#788 – A Backing Field Stores Data for a Property

When you create a property, you’re creating a set of accessor methods to read and write the property’s value.  You also typically need a place to store the actual property value.

The data member where the property’s value is actually stored is known as a backing field, typically defined as a private field.

When you create an auto-implemented property, you don’t explicitly declare a backing field, but the compiler creates one for you in the IL that is generated.  Your code doesn’t have access to the field.

        // Backing field not declared, created automatically
        public int Age { get; set; }

If you create the property explicitly, then you’ll declare the backing field yourself.

        // Backing field
        private int age;

        // Property
        public int Age
        {
            get { return age; }
            set
            {
                if (value != age)
                    age = value;
            }
        }