June 29, 2022 -- take the first step with C ＃ -- add decision logic to the code using the "if", "else" and "else if" statements in C ＃

Learn how to branch the execution path of your code by evaluating Boolean expressions .

brief introduction

adopt C# programing language , You can build applications that use decision logic . By branching logic , Your application can execute different instructions according to a set of conditions .

Use if sentence

The most widely used branch statements are  if  sentence . if  Statement is a Boolean expression , The latter is enclosed in a set of parentheses . If the expression is true, execute  if  Code after statement . If the expression is false, Then skip  if  Code after statement .

Use if Statement to create a random number game

We will use  Random.Next()  Method to simulate throwing three six sided dice .

• If you roll any two dice to get the same value , You will get two bonus points for the same number of points on two dice .
• If you roll all three dice to get the same value , You will get six bonus points for three dice with the same number of points .
• If the sum of the three dice plus all bonus points is greater than or equal to 15, You win the game . otherwise , You lost .

step 1- Write code to generate three random numbers and display them in the output

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

Dice roll: 2 + 2 + 2 = 6

step 2- Add one if sentence , Based on total The value of the variable displays different messages

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if (total > 14)
{
    Console.WriteLine("You win!");
}

if (total < 15)
{
    Console.WriteLine("Sorry, you lose.");
}

Dice roll: 5 + 5 + 3 = 13
Sorry, you lose.

What is a Boolean expression ？

Boolean expressions return Boolean values （true  or  false） Arbitrary code for .

string.Contains()  Method to calculate whether a string contains another string

string message = "The quick brown fox jumps over the lazy dog.";
bool result = message.Contains("dog");
Console.WriteLine(result);

if (message.Contains("fox"))
{
    Console.WriteLine("What does the fox say?");
}

True
What does the fox say?

What is a code block ？

step 3- Add another if Statement to achieve double reward

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    Console.WriteLine("You rolled doubles! +2 bonus to total!");
    total += 2;
}

if (total >= 15)
{
    Console.WriteLine("You win!");
}

if (total < 15)
{
    Console.WriteLine("Sorry, you lose.");
}

Dice roll: 3 + 6 + 5 = 14
Sorry, you lose.

step 4- Add another if Statement to achieve triple reward

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    Console.WriteLine("You rolled doubles! +2 bonus to total!");
    total += 2;
}

if ((roll1 == roll2) && (roll2 == roll3)) 
{
    Console.WriteLine("You rolled triples! +6 bonus to total!");
    total += 6;
}

if (total >= 15)
{
    Console.WriteLine("You win!");
}

if (total < 15)
{
    Console.WriteLine("Sorry, you lose.");
}

Dice roll: 1 + 1 + 5 = 7
You rolled doubles! +2 bonus to total!
Sorry, you lose.

Logical problems and opportunities to improve code

review

Use “else” and “else if” sentence

By adding else and else if Statement to improve the code and fix bug

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    Console.WriteLine("You rolled doubles!  +2 bonus to total!");
    total += 2;
}

if ((roll1 == roll2) && (roll2 == roll3))
{
    Console.WriteLine("You rolled triples!  +6 bonus to total!");
    total += 6;
}

if (total >= 15)
{
    Console.WriteLine("You win!");
}
else 
{
    Console.WriteLine("Sorry, you lose.");
}

Dice roll: 5 + 1 + 4 = 10
Sorry, you lose.

step 1- Use if and else sentence , Instead of two separate if sentence

int roll1 = 6;
int roll2 = 6;
int roll3 = 6;

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    if ((roll1 == roll2) && (roll2 == roll3))
    {
        Console.WriteLine("You rolled triples!  +6 bonus to total!");
        total += 6;
    }
    else
    {
        Console.WriteLine("You rolled doubles!  +2 bonus to total!");
        total += 2;
    }
}

if (total >= 15)
{
    Console.WriteLine("You win!");
}
else 
{
    Console.WriteLine("Sorry, you lose.");
}

Dice roll: 6 + 6 + 6 = 18
You rolled triples!  +6 bonus to total!
You win!

step 2- Use nesting to eliminate the superposition of double rewards and triple rewards

  Players should only win one prize ：

• If the player's score is greater than or equal to 16, Win a new car .
• If the player's score is greater than or equal to 10, Win a new laptop .
• If the player's score is just 7, To win a chance to travel .
• otherwise , The player wins a kitten .

