C# 中对Excel的一些操作解释？

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;

namespace ExcelExport
{
    class Program
    {
        static void Main(string[] args)
        {
            ExportDataToExcel("Provider=SQLOLEDB.1;sever=localhost;uid=sa;password=271121;database=master;",
                    "select * from sysobjects", @"d:\11-12-1.xls", "sysobjects");

        }
         /// <summary>
        /// 直接导出数据到excel
        /// </summary>
        /// <param name="connectionString">连接字符串</param>
        /// <param name="sql">查询语句</param>
        /// <param name="fileName">文件名</param>
        /// <param name="sheetName">表名</param>

        static void ExportDataToExcel(string connectionString, string sql, string fileName, string sheetName)
        {
            Excel._Application app = new Excel.ApplicationClass();
            Excel.Workbook wb = (Excel.WorkbookClass)app.Workbooks.Add(Missing.Value);
            Excel.Worksheet ws = wb.Worksheets.Add(Missing.Value, Missing.Value, Missing.Value, Missing.Value) as Excel.Worksheet;
            ws.Name = sheetName;
            try
            {
                Excel.QueryTable qt = ws.QueryTables.Add("OLEDB;" + connectionString,
                    ws.get_Range("A1", Missing.Value), sql);
                qt.Refresh(false);//是否异步查询
            }
            catch (Exception ex)
            {
                string str = ex.Message;
            }
            finally
            {
                wb.Saved = true;
                wb.SaveCopyAs(fileName);//保存
                app.Quit();//关闭进程
            }

        }

    }
}
麻烦给我解释一下那个函数里面的语句，谢谢
（菜） --------------------编程问答-------------------- 这有啥好解释的啊！OLEDB 去查询excel啊

补充：.NET技术 ,  C#

C# 中对Excel的一些操作 解释？

C# 中对Excel的一些操作解释？