If-Then-Else compared with Select Case

This article is extracted from Lesson 7 of the About Visual Basic "Complete Course" for VB.NET. Sign up for the entire course at ... this signup page.

In this lesson, we show you how Select Case and If-Then-Else can actually be used for exactly the same programming problem. It's up to you, as a programmer, to decide which one works best.

Click Here to see an example of the basic If-Then-Else syntax in the Microsoft documentation. Click the "Back" button in your browser to return.

We will use code taken from the text used for the "Complete Course", Microsoft Visual Basic .NET Step by Step. Although this code is left justified here, copy and paste it into Visual Studio .NET and it will be formatted correctly.

Dim AdjustedIncome, TaxDue As Double
If AdjustedIncome <= 27050 Then
' 15% tax bracket
TaxDue = AdjustedIncome * 0.15
ElseIf AdjustedIncome <= 65550 Then
' 28% tax bracket
TaxDue = 4057.5 + ((AdjustedIncome - 27050) * 0.28)
ElseIf AdjustedIncome <= 136750 Then
' 31% tax bracket
TaxDue = 4057.5 + ((AdjustedIncome - 65550) * 0.31)
ElseIf AdjustedIncome <= 297350 Then
' 36% tax bracket
TaxDue = 4057.5 + ((AdjustedIncome - 136750) * 0.36)
Else
' 39.6% tax bracket
TaxDue = 4057.5 + ((AdjustedIncome - 297350) * 0.396)
End If

Whenever you have a series of decisions like this, a Select Case structure ought to be considered. Here's the same code using a Select Case Structure. Again, copy and paste this into the VB.NET editor in Visual Studio .NET for a correctly formatted version.

Select Case AdjustedIncome
Case Is <= 27050
' 15% tax bracket
TaxDue = AdjustedIncome * 0.15
Case Is <= 65550
' 28% tax bracket TaxDue = 4057.5 + ((AdjustedIncome - 27050) * 0.28)
Case Is <= 136750
' 31% tax bracket TaxDue = 4057.5 + ((AdjustedIncome - 65550) * 0.31)
Case Is <= 297350
' 36% tax bracket TaxDue = 4057.5 + ((AdjustedIncome - 136750) * 0.36)
Case Else
' 39.6% tax bracket TaxDue = 4057.5 + ((AdjustedIncome - 297350) * 0.396)
End Select

If you initialize AdjustedIncome to say, $1,000,000 (that is, a small, insignificant fraction of what Bill Gates makes in a year), you will find that you get exactly the same answer with either code. Use MsgBox or Debug.Write to see the answer. (If you use Debug.Write, make sure the Output window is displayed.)

So ...

Assignment: Which One Should You Use?

I'll give you MY answer in the "Complete Course" for VB.NET. Sign up for the entire course at ... this signup page.