Information Technology Reference
In-Depth Information
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;
}
}
To c r e a t e a n i m m u t a b l e t y p e , y o u n e e d t o e n s u r e t h a t t h e r e a r e n o h o l e s
that would allow clients to change your internal state. Value types do not
support derived types, so you do not need to defend against derived types
modifying fields. But you do need to watch for any fields in an immutable
type that are mutable reference types. When you implement your con-
structors for these types, you need to make a defensive copy of that muta-
ble type. All these examples assume that Phone is an immutable value type
because we're concerned only with immutability in value types:
