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LINQ Design Curiosity: Skip/Take vs. SkipWhile/TakeWhile

Is there any particular reason to have separate methods Skip and SkipWhile, rather than simply having overloads of the same method?
What I mean is, instead of Skip(int), SkipWhile(Func<TSource,bool>), and SkipWhile(Func<TSource,int,bool>), why not have Skip(int), Skip(Func<TSource,bool>), and Skip(Func<TSource,int,bool>)? I'm sure there's some reason for it, as the whole LINQ system was designed by people with much more experience than me, but that reasoning is not apparent.
The only possibility that's come to mind has been issues with the parser for the SQL-like syntax, but that already distinguishes between things like Select(Func<TSource,TResult>) and Select(Func<TSource,int,TResult>), so I doubt that's why.
The same question applies to Take and TakeWhile, which are complimentary to the above.
Edit: To clarify, I am aware of the functional differences between the variants, I'm merely asking about the design decision on the naming of the methods.

IMO, the only reason would be better readability. Skip sound like “Skip N number of records”, while SkipWhile sounds like “Skip until a condition is met”. These names are self-explanatory

The "While" indicates that LINQ will only skip while the lambda expression evaluates to true, and will stop skipping as soon as it is no longer true. This is a very different thing from just skipping a fixed number of items.
The same reasoning holds true for Take, of course.
All is well in the interest of clarity!

Do you like languages that let you put the "then" before the "if"?

I was reading through some C# code of mine today and found this line:
if (ProgenyList.ItemContainerGenerator.Status != System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated) return;
Notice that you can tell without scrolling that it's an "if" statement that works with ItemContainerGenerator.Status, but you can't easily tell that if the "if" clause evaluates to "true" the method will return at that point.
Realistically I should have moved the "return" statement to a line by itself, but it got me thinking about languages that allow the "then" part of the statement first. If C# permitted it, the line could look like this:
return if (ProgenyList.ItemContainerGenerator.Status != System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated);
This might be a bit "argumentative", but I'm wondering what people think about this kind of construct. It might serve to make lines like the one above more readable, but it also might be disastrous. Imagine this code:
return 3 if (x > y);
Logically we can only return if x > y, because there's no "else", but part of me looks at that and thinks, "are we still returning if x <= y? If so, what are we returning?"
What do you think of the "then before the if" construct? Does it exist in your language of choice? Do you use it often? Would C# benefit from it?

Let's reformat that a bit and see:
using System.Windows.Controls.Primitives;
...
if (ProgenyList.ItemContainerGenerator.Status != GeneratorStatus.ContainersGenerated)
{
return;
}
Now how hard is it to see the return statement? Admittedly in SO you still need to scroll over to see the whole of the condition, but in an IDE you wouldn't have to... partly due to not trying to put the condition and the result on the same line, and party due to the using directive.
The benefit of the existing C# syntax is that the textual order reflects the execution order - if you want to know what will happen, you read the code from top to bottom.
Personally I'm not a fan of "return if..." - I'd rather reformat code for readability than change the ordering.

I don't like the ambiguity this invites. Consider the following code:
doSomething(x)
if (x > y);
doSomethingElse(y);
What is it doing? Yes, the compiler could figure it out, but it would look pretty confusing for a programmer.

Yes.
It reads better. Ruby has this as part of its syntax - the term being 'statement modifiers'
irb(main):001:0> puts "Yay Ruby!" if 2 == 2
Yay Ruby!
=> nil
irb(main):002:0> puts "Yay Ruby!" if 2 == 3
=> nil
To close, I need to stress that you need to 'use this with discretion'. The ruby idiom is to use this for one-liners. It can be abused - however I guess this falls into the realm of responsible development - don't constrain the better developers by building in restrictions to protect the poor ones.

It's look ugly for me. The existing syntax much better.
if (x > y) return 3;

I think it's probably OK if the scope were limited to just return statements. As I said in my comment, imagine if this were allowed:
{
doSomething();
doSomethingElse();
// 50 lines...
lastThink();
} if (a < b);
But even just allowing it only on return statements is probably a slippery slope. People will ask, "return x if (a); is allowed, so why not something like doSomething() if (a);?" and then you're on your way down the slope :)
I know other languages do get away with it, but C#'s philosophy is more about making The One Right WayTM easy and having more than one way to do something is usually avoided (though with exceptions). Personally, I think it works pretty well, because I can look at someone else's code and know that it's pretty much in the same style that I'd write it in.

