7.2: If Statements

In this module we'll study if, else if, and else statements.

File Location

1. Right click on the solution you made in the first module.

2. Go to Add > New Project and select Console App (.NET Framework).

3. Name it 07_conditionals_if_else.

4. Write your code for this module within Program.cs of that project.

If, Else If, and Else Statements

In the previous module on booleans, we got a brief introduction to some if statements. if statements check to see if a condition is true or false. We also gave a challenge in that module that would require you to use the else & if else keywords. Let's add some code that will allow us to write else if statements:

class Program
{
    static void Main(string[] args)
    {
        //1
        Console.WriteLine("How are you feeling today from 1-5?");
        string feelingNumber = Console.ReadLine();

        //2
        if (feelingNumber == "5")
        {
            Console.WriteLine("That's great to hear!");
        }
        //3
        else if (feelingNumber == "4")
        {
            Console.WriteLine("Good stuff!");
        }
        else if (feelingNumber == "3")
        {
            Console.WriteLine("Hope things get better!");
        }
        else if (feelingNumber == "2")
        {
            Console.WriteLine("Oh. Sorry to hear that.");
        }
        else if (feelingNumber == "1")
        {
            Console.WriteLine("Dang. We hope your day gets better!");
        }
        //4
        else
        {
            Console.WriteLine("Sorry, we don't understand. Come back later.");
        }

        Console.ReadLine();
    }
}

Analysis

1. Here we set up a question in the console that asks a user to enter a value. We store that value in an integer variable.

2. We check if the number is 5. If it is we will execute another console statement. If the number is not 5 and the expression resolves to false, the program will continue to the else if statement.

3. else if statements are run if the previous if statements are false. You can have as many else if statements as you want.

4. The else statement goes at the end. Similar to the default in a switch, else statements are run if all previous statements are false.

Multiple if statements

If you have multiple if statements within a branch, your program will check all those if statements even if a previous one resulted in true. Not a bad thing, but handy to know especially when you get into the speed of your application.

Add the following code in your Program.cs file. But, before you run it, try to predict what will print and why.

class Program
{
    static void Main(string[] args)
    {
        bool isOn = true;
        bool isHot = false;

        if (isOn)
        {
            Console.WriteLine("The light is on, it's bright.");
        }

        if (isOn == true)
        {
            Console.WriteLine("The light is on.");
        }

        if (isOn && isHot)
        {
            Console.WriteLine("lights on and it's hot");
        }

        if (isOn || isHot)
        {
            Console.WriteLine("lights on or it is hot");
        }

        if (!isHot)
        {
            Console.WriteLine("it is not hot");
        }
    }
}