How to write event for dropdownlist to fill grid view in asp.net

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C#

Visual-Studio

Gridview

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Can anyone please help me out how to fill grid view based on dropdownlist value. Iam new to dotnet
my program:

Design Page:

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">

<table>
<tr>
<td>Empno: </td> <td></td>
<td>
    <asp:DropDownList ID="emplist" runat="server" DataSourceID="emplist1" 
        DataTextField="empCode" DataValueField="empCode">
    </asp:DropDownList>
    <asp:SqlDataSource ID="emplist1" runat="server" 
        ConnectionString="<%$ ConnectionStrings:euroTransConnectionString3 %>" 
        SelectCommand="SELECT DISTINCT [empCode] FROM [eurEvents_activity]">
    </asp:SqlDataSource>
    </td>
    <td></td>
  <td>
 
    <asp:DropDownList ID="atddroplist" runat="server" AutoPostBack="true">
        
        <asp:ListItem Selected="True" Value="1">Current Week</asp:ListItem>
        <asp:ListItem Value="2">Last Week</asp:ListItem>
        <asp:ListItem Value="3">Current Month</asp:ListItem>
        <asp:ListItem Value="4">Last Month</asp:ListItem>
        <asp:ListItem Value="5">Custom</asp:ListItem>
    </asp:DropDownList>

    </td>
    </tr>
    </table>
    <br />
    <asp:GridView ID="GridView1" AutoGenerateColumns="False"  runat="server">
    <Columns>

        <asp:BoundField DataField="EmpCode" HeaderText="EmpCode" />

        <asp:BoundField DataField="EventDate" HeaderText="EventDate" />

        <asp:BoundField DataField="InTime" HeaderText="InTime" />

        <asp:BoundField DataField="OutTime" HeaderText="OutTime" />

        </Columns>
    </asp:GridView>

   
</asp:Content>

My Business logic is:

namespace empatdList
{
    public class empatdListBI
    {
        # region Local Variables

        DbConnection connection = new DbConnection();

        DataTable tempData;
        // DataSet tempData1;
        SqlCommand command;
        SqlDataAdapter adapter;

        # endregion

        public DataTable LoadRecords(string empcode)
        {
            //This function used to Load QueryReport for the respective Fields
            try
            {
                command = new SqlCommand("sp_InOutDetails_LastMonth");
                command.CommandType = CommandType.StoredProcedure;
                command.Parameters.Add("@EmpCode", SqlDbType.VarChar).Value = empcode;
                

                adapter = new SqlDataAdapter(command);
                tempData = new DataTable();
                //tempData1 = new DataSet();
                command.Connection = connection.OpenConnection();
                adapter.Fill(tempData);
                command.ExecuteNonQuery();
            }

            catch (System.Data.SqlClient.SqlException ex)
            {
                HttpContext.Current.Session["Error"] = ex;

            }

            finally
            {
                connection.CloseConnection();
            }

            return tempData;

        }
    }
}

My source code is:

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;

namespace empatdList
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                binddropdown();
            }
        }

        protected void binddropdown()
        {
            empatdListBI c = new empatdListBI();
            DbConnection b = new DbConnection();
            SqlDataAdapter da = new SqlDataAdapter();
            DataTable dt = new DataTable();
            DataSet ds = new DataSet();
            b.OpenConnection();
            dt = c.LoadRecords(emplist.Text);

            GridView1.DataSource = dt;
            GridView1.DataBind();
            b.CloseConnection();
        }




    }
}

I had kept database connection in separate class. Please help me out where i am making mistake