Andrew Beaton :: FAQ » .NET

Run only one instance of a program in C#

Andrew — Fri, 13 Nov 2009 22:45:22 +0000

This example shows you how to ensure that only one instance of an application is running.

// Ensure only one instance of this application is running.
bool alone = false;
Mutex m = new Mutex(true, "", out alone);
 
if (!alone)
{
    Console.WriteLine("Another instance is already running.");
    Console.ReadKey();
    return;
}
 
Console.WriteLine("Running...\n");
Console.ReadKey();
 
// Needed to ensure only one instance is running.
GC.KeepAlive(m);

Restart a Windows service using C#

Andrew — Fri, 13 Nov 2009 22:38:05 +0000

This example shows how to start, stop and restart a windows service programmatically in C#.

Start service

The following method tries to start a service specified by a service name. Then it waits until the service is running or a timeout occurs.

public static void StartService(string serviceName, int timeoutMilliseconds)
{
    ServiceController service = new ServiceController(serviceName);
    try
    {
        TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds);
 
        service.Start();
        service.WaitForStatus(ServiceControllerStatus.Running, timeout);
    }
    catch
    {
        // ...
    }
}

Stop service

The following method tries to stop the specified service and it waits until the service is stopped or a timeout occurs.

public static void StopService(string serviceName, int timeoutMilliseconds)
{
    ServiceController service = new ServiceController(serviceName);
    try
    {
        TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds);
 
        service.Stop();
        service.WaitForStatus(ServiceControllerStatus.Stopped, timeout);
    }
    catch
    {
        // ...
    }
}

Restart service

This method combinates both previous methods. It tries to stop the service (and waits until it’s stopped) then it begins to start the service (and waits until the service is running). The specified timeout is used for both operations together.

public static void RestartService(string serviceName, int timeoutMilliseconds)
{
    ServiceController service = new ServiceController(serviceName);
    try
    {
        int millisec1 = Environment.TickCount;
        TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds);
 
        service.Stop();
        service.WaitForStatus(ServiceControllerStatus.Stopped, timeout);
 
        // count the rest of the timeout
        int millisec2 = Environment.TickCount;
        timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds - (millisec2-millisec1));
 
        service.Start();
        service.WaitForStatus(ServiceControllerStatus.Running, timeout);
   }
   catch
   {
       // ...
   }
}

Read source of a web page in C#

Andrew — Fri, 13 Nov 2009 22:31:03 +0000

This example shows how to read the source of a web page in C#.

// used to build entire input
StringBuilder sb = new StringBuilder();
 
// used on each read operation
byte[] buf = new byte[8192];
 
// prepare the web page we will be asking for
WebRequest request  = WebRequest.Create("http://andrewbeaton.com");
 
// execute the request
WebResponse response = request.GetResponse();
 
// we will read data via the response stream
Stream resStream = response.GetResponseStream();
 
string tempString = null;
int count = 0;
 
do
{
    // fill the buffer with data
    count = resStream.Read(buf, 0, buf.Length);
 
    // make sure we read some data
    if (count != 0) 
    {
        // translate from bytes to ASCII text
        tempString = Encoding.ASCII.GetString(buf, 0, count);
 
        // continue building the string
       sb.Append(tempString);
    }
}
while (count &gt; 0);