Introduction to Case Switches

Breaking a Case

Imagine you have a list of values that can each respond to a condition as being true but you want to consider only one of those values. To let you check each one of those values, the C# language provides the switch conditional statement. It takes a value as done when calling a method. It also has a body delimited by curly brackets. In its body, each value is preceded by the case keyword. The formula to create a switch statement is:

switch(expression)
{
    case choice1:
        statement1;
	break;
    case choice2:
        statement2;
	break;
    case choice-n:
        statement-n;
	break;
}

The object or expression that holds the value to examine is passed to the parentheses of switch. The body of the switch contains one or more sections that each starts with the case keyword. Each case section considers one possible value that is followed by a colon. After the case statement, write code that must be applied to only that outcome. The case clause must end with break;.

The switch statement accepts different types of expressions or values.

Practical Learning: Switching a String

1. Start Microsoft Visual Studio
2. In the Visual Studio 2019 dialog box, click Create a New Project and click Next (if Microsoft Visual Studio was already opened, on its main menu, click File -> New -> Project...)
3. In the list of projects templates, click Windows Forms App (.NET Framework)
4. Click Next
5. Change the project Name to PayrollEvaluation05
6. Click Create
7. In the Solution Explorer, right-click Form1.cs -> Rename
8. Type PayrollEvaluation and press Enter
9. Read the message box and click Yes
10. In the Toolbox, under Common Controls, click ComboBox
11. Click the form
12. While the combo box is selected on the form, in the Properties window, click Items and click its button
13. In the text box of the String Collection Editor, type each of the following strings:

    Nothing
    Utah
    Illinois
    Indiana
    Michigan
    Colorado
    Pennsylvania
    North Carolina

    

14. Click OK
15. Complete the design of the form as follows:

    

    Control	(Name)	Text	TextAlign
    Label		Gross Salary:
    TextBox	txtGrossSalary	0	Right
    Label		State:
    TextBox	cbxStates
    Button	btnCalculate	Calculate
    Label		txtEmployeeResidence
    TextBox	txtEmployeeResidence		Right
    Label		txtIncomeTax
    TextBox			Right
    Label		Net Pay:
    TextBox	txtNetPay		Right

16. Double-click eh Calculate button
17. Right-click inside the Code Editor and click Remove and Sort Usings

Switching a String

Probably the easiest type of value to deal with is text because it can hold any value. This means that the expression you want to consider could have disparate combinations of characters. Still in the body of the switch, each case section should deal with a valid value of the possible outcomes.

Practical Learning: Switching a String

1. Implement the event as follows:

   using System;
   using System.Windows.Forms;
   
   namespace PayrollPreparation07
   {
       public partial class PayrollEvaluation : Form
       {
           public PayrollEvaluation()
           {
               InitializeComponent();
           }
   
           private void btnCalculate_Click(object sender, EventArgs e)
           {
               double taxes = 0.00;
               string residence = "None";
               string state = cbxStates.Text;
               double salary = Convert.ToDouble(txtGrossSalary.Text);
               
               switch (state)
               {
                   case "Colorado":
                       taxes = salary * 4.63 / 100.00;
                       residence = "Colorado (4.63%)";
                       break;
                   case "Illinois":
                       taxes = salary * 3.75 / 100.00;
                       residence = "Illinois (3.75%)";
                   break;
                   case "Indiana":
                       taxes = salary * 3.3 / 100.00;
                       residence = "Indiana (3.3%)";
                       break;
                   case "Michigan":
                       taxes = salary * 4.25 / 100.00;
                       residence = "Michigan (4.25%)";
                       break;
                   case "North Carolina":
                       taxes = salary * 5.75 / 100.00;
                       residence = "North Carolina (5.75%)";
                       break;
                   case "Pennsylvania":
                       taxes = salary * 3.07 / 100.00;
                       residence = "Pennsylvania (3.07%)";
                       break;
                   case "Utah":
                       taxes = salary * 5 / 100.00;
                       residence = "Utah (5%)";
                       break;
               }
   
               txtEmployeeResidence.Text = residence;
               txtStateIncomeTax.Text = taxes.ToString("F"); 
               txtNetPay.Text = (salary - taxes).ToString("F");
           }
       }
   }

2. To execute the application, on the main menu,, click Debug -> Start Without Debugging

   

3. In the Gross Salary text box, type a number such as 2814.83
4. Click the arrow of the combo box to select a state:

   

5. From the list, click Indiana:

   

6. Click the Calculate button:

   

