├── .gitignore ├── README.md ├── SingleInstance_WPF.sln └── SingleInstance_WPF ├── App.xaml ├── App.xaml.cs ├── AssemblyInfo.cs ├── MainWindow.xaml ├── MainWindow.xaml.cs ├── SingleInstance.cs └── SingleInstance_WPF.csproj /.gitignore: -------------------------------------------------------------------------------- 1 | ## Ignore Visual Studio temporary files, build results, and 2 | ## files generated by popular Visual Studio add-ons. 3 | ## 4 | ## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore 5 | 6 | # User-specific files 7 | *.rsuser 8 | *.suo 9 | *.user 10 | *.userosscache 11 | *.sln.docstates 12 | 13 | # User-specific files (MonoDevelop/Xamarin Studio) 14 | *.userprefs 15 | 16 | # Mono auto generated files 17 | mono_crash.* 18 | 19 | # Build results 20 | [Dd]ebug/ 21 | [Dd]ebugPublic/ 22 | [Rr]elease/ 23 | [Rr]eleases/ 24 | x64/ 25 | x86/ 26 | [Aa][Rr][Mm]/ 27 | [Aa][Rr][Mm]64/ 28 | bld/ 29 | [Bb]in/ 30 | [Oo]bj/ 31 | [Ll]og/ 32 | [Ll]ogs/ 33 | 34 | # Visual Studio 2015/2017 cache/options directory 35 | .vs/ 36 | # Uncomment if you have tasks that create the project's static files in wwwroot 37 | #wwwroot/ 38 | 39 | # Visual Studio 2017 auto generated files 40 | Generated\ Files/ 41 | 42 | # MSTest test Results 43 | [Tt]est[Rr]esult*/ 44 | [Bb]uild[Ll]og.* 45 | 46 | # NUnit 47 | *.VisualState.xml 48 | TestResult.xml 49 | nunit-*.xml 50 | 51 | # Build Results of an ATL Project 52 | [Dd]ebugPS/ 53 | [Rr]eleasePS/ 54 | dlldata.c 55 | 56 | # Benchmark Results 57 | BenchmarkDotNet.Artifacts/ 58 | 59 | # .NET Core 60 | project.lock.json 61 | project.fragment.lock.json 62 | artifacts/ 63 | 64 | # StyleCop 65 | StyleCopReport.xml 66 | 67 | # Files built by Visual Studio 68 | *_i.c 69 | *_p.c 70 | *_h.h 71 | *.ilk 72 | *.meta 73 | *.obj 74 | *.iobj 75 | *.pch 76 | *.pdb 77 | *.ipdb 78 | *.pgc 79 | *.pgd 80 | *.rsp 81 | *.sbr 82 | *.tlb 83 | *.tli 84 | *.tlh 85 | *.tmp 86 | *.tmp_proj 87 | *_wpftmp.csproj 88 | *.log 89 | *.vspscc 90 | *.vssscc 91 | .builds 92 | *.pidb 93 | *.svclog 94 | *.scc 95 | 96 | # Chutzpah Test files 97 | _Chutzpah* 98 | 99 | # Visual C++ cache files 100 | ipch/ 101 | *.aps 102 | *.ncb 103 | *.opendb 104 | *.opensdf 105 | *.sdf 106 | *.cachefile 107 | *.VC.db 108 | *.VC.VC.opendb 109 | 110 | # Visual Studio profiler 111 | *.psess 112 | *.vsp 113 | *.vspx 114 | *.sap 115 | 116 | # Visual Studio Trace Files 117 | *.e2e 118 | 119 | # TFS 2012 Local Workspace 120 | $tf/ 121 | 122 | # Guidance Automation Toolkit 123 | *.gpState 124 | 125 | # ReSharper is a .NET coding add-in 126 | _ReSharper*/ 127 | *.[Rr]e[Ss]harper 128 | *.DotSettings.user 129 | 130 | # TeamCity is a build add-in 131 | _TeamCity* 132 | 133 | # DotCover is a Code Coverage Tool 134 | *.dotCover 135 | 136 | # AxoCover is a Code Coverage Tool 137 | .axoCover/* 138 | !.axoCover/settings.json 139 | 140 | # Visual Studio code coverage results 141 | *.coverage 142 | *.coveragexml 143 | 144 | # NCrunch 145 | _NCrunch_* 146 | .*crunch*.local.xml 147 | nCrunchTemp_* 148 | 149 | # MightyMoose 150 | *.mm.