Find, fix and prevent memory leaks in C # .NET: 8 best practices

For future students of the "C # Developer" course and all those interested, we prepared a translation of useful material.



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Anyone who has worked on a large corporate project knows that memory leaks are like rats in a big hotel. You may not notice them when there are few of them, but you should always be on the lookout in case they breed, sneak into the kitchen and dirty everything around.

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{
    private int _wiFiChangesCounter = 0;
 
    public MyClass(WiFiManager wiFiManager)
    {
        wiFiManager.WiFiSignalChanged += (s, e) => _wiFiChangesCounter++;
    }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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public class MyClass
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    public MyClass(WiFiManager wiFiManager)
    {
        Timer timer = new Timer(HandleTick);
        timer.Change(TimeSpan.FromSeconds(5), TimeSpan.FromSeconds(5));
    }
 
    private void HandleTick(object state)
    {
        // do something
    }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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    using (var stream = new FileStream(@"C:\Temp\SomeFile.txt",
                                       FileMode.OpenOrCreate))
    {
        // do stuff
 
    }// stream.Dispose() will be called even if an exception occurs
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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    private IntPtr _bufferPtr;
    public int BUFFER_SIZE = 1024 * 1024; // 1 MB
    private bool _disposed = false;
 
    public MyClass()
    {
        _bufferPtr =  Marshal.AllocHGlobal(BUFFER_SIZE);
    }
 
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    {
        if (_disposed)
            return;
 
        if (disposing)
        {
            // Free any other managed objects here.
        }
 
        // Free any unmanaged objects here.
        Marshal.FreeHGlobal(_bufferPtr);
        _disposed = true;
    }
 
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
 
    ~MyClass()
    {
        Dispose(false);
    }
}

      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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Process currentProc = Process.GetCurrentProcess();
var bytesInUse = currentProc.PrivateMemorySize64;
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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PerformanceCounter ctr1 = new PerformanceCounter("Process", "Private Bytes", Process.GetCurrentProcess().ProcessName);
PerformanceCounter ctr2 = new PerformanceCounter(".NET CLR Memory", "# Gen 0 Collections", Process.GetCurrentProcess().ProcessName);
PerformanceCounter ctr3 = new PerformanceCounter(".NET CLR Memory", "# Gen 1 Collections", Process.GetCurrentProcess().ProcessName);
PerformanceCounter ctr4 = new PerformanceCounter(".NET CLR Memory", "# Gen 2 Collections", Process.GetCurrentProcess().ProcessName);
PerformanceCounter ctr5 = new PerformanceCounter(".NET CLR Memory", "Gen 0 heap size", Process.GetCurrentProcess().ProcessName);
//...
Debug.WriteLine("ctr1 = " + ctr1 .NextValue());
Debug.WriteLine("ctr2 = " + ctr2 .NextValue());
Debug.WriteLine("ctr3 = " + ctr3 .NextValue());
Debug.WriteLine("ctr4 = " + ctr4 .NextValue());
Debug.WriteLine("ctr5 = " + ctr5 .NextValue());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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[Test]
void MemoryLeakTest()
{
  var weakRef = new WeakReference(leakyObject)
  // Ryn an operation with leakyObject
  GC.Collect();
  GC.WaitForPendingFinalizers();
  GC.Collect();
  Assert.IsFalse(weakRef.IsAlive);
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, .NET Memory Profiler SciTech dotMemory, API:

MemAssertion.NoInstances(typeof(MyLeakyClass));
MemAssertion.NoNewInstances(typeof(MyLeakyClass), lastSnapshot);
MemAssertion.MaxNewInstances(typeof(Bitmap), 10);
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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