Variable Types

1. Declaring Variables

Let's quickly recap how to create variables. To create a variable, you need to write a command like this:

type name;

Examples:

string s;

int x;

int a, b, c;
int d;

There are also some restrictions on the variable name. On one hand, it can be anything, but on the other — it can't have spaces, +, - and so on. It's best to use only Latin letters and numbers in variable names.

And again, remember that in C# it matters if you use uppercase or lowercase letters. int a is not the same as Int a.

By the way, in C# you can create a variable and assign it a value at the same time. This saves time and space:

int a = 5;

int a;
a = 5;

int b = 6; 

int b;
b = 6;

int c = 7;

int c;
c = 7;

int d = c + 1;

int d;
d = c + 1;

string s = "I'm Amigo";

string s;
s = "I'm Amigo";

Way more compact and clear.

Now that we've figured out how to create variables, let's meet the two most used types in C#: int (whole numbers) and string (text/strings).

2. Type int

You can store whole numbers in a variable of type int: 5, -10, 100500. You can also do all sorts of math with int: add, subtract, multiply, divide, and more. Examples:

int x = 1;					//	x will be 1
int y = x*2;				//  y will be 2
int z = 5*y*y + 2*y + 3;	//	z will be 20+4+3, will be 27

int a = 5;					//	a will be 5
int b = 1;					//  b will be 1
int c = (a-b) * (a+b);		//  c will be 4*6, will be 24

int a = 64;					//	a will be 64
int b = a/8;				//	b will be 8
int c = b/4;				//  c will be 2
int d = c*3;				//  d will be 6

If you didn't skip math in school, this should all make sense 🧐

3. Type string

The string type lets you store text strings. To set a text string in C#, you write the text and put double quotes around it. Example:

string s = "Amigo";

string s = "123";

string s = "Bond 007";

Looks easy, right? If so, here's another cool fact.

You can glue strings together in C# using the plus sign — +. Example:

string s1 = "Amigo" + " the best";	    //	s1 will contain Amigo the best
string s2 = "";	                        // 	s2 will contain an empty string — no characters at all

int x = 333;
string s3 = "Amigo" + x;	            // s3 will contain Amigo333

Check out the last example: we added a string and a number. It's simple: the number gets turned into a string, then the two strings are glued together. When you add strings and numbers, you always get a string.

4. Printing a Variable to the Screen

Seems pretty obvious and basic. So maybe you can already guess what command prints a variable to the screen?

It's actually super simple. To print something to the screen, we use the Console.WriteLine() command, passing in what we want to print as a parameter.

Console.WriteLine("Amigo");			// Amigo

Console.WriteLine("Ami" + "go");	// Amigo

string s1 = "Amigo";
Console.WriteLine(s1);				// Amigo

string s2 = "Am";
Console.WriteLine(s2 + "igo");		// Amigo

Hope that makes things a bit clearer. And whether you really got it or not, let's check right now. Practice is the real test: only by practicing can you see if you really get it.

5. The Coolest Way to Print a Variable

Recently, C# got a new, awesome way to print variables to the screen. You can put variable names right in the text, and C# will stick their values right in the middle.

To do this, just put a $ sign before the first double quote and that's it. Example:

string name = "Alex";
int age = 25;

Console.WriteLine($"My name is {name}. I'm {age} years old."); // My name is Alex. I'm 25 years old.

We put a dollar sign before the string (before the quotes) and write variable names inside curly braces in the string. That's it. It works like magic. Compare:

string name = "Alex";
int age = 25;

//classic way
Console.WriteLine("My name is " + name + ". I'm " + age + " years old.");

//cool way
Console.WriteLine($"My name is {name}. I'm {age} years old.");

On CodeGym you're learning the newest version of C#, so you get all the cool stuff right away. Enjoy! 😎

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C# SELF, level 1, lesson 4

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Simple arithmetic operations

Simple arithmetic operations

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C# SELF, level 1, lesson 4

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Using string interpolation

Using string interpolation

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