如何在c# windows窗体中使用n层体系结构使用数据库值填充组合框

using System.Data;
using System.Data.SqlClient;

namespace YourNamespace
{
    public class DataAccessLayer
    {
        public DataTable GetComboBoxData()
        {
            // 连接数据库
            using (SqlConnection connection = new SqlConnection("YourConnectionString"))
            {
                connection.Open();

                // 执行查询语句
                SqlCommand command = new SqlCommand("SELECT Id, Name FROM YourTable", connection);
                SqlDataReader reader = command.ExecuteReader();

                // 将查询结果填充到数据表中
                DataTable dataTable = new DataTable();
                dataTable.Load(reader);

                return dataTable;
            }
        }
    }
}

using System.Data;

namespace YourNamespace
{
    public class BusinessLogicLayer
    {
        private DataAccessLayer dataAccessLayer;

        public BusinessLogicLayer()
        {
            dataAccessLayer = new DataAccessLayer();
        }

        public DataTable GetComboBoxData()
        {
            // 调用DAL中的方法来检索数据
            return dataAccessLayer.GetComboBoxData();
        }
    }
}

using System;
using System.Windows.Forms;

namespace YourNamespace
{
    public partial class Form1 : Form
    {
        private BusinessLogicLayer businessLogicLayer;

        public Form1()
        {
            InitializeComponent();
            businessLogicLayer = new BusinessLogicLayer();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // 在窗体加载时，调用BLL中的方法来检索数据，并将其填充到组合框中
            comboBox1.DataSource = businessLogicLayer.GetComboBoxData();
            comboBox1.DisplayMember = "Name";
            comboBox1.ValueMember = "Id";
        }
    }
}