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.