I don't see any problem with
return 3 if (x > y);
It probably bothers you because you are not accustomed to the syntax. It is also nice to be able to say
return 3 unless y <= x
This is a nice syntax option, but I don't think that c# needs it.

I think Larry Wall was very smart when he put this feature into Perl. The idea is that you want to put the most important part at the beginning where it's easy to see. If you have a short statement (i.e. not a compound statement), you can put it before the if/while/etc. If you have a long (i.e. compound) statement, it goes in braces after the condition.

Personally I like languages that let me choose.
That said, if you refactor as well as reformat, it probably doesn't matter what style you use, because they will be equally readable:
using System.Windows.Controls.Primitives;
...
var isContainersGenerated =
ProgenyList.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated;
if (!isContainersGenerated) return;
//alternatively
return if (!isContainersGenerated);

There is a concern reading the code that you think a statement will execute only later to find out it might execute.
For example if you read "doSomething(x)", you're thinking "okay so this calls doSomething(x)" but then you read the "if" after it and have to realise that the previous call is conditional on the if statement.
When the "if" is first you know immediately that the following code might happen and can treat it as such.
We tend to read sequentially, so reading and going in your mind "the following might happen" is a lot easier than reading and then realising everything you just read needs to be reparsed and that you need to evaluate everything to see if it's within the scope of your new if statement.

Both Perl and Ruby have this and it works fine. Personally I'm fine with as much functionality you want to throw at me. The more choices I have to write my code the better the overall quality, right? "The right tool for the job" and all that.
Realistically though, it's kind of a moot point since it's pretty late for such a fundamental addition in C#'s lifecycle. We're at the point where any minor syntax change would take a lot of work to implement due to the size of the compiler code and its syntax parsing algorithm. For a new addition to be even considered it would have to bring quite a bit of functionality, and this is just a (not so) different way of saying the same thing.

Humans read beginning to end. In analyzing code flow, limits of the short term memory make it more difficult to read postfix conditions due to additional backtracking required. For short expressions, this may not be a problem, but for longer expressions it will incur significant overhead for users that are not seasoned in the language they are reading.

Agreed with confusing , I never heard about this construction before , so I think correct way using then before if must always contents the result of else, like
return (x > y) ? 3 : null;
else way there is no point of using Imperative constructions like
return 3 if (x > y);
return 4 if (x = y);
return 5 if (x < y);
imho It's kinda weird, because I have no idea where to use it...

It's like a lot of things really, it makes perfect sense when you use it in a limited context(a one liner), and makes absolutely no sense if you use it anywhere else.
The problem with that of course is that it'd be almost impossible to restrict the use to where it makes sense, and allowing its use where it doesn't make sense is just odd.
I know that there's a movement coming out of scripting languages to try and minimize the number of lines of code, but when you're talking about a compiled language, readability is really the key and as much as it might offend your sense of style, the 4 line model is clearer than the reversed if.

I think it's a useful construct and a programmer would use it to emphasize what is important in the code and to de-emphasize what is not important. It is about writing intention-revealing code.
I use something like this (in coffeescript):
index = bla.find 'a'
return if index is -1
The most important thing in this code is to get out (return) if nothing is found - notice the words I just used to explain the intention were in the same order as that in the code.
So this construct helps me to code in a way which reflects my intention slightly better.
It shouldn't be too surprising to realize that the order in which correct English or traditional programming-language grammar has typically required, isn't always the most effective or simplest way to create meaning.
Sometimes you need to let everything hang out and truly reassess what is really the best way to do something.

It's considered grammatically incorrect to put the answer before the question, why would it be any different in code?

Control Flow via Return vs. If/Else [closed]

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Which one is better (implicit control flow via return or control flow via if) -- see below. Please explain what you see as advantage/disadvantage to either one. I like option A because it's less code.
Flow via Return:
public ActionResult Edit(MyClass class)
{
if (!class.Editable)
return null;
class.Update();
return View();
}
Flow via If/Else:
public ActionResult Edit(MyClass class)
{
if (class.Editable)
{
class.Update();
return View();
}
else
{
return null;
}
}

There's not much difference in this specific example, but in general I like the first approach because it uses a guard clause to return early. If you start adding nested conditions to the second approach you'll see that your code readability will suffer. Guard clauses can go a long way toward reducing the nesting depth, and really enhance the readability of your code.

