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WindowsIdentity.Impersonate Methode

  • Referenz

Definition

Namespace:
System.Security.Principal
Assembly:
mscorlib.dll

Ermöglicht es, im Code die Identität eines anderen Windows-Benutzers anzunehmen.

Überlädt

Impersonate()

Nimmt die Identität des durch das WindowsIdentity-Objekt dargestellten Benutzers an.
Impersonate(IntPtr)

Nimmt die Identität des durch das angegebene Benutzertoken dargestellten Benutzers an.

Impersonate()

Nimmt die Identität des durch das WindowsIdentity-Objekt dargestellten Benutzers an.

public:
 virtual System::Security::Principal::WindowsImpersonationContext ^ Impersonate();
public virtual System.Security.Principal.WindowsImpersonationContext Impersonate ();
abstract member Impersonate : unit -> System.Security.Principal.WindowsImpersonationContext
override this.Impersonate : unit -> System.Security.Principal.WindowsImpersonationContext
Public Overridable Function Impersonate () As WindowsImpersonationContext

Gibt zurück

WindowsImpersonationContext

Ein Objekt, das den Windows-Benutzer vor dem Identitätswechsel darstellt. Es kann dazu verwendet werden, in den Kontext des ursprünglichen Benutzers zurückzukehren.

Ausnahmen

InvalidOperationException

Eine anonyme Identität hat versucht, einen Identitätswechsel durchzuführen.

SecurityException

Win32-Fehler.

Beispiele

Im folgenden Beispiel wird veranschaulicht, wie Sie ein Windows-Kontotoken durch Aufrufen der nicht verwalteten Win32-Funktion LogonUser abrufen und dieses Token verwenden, um die Identität eines anderen Benutzers zu annehmen und dann zur ursprünglichen Identität zurückzugeben.

// This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
// IMPORTANT NOTES: 
// This sample requests the user to enter a password on the console screen.
// Because the console window does not support methods allowing the password to be masked,
// it will be visible to anyone viewing the screen.
// On Windows Vista and later this sample must be run as an administrator. 

#using <System.dll>

using namespace System;
using namespace System::Runtime::InteropServices;
using namespace System::Security::Principal;
using namespace System::Security::Permissions;


[DllImport("advapi32.dll",SetLastError=true)]
bool LogonUser( String^ lpszUsername, String^ lpszDomain, String^ lpszPassword, int dwLogonType, int dwLogonProvider, IntPtr * phToken );

[DllImport("kernel32.dll",CharSet=CharSet::Auto)]
bool CloseHandle( IntPtr handle );

// Test harness.
// If you incorporate this code into a DLL, be sure to demand FullTrust.

[PermissionSetAttribute(SecurityAction::Demand,Name="FullTrust")]
int main()
{
   IntPtr tokenHandle = IntPtr(0);

   try
   {
      String^ userName;
      String^ domainName;
      
      // Get the user token for the specified user, domain, and password using the 
      // unmanaged LogonUser method.  
      // The local machine name can be used for the domain name to impersonate a user on this machine.
      Console::Write( "Enter the name of the domain on which to log on: " );
      domainName = Console::ReadLine();
      Console::Write( "Enter the login of a user on {0} that you wish to impersonate: ", domainName );
      userName = Console::ReadLine();
      Console::Write( "Enter the password for {0}: ", userName );
      const int LOGON32_PROVIDER_DEFAULT = 0;
      
      //This parameter causes LogonUser to create a primary token.
      const int LOGON32_LOGON_INTERACTIVE = 2;
      const int SecurityImpersonation = 2;
      tokenHandle = IntPtr::Zero;
      
      // Call LogonUser to obtain a handle to an access token.
      bool returnValue = LogonUser( userName, domainName, Console::ReadLine(), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,  &tokenHandle );
      Console::WriteLine( "LogonUser called." );
      if ( false == returnValue )
      {
         int ret = Marshal::GetLastWin32Error();
         Console::WriteLine( "LogonUser failed with error code : {0}", ret );
         throw gcnew System::ComponentModel::Win32Exception( ret );
      }
      Console::WriteLine( "Did LogonUser Succeed? {0}", (returnValue ? (String^)"Yes" : "No") );
      Console::WriteLine( "Value of Windows NT token: {0}", tokenHandle );
      
      // Check the identity.
      Console::WriteLine( "Before impersonation: {0}", WindowsIdentity::GetCurrent()->Name );
      
      // The token that is passed to the following constructor must 
      // be a primary token in order to use it for impersonation.
      WindowsIdentity^ newId = gcnew WindowsIdentity( tokenHandle );
      WindowsImpersonationContext^ impersonatedUser = newId->Impersonate();
      
