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Using Includes

The previous FAQ discussed the importance of using functions in your ASP to modularize your code. Unfortunately, a function written in one ASP file cannot be accessed by a separate ASP file. That is what includes are useful for (among other things).

Includes are similar to #include's in C++, or uses in Pascal. An include in ASP simply copies over the text from the specified file into the current file. For example, say you had a file named PrintHelloWorld.asp, which had the following code:

<%
    Response.Write("Hello, world!")
%>

Now, we can include that code in another ASP file.

<%@ LANGUAGE="VBSCRIPT" %>
<HTML>
<BODY>
    <!--#include file="PrintHelloWorld.asp"-->
</BODY>
</HTML>

This HTML file will output "Hello, World" to the client's browser screen. By using the include file, it was as if we had just typed the text from the file PrintHelloWorld.asp directly into the above source code.

To include a file, the syntax is like an HTML comment. You need the <!--, followed by a #include. You can then use one or two keywords, either file or virtual. What one you use depends on the location of the file you want to include relative to the current file. If the file you want to include is in the same directory or a subdirectory of where the current file is, use the file keyword, like we did in the example above.

If, however, the file is in a different directory altogether, you need to use virtual. For example, it could look like this:

<!--#include virtual="/scripts/PrintHelloWorld.asp"-->

or

<!--#include virtual="../ASPDirectory/PrintHelloWorld.asp"-->

Let's look at one more quick example of #include's. Imagine that we have a file in our scripts directory named SquareFunction.asp. In this file, we have an ASP function that will square a number. Here is what the file SquareFunction.asp would look like:

<%
    function Square(num)
        Square = num * num
    end function
%>

Now, if we have an ASP page that we want to use the square function, we would simply type the following code:

<%@ LANGUAGE="VBSCRIPT" %>

<!--#include virtual="/scripts/SquareFunction.asp"-->

<%
    Dim MyAge
    MyAge = CInt(20)
%>

<HTML>
<BODY>
    Scott is <%=MyAge%> years old.
But he feels as if he's <%=Square(MyAge)%>!
</BODY>
</HTML>

Note that it was if we had typed in the file SquareFunction.asp into the ASP file above. The use of include files in ASP is good programming technique, for it allows one copy of source code to be used multiple times. You should strive to write your ASP applications as modular as possible, and include files help you do just that!

Article Information
Article Title: Using Includes
Article Author: Scott Mitchell
Article URL: http://www.4GuysFromRolla.com/webtech/faq/Beginner/faq6.shtml

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