c＃winform活动目录：如果登录成功，则访问另一个表单

这是您的代码，已编辑。

1. 验证文本框（！string.Empty）。
2. 验证凭据。
3. 根据用户类型显示所需的表单。

当您正确分割代码时，这很容易做到。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using LibXmlSettings.Settings;
using Microsoft.ApplicationBlocks.Data;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.DirectoryServices;
using System.IO;
using System.Linq.Expressions;
using System.Runtime.InteropServices;

using System.DirectoryServices.AccountManagement;

namespace GestionnaireDesPlugins
{
    public partial class Login : Form
    {
        public Login(string accountName, string accountPassword)
        {
            InitializeComponent();
        }

        private void LoginOnClick(object sender, EventArgs e)
        {
            if (IsValid())
            {
                GetUser();
                // Do whatever you want
                ShowForm();
            }
        }

        private void GetUser()
        {
            try 
            {            
                LdapConnection connection = new LdapConnection("AD");
                NetworkCredential credential = new NetworkCredential(txtboxlogin.Text, txtboxpass.Text);
                connection.Credential = credential;
                connection.Bind();
            }
            catch (LdapException lexc)
            {
                String error = lexc.ServerErrorMessage;
                MessageBox.Show("error account or password.");
            }
            catch (Exception exc)
            {
                MessageBox.Show(exc.ToString());
            }
        }

        private bool IsValid()
        {
            // Check if the user haven't chosen an account
            if (!string.IsNullOrEmpty(txtboxlogin.Text) { return false; }

            // Check if the user haven't chosen an account
            if (!string.IsNullOrEmpty(txtboxpass.Text)) { return false; }

            // Check if the user haven't chosen an account
            if (!string.IsNullOrEmpty(comboBox1.Text)) { return false; }

            // Check if the password TextBox is empty
            if (!string.IsNullOrEmpty(textBox1.Text)) { return false; }
            using(PrincipalContext pc = new PrincipalContext(ContextType.Domain, "YOURDOMAIN"))
            {
                // validate the credentials
                bool isValid = pc.ValidateCredentials(txtboxlogin.Text, txtboxpass.Text);
            }
            return isValid;
        }

        private void ShowForm()
        {
            if (txtboxlogin.Text == "WantedAdminUser")
            {
                using (AdminForm form2 = new AdminForm())
                   form2.ShowDialog();
                Show(); 
            }
            else
            {
                using (user userform = new user())
                    userform.ShowDialog();
                Show();
            }
        }
    }
}

如前所述，由于您是C＃的新手，因此这里有一些建议：

1. 拆分您的代码：方法必须简短且按目的分开。对于您和任何使用您的代码的人来说，这都更加容易
2. 管理例外
3. 处置物体
4. 请注意，这txtboxlogin.Text == "WantedAdminUser"很危险。