C# - Conditions

In C#, conditions are used to control the flow of execution in a program based on whether certain conditions are true or false. Here’s a detailed overview of how to use conditional statements in C#:

1. If Statement

The if statement evaluates a condition and executes a block of code if the condition is true.

csharp
int number = 10;

if (number > 0)
{
    Console.WriteLine("The number is positive.");
}

2. If-Else Statement

The if-else statement allows you to execute one block of code if the condition is true, and another block if the condition is false.

csharp
int number = -5;

if (number > 0)
{
    Console.WriteLine("The number is positive.");
}
else
{
    Console.WriteLine("The number is not positive.");
}

3. If-Else If-Else Statement

The if-else if-else statement provides multiple conditions to check, executing code for the first true condition.

csharp
int number = 0;

if (number > 0)
{
    Console.WriteLine("The number is positive.");
}
else if (number < 0)
{
    Console.WriteLine("The number is negative.");
}
else
{
    Console.WriteLine("The number is zero.");
}

4. Switch Statement

The switch statement evaluates a variable and executes the code block corresponding to the case that matches the variable's value.

csharp
int dayOfWeek = 3; // Assume 1 = Monday, 2 = Tuesday, etc.

switch (dayOfWeek)
{
    case 1:
        Console.WriteLine("Monday");
        break;
    case 2:
        Console.WriteLine("Tuesday");
        break;
    case 3:
        Console.WriteLine("Wednesday");
        break;
    case 4:
        Console.WriteLine("Thursday");
        break;
    case 5:
        Console.WriteLine("Friday");
        break;
    case 6:
        Console.WriteLine("Saturday");
        break;
    case 7:
        Console.WriteLine("Sunday");
        break;
    default:
        Console.WriteLine("Invalid day of the week");
        break;
}

5. Switch Expression (C# 8.0+)

The switch expression provides a more concise and readable way to handle multiple conditions.

csharp
int dayOfWeek = 3; // Assume 1 = Monday, 2 = Tuesday, etc.

string dayName = dayOfWeek switch
{
    1 => "Monday",
    2 => "Tuesday",
    3 => "Wednesday",
    4 => "Thursday",
    5 => "Friday",
    6 => "Saturday",
    7 => "Sunday",
    _ => "Invalid day of the week"
};

Console.WriteLine(dayName);

6. Ternary Conditional Operator

The ternary conditional operator is a shorthand way of writing simple if-else statements.

csharp
int number = 10;
string result = number > 0 ? "Positive" : "Non-positive";
Console.WriteLine(result);

7. Null-Coalescing Operator

The null-coalescing operator (??) returns the left-hand operand if it is not null; otherwise, it returns the right-hand operand.

csharp
string name = null;
string displayName = name ?? "Unknown";
Console.WriteLine(displayName); // Outputs "Unknown"

8. Null-Coalescing Assignment Operator (C# 8.0+)

The null-coalescing assignment operator (??=) assigns the right-hand operand to the left-hand operand only if the left-hand operand is null.

csharp
string name = null;
name ??= "Default Name";
Console.WriteLine(name); // Outputs "Default Name"

Example

Here’s a complete example demonstrating the use of various conditional statements:

csharp
using System;

class Program
{
    static void Main()
    {
        int number = 15;
        
        // If-Else
        if (number % 2 == 0)
        {
            Console.WriteLine("The number is even.");
        }
        else
        {
            Console.WriteLine("The number is odd.");
        }

        // Switch
        int dayOfWeek = 5;
        string dayName = dayOfWeek switch
        {
            1 => "Monday",
            2 => "Tuesday",
            3 => "Wednesday",
            4 => "Thursday",
            5 => "Friday",
            6 => "Saturday",
            7 => "Sunday",
            _ => "Invalid day of the week"
        };

        Console.WriteLine($"Day of the week: {dayName}");

        // Ternary Operator
        string result = number > 10 ? "Greater than 10" : "10 or less";
        Console.WriteLine(result);

        // Null-Coalescing Operator
        string name = null;
        string displayName = name ?? "Anonymous";
        Console.WriteLine(displayName);
    }
}

This example demonstrates various ways to handle conditional logic in C#. Let me know if you need further explanations or examples!

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