Constructors and properties being set to private or public

Question

I am creating a class in C# and am being told that all of my properties should be public. I was taught that information hiding is common in C++ but idk if it is the same is C# or if the convention for doing so is different. The first example is how I was taught to do it. The 2nd example is how I am being taught to implement this class now. My question is this: Will this prevent me from using any of the properties with other classes or will it all work because of the constructor making them public?

Thank you all in advance

    class Book
    {
        string Title = null;
        string Author = null;
        int Year = 0;
        string CoverType = null;

        public Book (string aTitle, string anAuthor, int aYear, string aCoverType)
        {
            Title = aTitle;
            Author = anAuthor;
            Year = aYear;
            CoverType = aCoverType;
        }

Separation of examples

    
    public class Book
    {
        public string Title = null;
        public string Author = null;
        public int Year = 0;
        public string CoverType = null;

        public Book (string aTitle, string anAuthor, int aYear, string aCoverType)
        {
            Title = aTitle;
            Author = anAuthor;
            Year = aYear;
            CoverType = aCoverType;
        }

In general, no, fields/attributes should not be public. You can add `{ get; set; }` to make publicly mutable/accessible fields — OneCricketeer, Sep 07 '22 at 19:17
Does this answer your question? [What is the difference between a field and a property?](https://stackoverflow.com/questions/295104/what-is-the-difference-between-a-field-and-a-property) — Progman, Sep 07 '22 at 19:22

score 2 · Answer 1 · answered Sep 07 '22 at 19:20

Will this prevent me from using any of the properties with other classes

No. That's the definition of having public modifier.

However, as written in the Microsoft documentation public fields are "Generally not recommended"

The common approach is to expose properties with backing fields.

score 0 · Answer 2 · answered Sep 07 '22 at 19:24

You should separate properties and fields, i.e.

private int year = 0; // field
public int Year { get { return year;}} // Property, wrapping the field
public int Year2  => year; // Same as above, using more compact syntax
public String Author {get;} // auto-property, automatically adds a hidden field

The typical rule is to keep fields private, and if you need public access, wrap them in a property, or use an auto property. So it usually does not make much sense to make properties private, since the goal is usually to expose the underlying field.

I would also recommend using readonly properties whenever practical, i.e. {get;} or {get; init;}. If the property can never change, there is usually less problems with making it public.

score 0 · Answer 3 · answered Sep 07 '22 at 20:15

I suggest using properties instead of fields:

Let's set Title, ..., CoverType once in the consructor and prevent them form occasinal (erroneous) modifications
Let's validate input arguments, let's not use null as placeholder.

Code:

public class Book
{
    public string Title     { get; }
    public string Author    { get; }
    public int Year         { get; }
    public string CoverType { get; }

    public Book (string aTitle, string anAuthor, int aYear, string aCoverType)
    {
        Title = aTitle?.Trim() 
          ?? throw new ArgumentNullException(nameof(aTitle));
        
        Author = anAuthor?.Trim() 
          ?? throw new ArgumentNullException(nameof(anAuthor));
        
        Year = aYear > 1400 && aYear <= DateTime.Now.Year + 1
          ? aYear
          : new ArgumentOutOfRangeException(nameof(aYear)); 

        CoverType = aCoverType ?? "";
    }

    ...

Constructors and properties being set to private or public

3 Answers3