Using reflection to call a DLL but another DLL required is throwing an exception

Question

So i am using some reflection to call a function from a dll on a network drive. The problem is that the dll requires another dll and it is in that same folder but an exception is thrown.

Here is my code:

 try
        {
            Assembly loadedDLL = Assembly.LoadFrom(@"G:\Remote\Debug\BonderControlPanelSim.dll", AppDomain.CurrentDomain.Evidence);
            Type rtsObj = loadedDLL.GetType("Oe.Te.Ranorex.Instrument.BonderControlPanelSim");
            Object obj = Activator.CreateInstance(rtsObj);

            rtsObj.InvokeMember("Initialize", BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance, null, obj, new object[] { "COM3", 1, 2 });
            Thread.Sleep(1500);
            rtsObj.InvokeMember("PushStart", BindingFlags.InvokeMethod | BindingFlags.Public, null, obj, new object[] { "3" });
            Thread.Sleep(200);
            rtsObj.InvokeMember("Shutdown", BindingFlags.InvokeMethod | BindingFlags.Public, null, obj, null);

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

The exception I get is this:

{"Unable to load DLL 'SeaMAX.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"}

The SeaMAX.dll is required with the BonderControlPanelSim.dll.

My issue is that the dll is in the same folder... but my dll when reflection is used to invoke a member cant find the dll... but its there. Am I missing something

Answer 1

I think I'm familiar with this company and its products. This is unmanaged DLL, used for industrial I/O. The problem is that Windows cannot find the dependency, it isn't resolved by the CLR loader. You can help it by changing the current directory:

string oldPath = Environment.CurrentDirectory;
Environment.CurrentDirectory = @"G:\Remote\Debug";
Assembly loadedDLL = Assembly.LoadFrom(...);
Environment.CurrentDirectory = oldPath;
// etc..

This assumes seamax.dll is in the same directory as the assembly. It normally isn't. Pinvoking SetDllDirectory() is another trick, as is copying this DLL to a directory that's on the PATH environment variable.

Answer 2

My guess is that .net is not able to resolve the assembly reference. Attach to the AssemblyResolve Event of the AppDomain and load the assembly from the proper path : http://msdn.microsoft.com/en-us/library/system.appdomain.assemblyresolve(v=VS.90).aspx

Answer 3

  [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool SetDllDirectory(string dllPath);

SetDllDirectory(@"G:\\Remote\\Debug\\");