Variables

Fundamentals

Variables, sometimes called properties, are a core concept of programming. Similar to variables in math, you use variables in programming to store values. This allows you to reference them later.

In C#, variables have a few different parts:

• Type: the variable's type
• Name: a descriptive variable name
• Value: the variable's value

Below is a variable:

string myName = "Cody Winton";

• Type: string
• Name: myName
• Value: "Cody Winton"

Finally, the line of code is terminated with a semicolon: ;.

Strong and Static Typing

C# is a strongly, statically typed language, meaning that every variable has a type at compile time and you can't a variable's type after it has been set, though you can change its value.

Explicit Typing

C# allows for explicit typing of any variable. Let's see this in action as we define a few String variables:

string aString = "This is a String";
string aVal = "Can be 123 or @ or # or any other characters!";

aVal = "Testing val"; // The value of a variable can be changed

// This below would fail. 123 is not a string, since it is not surrounded by quotes
aVal = 123; // fails

// You can also set the value after creating the variable
string newVal;
newVal = "Testing new val";

Type Inference

C# also supports type inference, which means that you don't always have to explicitly specify a type. You can let the compiler try and understand the type of variable automatically.

The keyword var allows the compiler to infer type at compile time based on the provided value:

var aString = "This is a String";
var aVal = "Can be 123 or @ or # or any other characters!";

aVal = "Testing val"; // The value of a variable can be changed

// This below would fail. 123 is not a string, since it is not surrounded by quotes
aVal = 123; // fails

You cannot use the keyword var if you're not immediately setting the value of the variable:

var newVal; // This fails, since it cannot infer type. There is no provided value.
newVal = "Testing new val"; // You'll never reach this line of code

In C#, type inference is not required, but is considered "best practice".