Properties backing field - What is it good for?

Question

On one hand, I know that the advisable usage of Properties is to have a backing field, like in the following example:

    private int m_Capacity;

    public int Capacity
    {
        get { return m_Capacity > 0 ? m_Capacity : -666; }
        set { m_Capacity = value; }
    }

On the other hand, what benefit do I get from using the above example over discarding the field and using only the property for all purposes, like in the following example:

    public int Capacity
    {
        get { return Capacity > 0 ? Capacity : -666; }
        set { Capacity = value; }
    }

What is good about using a backing field for regular (non-auto-implemented) properties?

Answer 1

If you do this:

public int Capacity 
{ 
    get { return Capacity > 0 ? Capacity : -666; } 
    set { Capacity = value; } 
}

then your code will have an infinite recursion. It will never work. That's because the getter for Capacity is referencing itself. Same thing goes for the setter.

Unless you are using automatic properties, you need a backing field