7. Close the form and return to your programming environment
8. Start Microsoft Visual Studio and, on the Visual Studion 2019 dialog box, click Create a New Project (if Microsoft Visual Studio was already launched, on the main menu of, click File -> New -> Project...)
9. In the list of projects templates, click Winows Forms App (.NET Framework)
10. Click Next
11. Change the project Name to PayrollEvaluation06
12. Click Create
13. In the Solution Explorer, right-click PayrollEvaluation06 -> Add -> Class...
14. Change the name to Calculations
15. Click Add
16. Right-click inside the Code Editor -> Remove and Sort Usings
17. Change the class as follows:

    namespace PayrollEvaluation06
    {
        static public class Calculations
        {
            public static double Add(double a, double b)
            {
                return a + b;
            }
    
            static public double Subtract(double a, double b)
            {
                return a - b;
            }
    
            public static double Multiply(double a, double b)
            {
                return a * b;
            }
    
            public static double Add5(double a, double b, double c, double d, double e)
            {
                return a + b + c + d + e;
            }
    
            public static double Multiply3(double a, double b, double c)
            {
                return a * b * c;
            }
        }
    }

18. On the main menu, click Project -> Add Class...
19. Change the name to TimeSheet
20. Click Add
21. Right-click inside the Code Editor -> Remove and Sort Usings
22. Change the code as follows:

    namespace PayrollEvaluation06
    {
        public class TimeSheet
        {
            public double Monday { get; set; }
            public double Tuesday { get; set; }
            public double Wednesday { get; set; }
            public double Thursday { get; set; }
            public double Friday { get; set; }
    
            public TimeSheet()
            {
                Monday = 0.00;
                Tuesday = 0.00;
                Wednesday = 0.00;
                Thursday = 0.00;
                Friday = 0.00;
            }
    
            public TimeSheet(double mon, double tue,
                             double wed, double thu, double fri)
            {
                Monday = mon;
                Tuesday = tue;
                Wednesday = wed;
                Thursday = thu;
                Friday = fri;
            }
        }
    }

23. In the Solution Explorer, right-click Form1.cs and click Rename
24. Type PayrollPreparation (to get PayrollPreparation.cs) and press Enter
25. Read the message box and press Enter twice (to access the form)
26. Design the form as follows:

    

    Control	(Name)	Text	Other Properties
    GroupBox		Work Preparation
    Label		Hourly Salary:
    TextBox	txtHourlySalary	0.00	TextAlign: Right
    CheckBox	chkPaidOvertime	Paid Overtime	CheckAlign: MiddleRight
    Label		Monday
    Label		Tuesday
    Label		Wednesday
    Label		Thursday
    Label		Friday
    TextBox	txtMonday	0.00	Right
    TextBox	txtTuesday	0.00	Right
    TextBox	txtWednesday	0.00	Right
    TextBox	txtThursday	0.00	Right
    TextBox	txtFriday	0.00	Right
    Button	btnCalculate	Calculate
    GroupBox		Pay Summary
    Label		Time Worked:
    TextBox	txtTimeWorked		Right
    Label		Overtime:
    TextBox	txtOvertime	Right	Right
    Label		Net Pay:
    TextBox	txtNetPay		Right

27. Double-click the Calculate button
28. Right-click inside the Code Editor and click Remove and Sort Usings

Switching to a Boolean Value

If you want to consider one of two outcomes of a Boolean expression, pass a Boolean variable or an expression that produces a Boolean value to a switch statement. One case would consider a true value and another case would consider a false value.

Practical Learning: Switching to a Boolean Value

1. Change the document as follows:

   using System;
   using System.Windows.Forms;
   
   namespace PayrollEvaluation06
   {
       public partial class PayrollPreparation : Form
       {
           public PayrollPreparation()
           {
               InitializeComponent();
           }
   
           void EvaluateOvertimeSalary(TimeSheet ts, double hourlySalary)
           {
               double overtimePay;
               double overtime = 0.00;
               // mon + tue + wed + thu + fri
               double timeWorked = Calculations.Add5(ts.Monday, ts.Tuesday, ts.Wednesday, ts.Thursday, ts.Friday);
               double netPay = hourlySalary * timeWorked;
   
               if (timeWorked > 40.00)
               {
                   // timeWorked - 40.00
                   overtime = Calculations.Subtract(timeWorked, 40.00);
                   // hourlySalary * 1.50 * overtime
                   overtimePay = Calculations.Multiply3(hourlySalary, 1.50, overtime);
                   // (hourlySalary * 40.00) + overtimePay
                   netPay = Calculations.Add(Calculations.Multiply(hourlySalary, 40.00), overtimePay);
               }
   
