Re: ASCII byte array to float - C# Discussion Boards

2-Oct-09 11:44

Hi,

Is there a way to get the values in a a byte array which are in ASCII format and convert them into float? Let me explain:

My byte array when a number(integer) 79 is put in it, looks like this:

bData[0] = 55;
bData[1] = 57;
bData[2] = 0;
bData[4] = 0;

I want to take this data (from bData[]) and put it in a float variable as:

float fData = 79.0;

Is there a way to do this?
Thanks

Abhishek Sur2-Oct-09 12:02

Abhishek Sur

2-Oct-09 12:02

how about

float fData = Convert.ToSingle(bData[0]);

I hope this helps you.

Abhishek Sur
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akhanal2-Oct-09 12:07

2-Oct-09 12:07

This did not work with me. It gave weird values like, 4.23233-e

Abhishek Sur2-Oct-09 13:10

Abhishek Sur

2-Oct-09 13:10

what is the byte value that you are converting?

If the value is within 0 - 255, I think it will be parsed clearly.
Smile | :)

Can you tell me what is in bData[3]. check it. If its default(byte) / 0 it will parse clearly using Convert.ToSingle as I checked.
Debug your application and see for what value of byte you are getting this.(just curious) D'Oh! | :doh:

Abhishek Sur
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Luc Pattyn2-Oct-09 13:27

Luc Pattyn

2-Oct-09 13:27

The bytes contain ASCII characters (55 = '7'), not bit patterns that are part of a float.

Smile | :)

Luc Pattyn

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Abhishek Sur3-Oct-09 6:37

Abhishek Sur

3-Oct-09 6:37

oh... Thanks Luc.
Thumbs Up | :thumbsup:

Abhishek Sur
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PIEBALDconsult2-Oct-09 12:03

PIEBALDconsult

2-Oct-09 12:03

What's in bData[3] ?

Anyway, make it a string and parse it.

akhanal2-Oct-09 12:09

2-Oct-09 12:09

As I said in my question, it has integer value in ASCII format.

Can you show an example? Cause I think I already tried, encoding.ascii.getstring() but that did not work.

One spoonful

Luc Pattyn2-Oct-09 12:28

Luc Pattyn

2-Oct-09 12:28

akhanal wrote:
encoding.ascii.getstring() but that did not work.

really?

byte[] bData=new byte[5];
bData[0] = 55;
bData[1] = 57;
bData[2] = 0;
bData[3] = 0;
bData[4] = 0;
string s=Encoding.ASCII.GetString(bData);
float f=float.Parse(s);

Luc Pattyn

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Re: One spoonful

akhanal4-Oct-09 9:38

Are these hard C# interview questions? Really?? [modified]

4-Oct-09 9:38

Hi,

My mess, sorry!

I was doing:

float f = System.Convert.ToSingle(s);

instead of:

float f=float.Parse(s);

Anyways, that worked.
Thanks.

Re: One spoonful

Luc Pattyn4-Oct-09 9:51

Luc Pattyn

4-Oct-09 9:51

byte[] bData=new byte[5];
bData[0] = 55;
bData[1] = 57;
bData[2] = 0;
bData[3] = 0;
bData[4] = 0;
string s=Encoding.ASCII.GetString(bData);
float f=System.Convert.ToSingle(s);

works exactly the same as with float.Parse!

Smile | :)

Luc Pattyn

Local announcement (Antwerp region): Lange Wapper? Neen!

ewan2-Oct-09 10:09

Re: Are these hard C# interview questions? Really??

2-Oct-09 10:09

Hi All

I've been doing interviews for a large multi national company for a number of C# contractors to work on a greenfield winforms application. In the last month I've interviewed 28 candidates and only 6 have passed our first technical test which is a 1/2 hour telephone screening. What I'm wondering is if our basic questions are viewed by the community as not fair game. Our basic premise is that if you can't answer four out of five of these basic questions (first ten minutes of interview) there is little point in pursuing things further.

1) What is the base object in C#.NET, its public instance methods and when would you use them? - I'm astonished how few people get this. I generally forgive forgetting GetHashCode but Equals?! - only maybe 25% of people get 3 out of the 4 methods (or 5 if you count Finalize which in general we don't).
2) What is a delegate? What is the difference between delegate.Invoke and delegate.BeginInvoke? - Really asking do you know the difference between synchronous and asynchronous programming. - maybe 20% get this.
3) Give a two minute overview of how the garbage collector works? (Looking for what makes an object eligible for collection, when it runs, concept of generations, implications of having a finalizer etc) - very poor understanding out there - I've had 1 good explanation so far.
4) Explain the OO concept of polymorphism and how you can take advantage of it in C#? Why do you think Microsoft didn't make all methods virtual by default? - I.e. whats a virtual function and to understand the performance implications of them. - most get the first, nobody so far the second.
5) Is ArrayList/List<t> a thread safe collection? If not how would you make it thread safe? - most get its not, only some really have any idea how to make it thread safe.

