SqlConnection con = new SqlConnection(ConnStr);
string strQuery = "select  EmpName,ID from emp where Id>100";

 SqlDataAdapter ada = new SqlDataAdapter(strQuery, con);
 DataSet lds = new DataSet();
 ada.Fill(lds);

ddlname.DataSource = lds;
ddlname.DataTextField = "Empname"
ddlname.DataValueField = "Id"
ddlname.DataBind();
ddlName.Items.Insert(0, "-Select-");
        

using System;
using System.Data;
using System.Configuration;
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 _Default : System.Web.UI.Page 
{

    protected void Page_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection("Give your connection string here");
        string SQLQuery= "select  categoryID,ID from categorymaster";
        SqlDataAdapter ads = new SqlDataAdapter(SQLQuery, con);
 DataSet ds = new DataSet();
 ads.Fill(ds);
DropDownList1.DataSource = ds;
DropDownList1.DataTextField = "categoryID";
DropDownList1.DataValueField = "Id";
DropDownList1.DataBind();
    }
}