Connection is not closed error

plz check my code and tell me why dropdown binds two times and loop for year is running 2 times and in catch an error is thrown :connection is not closed..what the error in this code,i can't detect exactly where the problem is...plz check and reply me
Imports System Imports System.Data Imports system.Data.SqlClient Partial Class sel_dist Inherits System.Web.UI.Page Dim str As String = System.Configuration.ConfigurationManager.AppSettings("constr") Dim str1 As String = System.Configuration.ConfigurationManager.AppSettings("constr") Dim con As New SqlConnection(str) Dim dr As SqlDataReader Dim cmd As New SqlCommand Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click If yrdd.SelectedIndex <> 0 Then If distdd.SelectedIndex <> 0 Then If blockdd.SelectedIndex <> 0 Then ...