
 Proxy request failed=代理请求失败
 Proxy handshake failed=代理握手失败
 Register hotkey failed=注册热键失败

shadowsocks-csharp/Data/zh_tw.txt

@@ -130,6 +130,7 @@ System Proxy On: =系統代理已啟用：
 Running: Port {0}=正在運行：連接埠號碼 {0}
 Unexpected error, shadowsocks will exit. Please report to=非預期錯誤，Shadowsocks將退出。請提交此錯誤到
 Unsupported operating system, use Windows Vista at least.=不支持的作業系統版本，最低需求為Windows Vista。
+Unsupported .NET Framework, please update to 4.6.2 or later.=當前 .NET Framework 版本過低，最低需求為4.6.2。
 Proxy request failed=代理請求失敗
 Proxy handshake failed=代理握手失敗
 Register hotkey failed=註冊捷徑鍵失敗

shadowsocks-csharp/Program.cs

@@ -31,6 +31,14 @@ namespace Shadowsocks
                 return;
             }
 
+            // Check .NET Framework version
+            if (!Utils.IsSupportedRuntimeVersion())
+            {
+                MessageBox.Show(I18N.GetString("Unsupported .NET Framework, please update to 4.6.2 or later."),
+                "Shadowsocks Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
+                return;
+            }
+
             Utils.ReleaseMemory(true);
             using (Mutex mutex = new Mutex(false, $"Global\\Shadowsocks_{Application.StartupPath.GetHashCode()}"))
             {

shadowsocks-csharp/Util/Util.cs

@@ -208,7 +208,7 @@ namespace Shadowsocks.Util
             return new BandwidthScaleInfo(f, unit, scale);
         }
 
-        public static RegistryKey OpenRegKey( string name, bool writable, RegistryHive hive = RegistryHive.CurrentUser )
+        public static RegistryKey OpenRegKey(string name, bool writable, RegistryHive hive = RegistryHive.CurrentUser)
         {
             // we are building x86 binary for both x86 and x64, which will
             // cause problem when opening registry key
@@ -233,7 +233,8 @@ namespace Shadowsocks.Util
             }
         }
 
-        public static bool IsWinVistaOrHigher() {
+        public static bool IsWinVistaOrHigher()
+        {
             return Environment.OSVersion.Version.Major > 5;
         }
 
@@ -241,5 +242,35 @@ namespace Shadowsocks.Util
         [return: MarshalAs(UnmanagedType.Bool)]
         private static extern bool SetProcessWorkingSetSize(IntPtr process,
             UIntPtr minimumWorkingSetSize, UIntPtr maximumWorkingSetSize);
+
+
+        // See: https://msdn.microsoft.com/en-us/library/hh925568(v=vs.110).aspx
+        public static bool IsSupportedRuntimeVersion()
+        {
+            /*
+             * +-----------------------------------------------------------------+----------------------------+
+             * | Version                                                         | Value of the Release DWORD |
+             * +-----------------------------------------------------------------+----------------------------+
+             * | .NET Framework 4.6.2 installed on Windows 10 Anniversary Update | 394802                     |
+             * | .NET Framework 4.6.2 installed on all other Windows OS versions | 394806                     |
+             * +-----------------------------------------------------------------+----------------------------+
+             */
+            const int minSupportedRelease = 394802;
+
+            const string subkey = @"SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full\";
+            using (var ndpKey = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry32).OpenSubKey(subkey))
+            {
+                if (ndpKey?.GetValue("Release") != null)
+                {
+                    var releaseKey = (int)ndpKey.GetValue("Release");
+
+                    if (releaseKey >= minSupportedRelease)
+                    {
+                        return true;
+                    }
+                }
+            }
+            return false;
+        }
     }
 }