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POInvalidCastException: Unable to cast COM object of type x to interface type y
 

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    <p>I have some C# code written on machine #1 using Visual C# Express 2010. The code is dependent on some COM objects that are registered DLLs. It compiles and runs fine on machine #1. The COM objects are installed from a program called BostonWorkstation, which is installed on machines #1 and #2.</p> <ul> <li>Machine 1: <ul> <li>Code written on.</li> <li>Visual C# 2010 Express installed.</li> <li>The "BWS" DLLs are registered.</li> <li>The program runs just fine.</li> <li>Has .NET versions: v4.0, v4, v3.5, v3.0, v2.0</li> <li>32bit</li> </ul></li> </ul> <p><br /></p> <ul> <li>Machine 2: <ul> <li>The "BWS" DLLs are registered.</li> <li>The program errors with <code>System.InvalidCastException</code> (below).</li> <li>Visual C# 2010 Express not installed.</li> <li>Has .NET versions: v4, v3.5, v3.0, v2.0, v1.1</li> <li>32bit</li> </ul></li> </ul> <p><br /></p> <ul> <li>Machine 3: <ul> <li>The "BWS" DLLs are not registered.</li> <li>Visual C# 2010 Express installed.</li> <li>The program errors (as expected) with: <code>System.Runtime.InteropServices.COMException (...): Retrieving the COM class factory for component with CLSID {...} failed due to the following error: 80040154 Class not registered (...)</code></li> <li>32bit</li> </ul></li> </ul> <p>When I try to run that program (compiled on machine 1) on machine #2 which also has the same exact registered DLLs, but the program fails to run. I also tried running it on machine #3, which doesn't even have the DLLs and that gets a different error as expected.</p> <p>The runtime error on machine 2:</p> <blockquote> <p>1 Unable to load BostonWorkstation, error: System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'BostonWorkStation70.BostonWorkStation'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{8C8144EF-ADB7-48FD-A5BB-6E55B8382B3E}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)). at TestBWS.LoginForm() in C:\Documents and Settings\user\My Documents\Visual Studio 2010\Projects\project1\TestBWS\CodeFile1.cs:line 67</p> </blockquote> <p>(The Visual Studio folder reference is just the compile time path)</p> <p>Checking the registry on machine 1 I found this:</p> <blockquote> <p>HKEY_CLASSES_ROOT\Interface{8C8144EF-ADB7-48FD-A5BB-6E55B8382B3E}</p> </blockquote> <p>with a default REG_SZ value of <code>BostonWorkStation</code></p> <p>The code:</p> <pre><code> using BostonWorkStation70; //line 1 ... try { bwsLogin = new BostonWorkStation(); //line 67 } catch (Exception e) { Console.WriteLine("1 Unable to load BostonWorkstation, error: " + e); System.Console.ReadLine(); //pause the debug window return false; } </code></pre> <p>I have tried running ProcMon to compare the machines Process logs, but there are thousands of entries for just this program and I'm not seeing any missing references offhand. I ran a compare, but a successful Process log has 5x as many lines.</p> <p>From what I understand, running the program on machine 2 has it creating the BWS object as a generic <code>System.__ComObject</code> (instead of <code>BostonWorkStation70.BostonWorkStation</code>) and I don't know why. The DLLs etc are definitely correct on machine 2, otherwise I'd be getting that <code>Class not registered</code> error on runtime.</p> <p>Why will the compiled program not run on machine 2? All the dependent COMs/DLLs are on it.</p>
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    1. COJust guessing here, but I think a possible explanation might be that the COM object relies on another (possibly non-COM) DLL, which isn't found on the machine where it doesn't work.
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    2. COThe proxy/stub DLL would be my guess. Run SysInternals' ProcMon utility and compare the good vs the bad trace.
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    3. CO@HansPassant Good idea. I tried that, but the non-working spits out 1034 lines and the working spits out 6000+ lines (and that's not even fully running the program). This is a lot to compare.
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