C# Properties

What are Properties?

A property is a member that provides a flexible mechanism to read, write, or compute the value of a private field. Properties can be used as if they're public data members, but they're special methods called accessors.

This feature enables data to be accessed easily and still helps promote the safety (Encapsulation) and flexibility of methods.

Properties overview

• Properties enable a class to expose a public way of getting and setting values, while hiding implementation or verification code.

• A get property accessor is used to return the property value, and a set property accessor is used to assign a new value.

• The value keyword is used to define the value being assigned by the set accessor.

• We can have read-only properties also (use only get)

• We also have auto-implemented properties

Properties with backing fields

One basic pattern for implementing a property involves using a private backing field for setting and retrieving the property value. The get accessor returns the value of the private field, and the set accessor may perform some data validation before assigning a value to the private field.

The following example illustrates this pattern:

public class SaleItem
{
    string name;
    double cost;

    public SaleItem(string name, double cost)
    {
        this.name = name;
        this.cost = cost;
    }

    public string Name
    {
        get => name;
        set => name = value;
    }

    public double Price
    {
        get => cost;
        set => cost = value;
    }
}

Conversions & Validations

The get accessor returns the value of the private field, and the set accessor may perform some data validation before assigning a value to the private field. Both accessors may also perform some conversion or computation on the data before it's stored or returned.

The following example illustrates this pattern:

public class SaleItem
{
    string name;
    double cost;

    public SaleItem(string name, double cost)
    {
        this.name = name;
        this.cost = cost;
    }
    public string Name
    {
        get => name;
        set => name = value;
    }
    public double Price
    {
        get => cost;
        set
        {
            if(cost>0)
                cost = value;
        }
    }
}

Auto-implemented properties

In some cases, property get and set accessors just assign a value to or retrieve a value from a backing field without including any extra logic. By using auto-implemented properties, you can simplify your code while having the C# compiler transparently provide the backing field for you.

The following example repeats the previous one, except that Name and Price are auto-implemented properties. The example also removes the parameterized constructor, so that SaleItem objects are now initialized with a call to the parameterless constructor:

public class SaleItem
{
    public string Name { get; set; }
    public decimal Price { get; set; }
}