* 151 | AutoTest.Net/ 152 | 153 | # Web workbench (sass) 154 | .sass-cache/ 155 | 156 | # Installshield output folder 157 | [Ee]xpress/ 158 | 159 | # DocProject is a documentation generator add-in 160 | DocProject/buildhelp/ 161 | DocProject/Help/*.HxT 162 | DocProject/Help/*.HxC 163 | DocProject/Help/*.hhc 164 | DocProject/Help/*.hhk 165 | DocProject/Help/*.hhp 166 | DocProject/Help/Html2 167 | DocProject/Help/html 168 | 169 | # Click-Once directory 170 | publish/ 171 | 172 | # Publish Web Output 173 | *.[Pp]ublish.xml 174 | *.azurePubxml 175 | # Note: Comment the next line if you want to checkin your web deploy settings, 176 | # but database connection strings (with potential passwords) will be unencrypted 177 | *.pubxml 178 | *.publishproj 179 | 180 | # Microsoft Azure Web App publish settings. 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10 | private static System.Threading.Mutex _singleInstanceMutex; 11 | 12 | private void Application_Startup(object sender, StartupEventArgs e) 13 | { 14 | // Create SingleInstance Mutex 15 | _singleInstanceMutex = new System.Threading.Mutex(true, ApplicationSingleInstanceGuid); 16 | var isOnlyInstance = _singleInstanceMutex.WaitOne(TimeSpan.Zero, true); 17 | 18 | // TODO: Read from settings if you want your users to be able to opt-in to multiple instance or not 19 | var settings_AllowMultipleInstances = false; 20 | if (settings_AllowMultipleInstances || isOnlyInstance) 21 | { 22 | // Show main window 23 | StartupUri = new Uri("MainWindow.xaml", UriKind.Relative); 24 | 25 | // Release SingleInstance Mutex 26 | _singleInstanceMutex.ReleaseMutex(); 27 | } 28 | else 29 | { 30 | // Bring the already running application into the foreground 31 | SingleInstance.PostMessage((IntPtr)SingleInstance.HWND_BROADCAST, SingleInstance.WM_SHOWME, IntPtr.Zero, IntPtr.Zero); 32 | Shutdown(); 33 | } 34 | } 35 | ``` 36 | 37 | ## Bring to front already running application 38 | ```csharp 39 | private System.Windows.Interop.HwndSource _hwndSoure; 40 | 41 | protected override void OnSourceInitialized(EventArgs e) 42 | { 43 | base.OnSourceInitialized(e); 44 | 45 | _hwndSoure = System.Windows.Interop.HwndSource.FromHwnd(new System.Windows.Interop.WindowInteropHelper(this).Handle); 46 | _hwndSoure?.AddHook(HwndHook); 47 | } 48 | 49 | [DebuggerStepThrough] 50 | private IntPtr HwndHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) 51 | { 52 | // Single instance --> Show window 53 | if (msg == SingleInstance.WM_SHOWME) 54 | { 55 | BringWindowToFront(); 56 | handled = true; 57 | } 58 | 59 | return IntPtr.Zero; 60 | } 61 | 62 | private void BringWindowToFront() 63 | { 64 | if (WindowState == WindowState.Minimized) 65 | { 66 | WindowState = WindowState.Normal; 67 | } 68 | 69 | Activate(); 70 | } 71 | ``` 72 | 73 | ## Notes 74 | * Don't forget to use an unique identifier for every application 75 | * You can optionally add settings for the user to opt-in for single instance or multiple instance application 76 | * This sample uses .NET 5 but this also works with WPF app with framework 4.7.2 or 4.8 (and probably others, but those two are the ones I tested) 77 | -------------------------------------------------------------------------------- /SingleInstance_WPF.sln: -------------------------------------------------------------------------------- 1 |  2 | Microsoft Visual Studio Solution File, Format Version 12.00 3 | # Visual Studio Version 16 4 | VisualStudioVersion = 16.0.31019.194 5 | MinimumVisualStudioVersion = 