Include Files with ASP

By ServerWatch Staff (Send Email)
Posted Aug 24, 1999


by Robert Adamczyk

First, a little about myself:
My name is Robert Adamczyk but I go by "Check". I've been doing web development since around 1994 and have been programming since around 1982. I've programmed in C, C++, IAS indirect command files, DOS batch files, C shell and Korn shell scripts, Perl, Clipper, PowerBuilder, FoxPro, GWBasic, Basic, TI Extended Basic, QBasic, QuickBasic and Visual Basic. My current development efforts are directed towards Visual Basic. I use VB6 to write COM objects which are stored in Microsoft Transaction Server (MTS) and called from the VBScript in my ASP pages. I am the Webmaster of three websites with a combined average of over 20,000 hits a week. Do you have certain things that you cut and paste into a lot of your ASP pages? A better way to accomplish this might be to put the repeated code into a function or subroutine and save it in an include file.

Now on to the subject at hand, Include Files with ASP
Do you have certain things that you cut and paste into a lot of your ASP pages? A better way to accomplish this might be to put the repeated code into a function or subroutine and save it in an include file. This has a lot of advantages and only a few minor disadvantages.

The drawback to this is that the server has to open the include file which takes longer than if the code had been placed directly in the ASP file. Most of the time though, the difference in time is so small that it's unnoticable. You've got to decide how many functions and subroutines to put into each include file. Make sure to group your functions and subroutines in a manner that makes sense. Don't put functions and subroutines together that won't be used on the same page. Doing that will make the pages load slower, because they have to read in and process the functions and subroutines even if they aren't used. On the other hand, don't separate them too much because you will waste too much time opening a lot of include files.

The benifits of using include files with functions and subroutines is that the actual code is located in a single place. Lets say you use the cut and paste method instead of include files and you have the same block of code in 15 different files. You then find a bug in the code or find a faster way to accomplish the same thing. You would have to open and modify all 15 files to incorporate the changes. With include files, you make the change in one place and all 15 files use the updated code.

They can also be used to include an image or heading information in each of your files. It is good practice to use width and height attributes for image tags. Lets say you have a logo that you want displayed at the top of each page. Most of the time you would just put the <img tag at the top of each page. Now, if the logo changes, you could just replace the old logo file with the new logo file and all the pages will then show the new logo. However, what if the new logo has a different height or width? You're back to opening and modifying each and every page that uses the image.

If you use an include file instead, you can put the height and width tags in the include file and only modify one location when it changes. Again, don't over do these, since it is another file that has to be opened for the page to be displayed.

Now that I've mentioned the virtues of using include files, you're probably wondering how to use them. They are actually quite easy to implement. The first thing you need to do is open an empty text file. You place whatever code you are going to re-use in this file. Whatever you place in this file will be placed in your page exactly where you put the include tag. Since include files are actually implemented with an html tag and not through ASP code, you will need to place any ASP code inside <% %> tags within the include file. This means most of your include files will begin with <% and end with %>. If this include file will be used for an image then you will just put the <img tag by itself in the file. If this is for functions or subroutines, the file will look more like this:

myfile.asp
<%
Sub mysub
if len(session.username) > 1 then
%>
Welcome to our web site <%=session.username%>!
<% else %>
<a href="login.asp">Login Now</a>
<%
end if
End Sub

Function myfunc(page)
if page = "home" then
%>
<a href="/default.asp">SWYNK Homepage</a>
<%
end if
if page = "colhome" then
%>
<a href="default.asp">Check's Homepage</a>
<%
end if
End Function
%>

Most of the time, your include files should have an extension of .asp. This is so if someone guesses the url of your include file, it will be processed before being sent to the user. Normally this results in a blank page being displayed instead of your code. Saving them with the extention of .asp can make it a little confusing since you don't have an easy way of telling which are include files and which aren't. This can be solved by either naming them all inc_filename.asp or something similar, or putting them in a subdirectory called include or inc.

Once you have decided where to place your include files and what to call them the only thing left is to actually include them in your ASP pages. To do this you use the html server side include tag. It's format is:

 <!--#INCLUDE FILE="filename.asp"-->
or
<!--#INCLUDE FILE="path/filename.asp"--> For relative paths
or
<!--#INCLUDE FILE="/path/filename.asp"--> For absolute paths
This include tag must be placed outside any ASP code or it won't be processed. This means your page will look something like this:

mypage.asp
<%
Option Explicit
%>
<!--#INCLUDE FILE="myfile.asp"-->
<html><head><title>Your Page Title</title></head>
<body bgcolor="yellow">
<center>
<% mysub %><br>
<br>
The rest of your page text here.<br>
<br>
<%=myfunc("home")>  <%=myfunc("colhome")>
</center>
</body></html>

Assuming that the session.username variable has not been set, the above example page (mypage.asp) would be displayed as follows:

Login Now

The rest of your page text here.

SWYNK Homepage Check's Homepage

Obviously this examply is kind of weak since there isn't much code to it. You can however use this example as a shell and put some useful code in the function or subroutine.

If you are using this for an image, your page might look something like this:

<html><head><title>Your Page Title</title></head>
<body bgcolor="#FFFFFF">
<!--#INCLUDE FILE="logo.asp"--><br>
<br>
The rest of your page text here.<br>
<br>
</body></html>

In this case the line that says <!--#INCLUDE FILE="logo.asp"--> would be replaced with the code in the logo.asp file. Lets say the the logo.asp file contained the following code:

<img src="/images/logo.jpg" height="40 width="100" border="0">

The above example page would be sent to the user as follows:

<html><head><title>Your Page Title</title></head>
<body bgcolor="#FFFFFF">
<img src="/images/logo.jpg" height="40 width="100" border="0"><br>
<br>
The rest of your page text here.<br>
<br>
</body></html>

All of the above examples use the INCLUDE FILE tag to get the include files into the current ASP page. It is also possible to use the INCLUDE VIRTUAL tag to accomplish the same thing. The INCLUDE VIRTUAL tag however starts the path at the root directory of the webserver instead of the current directory. This same thing can be accomplished with the INCLUDE FILE tag by simply starting the filename with / as in:
<!--#INCLUDE FILE="/include/myinc.asp"-->
Instead of
<!--#INCLUDE VIRTUAL="include/myinc.asp"-->
In this example, the FILE tag requires one extra character. However, what if your include files only apply to a specific subdirectory? In this case the difference between the FILE tag and the VIRTUAL tag might look something like this:
<!--#INCLUDE FILE="include/myinc.asp"-->
Instead of
<!--#INCLUDE VIRTUAL="articles/smith/include/myinc.asp"-->
Because of this, I personally prefer to use the INCLUDE FILE tag vs the INCLUDE VIRTUAL tag.

Hopefully you can see from this article the powerful potential of include files. If used properly they can save you a lot of time while building and maintaining your site.

(Note: This page uses six include files)

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