I personally like the if/else approach. For one, your if statement is a positive, not a negative, making it easier to read. For two, you've encapsulated the conditions in curly brackets, and I'm a fan of that style.
Anyway, it's much easier to follow what's going on in the second than in the first. And that always wins in my book.

I prefer the second approach for the sake of readability and maintainability. Readability because it just reads 'cleaner' to me than the first approach, and maintainability because I don't have to worry about adding curly braces if I need to modify the if or else clauses. Further, the first approach is only 7 characters less than the second approach if you don't include new lines, which hardly seems a justification for choosing the first over the second.
That said, I actually prefer this:
public ActionResult Edit(MyClass class)
{
ActionResult rv = null;
if (class.Editable)
{
class.Update();
rv = View();
}
return rv;
}
It's more code, but I can now set a single breakpoint on the return statement to inspect the value being returned instead of having to set two breakpoints to do the same in the two choices you offered.

Both of those statements are controlling flow via an if statement. It's just a matter of how you handle the condition.
I'm always on the fence when it comes to writing logic statements like this. Part of me likes the first option because it's a little less code. The other part of me likes the second option because it's much easier to follow the flow of logic. With the first option, it's easy to miss the return statement which can lead to manageability issues in the future.
...and for that reason, the second option always wins in my book. It's better to write code that is easier to read and maintain than try to take shortcuts.

I would prefer the one I identify as being the one which EXECUTES less code.
If it is more common to class.Editable being false then I'd go for A.
But this example does not give much of an advantage in either case.
In any given situation a developer should analyze the input and adjust the code to be optimized on the most common input data.
EDIT:
To clarify:
By executes less code I in reality mean is most efficient...

Exit early - I prefer to see all the conditions that will cause the method to exit without doing much up front. I avoid else statements if I can at all avoid it.
This is actually a fairly prominent school of thought among the Code Contracts crowd.

under these circumstances, I would go with option A. In this case you are doing your input validation and then preventing execution of the rest of the code if the input is not valid (not editable). This keeps the entire body of the function out of a big if/else statement and makes it more readable.
However, I would also consider raising an exception rather than retuning a null - that is assuming that passing in a non-editable object into an "edit" function isn't a normal occurrence.

They are both valid options, and one isn't necessarily any better than the other. Which one you choose is, ultimately, personal preference. Yes, Option A results in slightly less code, but overall they are pretty much equal.
In both cases you are controlling flow via an if and a return. It's really a question of how you prefer to see your boolean logic - negative or positive?
Is ActionResult an enum or a base class? If it's an enum, why are you returning null when Edit returns what appears to be an enum? Wouldn't it be cleaner simply to return an ActionResult value that indicates no action was taken because the object wasn't in an editable state?

I prefer if/else, too. Legibility, readability and maintainability stands above anything else, for me.

First option, using return, is better, because:
you have a place to put all guards and preconditions, near your asserts and all that stuff.
for me, it's easier to think "let's see all that can be wrong, and return. From this point, I have everything I need and I am on the Happy Path
if you do use the if / else approach, you have all code in that method / function indented. Add other if, or for, and things start to get funny
One proponent of this method (return) is Marcus Zarra, in the Cocoa is my Girlfriend coding style

I prefer the first option, provided the case you check is a guard/precondition that needs to be met for the method call to be valid. Although you could argue if you should return null, or throw an (Argument)Exception. When a class isn't editable, should it really be a parameter for this method?
Maybe a better option would be to create an IEditable interface and implementing this on the class you're passing an instance of right now.

I also prefer option 1. For me, it reads better like a book. Also I'm always pained by there not being a return at the end of option 2.

Is Resharper correct?

