===========Class1.vb==============
Imports Microsoft.VisualBasic
Imports System.Data.SqlClient
Imports System.Data


Public Class Class1

Dim objcon As New SqlConnection(ConfigurationManager.ConnectionStrings("student").ConnectionString)
Dim objadp As SqlDataAdapter
Dim ds As Data.DataSet
Dim cmd As SqlCommand


Public Function selectdata(ByVal qry As String) As DataSet

objcon.Open()
objadp = New SqlDataAdapter(qry, objcon)
ds = New Data.DataSet
objadp.Fill(ds)
objcon.Close()
Return ds

End Function


Public Function qryexe(ByVal qry As String) As Boolean
objcon.Open()
cmd = New SqlCommand(qry, objcon)
Dim i As Integer = cmd.ExecuteNonQuery()
objcon.Close()
If i = 0 Then
Return False
Else
Return True
End If

End Function
End Class
====================Default.aspx.vb========================

Partial Class _Default
Inherits System.Web.UI.Page

Dim qry As String
Dim ds As New System.Data.DataSet
Dim obj As New Class1
Shared flag As Boolean = False
Shared chk As Boolean

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
chk = True
End Sub

Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
chk = False
End Sub

Protected Sub Button3_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button3.Click
qry = "delete from stud where name='" + DropDownList1.SelectedItem.Text + "'"
obj.qryexe(qry)
flag = False
Page_Load(sender, e)
trno.Text = ""
tname.Text = ""
tresult.Text = ""
End Sub

Public Sub display()
qry = "select * from stud where name='" + DropDownList1.SelectedItem.Text + "'"
ds = obj.selectdata(qry)
trno.Text = ds.Tables(0).Rows(0).Item("rno").ToString()
tname.Text = ds.Tables(0).Rows(0).Item("name")
tresult.Text = ds.Tables(0).Rows(0).Item("result")
End Sub

Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
ds.Clear()
display()
End Sub



Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If flag = False Then
ds.Clear()
qry = "select * from stud"
ds = obj.selectdata(qry)
DropDownList1.DataSource = ds
DropDownList1.DataTextField = ds.Tables(0).Columns("name").ToString()
DropDownList1.DataValueField = ds.Tables(0).Columns("rno").ToString()
DropDownList1.DataBind()

GridView1.DataSource = ds
GridView1.DataBind()



flag = True
End If
End Sub

Protected Sub Button4_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button4.Click
If chk = True Then
qry = "insert into stud(name,result) values('" + tname.Text.Trim + "','" + tresult.Text.Trim + "')"
obj.qryexe(qry)
Else
qry = "update stud set name='" + tname.Text.Trim + "',result='" + tresult.Text.Trim + "' where rno=" + trno.Text.Trim
obj.qryexe(qry)
End If
flag = False
Page_Load(sender, e)
trno.Text = ""
tname.Text = ""
tresult.Text = ""
End Sub


End Class
======================