改善C#編程的50個建議(16-20)

public class MyResourceHog : IDisposable
{
    // Flag for already disposed
    private bool alreadyDisposed = false;
    // Implementation of IDisposable.
    // Call the virtual Dispose method.
    // Suppress Finalization.
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
    // Virtual Dispose method
    protected virtual void Dispose(bool isDisposing)
    {
        // Don't dispose more than once.
        if (alreadyDisposed)
            return;
        if (isDisposing)
        {
            // elided: free managed resources here.
        }
        // elided: free unmanaged resources here.
        // Set disposed flag:
        alreadyDisposed = true;
    }
    public void ExampleMethod()
    {
        if (alreadyDisposed)
            throw new ObjectDisposedException(
            "MyResourceHog",
            "Called Example Method on Disposed object");
        // remainder elided.
    }
}

public class DerivedResourceHog : MyResourceHog
{
    // Have its own disposed flag.
    private bool disposed = false;
    protected override void Dispose(bool isDisposing)
    {
        // Don't dispose more than once.
        if (disposed)
            return;
        if (isDisposing)
        {
            // TODO: free managed resources here.
        }
        // TODO: free unmanaged resources here.
        // Let the base class free its resources.
        // Base class is responsible for calling
        // GC.SuppressFinalize( )
        base.Dispose(isDisposing);
        // Set derived class disposed flag:
        disposed = true;
    }
}

public class BadClass
{
    // Store a reference to a global object:
    private static readonly List finalizedList =
    new List();
    private string msg;
    public BadClass(string msg)
    {
        // cache the reference:
        msg = (string)msg.Clone();
    }
    ~BadClass()
    {
        // Add this object to the list.
        // This object is reachable, no
        // longer garbage. It's Back!
        finalizedList.Add(this);
    }
}

public struct Employee
{
    // Properties elided
    public string Position
    {
        get;
        set;
    }
    public decimal CurrentPayAmount
    {
        get;
        set;
    }
    public void Pay(BankAccount b)
    {
        b.Balance += CurrentPayAmount;
    }
}

public class Employee2
{
    // Properties elided
    public string Position
    {
        get;
        set;
    }
    public decimal CurrentPayAmount
    {
        get;
        set;
    }
    public virtual void Pay(BankAccount b)
    {
        b.Balance += CurrentPayAmount;
    }
}

public enum Planet
{
    // Default starts at 0 otherwise.
    Mercury = 1,
    Venus = 2,
    Earth = 3,
    Mars = 4,
    Jupiter = 5,
    Saturn = 6,
    Neptune = 7,
    Uranus = 8
    // First edition included Pluto.
}
Planet sphere = new Planet();

public struct Address2
{
    // remaining details elided
    public string Line1
    {
        get;
        private set;
    }
    public string Line2
    {
        get;
        private set;
    }
    public string City
    {
        get;
        private set;
    }
    public string State
    {
        get;
        private set;
    }
    public int ZipCode
    {
        get;
        private set;
    }
}

public Address2(string line1,
	string line2,
	string city,
	string state,
	int zipCode) :
	this()
{
	Line1 = line1;
	Line2 = line2;
	City = city;
	ValidateState(state);
	State = state;
	ValidateZip(zipCode);
	ZipCode = zipCode;
}

public struct Address3
    {
        // remaining details elided
        public string Line1
        {
            get { return Line1; }
        }
        private readonly string line1;
        public string Line2
        {
            get { return line2; }
        }
        private readonly string line2;
        public string City
        {
            get { return city; }
        }
        private readonly string city;
        public string State
        {
            get { return state; }
        }
        private readonly string state;
        public int ZipCode
        {
            get { return zip; }
        }
        private readonly int zip;
        public Address3(string line1,
        string line2,
        string city,
        string state,
        int zipCode) :
            this()
        {
            this.line1 = line1;
            this.line2 = line2;
            this.city = city;
            ValidateState(state);
            this.state = state;
            ValidateZip(zipCode);
            this.zip = zipCode;
        }
    }

public struct PhoneList
{
	private readonly Phone[] phones;
	public PhoneList(Phone[] ph)
	{
	  phones = ph;
	}
	public IEnumerable Phones
	{
	  get
	  {
	    return phones;
	  }
	}
}
Phone[] phones = new Phone[10];
// initialize phones
PhoneList pl = new PhoneList(phones);
// Modify the phone list:
// also modifies the internals of the (supposedly)
// immutable object.
phones[5] = Phone.GeneratePhoneNumber();

// Immutable: A copy is made at construction.
public struct PhoneList2
{
	private readonly Phone[] phones;
	public PhoneList2(Phone[] ph)
	{
	    phones = new Phone[ph.Length];
	    // Copies values because Phone is a value type.
	    ph.CopyTo(phones, 0);
	}
	public IEnumerable Phones
	{	
	  get
	  {
	    return phones;
	  }
	}
}
Phone[] phones2 = new Phone[10];
// initialize phones
PhoneList p2 = new PhoneList(phones);
// Modify the phone list:
// Does not modify the copy in pl.
phones2[5] = Phone.GeneratePhoneNumber();