When should I use If...ElseIf instead of Select Case in WinCC VBScript?

Use If...ElseIf when conditions compare different variables or expressions. Use Select Case when one expression is being matched against several discrete values or ranges.

Can Select Case use ranges in VBScript?

Yes. VBScript supports Case Is comparison expressions and numeric ranges such as Case 800 To 870.

What does And mean in a WinCC permissive?

And requires every listed Boolean condition to be true before the Then branch runs, which makes it suitable for multi-condition process permissives.

What is the difference between Or and Not in VBScript?

Or is true when at least one condition is true. Not reverses the Boolean result of a condition.

When is a nested If appropriate?

Use a nested If when a secondary decision only matters after a primary condition has already been satisfied. Avoid excessive nesting because it reduces readability.

IF, ElseIf & Select Case in WinCC VBScript

Learning Foundation: Decision Logic

This page has one defined job in the WinCC VBScript learning path. Master this foundation before using the same concept inside larger SCADA, SQL Server and reporting scripts.

BeginnerWinCC Explorer / Classic WinCCSQF Running Project

Prerequisite

Variables, comparisons and data conversion should already be clear.

Core concept

Decision structures route process values into the correct operator message, command, alarm state or sequence branch.

SQF practical connection

Evaluate furnace temperature, fan status, process event and operating mode using If/ElseIf and Select Case.

Expected competency

Build readable branch logic with If, ElseIf, Else, And/Or/Not and Select Case without creating unsafe command logic.

IF, ElseIf & Select Case in WinCC VBScript — ArchitectureCode-rendered HTML/CSS architecture; no image file required

Process Value

Read/convert the working value

TempAct

Condition

Evaluate engineering rule

TempAct >= TempSet

Branch

Choose the matching path

If / ElseIf / Else

Action

Set message/status/request

Status = "READY"

Verify

Trace the selected branch

MsgBox / Trace

Complete WinCC VBScript Learning Path

Use Previous/Next for the recommended practical order, or open any topic below as a reference.

Practical Uses of VBScript in WinCC WinCC VBScript Keywords: Syntax, Uses & Cheat Sheet WinCC VBScript Variables, Operators & Data Conversion IF, ElseIf & Select Case in WinCC VBScript WinCC VBScript Loops & Arrays: FOR, Do While, ReDim Sub, Function, ByVal & ByRef in WinCC VBScript Read and Write WinCC Tags with VBScript: HMIRuntime Guide Configure WinCC Global Script VBS Actions and Triggers WinCC VBScript Error Handling and Runtime Diagnostics WinCC VBScript Operator Input Validation and Command Gating Control WinCC Graphics Designer Objects with VBScript WinCC VBScript Screen Navigation, Faceplates and Reusable Instances WinCC VBScript Alarm and Event Handling WinCC VBScript Recipe and Batch Parameter Management Create a SQL Server Database and Table with WinCC VBScript (ADODB)SQL Server CRUD Operations with WinCC VBScript and ADODB Export WinCC Tag Data to CSV Using VBScript Generate Excel Reports from WinCC Using VBScript WinCC Explorer VBScript Object-Based Practice Lab Manual WinCC VBScripting Practice: 28 Hands-On SCADA Examples WinCC VBScript 05 Days Handwritten Code Manual

WinCC VB Scripting Training →

Project context: The examples assume the SQF process variables already contain current values. This chapter focuses only on VBScript decision logic; WinCC tag Read/Write is covered in Blog 07.

1. IF...THEN

Use a simple If when an action is required only when one condition is true.

If TempAct >= TempSet Then
    EventTo = "TEMPERATURE ACHIEVED"
End If

2. IF...ELSE

Use Else when exactly two outcomes are required.

If FanStatus Then
    EventTo = "FAN RUNNING"
Else
    EventTo = "FAN STOPPED"
End If

3. IF...ELSEIF...ELSE

Use ElseIf for multiple ordered ranges.

If TempAct < TempSet - 20 Then
    EventTo = "LOW TEMPERATURE"
ElseIf TempAct <= TempSet + 10 Then
    EventTo = "TEMPERATURE NORMAL"
Else
    EventTo = "HIGH TEMPERATURE"
End If

4. Nested IF

A nested If is useful when a secondary check only matters after a primary condition is satisfied.

