Marshal.GetLastWin32Error Method ()


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

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

Public Shared Function GetLastWin32Error As Integer

Return Value

Type: System.Int32

The last error code set by a call to the Win32 SetLastError function.

GetLastWin32Error exposes the Win32 GetLastError function 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 instead of writing your own platform invoke definition for GetLastError and calling it. The common language runtime can make internal calls to APIs that overwrite the GetLastError maintained by the operating system.

You can use this method to obtain error codes only if you apply the System.Runtime.InteropServices.DllImportAttribute to the method signature and set the SetLastError field totrue. 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.

The following example demonstrates calling the GetLastWin32Errormethod. The example first demonstrates calling the method with no error present and then demonstrates calling the method with an error present.

Imports System.Runtime.InteropServices

Module 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)> _
    Function MessageBox(ByVal hwnd As IntPtr, ByVal text As String, ByVal caption As String, ByVal type As UInt32) As Integer
    End Function

End Module

Module Program

    Sub 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.
        Dim errorVal As Integer

        errorVal = Marshal.GetLastWin32Error()

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

        ' 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.

        errorVal = Marshal.GetLastWin32Error()

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

    End Sub

    Sub Main(ByVal args() As String)


    End Sub

End Module

' 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


requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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