Introduction :   

Here i will explain How to bind the values into Dropdownlist in Asp.net and C# in page load. here Values will be passed to dropdownlist from DataSet.

Asp.Net Code :   

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Fourth Bottle</title>

</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="DropDownList1" AutoPostBack="false" runat="server">  </asp:DropDownList>
        
    </div>
    </form>
</body>
</html>

C# Code :       

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.Configuration;
using System.Data.SqlClient;


namespace SolutionName
{
    public partial class drop : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string Conec = ConfigurationManager.ConnectionStrings["Student"].ConnectionString;
            SqlConnection con = new SqlConnection(Conec);
            con.Open();
            SqlDataAdapter da = new SqlDataAdapter("select StudentID from StudentMarks", con);
            DataTable dt = new DataTable();
            da.Fill(dt);
            DropDownList1.DataSource = dt;
            DropDownList1.DataValueField = dt.Columns["StudentID"].ColumnName.ToString();
            DropDownList1.DataTextField = dt.Columns["StudentID"].ColumnName.ToString();
            DropDownList1.DataBind();

        }
}

}