I just don't think these are hard questions, especially given the daily rates we are offering, but maybe I'm being too hard? What do you think?

Whats really strange is we're doing a lot of Java interviews for the server side of things as well and we've seen plenty of great candidates. Maybe there are just lots and lots of very poor C# candidates out there and I'm getting my fair share of them!

Cheers!

modified on Friday, October 2, 2009 6:08 PM

Dave Kreskowiak2-Oct-09 10:27

Dave Kreskowiak

2-Oct-09 10:27

ewan wrote:
1) What is the base object in C#.NET, its public methods and when would you use them? - I'm astonished how few people get this. I generally forgive forgetting GetHashCode but Equals?! - only maybe 25% of people get 3 out of the 4 methods.

4 methods?? System.Object has 7. Equals, Finalize, GetHashCode, GetType, MemberwiseClone, ReferenceEquals and ToString.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...

Re: Are these hard C# interview questions? Really??

ewan2-Oct-09 10:31

Re: Are these hard C# interview questions? Really??

2-Oct-09 10:31

Fair point - badly phrased in my original post. The question does specify public instance methods not class (static) methods. We don't count Finalize as you can't call it directly but I would accept that. MemberwiseClone certainly wouldn't count as thats protected not public.

DaveyM692-Oct-09 10:35

DaveyM69

2-Oct-09 10:35

ewan wrote:
What is the base object in C#.NET

I would expect anyone applying to know this - plus the answer is in the question!

ewan wrote:
its public methods and when would you use them

How often do we actually use methods on object? I rarely do as the only use for object nowadays really is where generics are not appropriate, and at the first oportunity before doing anything with it it I unbox it. Not an excuse for not knowing the answer, but makes it a pointless question IMO.

ewan wrote:
What is a delegate? What is the difference between delegate.Invoke and delegate.BeginInvoke?

Fair question

ewan wrote:
Give a two minute overview of how the garbage collector works?

How often do you really need to know this? I don't fully understand it. More important is what is the dispose pattern and when/how should it be implemented.

ewan wrote:
Explain the OO concept of polymorphism and how you can take advantage of it in C#? Why do you think Microsoft didn't make all methods virtual by default?

Fair question(s)

ewan wrote:
Is ArrayList a thread safe collection? If not how would you make it thread safe?

I'd be asking why you're planning on using an ArrayList instead of List<T> and explaining that thread safety or lack of applies to nearly everything in the framework, and then explain the various methods and costs of trying to acheive it.

ewan wrote:
Are these hard C# interview questions? Really??

This may be better placed in the lounge Wink | ;)

Dave

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Re: Are these hard C# interview questions? Really??

ewan2-Oct-09 10:51

Re: Are these hard C# interview questions? Really??

2-Oct-09 10:51

Thanks - interesting points.

People have commented at work on if asking about public methods on object is useful. I don't think knowing all 4 (or 5!) is necessary I agree but when to use them is absolutely imperative. If you don't know when to override Equals for example you can't have done much C# - well imho. I might rephrase this going forward.

We ask about the garbage collector precisely because we want them to talk about Finalize vs Dispose and how the dispose pattern is connected to garbage collection (GC.SuppressFinalize etc). We also feel for the types of applications we use which often require a lot of memory analysis to detect memory not being freed it is imperative to know whats going on in the GC.

If you'd have answered my ArrayList like that you'd come straight in for second round!! ArrayList question does indeed go two ways - one is why is List<t> better than ArrayList. Second goes down into the threading route of what can and can't you lock on, alternatives to plain lock etc. It depends on the candidate.

Yeah - I post here very rarely so apologies if this is in the wrong place!

PIEBALDconsult2-Oct-09 13:25

PIEBALDconsult

2-Oct-09 13:25

ewan wrote:
we want them to talk about Finalize vs Dispose

Then ask them to.

Re: Are these hard C# interview questions? Really??

harold aptroot2-Oct-09 11:38

harold aptroot

2-Oct-09 11:38

They don't seem too hard to me, I'd probably need much more time to explain GC though
But ArrayList? I'd rather not even acknowledge its existence..

Shouldn't you also ask about starting a new thread vs threadpool and what else the threadpool is used for?
Or something like: give a short list of at least 5 synchronization primitives available in C#

Re: Are these hard C# interview questions? Really??

ewan2-Oct-09 12:04

Re: Are these hard C# interview questions? Really??

2-Oct-09 12:04

Thanks for your reply.

Absolutely - there are a lot more where they came from! We have specific questions around all of the things you mention.

Just to be clear though the point of my post was however not to ask for more questions but rather to ask are these unfair or unrealistic things to expect someone to know who wants $600+ a day?

harold aptroot2-Oct-09 12:31

harold aptroot

2-Oct-09 12:31

Oh, yea, sorry Smile | :)

How much is $600/day these days ? Is that considered to be a lot?

Re: Are these hard C# interview questions? Really??

ewan2-Oct-09 12:41