Lesson 14: Mastering Select Case in VB2022
Implementing efficient decision-making with multiple conditions in Visual Basic
Key Takeaway
Select Case is a powerful alternative to complex If..ElseIf structures when evaluating a single expression against multiple possible values. It creates cleaner, more readable code and is especially efficient for range-based comparisons.
Welcome to Lesson 14 of our Visual Basic 2022 Tutorial! In this lesson, you'll learn how to implement efficient decision-making with the Select Case structure. You'll discover how to simplify complex conditional logic, handle multiple scenarios elegantly, and create more maintainable code.
Learning Objectives
- Understand when to use Select Case vs. If..Then..Else
- Master the Select Case structure syntax
- Implement range-based comparisons with Case Is and To
- Combine multiple conditions in a single Case statement
- Handle unexpected values with Case Else
- Create practical applications with Select Case
- Optimize Select Case performance
14.1 Select Case Fundamentals
Select Case evaluates a single expression and executes code blocks based on matching values. It provides a cleaner alternative to complex If..ElseIf structures.
Select Case Structure Diagram
14.1.1 When to Use Select Case vs. If..ElseIf
Select Case is ideal when evaluating a single expression against multiple possible values. If..ElseIf is better for complex conditions with multiple variables.
| Criteria | Select Case | If..ElseIf |
|---|---|---|
| Expression | Evaluates one expression | Can evaluate multiple expressions |
| Readability | More readable for multiple values | Better for complex conditions |
| Range Handling | Excellent with "To" keyword | Requires logical operators |
| Performance | Slightly faster for many cases | Comparable for few conditions |
14.1.2 Basic Syntax
The fundamental structure of Select Case in VB2022:
Select Case expression Case value1 ' Code to execute when expression = value1 Case value2 ' Code to execute when expression = value2 Case value3 ' Code to execute when expression = value3 Case Else ' Code to execute when no match End Select
Best Practice
Always include a Case Else block to handle unexpected values. This ensures your program behaves predictably even with unexpected inputs.
14.2 Case Statement Variations
Select Case provides flexible ways to match values beyond simple equality.
14.2.1 Matching Multiple Values
You can match multiple values in a single Case statement by separating them with commas:
Dim day As Integer = DateTime.Now.DayOfWeek Select Case day Case DayOfWeek.Saturday, DayOfWeek.Sunday lblDayType.Text = "Weekend" btnWork.Enabled = False Case DayOfWeek.Monday To DayOfWeek.Friday lblDayType.Text = "Weekday" btnWork.Enabled = True Case Else lblDayType.Text = "Invalid day" End Select
14.2.2 Range Matching with To
The To keyword allows you to specify value ranges:
Dim temperature As Double = Double.Parse(txtTemp.Text) Select Case temperature Case Is < 0 lblStatus.Text = "Freezing" pnlWarning.BackColor = Color.Blue Case 0 To 10 lblStatus.Text = "Cold" pnlWarning.BackColor = Color.LightBlue Case 11 To 20 lblStatus.Text = "Cool" pnlWarning.BackColor = Color.Green Case 21 To 25 lblStatus.Text = "Room Temperature" pnlWarning.BackColor = Color.Yellow Case 26 To 30 lblStatus.Text = "Warm" pnlWarning.BackColor = Color.Orange Case Is > 30 lblStatus.Text = "Hot" pnlWarning.BackColor = Color.Red Case Else lblStatus.Text = "Invalid temperature" End Select
14.2.3 Comparison Matching with Is
The Is keyword allows for comparison-based matching:
Dim score As Integer = CInt(txtScore.Text) Dim grade As String Select Case score Case Is >= 90 grade = "A" Case Is >= 80 grade = "B" Case Is >= 70 grade = "C" Case Is >= 60 grade = "D" Case Else grade = "F" End Select lblGrade.Text = $"Grade: {grade}"
14.3 Practical Examples
Let's implement real-world applications using Select Case:
1 Traffic Light Simulator
Determine driver action based on traffic light color:
Private Sub BtnCheckLight_Click(sender As Object, e As EventArgs) Handles BtnCheckLight.Click Dim lightColor As String = txtLightColor.Text.ToLower() Select Case lightColor Case "red" lblAction.Text = "Stop" lblAction.ForeColor = Color.Red Case "yellow" lblAction.Text = "Prepare to stop" lblAction.ForeColor = Color.Orange Case "green" lblAction.Text = "Go" lblAction.ForeColor = Color.Green Case "flashing red" lblAction.Text = "Stop and proceed with caution" lblAction.ForeColor = Color.DarkRed Case Else lblAction.Text = "Invalid light color" lblAction.ForeColor = Color.Black End Select End Sub
2 Shipping Cost Calculator
Calculate shipping costs based on weight and destination:
Private Sub BtnCalculate_Click(sender As Object, e As EventArgs) Handles BtnCalculate.Click Dim weight As Double Dim zone As String = cboZone.SelectedItem.ToString() Dim cost As Decimal = 0 If Double.TryParse(txtWeight.Text, weight) Then ' Calculate base cost based on weight Select Case weight Case 0 To 1 cost = 5.0 Case 1.01 To 5 cost = 8.5 Case 5.01 To 10 cost = 12.75 Case Is > 10 cost = 12.75 + (weight - 10) * 0.75 Case Else MessageBox.Show("Invalid weight entered") Return End Select ' Apply zone multiplier Select Case zone Case "International" cost *= 1.5 Case "Remote" cost *= 1.2 Case "Local" ' No additional charge Case Else MessageBox.Show("Please select a valid zone") Return End Select lblCost.Text = cost.ToString("C") Else MessageBox.Show("Please enter a valid weight") End If End Sub
3 User Role Permissions
Control UI elements based on user roles:
Private Sub SetUserPermissions(role As String) ' Reset all permissions btnEdit.Enabled = False btnDelete.Enabled = False btnAdmin.Visible = False Select Case role Case "Administrator" btnEdit.Enabled = True btnDelete.Enabled = True btnAdmin.Visible = True lblWelcome.Text = "Admin Dashboard" Case "Editor" btnEdit.Enabled = True lblWelcome.Text = "Editor Dashboard" Case "Viewer" lblWelcome.Text = "Viewer Dashboard" Case Else MessageBox.Show("Invalid user role") Application.Exit() End Select End Sub
14.3.1 Day of Week Name
Convert a numeric day to its name using Select Case:
Private Sub BtnGetDay_Click(sender As Object, e As EventArgs) Handles BtnGetDay.Click Dim dayNumber As Integer ' Validate input If Not Integer.TryParse(txtDayNumber.Text, dayNumber) Or dayNumber < 1 Or dayNumber > 7 Then lblResult.Text = "Please enter a number between 1 and 7" Return End If ' Convert number to day name Dim dayName As String Select Case dayNumber Case 1 : dayName = "Sunday" Case 2 : dayName = "Monday" Case 3 : dayName = "Tuesday" Case 4 : dayName = "Wednesday" Case 5 : dayName = "Thursday" Case 6 : dayName = "Friday" Case 7 : dayName = "Saturday" End Select lblResult.Text = $"Day {dayNumber} is {dayName}" lblResult.BackColor = Color.LightBlue End Sub
Lesson Summary
In this lesson, we've covered essential concepts about the Select Case structure in VB2022:
Structure
Select Case expression, Case values, Case Else, End Select
Matching Techniques
Exact values, value lists, ranges (To), comparisons (Is)
Best Practices
Always include Case Else, order cases logically, keep it readable
Use Cases
Menu systems, role-based permissions, grading systems, state machines
Performance
More efficient than If..ElseIf for multiple comparisons of the same expression
These skills will help you create more efficient and readable decision-making logic. In the next lesson, we'll explore looping structures to handle repetitive tasks.
Exercises
Practice what you've learned with these exercises:
Exercise 1: Simple Calculator
Create a calculator that:
- Takes two numbers and an operator (+, -, *, /)
- Uses Select Case to determine which operation to perform
- Handles division by zero with an error message
- Displays the result formatted to two decimal places
Exercise 2: Temperature Range Classifier
Build an application that:
- Accepts a temperature in Celsius or Fahrenheit
- Classifies the temperature into categories (Freezing, Cold, Cool, etc.)
- Uses Select Case with range matching
- Converts between temperature scales if needed
Exercise 3: Zodiac Sign Finder
Implement a solution that:
- Takes a birth month and day as input
- Uses Select Case to determine the zodiac sign
- Displays the sign's characteristics
- Handles invalid dates appropriately
Next Lesson
Ready to learn about repetitive tasks? Continue to Lesson 15: Looping in VB2022.
Related Resources
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