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POManagementObject leaking in C# COM DLL
 

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    <p>I have a C# COM DLL that calls WMI using the <code>System.Management</code> namespace. The DLL is being loaded into a C++ service. Every time I call the into the WMI classes I'm seeing a HUGE memory leak. After about an hour I am well over 1 GB of memory used. </p> <p>If I take the same COM DLL and load it into PowerShell using <code>Reflection.LoadFrom</code> it does not leak memory. I have modified the DLL like so and it no longer leaks (still loading into the service with COM):</p> <pre><code>public class MyComObject { public void CallCom() { CallSomeWMIStuff(); } } </code></pre> <p>To this. This no longer leaks!</p> <pre><code>public class MyComObject { public void CallCom() { //CallSomeWMIStuff(); } } </code></pre> <p>Here's an example of some of the WMI code:</p> <pre><code>var scope = new ManagementScope( "root\\cimv2" ); scope.Connect(); using (var myservice = GetService("SomeService", scope)) { //Some Stuff } ... ManagementObject GetService(string serviceName, MangementScope scope) { ManagementPath wmiPath = new ManagementPath( serviceName ); using (ManagementClass serviceClass = new ManagementClass( scope, wmiPath, null )) { using (ManagementObjectCollection services = serviceClass.GetInstances()) { ManagementObject serviceObject = null; // If this service class does not have an instance, create one. if (services.Count == 0) { serviceObject = serviceClass.CreateInstance(); } else { foreach (ManagementObject service in services) { serviceObject = service; break; } } return serviceObject; } } } </code></pre> <p>EDIT: C++ Snippet:</p> <pre><code>NAMESPACE::ICSharpComPtr pCSharpCom = NULL; HRESULT hr = pCSharpCom .CreateInstance(NAMESPACE::CLSID_CSharpCom); if (FAILED(hr)) { Log("Failed (hr=%08x)", hr); return hr; } try { _bstr_t bstrData = pCSharpCom -&gt;GetData(); strLine = (LPCTSTR)bstrData; strMessage += strLine; } catch (_com_error&amp; err) { _bstr_t desc = GetErrorMessage(err); Log("Excepton %S", (const wchar_t*)desc); return 0; } pCSharpCom -&gt;Release(); </code></pre> <p>Has anyone seen anything like this? We are seeing a similar issue with C++\CLI that's loading a different WMI related DLL directly. </p> <p>Eventually, the WMI service will no longer be responsive and I will have to restart that service as well. </p> <p>Edit:</p> <p>This has to do with the apartment state of the COM object. Added a <code>CoInitializeEx</code> rather than a <code>CoInitialize</code>. I set the thread to MTA. At first it didn't look like this was working until I realized that first time the method was called we were seeing the thread state set to STA rather than MTA! Every subsequent call would be MTA. If I returned right away, before calling the <code>System.Management</code> classes when the thread was STA, I would no longer leak memory! </p> <p>Any idea why the first one would be STA?</p>
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    1. USAdam Driscoll
    1. USAdam Driscoll
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    1. COThis happens when the garbage collector doesn't run, the RCWs don't get cleaned up. You probably just don't generate enough garbage. Check this with perfmon.exe. GC.Collect is the workaround.
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      1. USHans Passant
    2. COI tried this as well. It didn't seem to help.
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      1. USAdam Driscoll
    3. COAfter some further investigation GC.Collect is not helping the situation. It's still growing in memory and handles.
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      1. USAdam Driscoll
 

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