public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
 
    //Abfüllen
    protected void btnFüllen_Click(object sender, EventArgs e)
    {
        Füllen();
    }
 
    protected void Füllen()
    {
        fs.Controls.Add(new CheckBox { ID = "chk1", Text = "CHK1" });
        fs.Controls.Add(new CheckBox { ID = "chk2", Text = "CHK2" });
        fs.Controls.Add(new CheckBox { ID = "chk3", Text = "CHK3" });
        fs.Controls.Add(new CheckBox { ID = "chk4", Text = "CHK4" });
        fs.Controls.Add(new CheckBox { ID = "chk5", Text = "CHK5" });
    }
 
 
    //Auslesen
    protected void btnAuslesen_Click(object sender, EventArgs e)
    {
        foreach (Control ctrl in fs.Controls )
        {
            if (ctrl is CheckBox)
            {
                Response.Write((ctrl as CheckBox).ID + " = " + (ctrl as _
                  CheckBox).Checked + "<br/>" );
            }
        }
    }
 
}