static void Main(string[] args)
{
var dictionary = new Dictionary <string, Foo>();
Func <string, Foo> createValue = (key) =>
{
var foo = new Foo {
ID = key
};
dictionary.Add(key, foo);
return(foo);
};
// this wrapper object is not useable, since no key has been specified for it yet
var wrapper = new KeyedValueWrapper <string, Foo>(dictionary.TryGetValue, createValue);
// create wrapper1 based on the wrapper object but changing the key to "ABC"
var wrapper1 = wrapper.Change("ABC");
var wrapper2 = wrapper1;
Foo foo1 = wrapper1.Value;
Foo foo2 = wrapper2.Value;
Console.WriteLine("foo1 and foo2 are equal? {0}", object.ReferenceEquals(foo1, foo2));
// Output: foo1 and foo2 are equal? True
// create wrapper1 based on the wrapper object but changing the key to "BCD"
var wrapper3 = wrapper.Change("BCD");
var wrapper4 = wrapper3;
Foo foo3 = wrapper3.Value;
dictionary = new Dictionary <string, Foo>(); // throw a curve ball by reassigning the dictionary variable
Foo foo4 = wrapper4.Value;
Console.WriteLine("foo3 and foo4 are equal? {0}", object.ReferenceEquals(foo3, foo4));
// Output: foo3 and foo4 are equal? True
Console.WriteLine("foo1 and foo3 are equal? {0}", object.ReferenceEquals(foo1, foo3));
// Output: foo1 and foo3 are equal? False
}
static void Main(string[] args)
{
// this wrapper object is not useable, since no key has been specified for it yet
var wrapper = new KeyedValueWrapper <string, Foo>(new Dictionary <string, Foo>(), (key) => new Foo {
ID = key
});
// create wrapper1 based on the wrapper object but changing the key to "ABC"
var wrapper1 = wrapper.Change("ABC");
var wrapper2 = wrapper1;
Foo foo1 = wrapper1.Value;
Foo foo2 = wrapper2.Value;
Console.WriteLine("foo1 and foo2 are equal? {0}", object.ReferenceEquals(foo1, foo2));
// Output: foo1 and foo2 are equal? True
// create wrapper1 based on the wrapper object but changing the key to "BCD"
var wrapper3 = wrapper.Change("BCD");
var wrapper4 = wrapper3;
Foo foo3 = wrapper3.Value;
Foo foo4 = wrapper4.Value;
Console.WriteLine("foo3 and foo4 are equal? {0}", object.ReferenceEquals(foo3, foo4));
// Output: foo3 and foo4 are equal? True
Console.WriteLine("foo1 and foo3 are equal? {0}", object.ReferenceEquals(foo1, foo3));
// Output: foo1 and foo3 are equal? False
// Counter-example: manipulating the dictionary instance that was provided to the wrapper can disrupt expected behavior
var dictionary = new Dictionary <string, Foo>();
var wrapper5 = wrapper.Change("CDE", dictionary);
var wrapper6 = wrapper5;
Foo foo5 = wrapper5.Value;
dictionary.Clear();
Foo foo6 = wrapper6.Value;
// one might expect this to be true:
Console.WriteLine("foo5 and foo6 are equal? {0}", object.ReferenceEquals(foo5, foo6));
// Output: foo5 and foo6 are equal? False
}