如何在单击按钮时创建用于选择目的地的浏览窗口

我有一个简单的按钮从MySQL导出数据库表到excel文件。到目前为止，它的目标是硬编码到C:/drive。当你按下导出按钮，你得到excel文件自动导出到C:没有用户能够看到它。下面是代码:

//button for Exporting to Excel (.xls)
    //hardcoded destination to C:/
    protected void Button2_Click(object sender, EventArgs e)
    {
        try
        {
            string connectionString = "server=localhost; UserId=root; database=dbcss; ";
            MySqlConnection con = new MySqlConnection(connectionString);
            con.Open();
            string getProject = ddlProjectID.SelectedValue; //get the already selected project from the dropdown menu
            //create sql command object
            string cmdText = "SELECT 'activity_id', 'activity_name', 'wbs_no', 'activity_status', 'wbs_name', 'sequence', 'pad', 'project_id', 'start_date', 'finish_date' INTO OUTFILE 'C://TASK.xls' FROM management WHERE project_id = '" + getProject + "';";
            MySqlCommand cmd = new MySqlCommand(cmdText, con);
            cmd.ExecuteNonQuery();
            con.Close();
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
    }

我怎么做一个窗口弹出，你可以浏览你的电脑和选择目的地?

任何帮助将不胜感激谢谢,)