对象未设置为类调用时的实例错误

我设置了三个模型。我不确定我是不是用了最好的方法，但这是我能很容易理解的方法。我调用DepartmentProfile类。找到的第一个用户不是管理器，因此它进入else语句，成功地填充了AD_UserProfile并将其添加到DepartmentProfile类。

第二个用户是部门经理，因此它进入if语句并在第一行出错，因为object没有设置为object的实例。我错过了什么?我没有正确设置模型吗?

出错时

public class AD_UserProfile
    {
        public string distinguishedName { get; set; }
        public string email { get; set; }
        public string manager { get; set; }
        public string name { get; set; }
        public string userPrincipalName { get; set; } // Useful if we need to allow a user to 'log on' as a different user.  
        public string userName { get; set; } 
    }
public class AD_ManagerProfile
    {
        public string distinguishedName { get; set; }
        public string email { get; set; }
        public string manager { get; set; }
        public string name { get; set; }
        public string userPrincipalName { get; set; } // Useful if we need to allow a user to 'log on' as a different user.  
        public string userName { get; set; }
    }
public class AD_DepartmentProfile
    {
        public AD_DepartmentProfile()
        {
            this.AD_UserProfile = new HashSet<AD_UserProfile>();
        }
        public string name { get; set; }
        public virtual AD_ManagerProfile AD_ManagerProfile { get; set; }
        public virtual ICollection<AD_UserProfile> AD_UserProfile { get; set; }
    }

下面是类的调用:

public void GetDepartmentInfo(string department, string owner = "jeremy")
        {
            DirectoryEntry de = new DirectoryEntry("LDAP://server.server.com");
            DirectorySearcher ds = new DirectorySearcher(de);
            ds.Filter = ("(&(objectCategory=person)(objectClass=User)(department=" + department + "))");
            ds.SearchScope = SearchScope.Subtree;
            AD_DepartmentProfile dp = new AD_DepartmentProfile();
            dp.name = department; // assign department name
            foreach (SearchResult temp in ds.FindAll())
            {
                if (owner == temp.Properties["sAMAccountName"][0].ToString())
                {
                    //Current user is manager of department
                    dp.AD_ManagerProfile.distinguishedName = temp.Properties["distinguishedName"][0].ToString();  // This line errors out with instance not set to object error.
                    dp.AD_ManagerProfile.email = temp.Properties["mail"][0].ToString();
                    dp.AD_ManagerProfile.manager = temp.Properties["manager"][0].ToString();
                    dp.AD_ManagerProfile.name = temp.Properties["name"][0].ToString();
                    dp.AD_ManagerProfile.userPrincipalName = temp.Properties["userPrincipalName"][0].ToString();
                    dp.AD_ManagerProfile.userName = temp.Properties["sAMAccountName"][0].ToString();
                }
                else
                {
                    //Current user is in department and does not manage it
                    AD_UserProfile p = new AD_UserProfile();
                    p.distinguishedName = temp.Properties["distinguishedName"][0].ToString();
                    p.email = temp.Properties["mail"][0].ToString();
                    p.manager = temp.Properties["manager"][0].ToString();
                    p.name = temp.Properties["name"][0].ToString();
                    p.userPrincipalName = temp.Properties["userPrincipalName"][0].ToString();
                    p.userName = temp.Properties["sAMAccountName"][0].ToString();
                    dp.AD_UserProfile.Add(p);
                }
            }
        }

if (owner == temp.Properties["sAMAccountName"][0].ToString())
{
    //Current user is manager of department
    dp.AD_ManagerProfile = new AD_ManagerProfile();
    dp.AD_ManagerProfile.distinguishedName = temp.Properties["distinguishedName"][0].ToString();  // This line errors out with instance not set to object error.

public AD_DepartmentProfile()
{
    this.AD_UserProfile = new HashSet<AD_UserProfile>();
    this.AD_ManagerProfile = new AD_ManagerProfile();
}