USE OF WEB SERVER CONTROL IN ASP.NET

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
public partial class _Default : System.Web.UI.Page

{

 protected void Page_Load(object sender, EventArgs e)

{

}

protected void CheckBox1_CheckedChanged(object sender, EventArgs e)

{

if (CheckBox1.Checked == true)

{

ListBox1.Items.Add(CheckBox1.Text);

}

else

}

ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox1.Text));

}

}

protected void CheckBox2_CheckedChanged(object sender, EventArgs e)

{

if (CheckBox2.Checked == true)

{

ListBox1.Items.Add(CheckBox2.Text);

}

else

{

ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox2.Text));

}

}

protected void CheckBox3_CheckedChanged(object sender, EventArgs e)

{

if (CheckBox3.Checked == true)

{

ListBox1.Items.Add(CheckBox3.Text);

}

else

{

ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox3.Text));

}

}

protected void CheckBox4_CheckedChanged(object sender, EventArgs e)

{

 if (CheckBox4.Checked == true)

{

 ListBox1.Items.Add(CheckBox4.Text);
            }
 else
            {
 ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox4.Text));
            }
            }
 protected void CheckBox5_CheckedChanged(object sender, EventArgs e)
            {
 if (CheckBox5.Checked == true)
            {
 ListBox1.Items.Add(CheckBox5.Text);
            }
 else
            {
 ListBox1.Items.Remove(ListBox1.Items.FindByText(CheckBox5.Text));
            }
            }

            }