how to select drop down box list in my data sheet

-------Select ---- TagIndex1 TagIndex2 TagIndex3 TagIndex4 TagIndex5 TagIndex6

TargetControlID="txtfromdate" Format="yyyy-MM-dd hh:mm:ss">

TargetControlID="txttodate" Format="yyyy-MM-dd hh:mm:ss">

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Data;

using System.Data.SqlClient;

using System.Text;

using System.Configuration;

using System.IO;

using System.Web.Services;

public partial class TagIndexdemo : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

[WebMethod]

public static ListgetChartData()

{

var returnData = new List();

var Con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["demoConnectionString2"].ConnectionString);

Con.Open();

SqlCommand cmd = new SqlCommand();

cmd.CommandType = CommandType.StoredProcedure;

cmd.CommandText = "ProCreateTagIndex ";

cmd.Connection = Con;

SqlDataAdapter adapter = new SqlDataAdapter(cmd);

DataSet ds = new DataSet();

try

{

adapter.Fill(ds);

}

catch (Exception ex)

{

throw ex;

}

finally

{

Con.Close();

Con.Dispose();

}

var chartLabel = new StringBuilder();

var chartData = new StringBuilder();

var chartData1 = new StringBuilder();

var chartData2 = new StringBuilder();

var chartData3 = new StringBuilder();

var chartData4 = new StringBuilder();

chartLabel.Append("[");

chartData.Append("[");

chartData1.Append("[");

chartData2.Append("[");

chartData3.Append("[");

chartData4.Append("[");

foreach (DataRow row in ds.Tables[0].Rows)

{

chartLabel.Append(string.Format("'{0}',", row["DateAndTime"].ToString()));

chartData.Append(string.Format("'{0}',", row["TagIndex1"].ToString()));

chartData1.Append(string.Format("'{0}',", row["TagIndex2"].ToString()));

chartData2.Append(string.Format("'{0}',", row["TagIndex3"].ToString()));

chartData3.Append(string.Format(" '{0}',", row["TagIndex4"].ToString()));

chartData4.Append(string.Format("' {0}',", row["TagIndex5"].ToString()));

}

chartData.Length--; //For removing ','

chartData.Append("]");

chartData1.Length--; //For removing ','

chartData1.Append("]");

chartData2.Length--; //For removing ','

chartData2.Append("]");

chartData3.Length--; //For removing ','

chartData3.Append("]");

chartData4.Length--; //For removing ','

chartData4.Append("]");

chartLabel.Length--; //For removing ','

chartLabel.Append("]");

returnData.Add(chartLabel.ToString());

returnData.Add(chartData.ToString());

returnData.Add(chartData1.ToString());

returnData.Add(chartData2.ToString());

returnData.Add(chartData3.ToString());

returnData.Add(chartData4.ToString());

return returnData;

}

protected void Btnsubmit_Click(object sender, EventArgs e)

{

}

}