Gathering Information
With HTML Forms
A common way to prompt users for information is to put a form on a page.
Users can enter information or select choices using text boxes, option
buttons, drop-down lists, and checkboxes. They then submit the form by
clicking a button, and the information becomes available to your
application.
You can define forms in these ways:
-
Use Microsoft® Visual InterDev™ design-time controls and then
write handlers for their events. This method allows you to work visually
with your form's controls and use object-oriented techniques for
scripting. It also makes it easy to bind form controls to a database.
-
Create an HTML form. This is the traditional HTML way of creating forms.
You might use this method if you thought that the page might be edited
using tools outside of Visual InterDev.
Using design-time controls is easier and more powerful, because it allows
you to use the scripting object model for designing forms..
The sections below describe how to create and work with HTML forms in the
traditional HTML manner.
Defining HTML Forms
You create an HTML form on a page with the <FORM> tag.
Note Do not add an HTML form to a page that contains Visual
InterDev design-time controls, because the page already contains a form
used to manage the controlsTo create an HTML form
-
Select the text that you want to enclose in a form, and then from the
HTML menu choose Form.
The editor puts <FORM> and </FORM> tags around your selection. The form's
ID and NAME attributes are automatically assigned unique values, which you
can change if you want.
Note If you enclose existing HTML controls
in a form, they appear inside the form's node in the
Script Outline
window.
-
Specify the name of an .asp file that will be used to process the form
by assigning it to the ACTION attribute:
3.
<FORM NAME="FormName"
ACTION="ASPFileName.asp">
-
Specify how the form information will be sent to the server using the
METHOD attribute:
5.
<FORM NAME="FormName"
ACTION="ASPFileName.asp"
METHOD="method">
To send the information as part of the HTTP header (so it can be extracted
using the Forms collection of the server's Request object), set METHOD to
"POST".
To send the information as a search string to the .asp file (so it can be
extracted using the Request object's QueryString collection), set METHOD
to "GET".
After defining the form, you can define controls such as text boxes,
buttons, and so on.
Note You can use design-time controls to create the user
interface for your application.
To create controls in the form
-
Drag controls from the HTML tab of the Toolbox onto the form.
The control's ID and NAME attributes are automatically assigned unique
values. You can change these values if you want.
Note When you drag HTML controls into an
HTML form, they appear inside the form's node in the
Script Outline
window.
For example, a form that contains a text box and a Submit button might
look like this after you dragged the controls from the Toolbox and edited
them:
<FORM
NAME="Form1" NAME="frmMyForm" ACTION="process.asp" METHOD="post">
Enter your name:
<INPUT TYPE=text NAME=text1 ID=Text1>
<INPUT TYPE="submit" VALUE="Submit" ID=Submit1 NAME=Submit1>
</FORM>
Processing Form
Information Before Submitting
In simple forms, no processing is required on the client: the user clicks
the Submit button, and the browser handles the tasks of gathering the data
and sending it to the server. However, you can process forms by writing
client scripts to handle button clicks and so on.
A typical example is to write a script that validates user input before
the form is posted. But in client script you can have access to the events
fired for all the form's controls, so you can write handlers for any
purpose you need, including replacing server processing altogether.
Note The scripting object model allows you to script design-time
controls easily. To process forms in a client script
-
Write an event handler for the form's onsubmit event or for the events
associated with individual controls, such as a button's onclick event or
a text box's onblur event.
To determine the value of a specific control, you reference it using an
object hierarchy that goes from document to form to control to property.
The following illustrates a simple validation routine in a form's onsubmit
event handler:
<SCRIPT LANGUAGE="VBScript">
Function form1_onsubmit()
If
Len(document.form1.text1) < 1 then
MsgBox("You must enter a name!")
form1_onsubmit = False ' This cancels the submission
Else
' Information automatically sent to server
End If
End
Function
</SCRIPT>
Processing Forms on the
Server
In Visual InterDev, forms are usually handled by an .asp file on the
server.
To process a form in server script
-
On the target ASP page, use the Forms collection of the server Request
object to extract values from the form.
The Forms collection is like an array that holds the values of all the
controls in the form. You can extract the values of individual controls by
referencing them by name in the Forms collection.
For example, the following script gets the values of several fields on the
form using the names assigned in the form to the <INPUT> tags, and puts
them into Session object variables to be used elsewhere in the
application:
<%
Session("LastName") = Request.Form("LastName")
Session("BirthDate") = Request.Form("Birthdate")
%>
Creating Dynamic
Information in a Hidden Field
If you want to pass information that is not directly entered by a user,
you can use a hidden field.
Note If you use the scripting object model and design-time
controls, information is automatically available in server scripts.
To create information in a hidden field
-
In a form, create an <INPUT> tag and set its TYPE attribute to HIDDEN,
as in the following example:
2.
<FORM
NAME=frmEmployee METHOD=POST ACTION=process.asp>
3.
[...]
4.
<INPUT TYPE="Hidden" NAME="ExtraInfo">
5.
</FORM>
-
Put information into the hidden field using a client script.
For example, you can load the hidden field just before the form is
submitted by writing a handler for the form's onsubmit event. The
following simple example puts the current time into the hidden field:
<SCRIPT Language="VBScript>
Function frmEmployee_onsubmit
document.frmEmployee.ExtraInfo = time
End
Function
</SCRIPT>
When the form is submitted, you can get the information out of the hidden
field using server script exactly the way you get information out of any
other form element, as in the following example:
<%Session("UpdateTime")
= Request.Form("ExtraInfo")
Posting Information to
the Same File
Instead of always creating a separate .asp file to process the contents of
a form on an .htm file, you can put both on the same ASP page: the form
and the script that processes the form. This can simplify your application
and make it easier for users.
For example, it is typical to have three or more pages associated with a
form: the page with the form, another with the script that processes the
form, and a third with an error message. However, if the form is posted to
the file it appears on, you can send informational messages along with the
context of the form and you only have to create one page.
To post information to the same file
-
Create the form in an .asp file.
-
In the ACTION attribute of the form, specify the name of the file as the
target URL.
-
In the server script at the top of the .asp file, use the Request object
to check whether information is being passed to the file. If so, the
form has been submitted, and you can process it. Otherwise, assume the
form is being displayed for the first time.
The GetEmail.asp file below is an example of this. The script determines
whether the user has entered an e-mail address, and if so, whether it is
valid. In each case, the script produces an appropriate message, which
then appears beneath the form as feedback to the user.
<HTML>
<BODY>
<!--
GetEmail.asp -->
<%
If
IsEmpty(Request("Email")) Then
Msg = "Please enter your email address."
ElseIf InStr(Request("Email"), "@") = 0 Then
Msg = "Please enter an email address" & _
" in the form username@location."
Else
' In a real application, the following message
' would be replaced by actual processing.
Msg = "This script could process the " & _
"valid Email address now."
End If
%>
<FORM
METHOD="POST" ACTION="GetEmail.asp">
<PRE>
Email: <INPUT TYPE="TEXT" NAME="Email" SIZE=30
VALUE="<%= Request("Email")%>">
<%=
Msg %><P>
<INPUT TYPE="Submit" VALUE="Submit">
</PRE>
</FORM>
</BODY>
</HTML>
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