5.3 Properties & Fields

Let’s go over fields and properties in C# — fundamental ways to store and manage data inside a class.

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📌 1. Fields

A field is a variable declared inside a class to hold data.

Key Points

• Usually declared as private for encapsulation

• Can be public, but it’s better to use properties

• Stores the actual data of an object

Example

public class Person
{
    public string Name;   // Public field
    private int age;      // Private field
 
    public void SetAge(int value)
    {
        if (value >= 0)
            age = value;
    }
 
    public int GetAge()
    {
        return age;
    }
}

• Name is a public field — accessible directly

• age is private — accessed via methods to control changes

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📌 2. Properties

A property is a member that provides controlled access to a field. Can be thought of as a defined function inside a class, not to be confused with custom functions inside a class- which are called Methods. See 4.4 Methods within classes

• Combines get (read) and set (write) accessors

• Can include logic/validation inside get/set

• Preferred over public fields for encapsulation

Example: Basic Property

public class Person
{
    private int age;
 
    public int Age
    {
        get { return age; }               // Read
        set 
        {
            if (value >= 0)                // Validation
                age = value;
        }                                  // Write
    }
}

Usage

Person person = new Person();
person.Age = 25;        // Calls set accessor
Console.WriteLine(person.Age); // Calls get accessor

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📌 3. Auto-Implemented Properties

C# allows simpler syntax when no extra logic is needed:

public class Person
{
    public string Name { get; set; }  // Automatically creates a hidden backing field
}
 
Person person = new Person();
person.Name = "Alice";
Console.WriteLine(person.Name);

• Automatically creates a private field behind the scenes

• Can also make read-only or write-only:

public string Name { get; private set; } // Can only set inside the class

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📌 4. Properties vs Fields

Feature	Field	Property
Access	Direct	Controlled via get/set
Encapsulation	Weak (if public)	Strong
Validation	Must use separate methods	Can include logic in set/get
Syntax	public int age;	public int Age { get; set; }
Backing Field	Explicit or automatic	Can be auto-implemented

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📌 5. Best Practices

1. Keep fields private and expose them via properties.

2. Use properties for validation or computed values.

3. Use auto-implemented properties for simple storage.

4. Name fields in camelCase and properties in PascalCase.

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✅ Tip:

• Fields = raw data

• Properties = controlled access to data