Conditional Switches
Conditional Switches
Case Switches
To let you create a conditional statement that considers various outcomes, the C# language provides a keyword named switch. It is used to create a statement that different values of the same type one after another. The primary formulat to follow is:
switch(expression) { case choice1: statement1; break; case choice2: statement2; break; case choice-n: statement-n; break; }
Put the value or expression to evaluate in the parentheses of switch, This is followed by a body delimited by an opening and a closing curly bracket. In the curly bracket, create a section for each possible value passed to switch. Each sections starts with the case keyword followed by a possible and a colon. The section must end with the break keyword and a semicolon.
Between the colon and the break; expression, create a clause that would execute if the value of the case is valid.
Practical Learning: Introducing Conditional Switches
namespace Chemistry04
{
public class Element
{
public string Symbol;
public string ElementName;
public int AtomicNumber;
public double AtomicWeight;
public Element(int number)
{
AtomicNumber = number;
}
public Element(string symbol)
{
Symbol = symbol;
}
public Element(int number, string symbol, string name, double mass)
{
Symbol = symbol;
ElementName = name;
AtomicWeight = mass;
AtomicNumber = number;
}
}
}A Default Switch
When establishing the possible outcomes that a switch statement should consider, at times there will be possibilities other than those listed and you will likely want to consider them. The group of statements that don't fit any of the valid cases can be handled by a section created uwing the default keyword. The default case would be considered if none of the listed cases matches the supplied answer. The syntax of the switch statement that considers the default case would be:
switch(expression) { case choice1: statement1; break; case choice2: statement2; break; case choice-n: statement-n; break; default: other-possibility; break; }
By tradition, the default case is usually created the last; but that's only a suggestion. The default case can appear as the first or between any two cases.
Categories of Switching Values
Switching to a Boolean Value
The switch is used to consider various types of values.
When creating a switch statement, you can make it consider Boolean values. To do this, pass a Boolean value or variable to switch(). For one case, use a true value. For the other case, you can use a false value. Here is an example:
using static System.Console;
public class VaccinationCampaign
{
public static int Main()
{
bool pregnancy = false;
Write("Is the patient pregnant (type True or False)? ");
pregnancy = bool.Parse( ReadLine());
Clear();
switch (pregnancy)
{
case true:
WriteLine("Department of Health");
WriteLine("--------------------------------------------------");
WriteLine("For a pregnant patient, the following vaccinations are recommended:");
WriteLine("1. Influenza (Inactivated)");
WriteLine("2. Tdap");
WriteLine("3. Hepatitis B: The patient should consult her physician");
break;
case false:
WriteLine("The patient will not need pregnacy recommendations");
break;
}
WriteLine("==================================================");
return 0;
}
}
Here is an example of running the program:
Is the patient pregnant (type True or False)? True
The second part would be:
Department of Health -------------------------------------------------- For a pregnant patient, the following vaccinations are recommended: 1. Influenza (Inactivated) 2. Tdap 3. Hepatitis B: The patient should consult her physician ================================================== Press any key to continue . . .
A Boolean value is considered as being True or else. As a result, you can one true case and the other would be a default clause. Here is an example:
using static System.Console;
public class VaccinationCampaign
{
public static int Main()
{
bool pregnancy = false;
Write("Is the patient pregnant (type True or False)? ");
pregnancy = bool.Parse( ReadLine());
Clear();
switch (pregnancy)
{
case true:
WriteLine("Department of Health");
WriteLine("--------------------------------------------------");
WriteLine("For a pregnant patient, the following vaccinations are recommended:");
WriteLine("1. Influenza (Inactivated)");
WriteLine("2. Tdap");
WriteLine("3. Hepatitis B: The patient should consult her physician");
break;
default:
WriteLine("The patient will not need a pregnacy text");
break;
}
WriteLine("==================================================");
return 0;
}
}
Switching to Integral Values
A switch can consider integral values. In this case, you can pass eother a constant value or an integer-based variable to it. Then in each case, process each of the outcomes.
