Declare and assign variables

  • 6 minutes

Tip

See the Text and images tab for more details!

A variable is a container that holds a value. Unlike hard-coded literals, variables can change as your program runs. Variables let you store information from users, calculations, or other sources, then use that information later in your code.

Declaring a variable

To create a variable, you declare its data type and give it a name:

string name;

This creates a variable called name that can only hold string values. Once you declare a variable with a type, it can never hold a different type.

Assigning a value

To put a value into a variable, use the assignment operator (=):

string name;
name = "Alice";

Assignment flows from right to left: the value on the right ("Alice") gets stored in the variable on the left (name).

You can declare and assign in one line:

string name = "Alice";
int age = 25;
decimal temperature = 98.6;
bool isRaining = true;

Using your variables

Once you've assigned a value, you can use the variable anywhere you'd use the literal:

string greeting = "Hello";
Console.WriteLine(greeting);           // Output: Hello

int messageCount = 5;
Console.WriteLine(messageCount + 1);   // Output: 6

Variable naming

Keep these conventions in mind when naming variables:

  • Use camelCase: Start with a lowercase letter, then capitalize the first letter of each word after that (firstName, totalPrice, isActive)
  • Use descriptive names that clearly show what the variable holds (userName instead of u)
  • Use full words, not abbreviations (name instead of nm)

Good variable names make your code easier to read and understand.