Properties: controlled access

The problem with public fields

A public field hands out raw state — anyone can write account.Balance = -999; and your object is now lying. Fields should be private; the question is how outsiders read state they need.

Properties look like fields, run like methods

A property is accessed with field syntax but compiles to method calls:

class Account
{
    private decimal balance;                 // hidden state

    public decimal Balance                   // controlled access
    {
        get { return balance; }
        private set { balance = value; }     // only the class may change it
    }
}

Readers write account.Balance — indistinguishable from a field at the call site. Writers hit your code, where the invariant lives. value is the incoming assignment inside set.

Auto-properties and validation

When both accessors just wrap a hidden field, let C# generate it:

public string Name { get; }             // get-only: set once in constructor
public int Hits { get; private set; }   // read anywhere, mutate inside methods

When a settable property must keep a rule, validate in set:

private int health;
public int Health
{
    get { return health; }
    set { health = Math.Clamp(value, 0, 100); }   // always in [0, 100]
}

Math.Clamp(value, min, max) pins a number into range — every modern .NET has it. The habit that matters: state is private, behavior is public. Methods and setters are the only doors, and each door can enforce the rules.