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Marshal.GetLastWin32Error Method

Returns the error code returned by the last unmanaged function called using platform invoke that has the DllImportAttribute.SetLastError flag set.

Namespace:  System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)

[SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
public static int GetLastWin32Error()

Return Value

Type: System.Int32
The last error code set by a call to the Win32 SetLastError API method.

GetLastWin32Error exposes the Win32 GetLastError API method from Kernel32.DLL. This method exists because it is not safe to make a direct platform invoke call to GetLastError to obtain this information. If you want to access this error code, you must call GetLastWin32Error rather than writing your own platform invoke definition for GetLastError and calling it. The common language runtime can make internal calls to APIs that overwrite the operating system maintained GetLastError.

You can only use this method to obtain error codes if you apply the System.Runtime.InteropServices.DllImportAttribute to the method signature and set the SetLastError field to true. The process for this varies depending upon the source language used: C# and C++ are false by default, but the Declare statement in Visual Basic is true. For additional information about the GetLastError and SetLastError Win32 API methods, see the MSDN Library.

NoteNote:

This method uses SecurityAction.LinkDemand to prevent it from being called from untrusted code; only the immediate caller is required to have SecurityPermissionAttribute.UnmanagedCode permission. If your code can be called from partially trusted code, do not pass user input to Marshal class methods without validation. For important limitations on using the LinkDemand member, see Demand vs. LinkDemand.

The following code example demonstrates calling the GetLastWin32Error method. The code example first demonstrates calling the method with no error present and then demonstrates calling the method with an error present.

using System;
using System.Runtime.InteropServices;

internal class Win32
{
    // Use DllImportAttribute to inport the Win32 MessageBox 
    // function.  Set the SetLastError flag to true to allow 
    // the function to set the Win32 error.
    [DllImportAttribute("user32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    public static extern int MessageBox(IntPtr hwnd, String text, String caption, uint type);

}

class Program
{

    static void Run()
    {
        // Call the MessageBox with normal parameters.

        Console.WriteLine("Calling Win32 MessageBox without error...");

        Win32.MessageBox(new IntPtr(0), "Press OK...", "Press OK Dialog", 0);

        // Get the last error and display it. 
        int error = Marshal.GetLastWin32Error();

        Console.WriteLine("The last Win32 Error was: " + error);

        // Call the MessageBox with an invalid window handle to 
        // produce a Win32 error.

        Console.WriteLine("Calling Win32 MessageBox with error...");

        Win32.MessageBox(new IntPtr(123132), "Press OK...", "Press OK Dialog", 0);

        // Get the last error and display it.

        error = Marshal.GetLastWin32Error();

        Console.WriteLine("The last Win32 Error was: " + error);
    }

    static void Main(string[] args)
    {
        Run();
    }
}
// This code example displays the following to the console:  
// 
// Calling Win32 MessageBox without error... 
// The last Win32 Error was: 0 
// Calling Win32 MessageBox with error... 
// The last Win32 Error was: 1400

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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