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4GuysFromRolla.com : ASP FAQS : Forms


Question:

How do I make my forms show what the user chose before? That is, how do I show which OPTION the user previouly selected? Which checkbox? Which radio button?


[Print this FAQ]

Answer: The principle for all three of these is the same: You have to add an HTML keyword to the appropriate choice.

Examples, in standard HTML:

<FORM Name="TheForm" Action="nextPage.asp" Method="Post">
<P> I like:
    <SELECT Name="Fruit">
        <OPTION Value="*"> -- choose one --
        <OPTION Value=A> Apples
        <OPTION Value=B SELECTED> Bananas
        <OPTION Value=C> Cantaloupes
    </SELECT>
<P> I am:
    <INPUT Type=Radio Name="Gender" Value="F"> Female
    <INPUT Type=Radio Name="Gender" Value="M"> Male
    <INPUT Type=Radio Name="Gender" Value="U" CHECKED> Undecided
<P> I read (check all that apply):
    <INPUT Type=CheckBox Name="Read" Value=1> Time
    <INPUT Type=CheckBox Name="Read" Value=2> Newsweek
    <INPUT Type=CheckBox Name="Read" Value=3 CHECKED> National Enquirer
</FORM>


So your only challenge, in ASP, is to figure out how to put the word SELECTED or CHECKED (as appropriate) into the choice that matches the value the user chose before.

And while there are many, many, many ways to do this, we will just show two simple methods here.

The Most Basic Method


The easiest to understand--but the ugliest from a coding standpoint--is to simply put a test for a match into each of the possible choices:

<SELECT Name="Fruit">
    <OPTION Value="*"> -- choose one --
    <OPTION Value="A"
        <% If RS("Fruit")="A" Then Response.Write "SELECTED"%>
        > Apples
    <OPTION Value="B"
        <% If RS("Fruit")="B" Then Response.Write "SELECTED"%>
        > Bananas
    <OPTION Value="C"
        <% If RS("Fruit")="C" Then Response.Write "SELECTED"%>
        > Cantaloupes
</SELECT>


Naturally, the code for check boxes and radio buttons is essentially identical, save only that you write "CHECKED" instead of "SELECTED".

A First Level Improvement


If you don't understand how to code and use subroutines in VBScript, may I suggest that skip this for now. Come back to it later, when your understanding of the language is a little deeper.

And, as that last paragraph implies, we will use a subroutine to improve the code:

<%
Sub makeOpt( val, txt, testval )
    Response.Write "<OPTION VALUE='" & val & "'"
    If val = testval Then Response.Write " SELECTED"
    Response.Write ">" & txt & "</OPTION>"
End Sub
%>



That subroutine accepts the value and text for a given option as well as a testval. It creates the <OPTION> in your HTML, adding the SELECTED keyword if appropriate.

So you would invoke it thus:

<SELECT Name="Fruit">
    <OPTION Value="*"> -- choose one --
    <% makeOpt "A", "Apples", RS("Fruit") %>
    <% makeOpt "B", "Bananas", RS("Fruit") %>
    <% makeOpt "C", "Cantaloupes", RS("Fruit") %>
</SELECT>


Again, hopefully the extension to checkboxes and radio buttons is obvious. One SUB for each type would do for an entire form, depending on how you wrote it.

There are many many other ways to accomplish this. And there are some trickier situations that have to be addressed: What do you do when the list of options comes from the database, too? What do you do about the fact that a user might check multiple check boxes or, if allowed, make multiple <SELECT> choices?

Stay tuned to this FAQ.


FAQ posted by Bill Wilkinson at 4/26/2002 7:02:25 PM to the Forms category. This FAQ has been viewed 61,683 times.

Do you have a FAQ you'd like to suggest? Suggestions? Comments? If so, send it in! Also, if you'd like to be a FAQ Admin (creating/editing FAQs), let me know! If you are looking for other FAQs, be sure to check out the 4Guys FAQ and Commonly Asked Messageboard Questions!

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