🔀 Classic ASP – Conditionals – Control Flow with If, ElseIf, and Select Case

🧲 Introduction – What Are Conditionals in Classic ASP?

Conditionals in Classic ASP let you make decisions in your code using VBScript. They determine which blocks of code to execute based on specific conditions, such as a user’s input, time of day, or application state.

🎯 In this guide, you’ll learn:

• How to use If...Then...Else, ElseIf, and Select Case
• Write clean, readable control logic
• Combine conditions with server output
• Avoid common pitfalls in Classic ASP logic

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✅ Basic If...Then Syntax

<%
Dim isLoggedIn
isLoggedIn = True

If isLoggedIn Then
    Response.Write "Welcome back!"
End If
%>

🧪 Output:
Welcome back!

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🔁 If...Then...ElseIf...Else Statement

<%
Dim score
score = 78

If score >= 90 Then
    Response.Write "Grade: A"
ElseIf score >= 80 Then
    Response.Write "Grade: B"
Else
    Response.Write "Grade: C"
End If
%>

🧪 Output:
Grade: C

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🔀 Select Case Statement

The Select Case structure is useful for checking one value against multiple options:

<%
Dim userRole
userRole = "editor"

Select Case userRole
    Case "admin"
        Response.Write "You have full access."
    Case "editor"
        Response.Write "You can edit content."
    Case "viewer"
        Response.Write "Read-only access."
    Case Else
        Response.Write "Unknown role."
End Select
%>

🧪 Output:
You can edit content.

---

📥 Nesting Conditionals

You can nest If statements to create more advanced logic:

<%
Dim age, country
age = 18
country = "USA"

If country = "USA" Then
    If age >= 18 Then
        Response.Write "You can vote in the USA."
    Else
        Response.Write "You are underage in the USA."
    End If
End If
%>

🧪 Output:
You can vote in the USA.

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❓ Using Conditions in HTML Output

<%
Dim isPremium
isPremium = False
%>

<p>Your plan: 
<%
If isPremium Then
    Response.Write "Premium"
Else
    Response.Write "Standard"
End If
%>
</p>

🧪 Output:

Your plan: Standard

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❌ Common Mistakes

❌ Mistake	✅ Correction
Forgetting End If or End Select	Always close blocks properly
Using = instead of <> for not equal	Use <> for inequality
Missing ElseIf spacing	Use ElseIf (not Else If) in VBScript

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📘 Best Practices for Classic ASP Conditionals

✅ Do:

• Use If...Then for simple comparisons
• Prefer Select Case for many known values
• Keep logic readable with proper indentation

❌ Avoid:

• Excessive nesting – abstract logic into functions
• Mixing business logic with markup
• Using = instead of Is for object comparison

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📌 Summary – Recap & Next Steps

Classic ASP conditionals let you control the flow of your VBScript server-side logic. Whether you’re deciding what to display or how to process data, mastering If...Then and Select Case is essential for building dynamic web apps.

🔍 Key Takeaways:

• Use If, ElseIf, Else for conditional branches
• Select Case is cleaner for multi-value comparisons
• Always close logic blocks with End If, End Select

⚙️ Real-world Use Cases:

• Display user-specific menus
• Grade calculation systems
• Show/hide content based on login state or user role

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❓ FAQs – Classic ASP Conditionals

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❓ Can I use nested Ifs in Classic ASP?
✅ Yes, but keep nesting to a minimum for readability.

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❓ What is the syntax for “not equal” in VBScript?
✅ Use <>. Example: If score <> 100 Then ...

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❓ Is ElseIf one word or two?
✅ One word. Use ElseIf in VBScript, not Else If.

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