               txtTimeWorked.Text = timeWorked.ToString("F");
               txtOvertime.Text = overtime.ToString("F");
               txtNetPay.Text = netPay.ToString("F");
           }
   
           private void btnCalculate_Click(object sender, EventArgs e)
           {
               double mon = Convert.ToDouble(txtMonday.Text);
               double tue = Convert.ToDouble(txtTuesday.Text);
               double wed = Convert.ToDouble(txtWednesday.Text);
               double thu = Convert.ToDouble(txtThursday.Text);
               double fri = Convert.ToDouble(txtFriday.Text);
   
               double hSalary = Convert.ToDouble(txtHourlySalary.Text);
   
               TimeSheet record = new TimeSheet(mon, tue, wed, thu, fri);
   
               switch (chkPaidOvertime.Checked)
               {
                   case true:
                       EvaluateOvertimeSalary(record, hSalary);
                       break;
                   case false:
                       double timeWorked = Calculations.Add5(ts.Monday, ts.Tuesday, ts.Wednesday, ts.Thursday, ts.Friday);
   
                       txtTimeWorked.Text = timeWorked.ToString("F");
                       txtOvertime.Text = "0.00";
                       txtNetPay.Text = (timeWorked * hSalary).ToString("F");
                       break;
               }
           }
       }
   }

2. To execute the project, press Ctrl + F5

   

3. In the Hourly Salary text box, type a decimal number such as 25.85
4. In each days text box, type a decimal number between 0 and 8 but divisible by 0.50. Here are examples:

   

5. Click the Calculate button:

   

6. Click the Paid Overtime check box
7. Click the Calculate button:

   

8. Close the form and return to your programming environment
9. To create an enumeration, change the document as follows:
10. On the main menu of Microsoft Visual Studio, click File -> New -> Project...
11. In the list of projects templates, click Windows Forms App (.NET Framework)
12. Click Next
13. Change the project Name to Chemistry07
14. Click Add
15. On the main menu, click Project -> Add Class...
16. Replace the name with Element
17. Click Add
18. Change the code as follows:

    namespace Chemistry07
    {
        public enum Phase
        {
            Gas,
            Liquid,
            Solid,
            Unknown
        }
        public class Element
        {
            public string Symbol       { get; set; }
            public string ElementName  { get; set; }
            public int    AtomicNumber { get; set; }
            public double AtomicWeight { get; set; }
            public Phase  Phase        { get; set; }
    
            public Element()                 {}
            public Element(int number)    => AtomicNumber = number;
            public Element(string symbol) => Symbol = symbol;
    
            public Element(int number, string symbol, string name, double mass, Phase phase)
            {
                ElementName = name;
                AtomicWeight = mass;
                Phase = phase;
                Symbol = symbol;
                AtomicNumber = number;
            }
        }
    }

19. In the Solution Explorer, right-click Form1.cs -> Rename
20. Type Chemistry to get Chemistry.cs
21. Press Enter three times (to accept the name and access the form
22. Design the form as follows:

    

    Control	(Name)	Text
    Label		Enter Atomic #::
    TextBox	txtValueEntered
    Button	btnFind	Find
    GroupBox		Element Detais
    Label		Atomic Number:
    TextBox	txtAtomicNumber
    Label		Symbol:
    TextBox	txtSymbol
    Label		Element Name:
    TextBox	txtElementName
    Label		Atomic Weight:
    TextBox	txtAtomicWeight
    Label		Phase:
    TextBox	txtPhase

23. Double-click the Find button
24. Right-click inside the Code Editor and click Remove and Sort Usings

Switching Integral Values

Switching an Integer

Probably the most regularly used type of value in a switch expression is a natural number. The object or expression passed to the switch can come from any source as long as it represents a constant integer.

Practical Learning: Introducing Logical Disjunctions

1. Implement the event as follows:

   using System;
   using System.Windows.Forms;
   
   namespace Chemistry07
   {
       public partial class Chemistry : Form
       {
           public Chemistry()
           {
               InitializeComponent();
           }
   
