Update multiple rows in datalist using checkbox

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C#

I'm trying to update multiple rows by using checkbox in datatlist.
and I want to update only on column in database.


I want to update only "status" column in database, in those rows of datalist where checkbox is checked.

What I have tried:

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select * from a1_form where status='Requested for approval'";
cmd.ExecuteNonQuery();

DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);

DataList1.DataSource = dt;
DataList1.DataBind();

con.Close();
}
protected void Button1_Click(object sender, EventArgs e)
{
foreach (DataListItem dl in DataList1.Items)
{
CheckBox cb = (CheckBox)dl.FindControl("CheckBox1");
if (cb != null)
{
if (cb.Checked)
{
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select * from a1_form where status='Requested for approval'";
cmd.ExecuteNonQuery();

DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);

foreach (DataRow dr in dt.Rows)
{
dr["status"]="Approved";
}

con.Close();

}
}
}

}
}