Hello everyone, I have quite strange behaviour calling SymGetModuleInfo64 from C# code.I always get ERROR_INVALID_PARAMETER (87) with Marshal.GetLastWin32Error().I have already read a lot of posts regarding problems with frequent updates of IMAGEHLP_MODULE64 struct and I just downloaded latest Debugging Tools For Windows (x86) , loaded dbghelp.dll from that location and I was quite sure it would work.Nevertheless I am getting the same error.Can anyone point me what is wrong here? IMAGEHLP_MODULE64 struct is defined in my code as follows : [StructLayout(LayoutKind.Sequential)] public struct IMAGEHELP_MODULE64 { //************************************************ public int SizeOfStruct; public long BaseOfImage; public int ImageSize; public int TimeDateStamp; public int CheckSum; public int NumSyms; public SymType SymType; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)] public string ModuleName; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)] public string ImageName; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)] public string LoadedImageName; //************************************************ //new elements v2 //************************************************* [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)] public string LoadedPdbName; public int CVSig; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 780)] public string CVData; public int PdbSig; public GUID PdbSig70; public int PdbAge; public bool PdbUnmatched; public bool DbgUnmatched; public bool LineNumbers; public bool GlobalSymbols; public bool TypeInfo; //************************************************ //new elements v3 //************************************************ public bool SourceIndexed; public bool Publics; //************************************************ //new elements v4 //************************************************ public int MachineType; public int Reserved; //************************************************ } the piece of code that actually calls SymGetModuleInfo64 is like this : public void GetSymbolInfo(IntPtr hProcess,long modBase64,out bool success) { success = false; DbgHelp.IMAGEHELP_MODULE64 moduleInfo = new DbgHelp.IMAGEHELP_MODULE64(); moduleInfo.SizeOfStruct = Marshal.SizeOf(moduleInfo); try { success = DbgHelp.SymGetModuleInfo64(hProcess, modBase64, out moduleInfo); if (success) { //Do the stuff here } } catch (Exception exc) { } } Im stuck here...always with error 87.Please someone points me to the right direction. By the way modBase64 is value previously populated by : modBase64 = DbgHelp.SymLoadModule64(_handle, IntPtr.Zero, fileName, null, baseAddress, size); where _handle is process handle of process being debugged,fileName is path of current loaded module, baseAddress is address base of currently loaded module and size is of course the size of current loaded module.I call this code when I get LOAD_DLL_DEBUG_EVENT. Edit : Sorry, I forgot to mention that SymGetModuleInfo64 signature is like this : [DllImport("dbghelp.dll", SetLastError = true)] public static extern bool SymGetModuleInfo64(IntPtr hProcess, long ModuleBase64, out IMAGEHELP_MODULE64 imgHelpModule); Best regards, Civa