Variables & Data Types

C# variables need an explicit type: int age = 21;.

Example: explicit type vs. var

using System;

class Program {
    static void Main() {
        string name = "Ada";
        var age = 21;
        Console.WriteLine($"{name} is {age} years old.");
    }
}

Ada is 21 years old.

var lets the compiler infer the type from the assigned value — age is still genuinely an int here, fixed at compile time, just written without spelling the type out explicitly. This is different from a dynamically-typed language: it's purely a shorthand for the compiler to figure out what you clearly meant, not permission for the variable to hold a different type later.