10.0.40219.1 6 | Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SingleInstance_WPF", "SingleInstance_WPF\SingleInstance_WPF.csproj", "{FEFF5C7E-8819-4ADE-8C1A-98376E8BD9D3}" 7 | EndProject 8 | Global 9 | GlobalSection(SolutionConfigurationPlatforms) = preSolution 10 | Debug|Any CPU = Debug|Any CPU 11 | Release|Any CPU = Release|Any CPU 12 | EndGlobalSection 13 | GlobalSection(ProjectConfigurationPlatforms) = postSolution 14 | {FEFF5C7E-8819-4ADE-8C1A-98376E8BD9D3}.Debug|Any CPU.ActiveCfg = Debug|Any CPU 15 | {FEFF5C7E-8819-4ADE-8C1A-98376E8BD9D3}.Debug|Any CPU.Build.0 = Debug|Any CPU 16 | {FEFF5C7E-8819-4ADE-8C1A-98376E8BD9D3}.Release|Any CPU.ActiveCfg = Release|Any CPU 17 | {FEFF5C7E-8819-4ADE-8C1A-98376E8BD9D3}.Release|Any CPU.Build.0 = Release|Any CPU 18 | EndGlobalSection 19 | GlobalSection(SolutionProperties) = preSolution 20 | HideSolutionNode = FALSE 21 | EndGlobalSection 22 | GlobalSection(ExtensibilityGlobals) = postSolution 23 | SolutionGuid = {BE7D1F59-2FC2-4FB3-B11C-696AB7CB3B25} 24 | EndGlobalSection 25 | EndGlobal 26 | -------------------------------------------------------------------------------- /SingleInstance_WPF/App.xaml: -------------------------------------------------------------------------------- 1 |  6 | 7 | 8 | 9 | 10 | -------------------------------------------------------------------------------- /SingleInstance_WPF/App.xaml.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Collections.Generic; 3 | using System.Configuration; 4 | using System.Data; 5 | using System.Linq; 6 | using System.Threading.Tasks; 7 | using System.Windows; 8 | 9 | namespace SingleInstance_WPF 10 | { 11 | public partial class App : Application 12 | { 13 | /// 14 | /// This identifier must be unique for each application. 15 | /// 16 | private const string ApplicationSingleInstanceGuid = "{910e8c27-ab31-4043-9c5d-1382707e6c93}"; 17 | private static System.Threading.Mutex _singleInstanceMutex; 18 | 19 | private void Application_Startup(object sender, StartupEventArgs e) 20 | { 21 | // Create SingleInstance Mutex 22 | _singleInstanceMutex = new System.Threading.Mutex(true, ApplicationSingleInstanceGuid); 23 | var isOnlyInstance = _singleInstanceMutex.WaitOne(TimeSpan.Zero, true); 24 | 25 | // TODO: Read from settings if you want your users to be able to opt-in to multiple instance or not 26 | var settings_AllowMultipleInstances = false; 27 | if (settings_AllowMultipleInstances || isOnlyInstance) 28 | { 29 | // Show main window 30 | StartupUri = new Uri("MainWindow.xaml", UriKind.Relative); 31 | 32 | // Release SingleInstance Mutex 33 | _singleInstanceMutex.ReleaseMutex(); 34 | } 35 | else 36 | { 37 | // Bring the already running application into the foreground 38 | SingleInstance.PostMessage((IntPtr)SingleInstance.HWND_BROADCAST, SingleInstance.WM_SHOWME, IntPtr.Zero, IntPtr.Zero); 39 | Shutdown(); 40 | } 41 | } 42 | } 43 | } 44 | -------------------------------------------------------------------------------- /SingleInstance_WPF/AssemblyInfo.cs: -------------------------------------------------------------------------------- 1 | using System.Windows; 2 | 3 | [assembly:ThemeInfo( 4 | ResourceDictionaryLocation.None, //where theme specific resource dictionaries are located 5 | //(used if a resource is not