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‎Flow.Launcher/Helper/SingleInstance.cs

Lines changed: 113 additions & 112 deletions
Original file line numberDiff line numberDiff line change
@@ -6,137 +6,138 @@
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// http://blogs.microsoft.co.il/arik/2010/05/28/wpf-single-instance-application/
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// modified to allow single instace restart
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namespace Flow.Launcher.Helper;
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public interface ISingleInstanceApp
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{
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void OnSecondAppStarted();
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}
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/// <summary>
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/// This class checks to make sure that only one instance of
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/// this application is running at a time.
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/// </summary>
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/// <remarks>
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/// Note: this class should be used with some caution, because it does no
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/// security checking. For example, if one instance of an app that uses this class
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/// is running as Administrator, any other instance, even if it is not
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/// running as Administrator, can activate it with command line arguments.
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/// For most apps, this will not be much of an issue.
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/// </remarks>
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public static class SingleInstance<TApplication> where TApplication: Application, ISingleInstanceApp
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namespace Flow.Launcher.Helper
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{
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#region Private Fields
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/// <summary>
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/// String delimiter used in channel names.
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/// </summary>
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private const string Delimiter = ":";
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/// <summary>
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/// Suffix to the channel name.
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/// </summary>
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private const string ChannelNameSuffix = "SingeInstanceIPCChannel";
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private const string InstanceMutexName = "Flow.Launcher_Unique_Application_Mutex";
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/// <summary>
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/// Application mutex.
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/// </summary>
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internal static Mutex SingleInstanceMutex { get; set; }
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#endregion
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#region Public Methods
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public interface ISingleInstanceApp
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{
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void OnSecondAppStarted();
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}
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/// <summary>
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/// Checks if the instance of the application attempting to start is the first instance.
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/// If not, activates the first instance.
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/// This class checks to make sure that only one instance of
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/// this application is running at a time.
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/// </summary>
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/// <returns>True if this is the first instance of the application.</returns>
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public static bool InitializeAsFirstInstance()
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/// <remarks>
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/// Note: this class should be used with some caution, because it does no
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/// security checking. For example, if one instance of an app that uses this class
23+
/// is running as Administrator, any other instance, even if it is not
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/// running as Administrator, can activate it with command line arguments.
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/// For most apps, this will not be much of an issue.
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/// </remarks>
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public static class SingleInstance<TApplication> where TApplication : Application, ISingleInstanceApp
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{
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// Build unique application Id and the IPC channel name.
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string applicationIdentifier = InstanceMutexName + Environment.UserName;
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string channelName = string.Concat(applicationIdentifier, Delimiter, ChannelNameSuffix);
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// Create mutex based on unique application Id to check if this is the first instance of the application.
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SingleInstanceMutex = new Mutex(true, applicationIdentifier, out var firstInstance);
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if (firstInstance)
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#region Private Fields
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/// <summary>
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/// String delimiter used in channel names.
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/// </summary>
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private const string Delimiter = ":";
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/// <summary>
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/// Suffix to the channel name.
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/// </summary>
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private const string ChannelNameSuffix = "SingeInstanceIPCChannel";
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private const string InstanceMutexName = "Flow.Launcher_Unique_Application_Mutex";
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/// <summary>
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/// Application mutex.
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/// </summary>
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internal static Mutex SingleInstanceMutex { get; set; }
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#endregion
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#region Public Methods
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/// <summary>
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/// Checks if the instance of the application attempting to start is the first instance.
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/// If not, activates the first instance.
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/// </summary>
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/// <returns>True if this is the first instance of the application.</returns>
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public static bool InitializeAsFirstInstance()
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{
67-
_ = CreateRemoteServiceAsync(channelName);
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return true;
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// Build unique application Id and the IPC channel name.
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string applicationIdentifier = InstanceMutexName + Environment.UserName;
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string channelName = string.Concat(applicationIdentifier, Delimiter, ChannelNameSuffix);
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// Create mutex based on unique application Id to check if this is the first instance of the application.
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SingleInstanceMutex = new Mutex(true, applicationIdentifier, out var firstInstance);
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if (firstInstance)
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{
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_ = CreateRemoteServiceAsync(channelName);
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return true;
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}
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else
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{
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_ = SignalFirstInstanceAsync(channelName);
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return false;
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}
6975
}
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else
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/// <summary>
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/// Cleans up single-instance code, clearing shared resources, mutexes, etc.
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/// </summary>
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public static void Cleanup()
7181
{
72-
_ = SignalFirstInstanceAsync(channelName);
73-
return false;
82+
SingleInstanceMutex?.ReleaseMutex();
7483
}
75-
}
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77-
/// <summary>
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/// Cleans up single-instance code, clearing shared resources, mutexes, etc.
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/// </summary>
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public static void Cleanup()
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{
82-
SingleInstanceMutex?.ReleaseMutex();
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}
85+
#endregion
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85-
#endregion
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#region Private Methods
8688

