如何使用c#获取active directory用户的不可变ID

using System.DirectoryServices;
using System.DirectoryServices.AccountManagement;

using (PrincipalContext context = new PrincipalContext(ContextType.Domain))
{
    // 在这里执行操作
}

using (PrincipalContext context = new PrincipalContext(ContextType.Domain))
{
    UserPrincipal user = UserPrincipal.FindByIdentity(context, IdentityType.SamAccountName, "用户名");
    if (user != null)
    {
        // 在这里执行操作
    }
}

using (PrincipalContext context = new PrincipalContext(ContextType.Domain))
{
    UserPrincipal user = UserPrincipal.FindByIdentity(context, IdentityType.SamAccountName, "用户名");
    if (user != null)
    {
        string immutableId = user.GetUnderlyingObject().Properties["msDS-ImmutableId"].Value.ToString();
        // 在这里执行操作
    }
}