Вивчайте Ланцюжок If-Else | Керуючі Структури

We can add additional conditions using the else if keyword. The additional conditions are evaluated in case the previous conditions are not met.

if (expression) 
{
    // code if first condition is met
}
else if (expression)
{
    // code if second condition is met
} else 
{
    // code if no condition is met
}

Let's consider an example with if else chain:

main.cs


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using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value_1 = 9;
			int value_2 = 7;
          
			if(value_1 < value_2)
			{
			    Console.WriteLine("Value 1 is smaller than Value 2");
			} 
			else if(value_1 > value_2)
			{
    			Console.WriteLine("Value 1 is bigger than Value 2");
			}
			else if(value_1 == value_2)
			{
    			Console.WriteLine("Value 1 is equal to Value 2");
			}
        }
    }
}

In the above program we chained conditions using if-else if. This is called conditional chaining. The first condition value_1 < value_2 is evaluated. Since it is false, the program skips to the next condition value_1 > value_2 which is true and hence it executes its code block and stops executing the chain further.

The main feature of conditional chaining is that it stops executing the chain as soon as a condition is met.

Consider the following code:

main.cs


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using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value = 10;

			if(value > 5)
			{
    			Console.WriteLine("Value is bigger than 5");
			}
			else if(value > 7)
			{
    			Console.WriteLine("Value is bigger than 7");
			}
			else if(value > 9)
			{
    			Console.WriteLine("Value is bigger than 9");
			}
        }
    }
}

Even though all three conditions are true, it stops executing on the first condition since it's a chain.

Now let's try writing it using simple if keywords without chaining:

main.cs


              123456789101112131415161718192021222324252627
            
using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value = 10;

			if(value > 5)
			{
    			Console.WriteLine("Value is bigger than 5");
			}

			if(value > 7)
			{
    			Console.WriteLine("Value is bigger than 7");
			}

			if(value > 9)
			{
    			Console.WriteLine("Value is bigger than 9");
			}
        }
    }
}

In the above case, each condition is evaluated individually and not treated as a part of any chain hence all three statements are outputted.

We can also add the else keyword at the end of the if-else chain which will execute if no condition is matched:

main.cs


              1234567891011121314151617181920212223242526
            
using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value_1 = 9;
			int value_2 = 7;

			if(value_1 < value_2)
			{
    			Console.WriteLine("Value 1 is smaller than Value 2");
			} 
			else if(value_1 > value_2)
			{
    			Console.WriteLine("Value 1 is bigger than Value 2");
			}
			else
			{
    			Console.WriteLine("Value 1 is equal to Value 2");
			}
        }
    }
}

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Suggested prompts:

Can you explain the difference between if-else chaining and separate if statements?

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We can add additional conditions using the else if keyword. The additional conditions are evaluated in case the previous conditions are not met.

if (expression) 
{
    // code if first condition is met
}
else if (expression)
{
    // code if second condition is met
} else 
{
    // code if no condition is met
}

Let's consider an example with if else chain:

main.cs


              1234567891011121314151617181920212223242526
            
using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value_1 = 9;
			int value_2 = 7;
          
			if(value_1 < value_2)
			{
			    Console.WriteLine("Value 1 is smaller than Value 2");
			} 
			else if(value_1 > value_2)
			{
    			Console.WriteLine("Value 1 is bigger than Value 2");
			}
			else if(value_1 == value_2)
			{
    			Console.WriteLine("Value 1 is equal to Value 2");
			}
        }
    }
}

The main feature of conditional chaining is that it stops executing the chain as soon as a condition is met.

Consider the following code:

main.cs


              12345678910111213141516171819202122232425
            
using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value = 10;

			if(value > 5)
			{
    			Console.WriteLine("Value is bigger than 5");
			}
			else if(value > 7)
			{
    			Console.WriteLine("Value is bigger than 7");
			}
			else if(value > 9)
			{
    			Console.WriteLine("Value is bigger than 9");
			}
        }
    }
}

Even though all three conditions are true, it stops executing on the first condition since it's a chain.

Now let's try writing it using simple if keywords without chaining:

main.cs


              123456789101112131415161718192021222324252627
            
using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value = 10;

			if(value > 5)
			{
    			Console.WriteLine("Value is bigger than 5");
			}

			if(value > 7)
			{
    			Console.WriteLine("Value is bigger than 7");
			}

			if(value > 9)
			{
    			Console.WriteLine("Value is bigger than 9");
			}
        }
    }
}

In the above case, each condition is evaluated individually and not treated as a part of any chain hence all three statements are outputted.

We can also add the else keyword at the end of the if-else chain which will execute if no condition is matched:

main.cs


              1234567891011121314151617181920212223242526
            
using System;

namespace ConsoleApp
{
    internal class Program
    {
        static void Main(string[] args)
        {
			int value_1 = 9;
			int value_2 = 7;

			if(value_1 < value_2)
			{
    			Console.WriteLine("Value 1 is smaller than Value 2");
			} 
			else if(value_1 > value_2)
			{
    			Console.WriteLine("Value 1 is bigger than Value 2");
			}
			else
			{
    			Console.WriteLine("Value 1 is equal to Value 2");
			}
        }
    }
}

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 3. Розділ 9