      // Check the identity.
      Console::WriteLine( "After impersonation: {0}", WindowsIdentity::GetCurrent()->Name );
      
      // Stop impersonating the user.
      impersonatedUser->Undo();
      
      // Check the identity.
      Console::WriteLine( "After Undo: {0}", WindowsIdentity::GetCurrent()->Name );
      
      // Free the tokens.
      if ( tokenHandle != IntPtr::Zero )
            CloseHandle( tokenHandle );
   }
   catch ( Exception^ ex ) 
   {
      Console::WriteLine( "Exception occurred. {0}", ex->Message );
   }

}

// This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
// IMPORTANT NOTES:
// This sample requests the user to enter a password on the console screen.
// Because the console window does not support methods allowing the password to be masked,
// it will be visible to anyone viewing the screen.
// On Windows Vista and later this sample must be run as an administrator.

using System;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;
using Microsoft.Win32.SafeHandles;
using System.Runtime.ConstrainedExecution;
using System.Security;

public class ImpersonationDemo
{
    [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword,
        int dwLogonType, int dwLogonProvider, out SafeTokenHandle phToken);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
    public extern static bool CloseHandle(IntPtr handle);

    // Test harness.
    // If you incorporate this code into a DLL, be sure to demand FullTrust.
    [PermissionSetAttribute(SecurityAction.Demand, Name = "FullTrust")]
    public static void Main(string[] args)
    {
        SafeTokenHandle safeTokenHandle;
        try
        {
            string userName, domainName;
            // Get the user token for the specified user, domain, and password using the
            // unmanaged LogonUser method.
            // The local machine name can be used for the domain name to impersonate a user on this machine.
            Console.Write("Enter the name of the domain on which to log on: ");
            domainName = Console.ReadLine();

            Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName);
            userName = Console.ReadLine();

            Console.Write("Enter the password for {0}: ", userName);

            const int LOGON32_PROVIDER_DEFAULT = 0;
            //This parameter causes LogonUser to create a primary token.
            const int LOGON32_LOGON_INTERACTIVE = 2;

            // Call LogonUser to obtain a handle to an access token.
            bool returnValue = LogonUser(userName, domainName, Console.ReadLine(),
                LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
                out safeTokenHandle);

            Console.WriteLine("LogonUser called.");

            if (false == returnValue)
            {
                int ret = Marshal.GetLastWin32Error();
                Console.WriteLine("LogonUser failed with error code : {0}", ret);
                throw new System.ComponentModel.Win32Exception(ret);
            }
            using (safeTokenHandle)
            {
                Console.WriteLine("Did LogonUser Succeed? " + (returnValue ? "Yes" : "No"));
                Console.WriteLine("Value of Windows NT token: " + safeTokenHandle);

                // Check the identity.
                Console.WriteLine("Before impersonation: "
                    + WindowsIdentity.GetCurrent().Name);
                // Use the token handle returned by LogonUser.
                using (WindowsIdentity newId = new WindowsIdentity(safeTokenHandle.DangerousGetHandle()))
                {
                    using (WindowsImpersonationContext impersonatedUser = newId.Impersonate())
                    {

                        // Check the identity.
                        Console.WriteLine("After impersonation: "
                            + WindowsIdentity.GetCurrent().Name);
                    }
                }
                // Releasing the context object stops the impersonation
                // Check the identity.
                Console.WriteLine("After closing the context: " + WindowsIdentity.GetCurrent().Name);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception occurred. " + ex.Message);
        }
    }
}
public sealed class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid
{
    private SafeTokenHandle()
        : base(true)
    {
    }

    [DllImport("kernel32.dll")]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [SuppressUnmanagedCodeSecurity]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool CloseHandle(IntPtr handle);

    protected override bool ReleaseHandle()
    {
        return CloseHandle(handle);
    }
}

' This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
' IMPORTANT NOTES: 
' This sample requests the user to enter a password on the console screen.
' Because the console window does not support methods allowing the password to be masked,
' it will be visible to anyone viewing the screen.
' On Windows Vista and later this sample must be run as an administrator. 