           private void btnFind_Click(object sender, EventArgs e)
           {
               Element H = new Element(1, "H", "Hydrogen", 1.008, Phase.Gas);
               Element He = new Element(2, "He", "Helium", 4.002602, Phase.Gas);
               Element Li = new Element(3, "Li", "Lithium", 6.94, Phase.Solid);
               Element Be = new Element(4, "Be", "Beryllium", 9.0121831, Phase.Solid);
               Element B = new Element(5, "B", "Boron", 10.81, Phase.Solid);
               Element C = new Element(name: "Carbon", mass: 12.011, symbol: "C", number: 6, phase: Phase.Solid);
               Element N = new Element(7);
               N.Symbol = "N";
               N.AtomicWeight = 14.007;
               N.ElementName = "Nitrogen";
               N.Phase = Phase.Gas;
               Element O = new Element("O")
               {
                   AtomicNumber = 8,
                   ElementName = "Oxygen",
                   AtomicWeight = 15.999,
                   Phase = Phase.Gas
               };
               Element F = new Element("F") {  AtomicNumber = 9, ElementName = "Fluorine",
                                               AtomicWeight = 15.999,  Phase = Phase.Gas  };
               Element Ne = new Element("Ne")
               {
                   AtomicNumber = 10, ElementName = "Neon",
                   AtomicWeight = 20.1797, Phase = Phase.Gas
               };
               Element Na = new Element(11, "Na", "Sodium", 22.98976928, Phase.Solid);
               Element Mg = new Element(12, "Mg", "Magnesium", 24.305, Phase.Solid);
               Element Al = new Element(13, "Al", "Aluminium", 26.9815385, Phase.Solid);
               Element Si = new Element() { ElementName = "Silicon", AtomicWeight = 28.085, Symbol = "Si", AtomicNumber = 14, Phase = Phase.Solid };
               Element P = new Element() {
                   ElementName = "Phosphorus", AtomicWeight = 30.973761998,
                   Symbol = "P", AtomicNumber = 15, Phase = Phase.Solid };
               Element S = new Element(16, "S", "Sulfur", 32.06, Phase.Solid);
               Element Cl = new Element() { ElementName = "Chlorine", AtomicWeight = 35.446, Symbol = "Cl", AtomicNumber = 17, Phase = Phase.Gas };
               Element Ar = new Element() { ElementName = "Argon", AtomicWeight = 39.792, Symbol = "Ar", AtomicNumber = 18, Phase = Phase.Gas };
               Element K  = new Element() { ElementName = "Potassium", Symbol = "K", Phase = Phase.Solid, AtomicWeight = 39.0983, AtomicNumber = 19 };
               Element Ca = new Element() { Symbol = "Ca", Phase = Phase.Solid, AtomicNumber = 20, ElementName = "Calcium", AtomicWeight = 40.078 };
               Element Sc  = new Element() { AtomicNumber = 21, Symbol = "Sc", AtomicWeight = 44.9559085, Phase = Phase.Solid, ElementName = "Scandium" };
   
               Element selected = new Element();
               int number = int.Parse(txtValueEntered.Text);
   
               switch (number)
               {
                   case 20:
                       selected = Ca;
                       break;
                   case 12:
                       selected = Mg;
                       break;
                   case 5:
                       selected = B;
                       break;
                   case 17:
                       selected = Cl;
                       break;
                   case 15:
                       selected = P;
                       break;
                   case 6:
                       selected = C;
                       break;
                   case 21:
                       selected = Sc;
                       break;
                   case 7:
                       selected = N;
                       break;
                   case 9:
                       selected = F;
                       break;
                   case 2:
                       selected = He;
                       break;
                   case 10:
                       selected = Ne;
                       break;
                   case 11:
                       selected = Na;
                       break;
                   case 4:
                       selected = Be;
                       break;
                   case 13:
                       selected = Al;
                       break;
                   case 3:
                       selected = Li;
                       break;
                   case 19:
                       selected = K;
                       break;
                   case 14:
                       selected = Si;
                       break;
                   case 16:
                       selected = S;
                       break;
                   case 8:
                       selected = O;
                       break;
                   case 18:
                       selected = Ar;
                       break;
               }
   
               txtSymbol.Text = selected.Symbol;
               txtAtomicNumber.Text = selected.AtomicNumber.ToString();
               txtElementName.Text = selected.ElementName;
               txtAtomicWeight.Text = selected.AtomicWeight.ToString();
               txtPhase.Text = selected.Phase.ToString();
           }
       }
   }

2. To execute the project, on the main menu, click Debug -> Start Without Debugging:

   

3. In the top text box, type a number between 1 (included) and 21 (included). Here is an example:

   

4. Click the Find button:

   