Practical Learning: Introducing Integral Switches
using static System.Console;
namespace Chemistry04
{
public class Chemistry
{
private static void Describe(Element e)
{
WriteLine("Chemistry - " + e.ElementName);
WriteLine("------------------------");
WriteLine("Symbol: " + e.Symbol);
WriteLine("Element Name: " + e.ElementName);
WriteLine("Atomic Number: " + e.AtomicNumber);
WriteLine("Atomic Weight: " + e.AtomicWeight);
}
public static int Main()
{
Element elm = null;
Element h = new Element(1, "H", "Hydrogen", 1.008);
Element he = new Element(2, "He", "Helium", 4.002602);
Element li = new Element(3, "Li", "Lithium", 6.94);
Element be = new Element(4, "Be", "Beryllium", 9.0121831);
Element b = new Element(5, "B", "Boron", 10.81);
Element c = new Element(name: "Carbon", mass: 12.011, symbol: "C", number: 6);
Element n = new Element(number: 7, symbol: "N", name: "Nitrogen", mass: 14.007);
Element o = new Element(number: 8, symbol: "O", name: "Oxygen", mass: 15.999);
Element f = new Element(number: 9, symbol: "F", name: "Fluorine", mass: 15.999);
Element ne = new Element(number: 10, symbol: "Ne", name: "Neon", mass: 20.1797);
Element na = new Element(11, "Na", "Sodium", mass: 22.98976928);
Element mg = new Element(12, "Mg", "Magnesium", 24.305);
Element al = new Element(13, "Al", "Aluminium", 26.9815385);
WriteLine("Chemistry - Period Table");
WriteLine("------------------------------------------------");
Write("Type the atomic number of an element you want to review (1-15): ");
int answer = int.Parse(ReadLine());
Clear();
switch(answer)
{
case 1:
elm = h;
break;
case 2:
elm = he;
break;
case 3:
elm = li;
break;
case 4:
elm = be;
break;
case 5:
elm = b;
break;
case 6:
elm = c;
break;
case 7:
elm = n;
break;
case 8:
elm = o;
break;
case 9:
elm = f;
break;
case 10:
elm = ne;
break;
case 11:
elm = na;
break;
case 12:
elm = mg;
break;
case 13:
elm = al;
break;
default:
WriteLine("You must select a number between 1 (included) and 13 (included)");
break;
}
Describe(elm);
WriteLine("================================================");
return 0;
}
}
}Chemistry - Period Table ------------------------------------------------ Type the atomic number of an element you want to review (1-13):
Chemistry - Aluminium ------------------------ Symbol: Al Element Name: Aluminium Atomic Number: 13 Atomic Weight: 26.9815385 ================================================ Press any key to continue . . .
Switching Strings
A switch statement can be used to evaluate string values. To proceed, pass a double-quoted symbol or character, a string, or a variable that holds a string. For each case, process one of the values that can be considered.
Practical Learning: Switching Strings
using static System.Console;
namespace Chemistry04
{
public class Chemistry
{
private static void Describe(Element e)
{
WriteLine("Chemistry - " + e.ElementName);
WriteLine("------------------------");
WriteLine("Symbol: " + e.Symbol);
WriteLine("Element Name: " + e.ElementName);
WriteLine("Atomic Number: " + e.AtomicNumber);
WriteLine("Atomic Weight: " + e.AtomicWeight);
}
public static int Main()
{
Element elm = null;
Element h = new Element(1, "H", "Hydrogen", 1.008);
Element he = new Element(2, "He", "Helium", 4.002602);
Element li = new Element(3, "Li", "Lithium", 6.94);
Element be = new Element(4, "Be", "Beryllium", 9.0121831);
Element b = new Element(5, "B", "Boron", 10.81);
Element c = new Element(name: "Carbon", mass: 12.011, symbol: "C", number: 6);
Element n = new Element(number: 7, symbol: "N", name: "Nitrogen", mass: 14.007);
Element o = new Element(number: 8, symbol: "O", name: "Oxygen", mass: 15.999);
Element f = new Element(number: 9, symbol: "F", name: "Fluorine", mass: 15.999);
Element ne = new Element(number: 10, symbol: "Ne", name: "Neon", mass: 20.1797);
Element na = new Element(11, "Na", "Sodium", mass: 22.98976928);
Element mg = new Element(12, "Mg", "Magnesium", 24.305);
Element al = new Element(13, "Al", "Aluminium", 26.9815385);
Element si = new Element() { ElementName = "Silicon", AtomicWeight = 28.085, Symbol = "Si", AtomicNumber = 14 };
Element p = new Element() { ElementName = "Phosphorus", AtomicWeight = 30.973761998, Symbol = "P", AtomicNumber = 15 };
Element s = new Element(16, "S", "Sulfur", 32.06);
WriteLine("Chemistry - Periodic Table");
WriteLine("------------------------------------------------");
Write("Type the chemical symbol of an element you want to review (from H to S): ");
string answer = ReadLine();
Clear();
switch (answer)
{
default:
WriteLine("You must type H, He, Li, Be, B, C, N, O, F, Ne, Na Mg, Al, Si, P, or S.");
break;
case "H":
elm = h;
break;
case "He":
elm = he;
break;
case "Li":
elm = li;
break;
case "Be":
elm = be;
break;
case "B":
elm = b;
break;
case "C":
elm = c;
break;
case "N":
elm = n;
break;
case "O":
elm = o;
break;
case "F":
elm = f;
break;
case "Ne":
elm = ne;
break;
case "Na":
elm = na;
break;
case "Mg":
elm = mg;
break;
case "Al":
elm = al;
break;
case "Si":
elm = si;
break;
case "P":
elm = p;
break;
case "S":
elm = s;
break;
}
Describe(elm);
WriteLine("================================================");
return 0;
}
}
}Chemistry - Periodic Table ------------------------------------------------ Type the chemical symbol of an element you want to review (from H to S):
Chemistry - Silicon ------------------------ Symbol: Si Element Name: Silicon Atomic Number: 14 Atomic Weight: 28.085 ================================================ Press any key to continue . . .