I just installed Reshaper 4.5 and it has come up with the following suggestions:
return this.GetRuleViolations().Count() == 0; -- REMOVE this.
new string[] { this.ID.ToString(), this.Registration } -- REMOVE string, MAKE ANONYMOUS TYPE
int i = Method.GetNumber(); -- REPLACE int WITH var
Should I do these?
I think in some cases it is going to make the code less readable but will it improve performance? what are the benefits of making these changes?
Thanks

1) The explicit this pointer is only necessary when the reference would otherwise be ambiguous. Since GetRuleViolations is defined on the type, you most likely do not need this.
Another point here is that if GetRuleViolations return an IEnumerable of something, you will generally be much better off using Any() instead of Count() == 0 as you risk enumerating the entire sequence.
2) String can be inferred from the initialization.
3) Resharper prefers var over specific types.

Apart from the obvious benefit of your little square going green, if you are writing code that will be maintained by someone else later, it makes good sense not to use your personal preference in coding syntax. Resharper is becoming useful in formatting code in a way that is recognisable to a very wide audience.
I belong to the school of thought that says it doesn't matter who's way is right. If we all stick to a pattern, we'll all find it easier to read each others code.
So, in my humble opinion, don't change the default resharper settings. Just accept that if you use the defaults, you make life simple for everyone.

I think the first one is for the purpose, if you want to make "GetRuleViolations()" a static method. Then you have not to remove the "this" identifier.

For the 3rd one - the one that annoys me the most. It provides the reader with less information and i think it's just a matter of showing off a newish feature.
I'd say - use var when you know the return type and use the correct object type when you do not like this:
var reader = new XmlReader(.... // Implicit
XmlReader reader = SomeClass.GetReader() // Explicit when you can't be sure

First one: Resharper is asking about removing this which is just a style thing to me. Nothing more, keeping it won't harm performance in any way. It is just a matter of readability.
For second and third: Resharper normally prefers using var instead of specific data type, that's why the suggestions. I believe it is a matter of personal choice and provides no extra gain other than readability.

The first seems unclear to me. You usually don't have to prefix this. as long as there are no ambiguities, which I cannot tell from this example. Resharper is probably right. The other two won't improve performance, the compiled result will be the same. It's just a matter of taste and, of course, your coding guidelines.

The first one should be configurable. As far as I remember, you can tell ReSharper whether you want to have "this." in front of only fields, methods, both or none.
Using "var" will not change anything in the generated CIL code, so the performance will stay the same. I haven't used ReSharper for some time and I don't know why it promotes anonymous types so aggressively, but one advantage of "var" is that it's more resistant to change.
Meaning if, instead of calling Method.GetNumber(), you called a wrapper, eg. Filter(Method.GetNumber()) in the same line that returns a Nullable, you won't have to update the variable's type.

None of these will have any effect on performance, only on readability.
I find suggestions 1 and 2 to be more readable, and 3 less readable than your original code.
But you don't need to just follow these suggestions if, e.g., you find them less readable or if they violate your company's code style standard. When you put the cursor on the squiggly line, press Alt-Enter to show the list of Contex Actions. One of them will be to to change the severity of the inspection; you can not show it at all or show it as a hint. You can find a complete list of inspections at ReSharper | Options | Code Inspection | Inspection Severity.

Are these interview questions too challenging for beginners? [closed]

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Closed 11 years ago.
So I just interviewed two people today, and gave them "tests" to see what their skills were like. Both are entry level applicants, one of which is actually still in college. Neither applicant saw anything wrong with the following code.
I do, obviously or I wouldn't have picked those examples. Do you think these questions are too harsh for newbie programmers?
I guess I should also note neither of them had much experience with C#... but I don't think the issues with these are language dependent.
//For the following functions, evaluate the code for quality and discuss. E.g.
//E.g. could it be done more efficiently? could it cause bugs?
public void Question1()
{
int active = 0;
CheckBox chkactive = (CheckBox)item.FindControl("chkactive");
if (chkactive.Checked == true)
{
active = 1;
}
dmxdevice.Active = Convert.ToBoolean(active);
}
public void Question2(bool IsPostBack)
{
if (!IsPostBack)
{
BindlistviewNotification();
}
if (lsvnotificationList.Items.Count == 0)
{
BindlistviewNotification();
}
}
//Question 3
protected void lsvnotificationList_ItemUpdating(object sender, ListViewUpdateEventArgs e)
{
ListViewDataItem item = lsvnotificationList.Items[e.ItemIndex];
string Email = ((TextBox)item.FindControl("txtEmailAddress")).Text;
int id = Convert.ToInt32(((HiddenField)item.FindControl("hfID")).Value);
ESLinq.ESLinqDataContext db = new ESLinq.ESLinqDataContext();
var compare = from N in db.NotificationLists
where N.ID == id
select N;
if (compare.Count() > 0)
{
lblmessage.Text = "Record Already Exists";
}
else
{
ESLinq.NotificationList Notice = db.NotificationLists.Where(N => N.ID == id).Single();
Notice.EmailAddress = Email;
db.SubmitChanges();
}
lsvnotificationList.EditIndex = -1;
BindlistviewNotification();
}

