Marshal.getlastwin32error Clear Error
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Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Why does .NET not clear errors internally? up vote 0 down vote favorite I am running the following scenerio: SafeFileHandle handle = Win32API.CreateFile((deviceName + "\\" getlasterror c# pinvoke + pipeName), DesiredAccess.GENERIC_WRITE | DesiredAccess.GENERIC_READ, ShareMode.FILE_SHARE_WRITE | ShareMode.FILE_SHARE_READ, IntPtr.Zero, CreationDisposition.OPEN_EXISTING, FlagsAndAttributes.FILE_ATTRIBUTE_NORMAL | FlagsAndAttributes.FILE_FLAG_OVERLAPPED, IntPtr.Zero); // Marshal.GetLastWin32Error() returns 0 (success) bool pass = Win32API.WriteFile(writeHandle, message.ToArray(), (uint)message.Count, ref bytes_written, ref over_lapped); pass is false but to be expected since im running overlapped. The problem is Marshal.GetLastWin32Error() doesnt return ERROR_IO_PENDING it returns ERROR_ALREADY_EXISTS. Which is weird to me because the error didnt show that when I created the file, but when I write it shows up. Now I am trying to figure out how to close the handle that I dont seem to have access to or atleast get an explanation as to why this is happening. EDIT: Ok, I have norrowed the problem down and I know what is causing the problem. private void ErrorOccurred(string detailedError) { lock (mLogLock) { try { System.IO.File.AppendAllText("Device" + mDeviceHandle + "Log.txt", DateTime.Now.ToLongTimeString() + ": " + detailedError + Environment.NewLine); } catch (Exception ex) { System.Windows.Forms.Message
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Samples Retired content We’re sorry. The content you requested has been removed. You’ll be auto redirected in 1 second. System.Runtime.InteropServices Marshal http://stackoverflow.com/questions/1429369/why-does-net-not-clear-errors-internally Class Marshal Methods Marshal Methods GetLastWin32Error Method GetLastWin32Error Method GetLastWin32Error Method AddRef Method AllocCoTaskMem Method AllocHGlobal Method AreComObjectsAvailableForCleanup Method BindToMoniker Method ChangeWrapperHandleStrength Method CleanupUnusedObjectsInCurrentContext Method Copy Method CreateAggregatedObject Method CreateWrapperOfType Method DestroyStructure Method FinalReleaseComObject Method FreeBSTR Method FreeCoTaskMem Method FreeHGlobal Method GenerateGuidForType Method https://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.getlastwin32error(v=vs.110).aspx GenerateProgIdForType Method GetActiveObject Method GetComInterfaceForObject Method GetComInterfaceForObjectInContext Method GetComObjectData Method GetComSlotForMethodInfo Method GetDelegateForFunctionPointer Method GetEndComSlot Method GetExceptionCode Method GetExceptionForHR Method GetExceptionPointers Method GetFunctionPointerForDelegate Method GetHINSTANCE Method GetHRForException Method GetHRForLastWin32Error Method GetIDispatchForObject Method GetIDispatchForObjectInContext Method GetITypeInfoForType Method GetIUnknownForObject Method GetIUnknownForObjectInContext Method GetLastWin32Error Method GetManagedThunkForUnmanagedMethodPtr Method GetMethodInfoForComSlot Method GetNativeVariantForObject Method GetObjectForIUnknown Method GetObjectForNativeVariant Method GetObjectsForNativeVariants Method GetStartComSlot Method GetThreadFromFiberCookie Method GetTypedObjectForIUnknown Method GetTypeForITypeInfo Method GetTypeFromCLSID Method GetTypeInfoName Method GetTypeLibGuid Method GetTypeLibGuidForAssembly Method GetTypeLibLcid Method GetTypeLibName Method GetTypeLibVersionForAssembly Method GetUniqueObjectForIUnknown Method GetUnmanagedThunkForManagedMethodPtr Method IsComObject Method IsTypeVisibleFromCom Method NumParamBytes Method OffsetOf Method Prelink Method PrelinkAll Method PtrToStringAnsi Method PtrToStringAuto Method PtrToStringBSTR Method PtrToStringUni Method PtrToStructure Method QueryInterface Method ReadByte Method ReadInt16 Method ReadInt32 Method ReadInt64 Method ReadIntPtr Method ReAllocCoTaskMem Method ReAllocHGlobal Method Release Method ReleaseComObject Method ReleaseThreadCache Method SecureStringToBSTR Method SecureStringT
Nathan [MSFT]April 25, 20033 Share 0 0 In the Win32 world, calling the GetLastError API is often the mechanism to get additional error information when an API call fails. When calling https://blogs.msdn.microsoft.com/adam_nathan/2003/04/25/getlasterror-and-managed-code/ these same Win32 APIs in managed code via PInvoke or via "It Just Works (IJW)" in managed C++, the rules are slightly different. That's because the CLR itself could be making calls to the operating system as the call returns from unmanaged to managed code (when it unmarshals parameters, for instance) and these calls could easily invalidatethe last error. error codes For PInvoke, the solution is two-fold: 1)Mark the relevant PInvoke signature with SetLastError=true. This makes the CLR call GetLastError immediately after it calls the target unmanaged API and save the result. 2)Call Marshal.GetLastWin32Error (in System.Runtime.InteropServices) to retrieve the value that the CLR saved. Therefore, never define a PInvoke signature for GetLastErrorfrom kernel32.dll. If managed code calls such a marshal.getlastwin32error clear error method, it will not get reliable results. Here's a C# example thatretrieves the last error correctly. It forces a failure by passing an invalid drive name (XYZ) to the SetVolumeLabel API: using System.Runtime.InteropServices; public class ForceFailure { [DllImport("kernel32.dll", SetLastError=true)] static extern bool SetVolumeLabel( string lpRootPathName, string lpVolumeName); public static void Main () { if (SetVolumeLabel("XYZ:\\", "My Imaginary Drive ")) System.Console.WriteLine("It worked???"); else System.Console.WriteLine(Marshal.GetLastWin32Error()); } } Thisoutputs "123" to the console. Of course, this isn't a very satisfactory error message. In the Win32 world, you'd probably call the FormatMessage API next to get a meaningful message describing what error 123 means. You could definitely do the same thing in managed code with a PInvoke call to FormatMessage, but the .NET Framework provides a much simpler way to do this. The System.Component model namespace defines a Win32Exception class that internally calls FormatMessage for you! So if you change the previous code to the following: if (S