Switching an Enumeration
The value that a switch condition processes can be the members of an enumeration. Start by passing a variable declared from an enumeration or an expresison that produces a value from the enumeration. For each case, use one of the members of the enumeration. Here is an example:
using static System.Console;
namespace HotelManagement
{
public class Exercise
{
public enum AvailabilityStatus
{
Available,
Occupied,
Reserved,
NeedsService
}
static int Main()
{
WriteLine("Hotel Management");
int roomNumber = 204;
AvailabilityStatus status = AvailabilityStatus.Available;
WriteLine("Room #: " + roomNumber);
switch (status)
{
case AvailabilityStatus.Available:
WriteLine("The room is currently available.");
break;
case AvailabilityStatus.Occupied:
WriteLine("The room is currently rented to a customer.");
break;
case AvailabilityStatus.Reserved:
WriteLine("The room has been reserved to a customer.");
break;
case AvailabilityStatus.NeedsService:
WriteLine("The room needs service, such as maintenance, or something else.");
break;
}
return 0;
}
}
}
This would produce:
Hotel Management Room #: 204 The room is currently available. Press any key to continue . . .
Options on Using Conditional Switches
Combining Cases
Each of the cases we have used so far examined only one possibility before executing the corresponding statement. You can combine cases to execute the same statement. To do this, type a case, its value, and a semi-colon. Type another case using the same formula. When the cases have been listed, create the necessary statement(s) and end with a break line. Here is an example:
using static System.Console;
public class VaccinationCampaign
{
public static int Main()
{
int ageRange = 0;
string gender = "u";
string pregnancy = null;
string patientName = null;
WriteLine("Department of Health");
WriteLine("-------------------------------------------------------");
WriteLine("Patient's Diagnosis");
Write("Patient's Name: ");
patientName = ReadLine();
Write("Patient's Gender (m - Male, f - Female): ");
gender = ReadLine();
WriteLine("Patients Age Ranges");
WriteLine("1 - Toddler");
WriteLine("2 - Kid");
WriteLine("3 - Teen");
WriteLine("4 - Adult");
Write("Type the patient's age range: ");
ageRange = int.Parse(ReadLine());
switch (ageRange)
{
case 1:
WriteLine("The government recommends that you follow the immunication schedule for the first 15 months.");
break;
case 2:
WriteLine("Consult the child's pediatrician and the school system for the list of recommended as well as required vaccines.");
break;
case 3:
case 4:
Write("Is the patient pregnant (y/n)? ");
pregnancy = ReadLine();
break;
}
Clear();
WriteLine("Department of Health");
WriteLine("-------------------------------------------------------");
WriteLine("Patient's Diagnosis");
WriteLine("Name: " + patientName);
switch (gender)
{
case "m":
case "M":
WriteLine("Gender: Male");
break;
default:
WriteLine("Gender: Unknown");
break;
case "f":
case "F":
WriteLine("Gender: Female");
break;
}
WriteLine("Age Range: " + ageRange);
switch(pregnancy)
{
case "y":
case "Y":
WriteLine("The following vaccinations are recommended:");
WriteLine("1. Influenza (Inactivated)");
WriteLine("2. Tdap");
WriteLine("3. Hepatitis B: The patient should consult her physician");
break;
}
WriteLine("=======================================================");
return 0;
}
}
Here is an example of running the program:
Department of Health ------------------------------------------------------- Patient's Diagnosis Patient's Name: Yolanda Mishra Patient's Gender (m - Male, f - Female): F Patients Age Ranges 1 - Toddler 2 - Kid 3 - Teen 4 - Adult Type the patient's age range: 2
The second part would produce:
Department of Health ------------------------------------------------------- Patient's Diagnosis Name: Yolanda Mishra Gender: Female Age Range: 2 ======================================================= Press any key to continue . . .