I don't typically throw code at someone interviewing for a position and say "what's wrong?", mainly because I'm not convinced it really finds me the best candidate. Interviews are sometimes stressful and a bit overwhelming and coders aren't always on their A-game.
Regarding the questions, honestly I think that if I didn't know C#, I'd have a hard time with question 3. Question #2 is a bit funky too. Yes, I get what you're going for there but what if the idea was that BindlistviewNotification() was supposed to be called twice? It isn't clear and one could argue there isn't enough info. Question 1 is easy enough to clean up, but I'm not convinced even it proves anything for an entry-level developer without a background in C#.
I think I'd rather have something talk me through how they'd attack a problem (in pseudo-code or whatever language they are comfortable with) and assess them from that. Just a personal opinion, though.

I am a junior programmer, so I can give it a try:
"active" is unnecessary:
CheckBox chkactive = (CheckBox)item.FindControl("chkactive");
dmxdevice.Active = chkactive.Checked
You should use safe casting to cast to a CheckBox object. Of course, you should be able to find the checkbox through its variable name anyway.:
CheckBox chkactive = item.FindControl("chkactive") as CheckBox;
The second function could be more concise:
public void Question2(bool IsPostBack)
{
if (!IsPostBack || lsvnotificationList.Items.Count == 0)
{
BindlistviewNotification();
}
}
Only have time for those two, work is calling!
EDIT: I just realized that I didn't answer your question. I don't think this is complicated at all. I am no expert by any means and I can easily see the inefficiencies here. I do however think that this is the wrong approach in general. These language specific tests are not very useful in my opinion. Try to get a feeling for how they would attack and solve a problem. Anyone who can get past that test will be able to easily pick up a language and learn from their mistakes.

I think you are testing the wrong thing. You are obviously looking for a C# programmer, rather than a talented programmer (not that you cannot be a talented C# programmer). The guys might be great C++ programmers, for example. C# can be learned, smarts cannot. I prefer to ask for code during an interview, rather than presenting code in a specific language (example: implement an ArrayList and a LinkedList in any language).
When I was looking for 3 programmers earlier this year, to work mostly in C#, Java, PL/SQL, Javascript and Delphi, I looked for C/C++ programmers, and have not been disappointed. Any one can learn Java, not everyone has a sense of good arachitecture, data strutures and a grasp of new complex problems. C++ is hard, so it acts as a good filter. If I had asked find errors in this Java code, I would have lost them.
BTW, I am a team lead, been programming for 20 years with dozens of large projects developed on time and on budget, and I had no clue with what was wrong with question 2 or 3, having only a passing familiarity with C#, and certainly not with Linq, Not that I could not learn it.... I figured it out after a couple minutes, but would not expect a recent graduate to grasp it, all the LINQ code in question 3 is a distraction that hides the real problems.

Do you think these questions are too harsh for newbie programmers?
Yes, IMO they are too harsh.
Neither applicant saw anything wrong with the following code.
While there are plenty of 'possible problems', like not checking for null pointers, casting, etc, there don't appear to be any 'actual problems.' (eg: given sane input, the program looks like it will actually run).
I'd guess that a newbie programmer will get hung up on that.
As linq is pretty new, and still not in wide use, it's going to go way over the head of your newbies.
What is an ESLinqDataContext? If people have no idea what your object is or how it behaves, how are they supposed to know if it is being used correctly or not?
evaluate the code for quality and discuss
You only really learn to pick up stuff like invalid cast exceptions (let alone being able to judge and comment on 'code quality') from reasonable experience working with code similar to what's in front of you.
Perhaps I'm misunderstanding, but to me, an "entry level" position pretty much by definition has no expectation of prior experience, so it doesn't seem fair to grade them on criteria which require experience.

