export table sql to .txt with c# - sql

Question

I think I have a fairly simple question. I just need to know how to export fields from a table in an sql database using either asp.net or C#? Anyway to do this would be good.
I suppose I am looking for something like this, but perhaps simpler:
Export values from SQL Server to txt file
Whatever the case, I am trying to get values from a database to a .txt, like by pressing a button in asp.net or C#, based on criteria (like between certain dates, from a date field, or starting at a certain date with a certain user, and exporting a certain number of them). Any suggestions would help.
If I used the following code, what would I need to change so that if I wanted to select a certain column, like Note, in the database, and Date column, what would I need to do?
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
public partial class ExportText : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["MYLearningConnectionString"].ConnectionString);
conn.Open();
SqlDataAdapter da = new SqlDataAdapter("select * from tblUsers", conn);
DataSet ds = new DataSet();
da.Fill(ds);
ExportToText(ds.Tables[0], "DataTable");
}
protected void ExportToText(DataTable dataTable, string fileName)
{
HttpContext context = HttpContext.Current;
context.Response.Clear();
foreach (DataColumn column in dataTable.Columns)
{
context.Response.Write(column.ColumnName + ",");
}
context.Response.Write(Environment.NewLine);
foreach (DataRow row in dataTable.Rows)
{
for (int i = 0; i < dataTable.Columns.Count; i++)
{
context.Response.Write(row[i].ToString() + ",");
}
context.Response.Write(Environment.NewLine);
}
context.Response.ContentType = "text/csv";
context.Response.AppendHeader("Content-Disposition", "attachment; filename=" + fileName + ".txt");
context.Response.End();
}
}