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

对我来说，这两个下面的工作，确保你的域名是LDAP://在开始

//"LDAP://" + domainName
private void btnValidate_Click(object sender, RoutedEventArgs e)
{
    try
    {
        DirectoryEntry de = new DirectoryEntry(txtDomainName.Text, txtUsername.Text, txtPassword.Text);
        DirectorySearcher dsearch = new DirectorySearcher(de);
        SearchResult results = null;

        results = dsearch.FindOne();

        MessageBox.Show("Validation Success.");
    }
    catch (LdapException ex)
    {
        MessageBox.Show($"Validation Failure. {ex.GetBaseException().Message}");
    }
    catch (Exception ex)
    {
        MessageBox.Show($"Validation Failure. {ex.GetBaseException().Message}");
    }
}

private void btnValidate2_Click(object sender, RoutedEventArgs e)
{
    try
    {
        LdapConnection lcon = new LdapConnection(new LdapDirectoryIdentifier((string)null, false, false));
        NetworkCredential nc = new NetworkCredential(txtUsername.Text,
                               txtPassword.Text, txtDomainName.Text);
        lcon.Credential = nc;
        lcon.AuthType = AuthType.Negotiate;
        lcon.Bind(nc);

        MessageBox.Show("Validation Success.");
    }
    catch (LdapException ex)
    {
        MessageBox.Show($"Validation Failure. {ex.GetBaseException().Message}");
    }
    catch (Exception ex)
    {
        MessageBox.Show($"Validation Failure. {ex.GetBaseException().Message}");
    }
}

Windows身份验证失败的原因有很多:用户名或密码不正确、帐户被锁定、密码过期等等。为了区分这些错误，通过P/Invoke调用LogonUser API函数，如果函数返回false，检查错误代码:

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

using Microsoft.Win32.SafeHandles;

public static class Win32Authentication
{
    private class SafeTokenHandle : SafeHandleZeroOrMinusOneIsInvalid
    {
        private SafeTokenHandle() // called by P/Invoke
            : base(true)
        {
        }

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

    private enum LogonType : uint
    {
        Network = 3, // LOGON32_LOGON_NETWORK
    }

    private enum LogonProvider : uint
    {
        WinNT50 = 3, // LOGON32_PROVIDER_WINNT50
    }

    [DllImport("kernel32.dll", SetLastError = true)]
    private static extern bool CloseHandle(IntPtr handle);

    [DllImport("advapi32.dll", SetLastError = true)]
    private static extern bool LogonUser(
        string userName, string domain, string password,
        LogonType logonType, LogonProvider logonProvider,
        out SafeTokenHandle token);

    public static void AuthenticateUser(string userName, string password)
    {
        string domain = null;
        string[] parts = userName.Split('\\');
        if (parts.Length == 2)
        {
            domain = parts[0];
            userName = parts[1];
        }

        SafeTokenHandle token;
        if (LogonUser(userName, domain, password, LogonType.Network, LogonProvider.WinNT50, out token))
            token.Dispose();
        else
            throw new Win32Exception(); // calls Marshal.GetLastWin32Error()
    }
}

示例用法:

try
{
    Win32Authentication.AuthenticateUser("EXAMPLE\\user", "P@ssw0rd");
    // Or: Win32Authentication.AuthenticateUser("user@example.com", "P@ssw0rd");
}
catch (Win32Exception ex)
{
    switch (ex.NativeErrorCode)
    {
        case 1326: // ERROR_LOGON_FAILURE (incorrect user name or password)
            // ...
        case 1327: // ERROR_ACCOUNT_RESTRICTION
            // ...
        case 1330: // ERROR_PASSWORD_EXPIRED
            // ...
        case 1331: // ERROR_ACCOUNT_DISABLED
            // ...
        case 1907: // ERROR_PASSWORD_MUST_CHANGE
            // ...
        case 1909: // ERROR_ACCOUNT_LOCKED_OUT
            // ...
        default: // Other
            break;
    }
}

注意:LogonUser需要与您验证的域建立信任关系。

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!)

另一个.NET调用用于快速验证LDAP凭据:

using System.DirectoryServices;

using(var DE = new DirectoryEntry(path, username, password)
{
    try
    {
        DE.RefreshCache(); // This will force credentials validation
    }
    catch (COMException ex)
    {
        // Validation failed - handle how you want
    }
}