#36 – Variable Initialization and Definite Assignment

Variables must be assigned a value before they can be used.  You can declare a variable without initializing it, but attempting to reference the value of the variable before you’ve given it a value will result in a compiler error.

 int i;
 int j = i + 1;   // Error: Use of unassigned local variable 'i'

This requirement of definite assignment before use means that you are never able to reference an unassigned variable in C#.

It’s considered good practice to initialize a variable when you declare it.  This applies to both built-in types and custom types.

When you initialize a variable, the object that it references is said to be instantiated.

 Person p = new Person();
 int i = 0;