In this short tutorial, you will learn the key points of C# variables.

Initializing Variable

The C# compiler requires that any variable be initialized with some starting value before you refer to that variable in an operation. So you can not do the following in C#:

    class Program
    {
        static void Main(string[] args)
        {
            int i;
            Console.WriteLine($"i: {i}");
        }
    }

It will get compile error:

error CS0165: Use of unassigned local variable 'i'

Type Inference

C# can use Type Inference with keyword var, the compiler “infers” what the type of the variable is by what the variable is initialized to.

        static void Main(string[] args)
        {
            var str = "Hello World";
            Console.WriteLine($"{str}");
        }