I am not a C# programmer so I don't know what BindlistviewNotification does, but changing
public void Question2(bool IsPostBack)
{
if (!IsPostBack)
{
foo();
}
if (lsvnotificationList.Items.Count == 0)
{
foo();
}
}
to
public void Question2(bool IsPostBack)
{
if (!IsPostBack || lsvnotificationList.Items.Count == 0)
{
foo();
}
}
changes the function! If IsPostBack is false, foo is executed. If lsvnotificationList.Items.Count == 0 then foo is executed again. The revised code will only execute foo once.
You could argue that BindlistviewNotification can be executed several times without side effects or that IsPostBack can never be false and lsvnotificationList.Items.Count equal 0 at the same time, but those are language dependent and implementation dependent issues that cannot be resolved with the given code snippet.
Also, if this is a bug that's "supposed" to be caught in the interview, this isn't language agnostic at all. There's nothing that would tell me that this is supposed to be a bug.

As a newbie, I would expect employers to care more about what my thought processes were rather than whether the answer was "correct" or not. I could come up with some answers to these questions, but they probably wouldn't be right. :)
So with that said, I think you could get by with these questions, but you should definitely be a bit more liberal with what the "correct" answer is.
As long as those conditions were made clear, I think that it's a bad thing to get a blank sheet with no thoughts. This means that they either genuinely think the code is perfect (which we know is almost never true) or are too sheepish to share their thoughts (which is also a bad thing).

I don't think 1 and 2 are too difficult, #3 requires a decent understanding on how databinding and LINQ works in .NET, so it may be somewhat hard for an entry level person. I think these are fairly good questions for junior level developers who have some .NET experience.
For what its worth, my notes:
Question 1:
Using an integer as boolean
No null check on findControl
Excessive verbosity
My revision:
public void Question1()
{
CheckBox chkactive = item.FindControl("chkactive") as CheckBox;
if (chkActive != null)
dmxdevice.Active = chkActive.Checked;
else
dmxdevice.Active = false;
}
Question 2:
Excessive verbosity
Databinding will happen twice if its not a postback, and there are no items to bind.
My revision:
public void Question2(bool IsPostBack)
{
if (!IsPostBack || lsnotificationList.Items.Count == 0)
{
BindlistviewNotification();
}
}
Question 3:
Replace indexed loopup with getting e.Item.DataItem;
Add nullchecks to findControl calls.
Switch to TryParse and add a default id value.
Added better error handling
Document some major architectural issues, why are you querying the database from the frontend? Those LINQ queries could be optimized too.
Why not check for duplicates within the list items collection, and why not batch all updates with a single submit later?

So you asked this to someone with no c#, .net, asp.net or linq knowledge? I wouldn't expected anything on the paper?

My only advice is to make sure your test questions actually compile.
I think the value in FizzBuzz type questions is watching HOW somebody solves your problems.
Watching them load the solution in to the IDE, compile it, step through the code with a step through debugger, write tests for the apparent intended behavior and then refactoring the code such that it is more correct/maintainable is more valuable than knowing that they can read code and comprehend it.

Not knowing C#, it took me a bit longer, but I'm assuming #1 could be expressed as
dmxdevice.Active = ((CheckBox)item.FindControl("chkactive")).Checked == true
And in #2 the two conditions could be joined as an A OR B statement?
If that's what you're looking for, then no, those aren't too hard. I think #1 is something you might learn only after programming for a little while, but #2 seems easier.
Are you looking for them to catch null pointer exceptions also?

I think the first two are fine. The third may be a wee bit complicated for a graduate level interview, but maybe not, it depends whether they've done any .net coding before.
It has LINQ statements in there, and that's pretty new. Especially since many unis/colleges are a bit behind in teaching the latest technology. So I would say run with 1 & 2 and either simplify 3 or heavily comment it as others have mentioned

The first two appear to be more a test to see if a person can follow logically and realize that there is extra code. I'm not convinced that an entry level developer would understand that 'less is more' yet. However, if you explained the answer to Question 1 and they did not then extraplolate that answer to #2, I would be worried.

Question 3 appears to be a big ball of mud type of implementation. This is almost expected to be the style of a junior developer straight from college. I remember most of my profs/TAs in college never read my code -- they only ran the executable and then put in test sets. I would not expect a new developer to understand what was wrong with it...

