想ACCESS数据库插入新的用户

  public string AddUserN = ""; //定义用户名字符串
         public string paswrd1 = "";  //密码1
         public string paswrd2 = "";  //确认密码
         public string userKind = ""; //用户类型
         public string myconnstr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=ErLake.mdb";

         private void 添加用户frm_Load(object sender, EventArgs e)
         {

             loadtable();

         }

         private void button1_Click(object sender, EventArgs e)
         {
             userKind = comboBox1.Text.ToString();//获取用户类型
             //MessageBox.Show(userKind);
             AddUserN = textBox1.Text.Trim();
             paswrd1 = textBox2.Text.Trim();
             paswrd2 = textBox3.Text.Trim();
             if (userKind == "")
             {
                 MessageBox.Show("请选择添加的用户类型", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
             }
             else
             {

                 if (AddUserN == "")
                 {
                     MessageBox.Show("请填写用户名", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                 }
                 else
                 {
                     string sql = "Select count(*) from tb_admin where 用户名='" + AddUserN + "'";//查询表里用户名为输入用户名的条数（有几条数据）
                     OleDbConnection myconn = new OleDbConnection(myconnstr);
                     //打开数据库
                     myconn.Open();
                     //执行SQL
                     OleDbCommand commd = new OleDbCommand(sql, myconn);//

                     int n = (int)commd.ExecuteScalar();//得到条数
                     myconn.Close();//关闭

                     if (n >= )//存在
                     {
                         MessageBox.Show("该用户已存在！", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                     }
                     else
                     {
                         if (paswrd1 == "")
                         {
                             MessageBox.Show("请填写用户密码", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                         }
                         else
                         {

                             if (paswrd2 == "")
                             {
                                 MessageBox.Show("请填写确认的用户密码", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                             }
                             else
                             {
                                 if (paswrd1 == paswrd2)
                                 {
                                     //插入字符串
                                     string mySQL = "insert into tb_admin (用户名,权限,密码) values ('" + AddUserN + "','" + userKind + "','" + paswrd2 + "')";
                                     //创建连接实例
                                     OleDbConnection myconn1 = new OleDbConnection(myconnstr);
                                     //打开数据库
                                     myconn1.Open();
                                     //执行SQL
                                     OleDbCommand commd1 = new OleDbCommand(mySQL, myconn1);//
                                     //写入
                                     commd1.ExecuteNonQuery();
                                     //命令关闭连接
                                     commd1.Connection.Close();
                                     //数据库关闭连接
                                     myconn1.Close();
                                     //
                                     MessageBox.Show("增加用户成功", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);

                                     loadtable();//加载用户信息表

                                 }
                                 else
                                 {
                                     MessageBox.Show("密码填写不一致，请重新填写", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                                 }
                             }
                         }
                     }
                 }
             }
         }

         public void loadtable()
         {
             DataTable mytableall = new DataTable();
             string mysqlall = "select * from tb_admin ";
             OleDbDataAdapter da = new OleDbDataAdapter(mysqlall, myconnstr);//数据适配器
             da.Fill(mytableall);//填表
             dataGridView1.DataSource = mytableall;
         }