Imports System.Runtime.InteropServices
Imports System.Security.Principal
Imports System.Security.Permissions
Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.ConstrainedExecution
Imports System.Security

Module Module1

    Public Class ImpersonationDemo

        'Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
        '    ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
        '    ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
        '    ByRef phToken As IntPtr) As Boolean

        Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
            ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
            ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
            <Out()> ByRef phToken As SafeTokenHandle) As Boolean

        Public Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Boolean

        ' Test harness.
        ' If you incorporate this code into a DLL, be sure to demand FullTrust.
        <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
        Public Overloads Shared Sub Main(ByVal args() As String)
            Dim safeTokenHandle As SafeTokenHandle = Nothing
            Dim tokenHandle As New IntPtr(0)
            Try


                Dim userName, domainName As String

                ' Get the user token for the specified user, domain, and password using the 
                ' unmanaged LogonUser method.  
                ' The local machine name can be used for the domain name to impersonate a user on this machine.
                Console.Write("Enter the name of a domain on which to log on: ")
                domainName = Console.ReadLine()

                Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName)
                userName = Console.ReadLine()

                Console.Write("Enter the password for {0}: ", userName)

                Const LOGON32_PROVIDER_DEFAULT As Integer = 0
                'This parameter causes LogonUser to create a primary token.
                Const LOGON32_LOGON_INTERACTIVE As Integer = 2

                ' Call LogonUser to obtain a handle to an access token.
                Dim returnValue As Boolean = LogonUser(userName, domainName, Console.ReadLine(), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, safeTokenHandle)

                Console.WriteLine("LogonUser called.")

                If False = returnValue Then
                    Dim ret As Integer = Marshal.GetLastWin32Error()
                    Console.WriteLine("LogonUser failed with error code : {0}", ret)
                    Throw New System.ComponentModel.Win32Exception(ret)

                    Return
                End If
                Using safeTokenHandle
                    Dim success As String
                    If returnValue Then success = "Yes" Else success = "No"
                    Console.WriteLine(("Did LogonUser succeed? " + success))
                    Console.WriteLine(("Value of Windows NT token: " + safeTokenHandle.DangerousGetHandle().ToString()))

                    ' Check the identity.
                    Console.WriteLine(("Before impersonation: " + WindowsIdentity.GetCurrent().Name))

                    ' Use the token handle returned by LogonUser.
                    Using newId As New WindowsIdentity(safeTokenHandle.DangerousGetHandle())
                        Using impersonatedUser As WindowsImpersonationContext = newId.Impersonate()

                            ' Check the identity.
                            Console.WriteLine(("After impersonation: " + WindowsIdentity.GetCurrent().Name))

                            ' Free the tokens.
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Console.WriteLine(("Exception occurred. " + ex.Message))
            End Try
        End Sub
    End Class
End Module

Public NotInheritable Class SafeTokenHandle
    Inherits SafeHandleZeroOrMinusOneIsInvalid

    Private Sub New()
        MyBase.New(True)

    End Sub

    Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
            ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
            ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
            ByRef phToken As IntPtr) As Boolean
    <DllImport("kernel32.dll"), ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success), SuppressUnmanagedCodeSecurity()> _
    Private Shared Function CloseHandle(ByVal handle As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean

    End Function
    Protected Overrides Function ReleaseHandle() As Boolean
        Return CloseHandle(handle)

    End Function 'ReleaseHandle
End Class

Hinweise

Auf Windows NT-Plattformen muss der aktuelle Benutzer über ausreichende Rechte verfügen, um den Identitätswechsel zuzulassen.

Warnung

Vermeiden Sie die Verwendung dieser Methode mit dem Muster async/await. In einigen Fällen kann dies zu Zuverlässigkeitsproblemen führen, da der Identitätswechsel nicht wiederhergestellt wird, selbst wenn das resultierende WindowsImpersonationContext gelöscht wird. Verwenden Sie stattdessen RunImpersonated.

Hinweise für Aufrufer

Nach der Verwendung Impersonate()von ist es wichtig, die Undo() -Methode aufzurufen, um den Identitätswechsel zu beenden.

Gilt für:

Impersonate(IntPtr)

Nimmt die Identität des durch das angegebene Benutzertoken dargestellten Benutzers an.

public:
 static System::Security::Principal::WindowsImpersonationContext ^ Impersonate(IntPtr userToken);
public static System.Security.Principal.WindowsImpersonationContext Impersonate (IntPtr userToken);
static member Impersonate : nativeint -> System.Security.Principal.WindowsImpersonationContext
Public Shared Function Impersonate (userToken As IntPtr) As WindowsImpersonationContext

Parameter

userToken
IntPtr

nativeint

Das Handle eines Windows-Kontotokens. Dieses Token wird normalerweise durch einen Aufruf von nicht verwaltetem Code abgerufen, z. B. durch einen Aufruf der LogonUser-Funktion der Windows-API.

Gibt zurück

WindowsImpersonationContext

Ein Objekt, das den Windows-Benutzer vor dem Identitätswechsel darstellt. Es kann dazu verwendet werden, in den Kontext des ursprünglichen Benutzers zurückzukehren.