5. Close the form and return to your programming environment
6. On the main menu of Microsoft Visual Studio, click File -> New -> Project...
7. In the list of projects templates, click Windows Forms App (.NET Framework)
8. Click Next
9. Change the project Name to CompoundInterest3
10. Click Create
11. On the main menu, click Project -> Add New Item...
12. In the left list, under Visual C# Items, click Code and, in the middle list, click Code File
13. Change the file Name to Frequency
14. Click Add
15. In the empty document, type the following code:

    namespace CompoundInterest3
    {
        public enum CompoundFrequency
        {
            Daily,
            Weekly,
            Monthly,
            Quaterly,
            Semiannually,
            Annually
        }
    }

16. In the Solution Explorer, right-click Form1.cs -> Rename
17. Type CompoundInterest to get CompoundInterest.cs
18. Press Enter three times
19. Design the form as follows:

    

    Control	(Name)	Text	Other Properties
    Label		Principal:
    TextBox	txtPrincipal	0.00	TextAlign: Right
    Label		Interest Rate:
    TextBox	txtInterest Rate	0.00	TextAlign: Right
    Label		%
    Label		Periods:
    TextBox	txtPeriods	0	TextAlign: Right
    Label		Years:
    GroupBox		Compound Frequency
    RadioButton	rdoDaily	Daily	CheckAlign: MiddleRight
    RadioButton	rdoQuaterly	Quaterly	CheckAlign: MiddleRight
    RadioButton	rdoWeekly	Weekly	CheckAlign: MiddleRight
    RadioButton	rdoSemiannually	Semiannually	CheckAlign: MiddleRight
    RadioButton	rdoMonthly	Monthly	CheckAlign: MiddleRight
    RadioButton	rdoAnnually	Annually	CheckAlign: MiddleRight
    Button	btnCalculate	Calculate
    Label		Interest Earned:
    TextBox	txtInterestEarned		TextAlign: Right
    Label		Future Value:
    TextBox	txtFutureValue		TextAlign: Right

20. Double-click the Calculate button
21. Right-click the Code Editor and click Remove and Sort Usings

Switching an Enumeration

The switch operation supports values based on an enumeration. When creating the statement, you can pass an expression that holds the value of an enumeration. In the body of the switch clause, each case can represent one of the members of the enumeration.

Practical Learning: Introducing if...else if Conditions

1. Implement the event as follows:

   using System;
   using System.Windows.Forms;
   
   namespace CompoundInterest3
   {
       public partial class CompoundInterest : Form
       {
           public CompoundInterest()
           {
               InitializeComponent();
           }
   
           private void btnCalculate_Click(object sender, EventArgs e)
           {
               double frequency = 0.00;
               double principal = Convert.ToDouble(txtPrincipal.Text);
               double interestRate = Convert.ToDouble(txtInterestRate.Text);
               double periods = Convert.ToDouble(txtPeriods.Text);
   
               double iRate = interestRate / 100.00;
               CompoundFrequency compounding = CompoundFrequency.Daily;
   
               if (rdoDaily.Checked)
                   compounding = CompoundFrequency.Daily;
               if (rdoWeekly.Checked)
                   compounding = CompoundFrequency.Weekly;
               if (rdoMonthly.Checked)
                   compounding = CompoundFrequency.Monthly;
               if (rdoQuaterly.Checked)
                   compounding = CompoundFrequency.Quaterly;
               if (rdoSemiannually.Checked)
                   compounding = CompoundFrequency.Semiannually;
               if (rdoAnnually.Checked)
                   compounding = CompoundFrequency.Annually;
   
               switch (compounding)
               {
                   case CompoundFrequency.Daily:
                       frequency = 365.00;
                       break;
   
                   case CompoundFrequency.Weekly:
                       frequency = 52.00;
                       break;
   
                   case CompoundFrequency.Monthly:
                       frequency = 12.00;
                       break;
   
                   case CompoundFrequency.Quaterly:
                       frequency = 4.00;
                       break;
   
                   case CompoundFrequency.Semiannually:
                       frequency = 2.00;
                       break;
   
                   case CompoundFrequency.Annually:
                       frequency = 1.00;
                       break;
               }
   
               double futureValue = principal * Math.Pow((1.00 + (iRate / frequency)), frequency * periods);
               double interestEarned = futureValue - principal;
   
               txtInterestEarned.Text = interestEarned.ToString("F");
               txtFutureValue.Text = futureValue.ToString("F");
           }
       }
   }

2. To execute the application to test it, on the main menu, click Debug -> Start Without Debugging:

   

3. In the Principal text box, type a number such as 3685
4. In the Interest Rate text box, type a number such as 10.75

5. In the Periods text box, type a natural number such as 5
6. In the Compound Frequency group box, click one of the radio buttons such as Monthly:

   

7. Click the Calculate button:

   

8. Close the form and return to your programming environment
9. Close your programming environment

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