If-else statements
If-else statements
You can use if
statements to run code statement only if certain conditions are met. Here is an example:
var myNum = (93 + 41) / 12;
if (myNum == 11)
{
Console.WriteLine("They are equal!");
}
Inside the ()
beside if
, you should specify a boolean expression. If the expression is true
, the code inside { }
is executed. In this case, since myNum
is equal to 11
, They are equal!
is printed.
If the condition is false
, nothing happens! For example, since 10
is not greater than 11
, Print me!
will not show up to the console.
var happy = 10;
if (happy > 11)
{
Console.WriteLine("Print me!");
}
Use else
to tell the computer what to do if the condition is false. In this example, now I got printed instead!
will be printed to the console.
var happy = 10;
if (happy > 11)
{
Console.WriteLine("Print me!");
}
else
{
Console.WriteLine("I got printed instead!");
}
You can chain many cases together using else if
. Note that when using else if
, only the first case will be evaluated. For example, in the following code snippet, Statement
1 will be printed. We will skip the check that sad == 4
and Statement 2
will not be printed, even though sad == 4
is true
.
var sad = 4;
if (sad < 9)
{
Console.WriteLine("Statement 1");
}
else if (sad == 4)
{
Console.WriteLine("Statement 2");
}
else
{
Console.WriteLine("Statement 3");
}
You can also place if
statements inside other if
statements for some interesting behavior:
var num1 = 10;
var num2 = 20;
if (num1 < num2)
{
if (num2 < 30)
{
Console.WriteLine("Hello!");
}
else
{
Console.WriteLine("Hola!");
}
}
Working Together
Let’s write a program that first prints the following line to console:
Is coding fun?
Afterwards, the console waits for user input.
- If the user enters yes, the computer prints out
Yes, I'm glad you're enjoying it!
. - If the user enters no, the computer prints out
Oh no, that's too bad!
. - Otherwise, the computer prints out:
I don't understand you! Goodbye!
.
Fun Fact: Switch statements
Using multiple if
, else
statements could get very long and confusing. You can use switch
statements instead if you want to compare a single variable against multiple values. For example, the Working Together activity can be completed using the following piece of code:
var input = Console.ReadLine();
switch (input)
{
case "yes":
Console.WriteLine("Yes, I'm glad you're enjoying it!");
break;
case "no":
Console.WriteLine("Oh no, that's too bad!");
break;
default:
Console.WriteLine("I don't understand you! Goodbye!");
break;
}
Each case represents a possible value that the variable input might take. Make sure you use the break
statement to tell the computer that you have completed all the actions associated with this case.