Mastering C# Fundamentals: 'if`, `else if`, and Multiple Conditions

Meta Description

Learn how to use if, else if, and nested if statements in C# to make dynamic decisions in your applications. Discover how to combine multiple conditions with logical operators (&&, ||) to create flexible and robust control flows, with practical examples and clear explanations.

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Sequential Flow vs. Conditional Flow

In programming, conditional statements enable dynamic decision-making. Unlike sequential code, which executes in order, conditional code reacts to specific criteria. For instance, deciding whether an employee qualifies for a bonus depends on their salary, experience, and employment status.

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Visualization of Decision Flow

Here’s a simplified flowchart to represent decision-making for employee bonuses:

1. Input salary, experience, and full-time status.
2. Condition Check:
   • Is the salary < $50,000 OR experience > 5 years?
   • AND is the employee full-time?
3. Output Results:
   • If true: Eligible for bonus.
   • Otherwise: Not eligible for bonus.

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Understanding if, else, and Logical Operators

Basic if-else Statement

An if statement evaluates a Boolean condition. If true, it executes the corresponding block of code; otherwise, the else block runs (if provided).

Example 1: Simple Bonus Check

Console.WriteLine("Enter the employee's salary:");
double salary = double.Parse(Console.ReadLine());

if (salary < 50000)
{
    Console.WriteLine("Eligible for a bonus.");
}
else
{
    Console.WriteLine("Not eligible for a bonus.");
}

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Logical Operators: Combining Conditions

Logical operators help combine multiple conditions:

• && (AND): Both conditions must be true.
• || (OR): At least one condition must be true.

Example 2: Bonus Check with Logical Operators

Let’s add conditions for years of experience and full-time status:

Console.WriteLine("Enter the employee's salary:");
double salary = double.Parse(Console.ReadLine());

Console.WriteLine("Enter the employee's years of experience:");
int experience = int.Parse(Console.ReadLine());

Console.WriteLine("Is the employee full-time (true/false)?");
bool isFullTime = bool.Parse(Console.ReadLine());

if ((salary < 50000 || experience > 5) && isFullTime)
{
    Console.WriteLine("Eligible for a bonus.");
}
else
{
    Console.WriteLine("Not eligible for a bonus.");
}

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Using Nested if Statements for Complex Logic

Nested if statements enable multi-level checks. For instance:

• If the salary is < $40,000 OR experience is > 7 years, check:
  • If full-time, grant a special bonus.
  • If part-time with > 10 years of experience, grant a part-time special bonus.

Example 3: Nested if with Logical Operators

if (salary < 40000 || experience > 7)
{
    if (isFullTime)
    {
        Console.WriteLine("Eligible for a special bonus as a full-time employee.");
    }
    else if (experience > 10)
    {
        Console.WriteLine("Eligible for a special bonus as a part-time employee with over 10 years of experience.");
    }
    else
    {
        Console.WriteLine("Not eligible for a special bonus.");
    }
}
else
{
    Console.WriteLine("Not eligible for a bonus.");
}

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Comparison: else if vs. Nested if

Feature	else if	Nested if
Purpose	Checks mutually exclusive conditions.	Drills down into sub-conditions for detailed checks.
Code Example	if (salary < 50k) else if (salary > 100k)	if (salary < 40k) { if (isFullTime) {...} }
Usage	Sequential and straightforward conditions.	Hierarchical or dependent conditions.

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Common Pitfalls and Edge Cases

1. Boundary Conditions: Test values at the edge of conditions (e.g., $50,000 or $40,000).
2. Error Handling: Validate user inputs to prevent runtime errors.

   if (!double.TryParse(Console.ReadLine(), out double salary))
   {
       Console.WriteLine("Invalid input. Please enter a valid number.");
       return;
   }

1. Readability: Avoid deeply nested if blocks. Refactor into methods if necessary.

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Assignments

Easy:

Write a program that determines if a student passes or fails based on:

• Score >= 50 is a pass.
• Otherwise, it’s a fail.

Medium:

Extend the above to:

• Score >= 80: "Distinction."
• Score >= 50 and < 80: "Pass."
• Otherwise: "Fail."

Difficult:

Create a program to calculate shipping costs based on:

• Order value (< $50, $50-$100, > $100).
• Shipping destination (local, international).
• Membership status (premium, regular).

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Conclusion

By mastering conditional statements and logical operators, you can make your C# applications smarter and more dynamic. Whether using if-else for simple decisions or nested if for hierarchical logic, clear structure and testing ensure robust programs. Practice with the provided examples and assignments to enhance your skills further!