C# 如何在组合框中显示多个项目？

我试图在combobox中显示多个项目，但在C winform中显示错误和代码不可读

我的班级

       using System;
       using System.Collections.Generic;
       using System.Linq;
       using System.Text;
       using System.Threading.Tasks;

      namespace Booking_Management
      {
          public class classcombobox
      {
          public string EmployeeID { get; set; }
          public string FullName { get; set; }
          public string symbol { get; set; }
          public classcombobox(string EmployeeID, string FullName)
      {
        this.EmployeeID = EmployeeID;
        this.FullName = FullName;
      }
    }
  }

然后我将其添加到winform代码编辑器中的combobox中

    private void loadstaff()
    {
        string staff = "select EmployeeID, Name, Surname from tb_employee";
        DataTable dt = ClassConnection.DataParent(staff, "tbname");
        if (dt.Rows.Count > 0)
        {
            foreach (DataRow item in dt.Rows)
            {
                cmbeid.Properties.Items.Clear();
                for (int i = 0; i < dt.Rows.Count; i++)
                {

                    List<classcombobox> cmb = new List<classcombobox>();

                    //adding item from tabble to combobox                        
                    cmb.Add(new classcombobox(dt.Rows[i][0], dt.Rows[i][1] + dt.Rows[i][2])); /// Can not read. I don't know why? 

                     //use DevExpress ComboboxEdit
                    cmbeid.Properties.ItemSource = cmb; // itemsource unreadable by the system

                    //Try in System comboBox
                    comboBoxitem.ItemSource = cmb; //this the system also can not read 

                }
            }
        }
    }

有人能帮我吗

我需要在combobox中显示，当用户鼠标单击下拉的combobox时，它包含两列，如col_EmployeeID和col_fullname。

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这个源代码可能与我的目标匹配吗？

我想你可能想考虑使用一个列表框控件。