Errata

The second sentence is as follows:

Although not strictly necessary, all collections
leverage this functionality by supporting the
IEnumerable and IEnumerable interfaces,...

IEnumerable is duplicated in this sentence. So, which two interfaces do all
collections support?

Also, what does it mean to "support" an interface? Should this be "implement"
instead to be more clear?

The description does not scan properly. I have changed the first "to" to
"from" so that it now reads:

"The break statement transfers execution from the enclosing while loop...to
the next statement block."

Is this a correct interpretation?

The code fragment for LocalFile is wrong.

'public LocalFile(string name) : base(name)' will call Location's
constructor, not URL's.

static void Main() {
URL u = new URL();
LocalFile l = new LocalFile();

won't compile because both the URL constructor and the
LocalFile constructor require string args.

generates warnings, not errors. So, it appears that regardless of read-only
status, a field can be compiled without ever being assigned.

using System;

public class ReadOnly {

private static readonly int readOnlyStatic;
private static int writeableStatic;

public static void Main() {
Console.WriteLine(readOnlyStatic);
Console.WriteLine(writeableStatic);

ReadOnly r = new ReadOnly();
r.Foo();
}

private readonly int readOnlyInstance;
private int writeableInstance;

public void Foo() {
Console.WriteLine(readOnlyInstance);
Console.WriteLine(writeableInstance);
}

}

Maybe one more tab is needed for "if(args.cancel)" in set of property Position of
Slider. In the book, it looks as

if (position != value) {
if (Move != NULL) { // if invocation list not empty
MoveEventArgs args = new MoveEventArgs(value)
Movve(this, args); // fire event
if (args.cancel)
return
}
position = value;

indentation of if (args.cancel) seems to be wrong and misleading. Right way:
if (position != value) {
if (Move != NULL) { // if invocation list not empty
MoveEventArgs args = new MoveEventArgs(value)
Movve(this, args); // fire event
if (args.cancel)
return;
}
position = value;

...
// Using IEnumerator: substitute your typename for XXX
IEnumerator ie = myc.GetEnumerator();
while (myc.MoveNext()) {
XXX item = (XXX)myc.Current;
Console.WriteLine(item);
...
}

is incorrect in two ways. (1) Once the IEnumerator variable ie has
been initialized, the rest of the code should be using it instead of
myc. (2) The variable myc is not declared anywhere. The code section
above the incorrect section declares a MyCollection mcoll, and I
believe this is what was actually intended. Here is the same section
rewritten to correct these errors:

...
// Using IEnumerator: substitute your typename for XXX
IEnumerator ie = mcoll.GetEnumerator();
while (ie.MoveNext()) {
XXX item = (XXX)ie.Current;
Console.WriteLine(item);
...
}