Fire Select Query and populate GridView witth TextBox in ASP.Net

Html Code

<div>
        <asp:GridView ID="gvAttendences" runat="server" AutoGenerateColumns="false">
            <Columns>
                <asp:BoundField DataField="Std_id" HeaderText="Student Id" />
                <asp:BoundField DataField="StudentName" HeaderText="Name" />
                <asp:BoundField DataField="RollNo" HeaderText="Roll No" />
                <asp:BoundField DataField="AttendenceStatus" HeaderText="Attendence" />
                <asp:BoundField DataField="AttendenceDate" HeaderText="Date" DataFormatString="{0:dd/MM/yyyy}" />
            </Columns>
        </asp:GridView>
        <br />
        <br />
        <asp:TextBox ID="txtDate" runat="server"></asp:TextBox><span>&nbsp;Date Format: yyyy-MM-dd</span>
        <br />
        <br />
        <asp:Button ID="btnShowAttendences" runat="server" Text="Show Attendence" OnClick="ShowAttendences" />
    </div>

Code

 protected void ShowAttendences(object sender, EventArgs e)
    {
        this.gvAttendences.DataSource = this.GetData(this.txtDate.Text.Trim(), "Present");
        this.gvAttendences.DataBind();
    }

    private DataSet GetData(string date, string attendenceStatus)
    {       
        string connection = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
        using (SqlConnection con = new SqlConnection(connection))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT * FROM Table_Attendance WHERE AttendenceDate = @AttendenceDate AND AttendenceStatus = @AttendenceStatus", con))
            {
                cmd.Parameters.AddWithValue("@AttendenceDate", date);
                cmd.Parameters.AddWithValue("@AttendenceStatus", attendenceStatus);
                using (SqlDataAdapter da = new SqlDataAdapter())
                {
                    da.SelectCommand = cmd;
                    using (DataSet ds = new DataSet())
                    {
                        da.Fill(ds);
                        return ds;
                    }
                }
            }
        }
    }

Namespaces

using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;