最简单Login程序

 Protected Sub btnLogon_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnLogon.Click

        If Page.IsValid Then

            Dim SQL As String = "Select pwd ,username from sys_user where username=@uid "
            Dim myconnection As SqlConnection = New SqlConnection(System.Configuration.ConfigurationManager.AppSettings("connstring"))
            Dim mycommand As SqlCommand = New SqlCommand(SQL, myconnection)
            myconnection.Open()
            mycommand.Parameters.Add("@uid", SqlDbType.Char).Value = Trim(txtUserName.Text)
            mycommand.Parameters.Add("@pwd", SqlDbType.Char).Value = Trim(txtPwd.Text)
            Dim myreader As SqlDataReader = mycommand.ExecuteReader

            If myreader.Read Then
               
                Dim mdString As String = Trim(txtPwd.Text)

                If mdString = Trim(myreader.GetValue(0)) Then
               
                    myreader.Close()
                    myreader = Nothing
                    myconnection.Close()
                    myconnection = Nothing
                    Response.Redirect("index.html")

                Else
                    myreader.Close()
                    myreader = Nothing
                    myconnection.Close()
                    myconnection = Nothing
                    Response.Write("<script language='javascript'>alert('对不起，用户或密码错误!!');</script>")
                End If
            Else
                Response.Write("<script language='javascript'>alert('对不起，没有此用户');</script>")
            End If
        End If


    End Sub