C# - 列出 Active Directory 中的所有用戶帳戶時出錯

Question

我正在嘗試使用 Windows 表單列出 Active Directory 中所有基於用戶的帳戶的一些基本詳細信息（帶有基於帳戶是否啟用/禁用的自定義圖標）。 運行時，我收到此初始錯誤，並留下第二個屏幕截圖：

出於某種原因，該圖標位於第一列而不是第四列，我最終只有一個帳戶。 我的代碼：

try
{
    var domainName = System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().DomainName;
    MessageBox.Show(domainName);

    using (var context = new PrincipalContext(ContextType.Domain, domainName))
    {
        using (var searcher = new PrincipalSearcher(new UserPrincipal(context)))
        {
            foreach (var result in searcher.FindAll())
            {
                ListViewItem tmpItem = null;

                DirectoryEntry child = result.GetUnderlyingObject() as DirectoryEntry;
                switch (child.SchemaClassName)
                {
                    case "user":
                        int flag = (int)child.Properties["userAccountControl"].Value;
                        bool disabled = Convert.ToBoolean(flag & 0x0002);

                        if (disabled == false)
                        {
                            tmpItem = new ListViewItem(new string[] {
                                (string)child.Properties["givenName"].Value,
                                (string)child.Properties["sn"].Value,
                                (string)child.Properties["samAccountName"].Value
                                }, (int)AdImages.User);
                            this.listView_ad.Items.Add(tmpItem);
                        }
                        else
                        {
                            tmpItem = new ListViewItem(new string[] {
                                (string)child.Properties["givenName"].Value,
                                (string)child.Properties["sn"].Value,
                                (string)child.Properties["samAccountName"].Value
                                }, (int)AdImages.block);
                            this.listView_ad.Items.Add(tmpItem);
                        }
                    break;

                    case "organizationalUnit":
                        break;

                    case "container":
                        break;

                    case "computer":
                        break;

                    case "group":
                        break;

                    default:
                        break;
                }
            }
        }
    }
}
catch (Exception e)
{
    MessageBox.Show("ERROR : " + e, "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning);
}

編輯：刪除 try / catch 以獲得完整錯誤：

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at ComputeamPasswordManager.PasswordManager.getUsers()
   at ComputeamPasswordManager.PasswordManager.PasswordManager_Load(Object sender, EventArgs e)
   at System.Windows.Forms.Form.OnLoad(EventArgs e)
   at System.Windows.Forms.Form.OnCreateControl()
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl()
   at System.Windows.Forms.Control.WmShowWindow(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmShowWindow(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

編輯 2：在域設備上運行的 Visual Studio 的屏幕截圖...

Answer 1

嘗試改變這個（和類似的表達）：

(string)child.Properties["givenName"].Value

像這樣：

(string)child.Properties["givenName"]?.Value ?? ""

Answer 2

我需要做的就是以管理員身份運行 Visual Studio！