If TempAct >= TempSet Then
    If FanStatus Then
        EventTo = "PROCESS READY"
    Else
        EventTo = "TEMP READY - FAN STOPPED"
    End If
Else
    EventTo = "TEMPERATURE NOT READY"
End If

Do not over-nest conditions. When logic becomes difficult to read, split it into a Function in Blog 06.

5. AND — All Conditions Must Be True

Industrial permissives often require multiple conditions at the same time.

If TempAct >= TempSet _
And CpAct >= CpSet _
And OilAct >= OilSet _
And JacketAct >= JacketSet _
And FanStatus Then

    EventTo = "PROCESS READY"
Else
    EventTo = "PROCESS NOT READY"
End If

6. OR and NOT

Use Or when any listed condition may trigger the branch. Use Not to invert a Boolean condition.

If TempAct > TempSet + 20 Or OilAct < OilSet Then
    EventTo = "PROCESS DEVIATION"
End If

If Not FanStatus Then
    EventTo = "FAN NOT RUNNING"
End If

7. Select Case

Use Select Case when one variable has several discrete states.

Select Case SQFNo
    Case 1
        EventFrom = "SQF-01"
    Case 2
        EventFrom = "SQF-02"
    Case 3
        EventFrom = "SQF-03"
    Case Else
        EventFrom = "UNKNOWN SQF"
End Select

8. Select Case with Ranges

Case expressions can make range-based status logic easier to scan than a long chain of ElseIf statements.

Dim TempDeviation

TempDeviation = TempAct - TempSet

Select Case TempDeviation
    Case Is < -20
        EventTo = "LOW TEMPERATURE"
    Case -20 To 10
        EventTo = "TEMPERATURE NORMAL"
    Case Else
        EventTo = "HIGH TEMPERATURE"
End Select

9. Event_From → Event_To Mapping

A true transition requires both the previous state and the current state. Do not infer Event_From from FanStatus alone.

If PreviousFanStatus <> FanStatus Then

    If PreviousFanStatus = False And FanStatus = True Then
        EventFrom = "FAN STOP"
        EventTo = "FAN START"

    ElseIf PreviousFanStatus = True And FanStatus = False Then
        EventFrom = "FAN START"
        EventTo = "FAN STOP"
    End If

End If

10. Decision Logic Syntax Cheat Sheet

Use this quick reference to choose the correct VBScript decision structure in WinCC.

Keyword / Structure	Use	Core Syntax
If...Then	Run code only when one condition is true	`If condition Then ... End If`
If...Else	Choose between two outcomes	`If condition Then ... Else ... End If`
If...ElseIf...Else	Evaluate ordered multiple conditions	`If c1 Then ... ElseIf c2 Then ... Else ... End If`
Nested If	Run a secondary decision only after a primary condition	`If c1 Then If c2 Then ... End If End If`
And	Require every condition to be true	`If c1 And c2 Then`
Or	Allow any one condition to be true	`If c1 Or c2 Then`
Not	Invert a Boolean condition	`If Not FanStatus Then`
Select Case	Match one expression to several values	`Select Case x ... Case 1 ... Case Else ... End Select`
Case Is / To	Match ranges or comparison expressions	`Case Is < -20 / Case -20 To 10`

11. Participant Exercises

Complete these before loops and arrays.

Create Low/Normal/High Temp logic.

Create a four-condition process permissive using And.

Use Or for two process-deviation conditions.

Use Not with FanStatus.

Create Select Case for SQF 1, 2, 3.

Map Event_From and Event_To for a fan transition.

SQF Running Project Lab · Blog 04

Build the SQF process-ready decision

If TempAct >= TempSet _
And CpAct >= CpSet _
And OilAct >= OilSet _
And JacketAct >= JacketSet _
And FanStatus Then

    EventFrom = "PROCESS CHECK"
    EventTo = "PROCESS READY"
Else
    EventFrom = "PROCESS CHECK"
    EventTo = "PROCESS NOT READY"
End If

This decision later controls whether the SQF event is approved for logging/reporting.

Trainer Checkpoint

Participant should explain this chapter without copying the final program.

← Blog 03 Continue to Blog 05 →

FAQs

Why does this tutorial use SQF_DB.dbo.tblEvent?

One stable industrial dataset lets participants learn VBScript progressively without changing examples in every chapter.

Should participants memorize the complete SQL logger now?

No. Learn the current chapter first. The complete WinCC-to-SQL program is assembled in later chapters.

Are HMIRuntime and ADODB VBScript keywords?

No. They are runtime/COM objects used by VBScript. The language keywords control how the script is structured.