found in the page, 6 | // or application resource dictionaries) 7 | ResourceDictionaryLocation.SourceAssembly //where the generic resource dictionary is located 8 | //(used if a resource is not found in the page, 9 | // app, or any theme specific resource dictionaries) 10 | )] 11 | -------------------------------------------------------------------------------- /SingleInstance_WPF/MainWindow.xaml: -------------------------------------------------------------------------------- 1 |  9 | 10 | 11 | 12 | 13 | -------------------------------------------------------------------------------- /SingleInstance_WPF/MainWindow.xaml.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Collections.Generic; 3 | using System.Diagnostics; 4 | using System.Linq; 5 | using System.Text; 6 | using System.Threading.Tasks; 7 | using System.Windows; 8 | using System.Windows.Controls; 9 | using System.Windows.Data; 10 | using System.Windows.Documents; 11 | using System.Windows.Input; 12 | using System.Windows.Media; 13 | using System.Windows.Media.Imaging; 14 | using System.Windows.Navigation; 15 | using System.Windows.Shapes; 16 | 17 | namespace SingleInstance_WPF 18 | { 19 | /// 20 | /// Interaction logic for MainWindow.xaml 21 | /// 22 | public partial class MainWindow : Window 23 | { 24 | public MainWindow() 25 | { 26 | InitializeComponent(); 27 | } 28 | 29 | #region Handle WndProc messages (Single Instance) 30 | private System.Windows.Interop.HwndSource _hwndSoure; 31 | 32 | protected override void OnSourceInitialized(EventArgs e) 33 | { 34 | base.OnSourceInitialized(e); 35 | 36 | _hwndSoure = System.Windows.Interop.HwndSource.FromHwnd(new System.Windows.Interop.WindowInteropHelper(this).Handle); 37 | _hwndSoure?.AddHook(HwndHook); 38 | } 39 | 40 | [DebuggerStepThrough] 41 | private IntPtr HwndHook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) 42 | { 43 | // Single instance --> Show window 44 | if (msg == SingleInstance.WM_SHOWME) 45 | { 46 | BringWindowToFront(); 47 | handled = true; 48 | } 49 | 50 | return IntPtr.Zero; 51 | } 52 | 53 | private void BringWindowToFront() 54 | { 55 | if (WindowState == WindowState.Minimized) 56 | { 57 | WindowState = WindowState.Normal; 58 | } 59 | 60 | Activate(); 61 | } 62 | #endregion 63 | } 64 | } 65 | -------------------------------------------------------------------------------- /SingleInstance_WPF/SingleInstance.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Runtime.InteropServices; 3 | 4 | namespace SingleInstance_WPF 5 | { 6 | internal static class SingleInstance 7 | { 8 | public const int HWND_BROADCAST = 0xffff; 9 | public static readonly int WM_SHOWME = RegisterWindowMessage("WM_SHOWME"); 10 | [DllImport("user32")] 11 | public static extern bool PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam); 12 | [DllImport("user32")] 13 | public static extern int RegisterWindowMessage(string message); 14 | } 15 | } 16 | -------------------------------------------------------------------------------- /SingleInstance_WPF/SingleInstance_WPF.csproj: -------------------------------------------------------------------------------- 1 |  2 | 3 | 4 | WinExe 5 | net5.0-windows 6 | true 7 | 8 | 9 | 10 | --------------------------------------------------------------------------------