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POc# FindFirstDevice Marshaling
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copied!<p>I have a c# application running on winCE 6.0 version. I need to unload/reload the SD card driver at run time. I am attempting to do this via calling FindFirstDevice, then DeactivateDevice/ActivateDeviceEX calls. My problem is the FindFirstDevice() call always fails. I believe it to be a problem with the way I am marshalling the second parameter to it. Can anyone tell me what I am doing wrong? Here is the code:</p> <pre><code> [DllImport("coredll.dll", SetLastError = true)] public static extern int FindFirstDevice(DeviceSearchType searchType, IntPtr searchParam, ref DEVMGR_DEVICE_INFORMATION pdi); public bool MountSDCardDrive(string mRegPath) { const int INVALID_HANDLE_VALUE = -1; int handle = INVALID_HANDLE_VALUE; DeviceSearchType searchType = DeviceSearchType.DeviceSearchByDeviceName; DEVMGR_DEVICE_INFORMATION di = new DEVMGR_DEVICE_INFORMATION(); di.dwSize = (uint)Marshal.SizeOf(typeof(DEVMGR_DEVICE_INFORMATION)); string searchParamString = "*"; IntPtr searchParam = Marshal.AllocHGlobal(searchParamString.Length); Marshal.StructureToPtr(searchParamString, searchParam, false); handle = FindFirstDevice(searchType, searchParam, ref di); if (handle == INVALID_HANDLE_VALUE) { // Failure - print error int hFindFirstDeviceError = Marshal.GetLastWin32Error(); using (StreamWriter bw = new StreamWriter(File.Open(App.chipDebugFile, FileMode.Append))) { String iua = "DevDriverInterface: error from FindFirstDevice: " + hFindFirstDeviceError.ToString(); bw.WriteLine(iua); } return false; } ... (rest of code) </code></pre> <p>If I change the line <code>Marshal.StructureToPtr(searchParamString, searchParam, false);</code> to <code>searchParam = Marshal.StringToBSTR(searchParamString);</code>"I end up with error 1168 (ERROR_NOT_FOUND) instead of 18 (no more files). </p> <p>Note my intent is to use a <code>searchParamString</code> of "SDH1" when I get this working. I am currently using <code>searchParamString</code> of "*" in order to see something returned and rule out the particular string value.</p> <p>Thanks for any help you can give - Lynn</p>

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