c#TabControl中集成加载多个窗体，通过选项卡切换窗体并绑定数据库数据源

using DXApplication5;
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;

namespace TabControlExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void checkBox1_click(object sender, EventArgs e)
        {
            CheckChanged(sender);
            if (checkBox1.Checked==true )
            {
                comboBox1.Visible = true;
                comboBox2.Visible = false;
                string sql = string.Format("select U_Name from SYS_Users");
                
                //控件名.DataSource=数据集.数据表
                //comboBox1.DataSource = DBHlelper.Query(sql).Tables[0].Rows[0]["U_Name"];
                comboBox1.DataSource = DBHlelper.Query(sql).Tables[0];
                comboBox1.DisplayMember = "U_Name";
                comboBox1.ValueMember = "U_Name";
                }
        }


        private void checkBox2_click(object sender, EventArgs e)
        {
            CheckChanged(sender);
            if (checkBox2.Checked == true)
            {
                comboBox1.Visible = false;
                comboBox2.Visible = true;
            }
        }


        private void  CheckChanged(object sender)
        {
          
            if ((sender as CheckBox).Checked==true) {
                foreach(Control chk in ( sender as CheckBox).Parent.Controls )
                {
                    if(chk != sender && chk.GetType().ToString() == "System.Windows.Forms.CheckBox")
                    {
                        ((CheckBox)chk).Checked = false;
                    }

                }
            }
        }

    }
}