以下是一个使用ASP.NET Core和Novell.Directory.Ldap.NETStandard库连接到Active Directory的代码示例：

1. 首先，确保您的项目已经引用了Novell.Directory.Ldap.NETStandard库。您可以通过NuGet包管理器或使用dotnet命令行工具来安装该库。

2. 在您的ASP.NET Core项目中，创建一个名为ActiveDirectoryService的类，用于处理与Active Directory的连接和查询。在该类中，添加以下代码：

using Novell.Directory.Ldap;

public class ActiveDirectoryService
{
    private readonly string _adServer;
    private readonly int _adPort;
    private readonly string _adUsername;
    private readonly string _adPassword;

    public ActiveDirectoryService(string adServer, int adPort, string adUsername, string adPassword)
    {
        _adServer = adServer;
        _adPort = adPort;
        _adUsername = adUsername;
        _adPassword = adPassword;
    }

    public void ConnectAndQueryActiveDirectory()
    {
        using (var connection = new LdapConnection())
        {
            connection.Connect(_adServer, _adPort);
            connection.Bind(_adUsername, _adPassword);

            // 查询Active Directory的示例代码
            var searchBase = "DC=yourdomain,DC=com";
            var searchFilter = "(objectClass=user)";
            var searchScope = LdapConnection.SCOPE_SUB;
            var attributesToReturn = null; // 返回所有属性

            var searchRequest = new LdapSearchRequest(searchBase, searchFilter, searchScope, attributesToReturn);
            var searchResponse = (LdapSearchResponse)connection.SendRequest(searchRequest);

            foreach (LdapEntry entry in searchResponse.Entries)
            {
                // 处理查询结果的代码
                var username = entry.GetAttribute("samaccountname").StringValue;
                var email = entry.GetAttribute("mail").StringValue;

                // 输出查询结果的示例代码
                Console.WriteLine($"Username: {username}, Email: {email}");
            }
        }
    }
}

3. 在您的控制器类中，可以使用ActiveDirectoryService类来连接和查询Active Directory。例如，创建一个名为ActiveDirectoryController的控制器类，添加以下代码：

[ApiController]
[Route("[controller]")]
public class ActiveDirectoryController : ControllerBase
{
    private readonly ActiveDirectoryService _adService;

    public ActiveDirectoryController(ActiveDirectoryService adService)
    {
        _adService = adService;
    }

    [HttpGet]
    public IActionResult GetActiveDirectoryUsers()
    {
        _adService.ConnectAndQueryActiveDirectory();
        
        return Ok();
    }
}

4. 在Startup.cs文件中，将ActiveDirectoryService类注入到DI容器中。在ConfigureServices方法中添加以下代码：

services.AddSingleton(provider =>
{
    // 从配置文件中读取Active Directory的连接参数
    var adServer = Configuration["ActiveDirectory:Server"];
    var adPort = Int32.Parse(Configuration["ActiveDirectory:Port"]);
    var adUsername = Configuration["ActiveDirectory:Username"];
    var adPassword = Configuration["ActiveDirectory:Password"];

    return new ActiveDirectoryService(adServer, adPort, adUsername, adPassword);
});

5. 在appsettings.json文件中，添加Active Directory的连接参数配置。例如：

"ActiveDirectory": {
    "Server": "yourdomain.com",
    "Port": 389,
    "Username": "yourusername",
    "Password": "yourpassword"
}

现在，您可以访问ActiveDirectoryController的GetActiveDirectoryUsers方法来连接和查询Active Directory。例如，使用浏览器访问http://localhost:5000/ActiveDirectory，您将看到查询结果输出在控制台中。

请注意，上述代码示例仅供参考，您可能需要根据您的具体需求进行适当的调整和修改。