What did you expect to get out of this interview? Do your employees have to debug code without a debugger or something? Are you hiring somebody who will be doing only maintenance programming?
In my opinion these questions do little to enlighten you as to the abilities of the candidates.

This is a fine question if you're looking for a maintenance programmer, or tester.
However, this isn't a good test to detect a good programmer. A good programmer will pass this test, certainly, but many programmers that are not good will also pass it.
If you want a good programmer, you need to define a test that only a good programmer would pass. A good programmer has excellent problem solving skills, and knows how to ask questions to get to the kernel of a problem before they start working - saving both them and you time.
A good programmer can program in many different languages with only a little learning curve, so your 'code' test can consist of pseudo code. Tell them you want them to solve a problem and have them write the solution in pseudo code - which means they don't have access to all those nifty libraries. A good programmer knows how the libraries function and can re-create them if needed.
So... yeah, you're essentially asking textbook knowledge questions - items that show memorization and language knowledge, but not skills necessary to solve a problem.
-Adam

It's funny to see everyone jumping to change or fix the code. The questions targeted "efficiently? could it cause bugs?" Answers: Given enough time and money, sure each one could probably be made more efficient. Bugs, please try to avoid casting and writing difficult to read code (code should be self-documenting). If it doesn't have bugs it might after the next junior programmer tries to change it... Also, avoid writing code that appears to rely on state contained outside the scope of the method/function, those nasty global variables. If I got some insightful comments like this it might be appropriate to use this as a tool to create some good conversation. But, I think some better ice-breakers exist to determine if a persons critical thinking skills are appropriate and if they will fit in with the rest of the team. I don't think playing stump the programmer is very effective.

Question #1
boolean active = true;
Question #2
if ((!IsPostBack) || (lsvnotificationList.Items.Count == 0))
Question #3:
Do a total re-write and add comments. After a 30 second read I still can't tell what the code is trying todo.

I'm not a C# programmer. On Q1, there seem to be undeclared objects dmxdevice and item, which confuses me. However, there does seem to be a lot of obfuscation in the rest of the code. On Q2, lsvnotificationList is not declared, and it not clear to me why one test is abbreviated with ! and the other with == 0 -- but the tests could be combined with ||, it seems. In Q3, lsvnotificationList is not self-evidently declared, again. For the rest, it seems to be doing a database lookup using LINQ. I'd at least expect that to be factored into a function that validates the hidden field ID more transparently. But if you have other ideas, well...I'm still not a C# programmer.

Disclaimer: I come from a 4 year degree and a year's worth of professional Java experience.
The first two questions are quite straightforward and if a candidate doesn't see a better approach I would suspect it's because they haven't been paying attention in class ;-)
Most of the answers to the second question presented so far alter the functions behaviour. The function could very well be evaluated twice in the original code, although I can't say if that is the intent of the function. Side effects are important.
I would probably one-line the first function, myself.
The questions are fairly language agnostic, but they're not library agnostic, which I would argue is equally as important. If you're specifically looking for .NET knowledge, well and good, but without Google I couldn't tell you what an ESLinq.DataContext is, and my answer to the third question suffers accordingly. As it is, it's nearly incomprehensible to me.
I think you also have to be careful how you present the questions. There's nothing incorrect about the first two methods, per se. They're just a little more verbose than they should be.
I would just present them with the sheet and say, "What do you think of this code?"
Make it open ended, that way if they want to bring up error-handling/logging/commenting or other things, it doesn't limit the discussion.

A cursory glance indicates that most of the rest of the code suffers from poor structure and unnecessary conditionals etc. There's nothing inherently "wrong" with that, especially if the program runs as expected. Maybe you should change the question?
On the other hand, the casting doesn't look like it's being done correctly at all eg. (cast)object.Method() vs (cast)(object.Method()) vs ((cast)object).Method(). In the first case, it's not a language agnostic problem though - it depends on rules of precedence.
I don't think it was that hard, but it all depends on what you wanted to test. IMO, the smart candidate should have asked a lot of questions about the function of the program and the structure of the classes before attempting to answer. eg. How are they supposed to know if "item" is a global/member var if they don't ask? How do they know it's type? Do they even know if it supports a FindControl method? What about FindControl's return type?
I'm not sure how many colleges teach Linq yet though, so maybe you should remove that part.

