String vs. string in C#

Apart from knowing the language (c#, vb whatever) well, take a look at the underlying framework. Newcomers omit that part most of the time. Might help with lots of decisions.

- The importance of .Net framework for your program. What happens when you double click on a .Net exe? What happens at the start of a web application? Is the framework is always there or started per app?

- Spend some time with ildasm. Learn what a manifest is. What is it good for. What is Intermediate Language (IL)?

- Difference between reference and value types. Heap and stack.

- What is garbage collection? How the garbage collector is working? IDisposable pattern.

- Why generic classes are important? What was there before them?

- Static vs. instance method calls.

- Passing object references around and keeping a reference (hence preventing GC, especially important for Desktop apps with improper use of events and references)

- For desktop devs: UI thread, background threads, patterns to pass data between these two.

- Basic OO. Virtual methods, overrides, new keyword, interfaces.

- Why strings are immutable?

etc.

S_A_P• 12 years ago

There is a lot of misinformation around this as well. I've had a developer tell me that the difference is that string is immutable while String is mutable- this person was otherwise a pretty savvy and productive developer. I wonder how many bugs are out there where he was expecting a mutable object...

martindevans• 12 years ago

I opened this up because I saw the title and thought, "hmm that's strange, isn't string just an alias for String"? I'm pretty sure every C# dev I know would say the same. Then again if I was asked a trick question like this in an interview I might scratch around for some/any difference I could think of!

mattmanser• 12 years ago

He has only asked 8 people.

It's one of those things that after a few years you look at and wonder why there's string and String, int and Int32, you google it, you find out it's simply an alias.

So he's probably only interviewed juniors.

dtech2• 12 years ago

I have been working in C# for 2 weeks, and Googled this last week. I think it's kinda the difference between being interested in making things work, and understanding how the language works.

steveklabnik• 12 years ago

It's not like all interviewees have been fresh out of uni, in fact only one has been.

curryhoward• 12 years ago

Pretty terrible (but harmless) interview question. It reminds me of a pointless question I was asked once: name the 4 access modifiers in Java. That was the day I learned about "package-private".

arethuza• 12 years ago

If we wanted to play the trivia game I could ask what access modified was removed from Java? :-)

danbruc• 12 years ago

If you come to C# with a Java background you may easily be fooled to think it is similar to int and Integer or boolean and Boolean in case you are not aware that .NET has a unified type system. And, by the way, I hate these aliases because they mess up the look of the code - not only the syntax highlighting color which is easy to change, but now there are lower and upper case type names. Soooo ugly!

dandruffhead• 12 years ago

It's just an alias, but the way I use it is different. When declaring variable I opt for `string` but of course you should probably user `var`. But when calling method bound to the class, I would use `String`, i.e `String.format()`, etc

xtrumanx• 12 years ago

Do you also `Int32.Parse`?

I just stick with `string` everywhere.

Gmo• 12 years ago

I tend to do the same.

I find there is some kind of "logic" to this idea :D

alelefant• 12 years ago

Jon Skeet's answer about "string vs String" on Stack Overflow was particularly interesting: http://stackoverflow.com/a/215422/190750.

brudgers3• 12 years ago

Skeet's answer points out that the alias is required in enums...i.e. there is a difference.

Direct link to Skeet's answer: http://stackoverflow.com/a/215422

dtech2• 12 years ago

A difference which is relevant approximately 0% of the time.

mhomde• 12 years ago

"Capitalization." Check mate

brudgers3• 12 years ago

I don't see the point of this as an interview question unless the context includes the interviewee with their internet connected device in hand and obvious encouragement to find the right answer rather than recall it from memory.

It's particularly bad because there is no important fact to remember and imagination will fill in. An interview is high stress. What is valuable is the ability to Google under stress and the question and context will tend not to measure it.

chrisbennet• 12 years ago

This a great weeder question. Asking questions like this are often signs that:

(A) The interviewer doesn't know how to interview since they are wasting time asking questions that tell them very little about the candidate.

(B) The interviewer might be the type of interviewer who likes "trick" questions which can be a sign of someone who more interested in proving that they know something the interviewee doesn't.

Remember, the candidate is interviewing you/your company.

copsarebastards• 12 years ago

Yep. When I read this, my first thought was, "Aren't they the same thing?" And then "That's dumb. I probably wouldn't take that job."

px1999• 12 years ago

Definitely has an air of trick-questionness about it (which I'm not a big fan of) - I think that it could be better rephrased as either:

"When would you use string as opposed to String?" or "Why do you think that the corelib int Convert.ToInt32(double value) method has this name and return type?"

These are more open; allow the candidate to explain that there's little practical difference between string and System.String; that it comes down to coding style; that there are aliases for int to System.Int32, which are probably VC++ showing through a bit (both the fixed size integer types and the underlying problem that made them necessary/useful); that it helps non-.NET consumers know what "int" means etc etc.

IMO it's still not a great interview question though (once you verify that the developer knows the basics) - I think that a lot of devs wouldn't know the ins and outs of this, simply because they'll hardly ever need to appreciate the difference (ie put it in your coding standards that they need to use one and they can forget that the other exists almost entirely).

rootsofallevil• 12 years ago

I'm the author of the original blog post.

I like your way of phrasing the question, I think I'll start asking it that way, starting tomorrow: we're interviewing a chap for a mid-level dev position.

Like I said on the blog, I don't think it's a good question, I just keep asking it out of scientific curiosity, more than anything else.

nbevans• 12 years ago

Whilst it is a shitty idea for a question I'm not sure I could hire a .NET dev that didn't know this simple fact. Type aliases are common in many languages, not just .NET. Being unable to answer this question, or even make a correct guess at it (it's not exactly hard), suggests a larger problem with the candidate.

String vs. string in C#

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