How do you implement the state pattern?

Question

Accepted Answer

**State** — object behavior changes with state.

**Implementation:**
```csharp
public interface IState
{
    void Handle(VendingMachine machine);
}

public class IdleState : IState
{
    public void Handle(VendingMachine machine)
    {
        Console.WriteLine("Insert coin");
        machine.SetState(new HasCoinState());
    }
}

public class HasCoinState : IState
{
    public void Handle(VendingMachine machine)
    {
        Console.WriteLine("Dispensing");
        machine.SetState(new IdleState());
    }
}
```

**Key:** State for behavior per state.

C#: How do you implement the state pattern?