Implicit typing means you let the compiler figure out the data type of a variable based on the value you assign to it.
You use the keyword var for this.
var age = 25; // Compiler infers int
var name = "Alice"; // Compiler infers string
var price = 19.99; // Compiler infers double
var numbers = new int[] { 1, 2, 3 }; // Compiler infers int[]Behind the scenes, the compiler replaces var with the actual type.
So:
var age = 25;
is the same as:
int age = 25;
Rules of Implicit Typing
-
You must initialize the variable immediately.
var x; // ❌ Error: Compiler can’t infer type var y = 10; // ✅ OK, inferred as int -
Once inferred, the type is fixed — you can’t assign another type.
var z = 100; // int z = "hello"; // ❌ Error: can't change type -
Implicit typing does not mean dynamic typing.
-
var→ type decided at compile time (strongly typed). -
dynamic→ type decided at runtime.
-
When to use
✅ Good for:
-
Long or complex types (like LINQ queries).
-
When the type is obvious from the right-hand side.
var customers = new Dictionary<int, string>();
❌ Avoid when:
- It makes code less readable.
var x = GetData(); // ❌ unclear what type x is
⚡ In short: var lets you write less, but the type is still checked at compile time.