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    if ((roll1 == roll2) && (roll2 == roll3))
    {
        Console.WriteLine("You rolled triples!  +6 bonus to total!");
        total += 6;
    }
    else
    {
        Console.WriteLine("You rolled doubles!  +2 bonus to total!");
        total += 2;
    }
}

if (total >= 16)
{
    Console.WriteLine("You win a new car!");
}
else if (total >= 10)
{
    Console.WriteLine("You win a new laptop!");
}
else if (total == 7)
{
    Console.WriteLine("You win a trip for two!");
}
else
{
    Console.WriteLine("You win a kitten!");
}

Dice roll: 1 + 5 + 1 = 7
You rolled doubles!  +2 bonus to total!
You win a kitten!

step 3- Use if、else and else if Statements provide rewards , Instead of showing a victory or defeat message

  Players should only win one prize ：

• If the player's score is greater than or equal to 16, Win a new car .
• If the player's score is greater than or equal to 10, Win a new laptop .
• If the player's score is just 7, To win a chance to travel .
• otherwise , The player wins a kitten .

Random dice = new Random();

int roll1 = dice.Next(1, 7);
int roll2 = dice.Next(1, 7);
int roll3 = dice.Next(1, 7);

int total = roll1 + roll2 + roll3;

Console.WriteLine($"Dice roll: {roll1} + {roll2} + {roll3} = {total}");

if ((roll1 == roll2) || (roll2 == roll3) || (roll1 == roll3))
{
    if ((roll1 == roll2) && (roll2 == roll3))
    {
        Console.WriteLine("You rolled triples!  +6 bonus to total!");
        total += 6;
    }
    else
    {
        Console.WriteLine("You rolled doubles!  +2 bonus to total!");
        total += 2;
    }
}

if (total >= 16)
{
    Console.WriteLine("You win a new car!");
}
else if (total >= 10)
{
    Console.WriteLine("You win a new laptop!");
}
else if (total == 7)
{
    Console.WriteLine("You win a trip for two!");
}
else
{
    Console.WriteLine("You win a kitten!");
}

review

Challenge

Random random = new Random();
int daysUntilExpiration = random.Next(12);
int discountPercentage = 0;

// Your code goes here

Console.WriteLine(daysUntilExpiration);
if(daysUntilExpiration==1)
{
    discountPercentage=20;
    Console.WriteLine("Your subscription expires within a day!");
    Console.WriteLine("Renew now and save {0}%!",discountPercentage);
}
else if(daysUntilExpiration>1&&daysUntilExpiration<=5)
{
    discountPercentage=10;
    Console.WriteLine("Your subscription expires in {0} days.",daysUntilExpiration);
    Console.WriteLine("Renew now and save {0}%!",discountPercentage);
}
else if(daysUntilExpiration<=10)
{
    Console.WriteLine("Your subscription will expire soon. Renew now!");
}
else
{
    Console.WriteLine("Your subscription has expired.");
}

9
Your subscription will expire soon. Renew now!

11
Your subscription has expired.

5
Your subscription expires in 5 days.
Renew now and save 10%!

Solution ：

Random random = new Random();
int daysUntilExpiration = random.Next(12);
int discountPercentage = 0;

if (daysUntilExpiration == 0)
{
    Console.WriteLine("Your subscription has expired.");
}
else if (daysUntilExpiration == 1)
{
    Console.WriteLine("Your subscription expires within a day!");
    discountPercentage = 20;
}
else if (daysUntilExpiration <= 5)
{
    Console.WriteLine($"Your subscription expires in {daysUntilExpiration} days.");
    discountPercentage = 10;
}
else if (daysUntilExpiration <= 10)
{
    Console.WriteLine("Your subscription will expire soon. Renew now!");
}

if (discountPercentage > 0)
{
    Console.WriteLine($"Renew now and save {discountPercentage}%.");
}