Hi irshad123,

Check this example. Now please take its reference and correct your code.

HTML

<asp:Repeater ID="rptStudents" runat="server">
    <HeaderTemplate>
        <table id="tblStudents" class="table table-bordered" border="1" cellpadding="1"
            cellspacing="1" style="border-style: solid; border-width: thin; text-align: center;">
            <thead>
                <tr>
                    <th class="thright">StudentID</th>
                    <th class="thright">ispresnt1 </th>
                    <th class="thright">ispresent2</th>
                    <th class="thright">absent </th>
                    <th class="thright">notes</th>
                </tr>
            </thead>
    </HeaderTemplate>
    <ItemTemplate>
        <tbody>
            <tr>
                <td><asp:Label ID="lblCustomerId" runat="server" Text='<%# Eval("Id") %>' /></td>
                <td><asp:CheckBox ID="chkIspresent1" runat="server" CssClass="checkbox" Checked="true" /></td>
                <td><asp:CheckBox ID="chkIspresent2" runat="server" CssClass="checkbox" Checked="true" /></td>
                <td><asp:CheckBox runat="server" CssClass="checkbox" ID="chkIsAbsent" /></td>
                <td><asp:TextBox ID="txtNotes" runat="server"></asp:TextBox></td>
            </tr>
        </tbody>
    </ItemTemplate>
    <FooterTemplate>
        </table>
    </FooterTemplate>
</asp:Repeater>
<asp:Button ID="Button1" runat="server" Text="Save" OnClick="Button1_Click" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $("[id*=chkIsAbsent]").click(function () {
            if ($(this).is(":checked")) {
                $(this).closest("tr").find("input[type=checkbox]").not(this).removeAttr("checked");
            } else {
                $(this).closest("tr").find("input[type=checkbox]").not(this).attr('checked', 'checked');
            }
        });
    });
</script>

Namespaces

C#

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

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[1] { new DataColumn("Id") });
        dt.Rows.Add(1);
        dt.Rows.Add(2);
        dt.Rows.Add(3);
        dt.Rows.Add(4);
        rptStudents.DataSource = dt;
        rptStudents.DataBind();
    }
}

protected void Button1_Click(object sender, EventArgs e)
{
    foreach (RepeaterItem item in rptStudents.Items)
    {
        Label customerId = item.FindControl("lblCustomerId") as Label;
        CheckBox isAbsent = item.FindControl("chkIsAbsent") as CheckBox;
        TextBox notes= item.FindControl("txtNotes") as TextBox;
            
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandText = "INSERT INTO tblAttendance VALUES(@Id, @Present, @Note)";
                cmd.Parameters.AddWithValue("@Id", customerId.Text.Trim());
                cmd.Parameters.AddWithValue("@Present", isAbsent.Checked);
                cmd.Parameters.AddWithValue("@Note", notes.Text.Trim());
                cmd.Connection = con;
                con.Open();
                cmd.ExecuteNonQuery();
                con.Close();
            }
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As DataTable = New DataTable()
        dt.Columns.AddRange(New DataColumn(0) {New DataColumn("Id")})
        dt.Rows.Add(1)
        dt.Rows.Add(2)
        dt.Rows.Add(3)
        dt.Rows.Add(4)
        rptStudents.DataSource = dt
        rptStudents.DataBind()
    End If
End Sub

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
    For Each item As RepeaterItem In rptStudents.Items
        Dim customerId As Label = TryCast(item.FindControl("lblCustomerId"), Label)
        Dim isAbsent As CheckBox = TryCast(item.FindControl("chkIsAbsent"), CheckBox)
        Dim notes As TextBox = TryCast(item.FindControl("txtNotes"), TextBox)
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString

        Using con As SqlConnection = New SqlConnection(constr)
            Using cmd As SqlCommand = New SqlCommand()
                cmd.CommandText = "INSERT INTO tblAttendance VALUES(@Id, @Present, @Note)"
                cmd.Parameters.AddWithValue("@Id", customerId.Text.Trim())
                cmd.Parameters.AddWithValue("@Present", isAbsent.Checked)
                cmd.Parameters.AddWithValue("@Note", notes.Text.Trim())
                cmd.Connection = con
                con.Open()
                cmd.ExecuteNonQuery()
                con.Close()
            End Using
        End Using
    Next
End Sub

Screenshot