Ausnahmen

UnauthorizedAccessException

Windows hat den Windows NT-Statuscode STATUS_ACCESS_DENIED zurückgegeben.

OutOfMemoryException

Es ist nicht genügend Arbeitsspeicher verfügbar.

SecurityException

Der Aufrufer verfügt nicht über die ordnungsgemäßen Berechtigungen.

Beispiele

Im folgenden Beispiel wird veranschaulicht, wie Sie ein Windows-Kontotoken durch Aufrufen der nicht verwalteten Win32-Funktion LogonUser abrufen und dieses Token verwenden, um die Identität eines anderen Benutzers zu annehmen und dann zur ursprünglichen Identität zurückzugeben.

// This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
// IMPORTANT NOTES:
// This sample requests the user to enter a password on the console screen.
// Because the console window does not support methods allowing the password to be masked,
// it will be visible to anyone viewing the screen.
// On Windows Vista and later this sample must be run as an administrator.

using System;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Security.Permissions;
using Microsoft.Win32.SafeHandles;
using System.Runtime.ConstrainedExecution;
using System.Security;

public class ImpersonationDemo
{
    [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    public static extern bool LogonUser(String lpszUsername, String lpszDomain, String lpszPassword,
        int dwLogonType, int dwLogonProvider, out SafeTokenHandle phToken);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
    public extern static bool CloseHandle(IntPtr handle);

    // Test harness.
    // If you incorporate this code into a DLL, be sure to demand FullTrust.
    [PermissionSetAttribute(SecurityAction.Demand, Name = "FullTrust")]
    public static void Main(string[] args)
    {
        SafeTokenHandle safeTokenHandle;
        try
        {
            string userName, domainName;
            // Get the user token for the specified user, domain, and password using the
            // unmanaged LogonUser method.
            // The local machine name can be used for the domain name to impersonate a user on this machine.
            Console.Write("Enter the name of the domain on which to log on: ");
            domainName = Console.ReadLine();

            Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName);
            userName = Console.ReadLine();

            Console.Write("Enter the password for {0}: ", userName);

            const int LOGON32_PROVIDER_DEFAULT = 0;
            //This parameter causes LogonUser to create a primary token.
            const int LOGON32_LOGON_INTERACTIVE = 2;

            // Call LogonUser to obtain a handle to an access token.
            bool returnValue = LogonUser(userName, domainName, Console.ReadLine(),
                LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
                out safeTokenHandle);

            Console.WriteLine("LogonUser called.");

            if (false == returnValue)
            {
                int ret = Marshal.GetLastWin32Error();
                Console.WriteLine("LogonUser failed with error code : {0}", ret);
                throw new System.ComponentModel.Win32Exception(ret);
            }
            using (safeTokenHandle)
            {
                Console.WriteLine("Did LogonUser Succeed? " + (returnValue ? "Yes" : "No"));
                Console.WriteLine("Value of Windows NT token: " + safeTokenHandle);

                // Check the identity.
                Console.WriteLine("Before impersonation: "
                    + WindowsIdentity.GetCurrent().Name);
                // Use the token handle returned by LogonUser.
                using (WindowsImpersonationContext impersonatedUser = WindowsIdentity.Impersonate(safeTokenHandle.DangerousGetHandle()))
                {

                    // Check the identity.
                    Console.WriteLine("After impersonation: "
                        + WindowsIdentity.GetCurrent().Name);
                }
                // Releasing the context object stops the impersonation
                // Check the identity.
                Console.WriteLine("After closing the context: " + WindowsIdentity.GetCurrent().Name);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception occurred. " + ex.Message);
        }
    }
}
public sealed class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid
{
    private SafeTokenHandle()
        : base(true)
    {
    }

    [DllImport("kernel32.dll")]
    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
    [SuppressUnmanagedCodeSecurity]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool CloseHandle(IntPtr handle);

    protected override bool ReleaseHandle()
    {
        return CloseHandle(handle);
    }
}

' This sample demonstrates the use of the WindowsIdentity class to impersonate a user.
' IMPORTANT NOTES: 
' This sample requests the user to enter a password on the console screen.
' Because the console window does not support methods allowing the password to be masked,
' it will be visible to anyone viewing the screen.
' On Windows Vista and later this sample must be run as an administrator. 

