asp:image button is not working

asp:image button is not working

<asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="~/Images/button_search.gif" OnClick="ImageButton1_Click" />

protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
{
SqlCommand myCommand = new SqlCommand("sp_login", sqlcon);

myCommand.CommandType = CommandType.StoredProcedure;

SqlParameter username = new SqlParameter("@username", SqlDbType.VarChar, 250);

username.Value = txtusername.Text;

myCommand.Parameters.Add(username);

SqlParameter password = new SqlParameter("@password", SqlDbType.VarChar, 250);

password.Value = txtpassword.Text;

myCommand.Parameters.Add(password);


dr = myCommand.ExecuteReader();

if (dr.Read())
{
Response.Redirect("Permanentlogin.aspx");
}

sqlcon.Close();
}