Auto Property in C-Sharp

Properties and Encapsulation

When defining a private field in an object, one should pay attention to the property of the field. A property is like an intermediate for accessing the private field — let’s call it backing field —.

To do that, you also need accessors, which are defined by the keyword get and set.

For accessing a private field, a public property is created using the same name as the field, but in PascalCase, by convention. Applying the get-set implementation, it’s only possible to access the private field through the property, even when instantiating the object.

Keep in mind: using a primary constructor might not work with properties. One should create its own constructor referencing the property.

public struct Genre
{
    public Genre(string name) => this.Name = name;
 
    private string name; // Backing field
    public string Name // Property - Always use PascalCase for properties.
    {
        get
        {
            Console.WriteLine("Returning!!!");
            return name;
        }
        set
        {
            Console.WriteLine("Setting!!!");
            name = value;
        }
    }
}
 
Genre genre = new("Rock and Roll");
Console.WriteLine(genre.Name); // Returns "Returning" and "Rock and Roll"

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Validating data

One great feature of using properties, is to validate the data before making a change. For example, let’s check if the genre there are any white spaces in the string and replace by an underscore. Commonly, one would raise an exception on invalid data.

public struct Genre
{
    public Genre(string name) => this.Name = name;
 
    private string name; 
    public string Name
    // Refactored get-set for readability
    { 
        get => name;
        set => name = value.Replace(' ', '_');
    }
}
 
Genre genre = new("Rock and Roll");
Console.WriteLine(genre.Name);  // Returns Rock_and_Roll
 
genre.Name = "Trip Rock";
Console.WriteLine(genre.Name);  // Returns Trip_Rock

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Using init

There is also the init keyword, which is useful for creating immutable properties. Using init in the place of set, removes the possibility of changing the value of the backing field after instantiation. In other words, the field is only set during object construction, and any attempt to change it afterward will result in a compile error.

public struct Genre
{
    public Genre(string name) => this.Name = name;
 
    private string name; 
    public string Name
    {
        get => name;
        init => name = value.Replace(' ', '_');  // Replaced set by init
    }
}
 
Genre genre = new("Rock and Roll");
Console.WriteLine(genre.Name);
 
genre.Name = "Jazz"; // Raises compile error CS8852

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