Imports System.Runtime.InteropServices
Imports System.Security.Principal
Imports System.Security.Permissions
Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.ConstrainedExecution
Imports System.Security

Module Module1

    Public Class ImpersonationDemo

        'Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
        '    ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
        '    ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
        '    ByRef phToken As IntPtr) As Boolean

        Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
            ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
            ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
            <Out()> ByRef phToken As SafeTokenHandle) As Boolean

        Public Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Boolean

        ' Test harness.
        ' If you incorporate this code into a DLL, be sure to demand FullTrust.
        <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
        Public Overloads Shared Sub Main(ByVal args() As String)
            Dim safeTokenHandle As SafeTokenHandle
            Dim tokenHandle As New IntPtr(0)
            Try


                Dim userName, domainName As String

                ' Get the user token for the specified user, domain, and password using the 
                ' unmanaged LogonUser method.  
                ' The local machine name can be used for the domain name to impersonate a user on this machine.
                Console.Write("Enter the name of a domain on which to log on: ")
                domainName = Console.ReadLine()

                Console.Write("Enter the login of a user on {0} that you wish to impersonate: ", domainName)
                userName = Console.ReadLine()

                Console.Write("Enter the password for {0}: ", userName)

                Const LOGON32_PROVIDER_DEFAULT As Integer = 0
                'This parameter causes LogonUser to create a primary token.
                Const LOGON32_LOGON_INTERACTIVE As Integer = 2

                ' Call LogonUser to obtain a handle to an access token.
                Dim returnValue As Boolean = LogonUser(userName, domainName, Console.ReadLine(), LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, safeTokenHandle)

                Console.WriteLine("LogonUser called.")

                If False = returnValue Then
                    Dim ret As Integer = Marshal.GetLastWin32Error()
                    Console.WriteLine("LogonUser failed with error code : {0}", ret)
                    Throw New System.ComponentModel.Win32Exception(ret)

                    Return
                End If
                Using safeTokenHandle
                    Dim success As String
                    If returnValue Then success = "Yes" Else success = "No"
                    Console.WriteLine(("Did LogonUser succeed? " + success))
                    Console.WriteLine(("Value of Windows NT token: " + safeTokenHandle.DangerousGetHandle().ToString()))

                    ' Check the identity.
                    Console.WriteLine(("Before impersonation: " + WindowsIdentity.GetCurrent().Name))

                    ' Use the token handle returned by LogonUser.
                    Using impersonatedUser As WindowsImpersonationContext = WindowsIdentity.Impersonate(safeTokenHandle.DangerousGetHandle())

                        ' Check the identity.
                        Console.WriteLine(("After impersonation: " + WindowsIdentity.GetCurrent().Name))

                        ' Free the tokens.
                    End Using
                End Using
            Catch ex As Exception
                Console.WriteLine(("Exception occurred. " + ex.Message))
            End Try
        End Sub
    End Class
End Module

Public NotInheritable Class SafeTokenHandle
    Inherits SafeHandleZeroOrMinusOneIsInvalid

    Private Sub New()
        MyBase.New(True)

    End Sub

    Private Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As [String], _
            ByVal lpszDomain As [String], ByVal lpszPassword As [String], _
            ByVal dwLogonType As Integer, ByVal dwLogonProvider As Integer, _
            ByRef phToken As IntPtr) As Boolean
    <DllImport("kernel32.dll"), ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success), SuppressUnmanagedCodeSecurity()> _
    Private Shared Function CloseHandle(ByVal handle As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean

    End Function
    Protected Overrides Function ReleaseHandle() As Boolean
        Return CloseHandle(handle)

    End Function 'ReleaseHandle
End Class

Hinweise

Auf Windows NT-Plattformen muss der aktuelle Benutzer über ausreichende Rechte verfügen, um den Identitätswechsel zuzulassen.

Hinweis

Das Aufrufen der Impersonate(IntPtr) -Methode mit dem userToken Wert von Zero entspricht dem Aufrufen der Win32-Funktion RevertToSelf . Wenn zurzeit ein anderer Benutzer die Identität angibt, wird das Steuerelement auf den ursprünglichen Benutzer zurückgesetzt.

Weitere Informationen zu Aufrufen von nicht verwaltetem Code finden Sie unter Verwenden von nicht verwalteten DLL-Funktionen.

Warnung

Vermeiden Sie die Verwendung dieser Methode mit dem Muster async/await. In einigen Fällen kann dies zu Zuverlässigkeitsproblemen führen, da der Identitätswechsel nicht wiederhergestellt wird, selbst wenn das resultierende WindowsImpersonationContext gelöscht wird. Verwenden Sie stattdessen RunImpersonated.

Hinweise für Aufrufer

Nach der Verwendung Impersonate(IntPtr)von ist es wichtig, die Undo() -Methode aufzurufen, um den Identitätswechsel zu beenden.

Gilt für: