Question

I have this sample code

public class MyClass
{
    private static int tempKey = 0;

    public MyClass()
    {
        this.Key = --tempKey;
    }
    public int Key {get; set;}
}

What does –tempkey do exactly?

Answer 1

It decrements tempKey and returns new value. Compare with tempKey--, which also decrements tempKey, but returns the original value.

See Microsoft documentation here.

The increment operator (++) increments its operand by 1. The increment
operator can appear before or after its operand:

++ var 
var ++ 

Where:

var An expression that denotes a storage location or a property or an
indexer.

The first form is a prefix increment operation. The result of
the operation is the value of the operand after it has been
incremented.

The second form is a postfix increment operation. The result of the
operation is the value of the operand before it has been incremented.

EDIT: This is valid for C#. Visual Basic doesn’t have this increment/decrement operator.

In Visual Basic --tempKey is evaluated as -1 * (-1 * tempKey) which is equal to tempKey.