Assigning a value to a session

See more:

session

ASP.NET2

Hi
I have a dataList with an image button as template field. and a label holds a name.
I trying to make the button fire up a new page and pass the value of the label to a session.

I tried this code but it keep saying "Object reference not set to an instance of an object".

protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
{
    Label lk = (Label)DataList1.FindControl("APP01Label");
    Session["testName"] = lk.Text;
    ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('" + Session["testName"].ToString() + "');", true);
}

here I want to test it by showing the Session value in a message box.

thanks