试试这段代码 (注意:报告不能在windows server 2000上工作)

#region NTLogonUser
#region Direct OS LogonUser Code
[DllImport( "advapi32.dll")]
private static extern bool LogonUser(String lpszUsername, 
    String lpszDomain, String lpszPassword, int dwLogonType, 
    int dwLogonProvider, out int phToken);

[DllImport("Kernel32.dll")]
private static extern int GetLastError();

public static bool LogOnXP(String sDomain, String sUser, String sPassword)
{
   int token1, ret;
   int attmpts = 0;

   bool LoggedOn = false;

   while (!LoggedOn && attmpts < 2)
   {
      LoggedOn= LogonUser(sUser, sDomain, sPassword, 3, 0, out token1);
      if (LoggedOn) return (true);
      else
      {
         switch (ret = GetLastError())
         {
            case (126): ; 
               if (attmpts++ > 2)
                  throw new LogonException(
                      "Specified module could not be found. error code: " + 
                      ret.ToString());
               break;

            case (1314): 
               throw new LogonException(
                  "Specified module could not be found. error code: " + 
                      ret.ToString());

            case (1326): 
               // edited out based on comment
               //  throw new LogonException(
               //   "Unknown user name or bad password.");
            return false;

            default: 
               throw new LogonException(
                  "Unexpected Logon Failure. Contact Administrator");
              }
          }
       }
   return(false);
}
#endregion Direct Logon Code
#endregion NTLogonUser

除非你需要为“LogonException”创建自己的自定义异常

使用DirectoryServices非常简单的解决方案:

using System.DirectoryServices;

//srvr = ldap server, e.g. LDAP://domain.com
//usr = user name
//pwd = user password
public bool IsAuthenticated(string srvr, string usr, string pwd)
{
    bool authenticated = false;

    try
    {
        DirectoryEntry entry = new DirectoryEntry(srvr, usr, pwd);
        object nativeObject = entry.NativeObject;
        authenticated = true;
    }
    catch (DirectoryServicesCOMException cex)
    {
        //not authenticated; reason why is in cex
    }
    catch (Exception ex)
    {
        //not authenticated due to some other exception [this is optional]
    }

    return authenticated;
}

需要NativeObject访问来检测坏的用户/密码

我们在内部网做这些

你必须使用System.DirectoryServices;

下面是代码的核心部分

using (DirectoryEntry adsEntry = new DirectoryEntry(path, strAccountId, strPassword))
{
    using (DirectorySearcher adsSearcher = new DirectorySearcher(adsEntry))
    {
        //adsSearcher.Filter = "(&(objectClass=user)(objectCategory=person))";
        adsSearcher.Filter = "(sAMAccountName=" + strAccountId + ")";

        try
        {
            SearchResult adsSearchResult = adsSearcher.FindOne();
            bSucceeded = true;

            strAuthenticatedBy = "Active Directory";
            strError = "User has been authenticated by Active Directory.";
        }
        catch (Exception ex)
        {
            // Failed to authenticate. Most likely it is caused by unknown user
            // id or bad strPassword.
            strError = ex.Message;
        }
        finally
        {
            adsEntry.Close();
        }
    }
}

如果你使用的是。net 3.5或更新版本，你可以使用System.DirectoryServices.AccountManagement命名空间轻松验证你的凭证:

// create a "principal context" - e.g. your domain (could be machine, too)
using(PrincipalContext pc = new PrincipalContext(ContextType.Domain, "YOURDOMAIN"))
{
    // validate the credentials
    bool isValid = pc.ValidateCredentials("myuser", "mypassword");
}

它简单，可靠，在你的端是100%的c#托管代码——你还能要求什么呢?: -)

在这里阅读所有内容:

在.NET Framework 3.5中管理目录安全主体 System.DirectoryServices.AccountManagement上的MSDN文档

更新:

正如在另一个SO问题(及其答案)中概述的那样，对于用户的旧密码，这个调用可能会返回True。只是要注意这种行为，如果发生这种情况不要太惊讶:-)(感谢@MikeGledhill指出这一点!)

不幸的是，没有“简单”的方法来检查AD上的用户凭据。

使用到目前为止所介绍的每一种方法，你可能会得到一个假阴性:用户的信用将是有效的，但AD在某些情况下将返回false:

用户需要在下次登录时更改密码。 用户密码已过期。

ActiveDirectory不允许您使用LDAP来确定密码是否由于用户必须更改密码或密码是否过期而无效。

要确定密码更改或密码过期，您可以调用Win32:LogonUser()，并检查以下2个常量的windows错误码:

Error_password_must_change = 1907 Error_password_expired = 1330

如果你被。net 2.0和托管代码困住了，这里有另一种处理本地和域帐户的方法:

using System;
using System.Collections.Generic;
using System.Text;
using System.Security;
using System.Diagnostics;

static public bool Validate(string domain, string username, string password)
{
    try
    {
        Process proc = new Process();
        proc.StartInfo = new ProcessStartInfo()
        {
            FileName = "no_matter.xyz",
            CreateNoWindow = true,
            WindowStyle = ProcessWindowStyle.Hidden,
            WorkingDirectory = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData),
            UseShellExecute = false,
            RedirectStandardError = true,
            RedirectStandardOutput = true,
            RedirectStandardInput = true,
            LoadUserProfile = true,
            Domain = String.IsNullOrEmpty(domain) ? "" : domain,
            UserName = username,
            Password = Credentials.ToSecureString(password)
        };
        proc.Start();
        proc.WaitForExit();
    }
    catch (System.ComponentModel.Win32Exception ex)
    {
        switch (ex.NativeErrorCode)
        {
            case 1326: return false;
            case 2: return true;
            default: throw ex;
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }

    return false;
}