Classic ASP – Syntax – Understand the Building Blocks of Classic ASP
Introduction – Why Classic ASP Syntax Still Matters
Classic ASP syntax defines how to write and organize server-side scripts using VBScript or JScript inside .asp files. Even though it’s a legacy framework, understanding Classic ASP syntax is critical for maintaining existing applications, handling server-side logic, and outputting dynamic HTML.
In this guide, you’ll learn:
- How Classic ASP code is structured
- Syntax for variables, control flow, functions, and server objects
- Inline vs block scripting
- Common mistakes and best practices
Basic Syntax Overview
Classic ASP code is embedded within special <% ... %> delimiters in .asp files.
<html>
<body>
<%
Response.Write "Hello, World!"
%>
</body>
</html>
Output:Hello, World!
ASP Code Tags
| Tag | Description |
|---|---|
<% ... %> | General server-side script block |
<%= ... %> | Outputs result of expression inline |
Example Using <%=
<%
Dim name
name = "Vaibhav"
%>
<p>Hello, <%= name %></p>
Output: Hello, Vaibhav
Declaring Variables
<%
Dim x
x = 10
%>
VBScript variables are declared using Dim. Types are inferred dynamically.
Control Flow Statements
If…Then…Else
<%
Dim score
score = 85
If score >= 90 Then
Response.Write "Grade A"
ElseIf score >= 80 Then
Response.Write "Grade B"
Else
Response.Write "Grade C"
End If
%>
For Loop
<%
For i = 1 To 3
Response.Write "Line " & i & "<br>"
Next
%>
While and Do…Loop
<%
Dim i
i = 1
Do While i <= 3
Response.Write "Count: " & i & "<br>"
i = i + 1
Loop
%>
Functions and Subroutines
<%
Function Add(a, b)
Add = a + b
End Function
Response.Write Add(5, 7)
%>
Output: 12
Common Server Objects in Syntax
| Object | Example Usage |
|---|---|
Request | Request.QueryString("name") |
Response | Response.Write "Hello" |
Session | Session("user") = "Admin" |
Server | Server.MapPath("/data") |
Example – Combining All Syntax
<%
Dim name
name = Request.QueryString("name")
If name = "" Then
name = "Guest"
End If
Response.Write "Welcome, " & name & "!"
%>
URL: page.asp?name=John
Output: Welcome, John!
Common Syntax Mistakes
| Mistake | Correction |
|---|---|
Missing End If or Next | Always close control blocks |
Using = instead of & for string concat | Use & for VBScript strings |
Using variables without Dim | Always declare variables explicitly |
Best Practices for Classic ASP Syntax
Do:
- Use
Option Explicitto enforce variable declaration - Indent and comment your code for clarity
- Separate logic into functions or include files
Avoid:
- Embedding too much logic directly in HTML
- Skipping closing tags (e.g.,
End If,Next) - Relying on global variables without scoping
Summary – Recap & Next Steps
Classic ASP syntax uses VBScript-like rules for declaring variables, writing logic, and producing dynamic content. Mastery of this syntax is crucial for maintaining and updating legacy ASP applications.
Key Takeaways:
- Use
<% ... %>for blocks and<%= ... %>for inline output - Declare variables using
Dimand concatenate strings with& - Master
If,For, andFunctionsyntax for full control
Real-world Use Cases:
- Creating dynamic pages with form data
- Conditionally showing elements in response to user state
- Looping through recordsets or lists
FAQs – Classic ASP Syntax
Is Classic ASP case-sensitive?
No. Classic ASP (VBScript) is not case-sensitive.
What does <%= %> do in Classic ASP?
It outputs the result of an expression directly to the page.
Can I mix VBScript and JScript in the same file?
No. A single ASP page must declare and use one language consistently.
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