Use the var keyword

  • 10 minutes

Tip

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So far, you've explicitly declared the data type of each variable. But C# has a shorthand: the var keyword, which lets the compiler figure out the type for you.

Using the var keyword

When you assign a value to a var variable, C# automatically determines its data type based on the assigned value:

var name = "Alice";           // C# sees a string, so name is string
var age = 25;                 // C# sees a whole number, so age is int
var price = 19.99;            // C# sees a decimal, so price is double

This is equivalent to writing:

string name = "Alice";
int age = 25;
double price = 19.99;

When to use var

Use var when:

  • The type is obvious from the value (like var count = 5; clearly creates an int)
  • It makes your code easier to read
  • You're working with complex types

Use explicit types when:

  • You want to be extra clear about what type something is
  • You're just starting out (it helps you learn the data types)

Important: var is still typed

Don't think of var as "any type." Once C# determines the type, that variable is locked to that type:

var count = 10;      // count is an int
count = "five";      // ERROR! Can't assign a string to an int variable

Try it yourself

Experiment with var in the C# Code Editor:

var message = "Hello!";
var favorite = 42;
var average = 87.5;

Console.WriteLine(message);
Console.WriteLine(favorite);
Console.WriteLine(average);

The var keyword is a convenience feature that saves typing, but it's optional. You can always use explicit types if you prefer.