Here is another test of the program:
Department of Health ------------------------------------------------------- Patient's Diagnosis Patient's Name: Jennifer Humbleton Patient's Gender (m - Male, f - Female): f Patients Age Ranges 1 - Toddler 2 - Kid 3 - Teen 4 - Adult Type the patient's age range: 3 Is the patient pregnant (y/n)? Y
The second part would produce:
Department of Health ------------------------------------------------------- Patient's Diagnosis Name: Jennifer Humbleton Gender: Female Age Range: 3 The following vaccinations are recommended: 1. Influenza (Inactivated) 2. Tdap 3. Hepatitis B: The patient should consult her physician ======================================================= Press any key to continue . . .
In the above example, we used only two cases as a combination. You can combine as many cases as necessary.
Practical Learning: Combining Switches
using static System.Console;
namespace Chemistry04
{
public class Chemistry
{
private static void Describe(Element e)
{
WriteLine("Chemistry - " + e.ElementName);
WriteLine("------------------------");
WriteLine("Symbol: " + e.Symbol);
WriteLine("Element Name: " + e.ElementName);
WriteLine("Atomic Number: " + e.AtomicNumber);
WriteLine("Atomic Weight: " + e.AtomicWeight);
}
public static int Main()
{
Element elm = null;
Element h = new Element(1, "H", "Hydrogen", 1.008);
Element he = new Element(2, "He", "Helium", 4.002602);
Element li = new Element(3, "Li", "Lithium", 6.94);
Element be = new Element(4, "Be", "Beryllium", 9.0121831);
Element b = new Element(5, "B", "Boron", 10.81);
Element c = new Element(name: "Carbon", mass: 12.011, symbol: "C", number: 6);
Element n = new Element(number: 7, symbol: "N", name: "Nitrogen", mass: 14.007);
Element o = new Element(number: 8, symbol: "O", name: "Oxygen", mass: 15.999);
Element f = new Element(number: 9, symbol: "F", name: "Fluorine", mass: 15.999);
Element ne = new Element(number: 10, symbol: "Ne", name: "Neon", mass: 20.1797);
Element na = new Element(11, "Na", "Sodium", mass: 22.98976928);
Element mg = new Element(12, "Mg", "Magnesium", 24.305);
Element al = new Element(13, "Al", "Aluminium", 26.9815385);
Element si = new Element() { ElementName = "Silicon", AtomicWeight = 28.085, Symbol = "Si", AtomicNumber = 14 };
Element p = new Element() { ElementName = "Phosphorus", AtomicWeight = 30.973761998, Symbol = "P", AtomicNumber = 15 };
Element s = new Element(16, "S", "Sulfur", 32.06);
Element cl = new Element() { ElementName = "Chlorine", AtomicWeight = 35.446, Symbol = "Cl", AtomicNumber = 17 };
WriteLine("Chemistry - Periodic Table");
WriteLine("------------------------------------------------");
Write("Type the chemical symbol of an element you want to review (from H to Cl): ");
string answer = ReadLine();
Clear();
switch (answer)
{
default:
WriteLine("You must type H, He, Li, Be, B, C, N, O, F, Ne, Na Mg, Al, Si, P, S, or Cl.");
break;
case "cl":
case "Cl":
case "cL":
case "CL":
elm = cl;
break;
case "h":
case "H":
elm = h;
break;
case "he":
case "HE":
case "He":
case "hE":
elm = he;
break;
case "li":
case "Li":
case "LI":
case "lI":
elm = li;
break;
case "be":
case "Be":
case "bE":
case "BE":
elm = be;
break;
case "b":
case "B":
elm = b;
break;
case "C":
case "c":
elm = c;
break;
case "N":
case "n":
elm = n;
break;
case "o":
case "O":
elm = o;
break;
case "F":
case "f":
elm = f;
break;
case "NE":
case "ne":
case "Ne":
case "nE":
elm = ne;
break;
case "Na":
case "na":
case "NA":
case "nA":
elm = na;
break;
case "MG":
case "mG":
case "Mg":
case "mg":
elm = mg;
break;
case "Al":
case "AL":
case "aL":
case "al":
elm = al;
break;
case "SI":
case "Si":
case "sI":
case "si":
elm = si;
break;
case "p":
case "P":
elm = p;
break;
case "S":
case "s":
elm = s;
break;
}
Describe(elm);
WriteLine("================================================");
return 0;
}
}
}Chemistry - Periodic Table ------------------------------------------------ Type the chemical symbol of an element you want to review (from H to Cl):
Chemistry - Chlorine ------------------------ Symbol: Cl Element Name: Chlorine Atomic Number: 17 Atomic Weight: 35.446 ================================================ Press any key to continue . . .
Nesting and Switches
When you have created a conditional statement (if, if...else, and their variants), you can create a switch statement in the body of such a condition. This is referred to as nesting the statement.
In body of a case of a switch statement, you can create one or more conditional statements. This also is referred to as nesting.
Practical Learning: Ending the Lesson
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