No one's answering #3 with code. That should indicate how people feel about it. Usually stackoverflowers meet these head-first.
Here's my stab at it. I had to look up the EventArgs on msdn to know the properties. I know LINQ because I've studied it closely for the past 8 months. I don't have much UI experience, so I can't tell if the call to bind in the event handler is bad (or other such things that would be obvious to a UI coder).
protected void lsvnotificationList_ItemUpdating(object sender, ListViewUpdateEventArgs e)
{
string Email = e.NewValues["EmailAddress"].ToString();
int id = Convert.ToInt32(e.NewValues["ID"]);
using (ESLinq.ESLinqDataContext db = new ESLinq.ESLinqDataContext(connectionString))
{
List<NotificationList> compare = db.NotificationLists.Where(n => n.ID = id).ToList();
if (!compare.Any())
{
lblmessage.Text = "Record Does Not Exist";
}
else
{
NotificationList Notice = compare.First();
Notice.EmailAddress = Email;
db.SubmitChanges();
}
}
lsvnotificationList.EditIndex = -1;
BindlistviewNotification();
}

While people here obviously have no trouble hitting this code in their spare time, as someone who went through the whole job search/interviewing process fresh out of collage about a year ago I think you have to remember how stressful questions like these can be. I understand you were just looking for thought process, but I think you would get more out of people if you brought questions like this up casually and conversationally after you calm the interviewee down. This may sound like a cop out, but questions about code that will technically work, but needs some pruning, can be much more difficult then correcting code that doesn't compile, because people will assume that the examples are suppose to not compile, and will drive themselves up a wall trying to figure out the trick to your questions. Some people never get stressed by interview questions, but alot do, even some talented programmers that you probably don't want to rule out, unless you are preparing them for a situation where they have to program with a loaded gun to their head.
The code itself in question 3 seems very C# specific. I only know that as LINQ because someone pointed it out in the answers here, but coming in as a Java developer, I would not recognize that at all. I mean do you really expect colleges to teach a feature that was only recently introduced in .net 3.5?
I'd also liked to point out how many people here were tripped up by question 2, by streamlining the code, they accidentally changed the behavior of the code. That should tell you alot about the difficulty of your questions.

Ok, so after staying up well past my bedtime to read all the answers and comment on most of them...
General concensus seems to be that the questions aren't too bad but, especially for Q3, could be better served by using pseudo-code or some other technique to hide some of the language specific stuff.
I guess for now I'll just not weigh these questions in too heavily.
(Of course, their lack of SQL knowledge is still disturbing... if only because they both had SQL on their resume. :( )

I'll have to say that my answer to these problems is that without comments (or documentation) explaining what the code is MEANT to do, there is little reason to even look at the code. The code does EXACTLY what it does. If you change it to do something else, even change it to prevent throwing an exception, you may make it do something unintended and break the larger program.
The problem with all three questions is that there is no intent. If you modify the code, you are assuming that you know the intent of the original coder. And that assumption will often be wrong.
And to answer the question: Yes, this is too difficult for most junior programmers, because documenting code is never taught.

Okey I'm not going to answer the C# questions from what I see here you have enough candidates that would do fine in a job interview with you.
I do think that the tests won't give you a good view of a persons programming skills. Have a look at Joel's interviewing Guide:
http://www.joelonsoftware.com/articles/fog0000000073.html
He talks about two things when it comes to possible candidates: are they smart AND do they get the job done (now that's a powerful combination).Let your candidates talk a bit about projects they did or what they're toying around with at home. Find out if they are passionate about programming. Some experience is nice of course, just don't ask them to do tricks.

Q1 also has a potential InvalidCastException on the item.FindControl() line.
I don't think Q1 or Q2 are outside the realms of being too hard, even for non C# users. Any level code should be able to see that you should be using a boolean for active, and only using one if statement.
Q3 though atleast needs comments as someone else noted. That's not basic code, especially if you're targeting non-C# users with it too.

In question 2 for better modularity I would suggest passing the count of lsvnotificationList.Items as a parameter:
public void Question2(bool IsPostBack, int listItemsCount)
{
if (!IsPostBack || listItemsCount == 0)
BindlistviewNotification();
}