Master C# Programming From Scratch

Decision Making

Decision Making in programming is similar to decision making in real life. In programming too, a certain block of code needs to be executed when some condition is fulfilled. A programming language uses control statements to control the flow of execution of program based on certain conditions. Below are some decision-making statements.

1. if Statement

   The if statement checks the given condition. If the condition evaluates to be true then the block of code/statements will execute otherwise not.

   Static Code Layout Reference

   if ( condition ) {
   

     //code to be executed

   }
   

   Note:If the curly brackets { } are not used with if statements then the statement just next to it is only considered associated with the if statement.

   Static Code Layout Reference

   string name = "CIIT";
   
   // Using if statement
   if (name == "CIIT") {
     Console.WriteLine("Welcome to CIIT Training Institute");
   }
   

2. if-else Statement

   Use this when we want one action to happen if the condition is true, and an alternative action to happen if it is false

   Static Code Layout Reference

   int num = 20;
   
   if (num % 2 == 0)
   {
     Console.WriteLine($"The number {num} is an even.");
   }
   else
   {
     Console.WriteLine($"The number {num} is an odd.");
   }

3. else if Statement (Multiple Conditions)

   If you need to test multiple distinct conditions, you can chain them using else if The computer checks them in order and runs the code for the first condition that evaluates to true

   Static Code Layout Reference

   int percentage = 85;
   
   if (percentage >= 80)
   {
      Console.WriteLine("Grade: Excellent");
   }
   else if (percentage >= 60)
   {
      Console.WriteLine("Grade: Good"); // This will execute
   }
   else if (percentage >= 40)
   {
      Console.WriteLine("Grade: Average");
   }
   else
   {
      Console.WriteLine("Grade: Poor"); // Fail if no conditions match
   }
   

4. Combining Conditions with Logical Operators

   We can check multiple conditions inside a single if statement using logical operators:

   • && (AND): Both conditions must be true.

   • || (OR): At least one condition must be true.

   • ! (NOT): Reverses the truth of the condition

   Static Code Layout Reference

   int a=10;
   int b=20;
   int c= 30;
   
   if (a > b && a>c)
   {
     Console.WriteLine($"{a} is greatest");
   }
   else if(b>a && b>c)
   {
     Console.WriteLine($"{b} is greatest");
   }
   else if(a==b && b>c && c==a)
   {
     Console.WriteLine($"all are equal");
   }
   else
   {
     Console.WriteLine($"{c} is greatest");
   }
   

Switch Case Statement

In C#, the switch statement is a control flow structure used to execute a specific block of code out of multiple choices. It is a cleaner, more readable alternative to an if-else if ladder when you are comparing one variable against a list of concrete values.

Traditional switch Statement

The traditional switch evaluates a variable (the expression) and matches it against various case labels.

Grouping Multiple Cases

If multiple cases share the exact same code, you can stack them together without a break between them.

Modern C# switch Expressions

Introduced in C# 8.0, the switch expression provides a much cleaner, more compact syntax when you want to return a value from the switch block.

Instead of case and break, it uses the lambda arrow (=>), and replacing default is the discard underscore (_).

Advanced Switch with Type Checking (is Pattern)

You can use switch to inspect the type of an object, combining the logic of the is operator with branching.