C# by Example: If Else


public void Main() {

Here is a basic example if an if/else statement. In C#, we need parenthesis after the if statement, and curly braces for the code.


    if(7%2 == 0){
        Console.WriteLine("7 is even")
    } else {
        Console.WriteLine("7 is odd")
    }

You can have an if statement without an else.


    if(8%4 == 0){
        Console.WriteLine("8 is divisible by 4")
    }

You can write "one-liners" without curly braces. This is nice for simple checks.
The whitespace doesn't matter. The if statement "if()statement" simply does-or-doesn't execute the following statement. We usually enclose that statement in a statement block. For those learning C#, I advise against writing code like this. CSharp doesn't care about line breaks or indentation, but this code looks like it does care about indentation, it's often misleading for students.


    if(21%3 == 0)
       Console.WriteLine("21 is divisible by 3");

Consider the following situation. Both lines look like they are part of the if statement, but they aren't. Without curly braces, the if statement conditionally executes only a single following statement.

Because of this common mistake, I advise beginners to always use curly braces.


    if(false)
        Console.WriteLine("This line is part of the if statement.");
        Console.WriteLine("THis line is not. It will be executed no matter what is in the conditional.");

C# has conditional operators like && for "and" and || for "or".


    if(8%2 == 0 || 7%2 == 0) {
        Console.WriteLine("either 8 or 7 are even")
    }

You can chain if/else statements. It's not considered good practice to have long if/ifelse/ifelse/ifelse/ifelse/else chains. Sometimes you gotta do what you gotta do - I won't judge.


    int num = 42;
    if(num<0) {
        Console.WriteLine(num, "is negative")
    } else if num < 10 {
        Console.WriteLine(num, "has 1 digit")
    } else {
        Console.WriteLine(num, "has multiple digits")
    }
}

Next example: Functions.