87-
#region Private Methods
88-
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/// <summary>
90-
/// Creates a remote server pipe for communication.
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/// Once receives signal from client, will activate first instance.
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/// </summary>
93-
/// <param name="channelName">Application's IPC channel name.</param>
94-
private static async Task CreateRemoteServiceAsync(string channelName)
95-
{
96-
using NamedPipeServerStream pipeServer = new NamedPipeServerStream(channelName, PipeDirection.In);
97-
while (true)
89+
/// <summary>
90+
/// Creates a remote server pipe for communication.
91+
/// Once receives signal from client, will activate first instance.
92+
/// </summary>
93+
/// <param name="channelName">Application's IPC channel name.</param>
94+
private static async Task CreateRemoteServiceAsync(string channelName)
9895
{
99-
// Wait for connection to the pipe
100-
await pipeServer.WaitForConnectionAsync();
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// Do an asynchronous call to ActivateFirstInstance function
103-
Application.Current?.Dispatcher.Invoke(ActivateFirstInstance);
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// Disconect client
106-
pipeServer.Disconnect();
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using NamedPipeServerStream pipeServer = new NamedPipeServerStream(channelName, PipeDirection.In);
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while (true)
98+
{
99+
// Wait for connection to the pipe
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await pipeServer.WaitForConnectionAsync();
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102+
// Do an asynchronous call to ActivateFirstInstance function
103+
Application.Current?.Dispatcher.Invoke(ActivateFirstInstance);
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105+
// Disconect client
106+
pipeServer.Disconnect();
107+
}
107108
}
108-
}
109109

110-
/// <summary>
111-
/// Creates a client pipe and sends a signal to server to launch first instance
112-
/// </summary>
113-
/// <param name="channelName">Application's IPC channel name.</param>
114-
/// <param name="args">
115-
/// Command line arguments for the second instance, passed to the first instance to take appropriate action.
116-
/// </param>
117-
private static async Task SignalFirstInstanceAsync(string channelName)
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{
119-
// Create a client pipe connected to server
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using NamedPipeClientStream pipeClient = new NamedPipeClientStream(".", channelName, PipeDirection.Out);
110+
/// <summary>
111+
/// Creates a client pipe and sends a signal to server to launch first instance
112+
/// </summary>
113+
/// <param name="channelName">Application's IPC channel name.</param>
114+
/// <param name="args">
115+
/// Command line arguments for the second instance, passed to the first instance to take appropriate action.
116+
/// </param>
117+
private static async Task SignalFirstInstanceAsync(string channelName)
118+
{
119+
// Create a client pipe connected to server
120+
using NamedPipeClientStream pipeClient = new NamedPipeClientStream(".", channelName, PipeDirection.Out);
121121

122-
// Connect to the available pipe
123-
await pipeClient.ConnectAsync(0);
124-
}
122+
// Connect to the available pipe
123+
await pipeClient.ConnectAsync(0);
124+
}
125125

126-
/// <summary>
127-
/// Activates the first instance of the application with arguments from a second instance.
128-
/// </summary>
129-
/// <param name="args">List of arguments to supply the first instance of the application.</param>
130-
private static void ActivateFirstInstance()
131-
{
132-
// Set main window state and process command line args
133-
if (Application.Current == null)
126+
/// <summary>
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/// Activates the first instance of the application with arguments from a second instance.
128+
/// </summary>
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/// <param name="args">List of arguments to supply the first instance of the application.</param>
130+
private static void ActivateFirstInstance()
134131
{
135-
return;
132+
// Set main window state and process command line args
133+
if (Application.Current == null)
134+
{
135+
return;
136+
}
137+
138+
((TApplication)Application.Current).OnSecondAppStarted();
136139
}
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138-
((TApplication)Application.Current).OnSecondAppStarted();
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#endregion
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}
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#endregion
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}

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