Silently quit when K290 is not connected.

KeyboardNotFoundException.cs

@@ -0,0 +1,12 @@
+namespace GrzegorzKozub.LogitechK290FnKeySwap
+{
+    using System;
+
+    internal class KeyboardNotFoundException : Exception
+    {
+        public KeyboardNotFoundException(string message)
+            : base(message)
+        {
+        }
+    }
+}

KeyboardService.cs

@@ -32,7 +32,7 @@ private static void SetFnKeyMode(FnKeyMode mode)
 
                 if (keyboard == null)
                 {
-                    throw new ApplicationException("Could not find Logitech K290 device. It's not connected or libusb-win32 is not installed.");
+                    throw new KeyboardNotFoundException("Could not find Logitech K290 device. It's not connected or libusb-win32 is not installed.");
                 }
 
                 var setupPacket = new UsbSetupPacket(0x40, 2, 0x001a, (short)mode, 0);
@@ -53,7 +53,11 @@ private static void SetFnKeyMode(FnKeyMode mode)
             }
             finally
             {
-                keyboard.Close();
+                if (keyboard != null)
+                {
+                    keyboard.Close();
+                }
+
                 UsbDevice.Exit();
             }
         }

LogitechK290FnKeySwap.csproj

@@ -47,6 +47,7 @@
     <Reference Include="Microsoft.CSharp" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="KeyboardNotFoundException.cs" />
     <Compile Include="KeyboardService.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />

Program.cs

@@ -23,6 +23,10 @@ internal static void Main(string[] arguments)
                     KeyboardService.SwapFnKey();
                 }
             }
+            catch (KeyboardNotFoundException)
+            {
+                Environment.Exit(1);
+            }
             catch (Exception exception)
             {
                 MessageBox.Show(exception.Message, "Logitech K290 Fn Key Swap");