[AccessD] From a reader

Not to mention that if she is running into problems with the current
system, a 'canned' solution would most likely carry those same issues
along with it.

A long time ago, I built a 'canned' solution that would display reports
from an access database across the web (and any 'UI' prompts, like
[Enter Product Number] that were in the query would be read, recreated
into a web format to be displayed to the user, and then the user's
response sent back to the actual .mdb).  It worked great.  Toyed with
the idea of doing the same for forms, and ran into a huge brick wall
with how Access subclasses the windows in its forms.  So I never took it
any further.

But to take an Access mdb, and just 'dump it' into a web application
loses the benefit of some of the great features a web application can
incorporate.

For instance, if you were to just create a Dropdown box, that
'populated' some fields in an ASP.NET application, ASP.Net would let you
make it 'look' like an access combobox, and act like it, but what's
happening in the background is clunky.  First, .Net is creating
javascript on the client side that is reacting to the 'OnClick' of the
combobox (or index changed event), then it's sending all the current web
form info back to the server (as a PostBack), where the web server then
does what your .Net (VB or C#) code wants to do, in filling in the
fields, and sends all that back to the user.  UGLY.  Works, but ugly.
If it's a huge form, or a very slow connection, that creates noticeable
pauses and reloads on the web page.  There is another solution:

You can create a generic handler, that uses JQuery (AJAX) on the client
side to just 'ask' the web server for the applicable data.

Here's a generic handler (.ashx file)

<%@ WebHandler Language="VB" Class="LoadDoctorInfo" %>
Imports System
Imports System.Web
Public Class LoadDoctorInfo : Implements IHttpHandler
    
    Public Sub ProcessRequest(ByVal context As HttpContext) Implements
IHttpHandler.ProcessRequest
        Dim intID As String = context.Request.QueryString("DoctorID")
        Dim strDocInfo As New StringBuilder
        Dim dr As New Doctor(intID)
        strDocInfo.Append("[{""DoctorName"":""" & dr.Name & """,")
        strDocInfo.Append("""Address1"":""" & dr.Address1 & """,")
        strDocInfo.Append("""Address2"":""" & dr.Address2 & """,")
        strDocInfo.Append("""City"":""" & dr.City & """,")
        strDocInfo.Append("""State"":""" & dr.State & """,")
        strDocInfo.Append("""Zip"":""" & dr.ZipCode & """,")
        strDocInfo.Append("""Phone"":""" & dr.Phone & """}]")
        context.Response.ContentType = "application/json"
        context.Response.ContentEncoding = Encoding.UTF8
        context.Response.Write(strDocInfo.ToString())
        context.Response.End()
    End Sub
 
    Public ReadOnly Property IsReusable() As Boolean Implements
IHttpHandler.IsReusable
        Get
            Return False
        End Get
    End Property

End Class

The above file is stored on the web server, and is called using the
follow javascript on the client end:

<asp:DropDownList ID="cmbDoctorAutoFill"
runat="server"></asp:DropDownList>
                                    <script
src="_scripts/jquery-1.2.6.js" type="text/javascript"></script>
                                    <script type="text/javascript"
language="javascript">
                                        $(document).ready(function () {
 
$("#cmbDoctorAutoFill").change(function () {
                                                var JDoctorID =
$("#cmbDoctorAutoFill > option[@selected]").attr("value");
                                                if (JDoctorID != '') {
 
$.getJSON('LoadDoctorInfo.ashx?DoctorID=' + JDoctorID, function
(docinfo) {
                                                        $.each(docinfo,
function () {
 
$("#txtDataDoctorName").val(this['DoctorName']);
 
$("#txtDataDoctorAddress1").val(this['Address1']);
 
$("#txtDataDoctorAddress2").val(this['Address2']);
 
$("#txtDataDoctorCity").val(this['City']);
 
$("#txtDataDoctorZip").val(this['Zip']);
 
$("#txtDataDoctorPhoneNumber").val(this['Phone']);
 
$("#cmbDataDoctorState").val(this['State']);
                                                        });
                                                    });
                                                }
                                            });
                                        });
                                    </script>

The drop down list is filled with doctors and their IDs, the
jquery-1.2.6.js file (which you can download from the web) has all the
code necessary to make the above code work.  It takes the ID of the
combo, queries the webserver's generic handler ('LoadDoctorInfo.ashx')
and then populates controls on the end user's form using data from
what's returned by the handler.  The user's form doesn't have to
'reload' against the webserver, and that interaction 'appears' to work
just like a combo box on an Access form would work.

There are several other tricks you can do with .asp pages which will
help increase the performance of an application.  While there may be
'canned' apps out there, which can stuff an application into a .Net
solution, I doubt it will be very finely tuned or optimized.  

Heck, one of the features of ASP.Net that I fell in love with, is how
easy it is to create a 'downloaded file' on the fly.  (Say on a data
form, you want to give the user the ability to download a .csv file of
the data they are working on, with .asp, I would create the .csv file in
a temp file, and then redirect them to that file... with ASP.Net, it's
extremely easy to just interrupt the outbound feed, and just send the
file on the fly.  Probably could have done that in classic asp, but the
tutorial to do that in asp.Net was quick and easy to find).  No more
temp files.  Very slick.

Drew

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Susan Harkins
Sent: Monday, January 31, 2011 7:51 PM
To: Access Developers discussion and problem solving
Subject: Re: [AccessD] From a reader

Darryl  -- I agree. She's looking for a canned solution and I've told
her 
there isn't any such thing -- but I thought I'd ask. You never know. :)

Susan H.
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