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• Entity Framework 5, separating business logic from model - Repository?

  - by bnice7

  I am working on my first public-facing web application and I’m using MVC 4 for the presentation layer and EF 5 for the DAL. The database structure is locked, and there are moderate differences between how the user inputs data and how the database itself gets populated. I have done a ton of reading on the repository pattern (which I have never used) but most of my research is pushing me away from using it since it supposedly creates an unnecessary level of abstraction for the latest versions of EF since repositories and unit-of-work are already built-in. My initial approach is to simply create a separate set of classes for my business objects in the BLL that can act as an intermediary between my Controllers and the DAL. Here’s an example class: public class MyBuilding { public int Id { get; private set; } public string Name { get; set; } public string Notes { get; set; } private readonly Entities _context = new Entities(); // Is this thread safe? private static readonly int UserId = WebSecurity.GetCurrentUser().UserId; public IEnumerable<MyBuilding> GetList() { IEnumerable<MyBuilding> buildingList = from p in _context.BuildingInfo where p.Building.UserProfile.UserId == UserId select new MyBuilding {Id = p.BuildingId, Name = p.BuildingName, Notes = p.Building.Notes}; return buildingList; } public void Create() { var b = new Building {UserId = UserId, Notes = this.Notes}; _context.Building.Add(b); _context.SaveChanges(); // Set the building ID this.Id = b.BuildingId; // Seed 1-to-1 tables with reference the new building _context.BuildingInfo.Add(new BuildingInfo {Building = b}); _context.GeneralInfo.Add(new GeneralInfo {Building = b}); _context.LocationInfo.Add(new LocationInfo {Building = b}); _context.SaveChanges(); } public static MyBuilding Find(int id) { using (var context = new Entities()) // Is this OK to do in a static method? { var b = context.Building.FirstOrDefault(p => p.BuildingId == id && p.UserId == UserId); if (b == null) throw new Exception("Error: Building not found or user does not have access."); return new MyBuilding {Id = b.BuildingId, Name = b.BuildingInfo.BuildingName, Notes = b.Notes}; } } } My primary concern: Is the way I am instantiating my DbContext as a private property thread-safe, and is it safe to have a static method that instantiates a separate DbContext? Or am I approaching this all wrong? I am not opposed to learning up on the repository pattern if I am taking the total wrong approach here.

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• What common programming problems are best solved by using prototypes and closures?

  - by vemv

  As much as I understand both concepts, I can't see how can I take advantage of JavaScript's closures and prototypes aside from using them for creating instantiable and/or encapsulated class-like blocks (which seems more of a workaround than an asset to me) Other JS features such as functions-as-values or logical evaluation of non-booleans are much easier to fall in love with... What common programming problems are best solved by using propotypal inheritance and closures?

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• Office lights on or off in programming department? How to decide? [closed]

  - by smp7d

  At my company, the programmers who sit in the same area are constantly fighting over whether the lights stay on or off. Because there is no official policy it makes it a particularly sticky situation. We are a typical cube-farm and we have those typical cube-farm fluorescent lights and smaller ones at our desks. With the lights off, it is difficult to read and you would probably need to turn on your desk light (which some people do anyway). All programmers in our department do most of their reading on their monitor because of the nature of our business. Some feel that we should have a vote to decide whether the lights stay on or off. A couple who prefer 'lights on' feel that the vote would need to be unanimous to turn them off as having them on is the more natural office setting. Those who want them off point out that all other departments keep their lights off. I have heard all of the arguments: -Fluorescent lights cause eye strain -Reading in dark causes eye strain -The desk lights can be used if light is needed -People from other departments feel uncomfortable approaching us in the "dark" -The monitors are harder to see in the light ... Right now, some of the developers turn off the lights and some turn them on. It really just depends who last walked by the switch. I am a bit sick of the controversy as it feels a bit childish at the moment. I'm tired of hearing about it and I'm tired of having to talk about it. I tried to help them decide but as I explained, voting wasn't enough. Do other programming departments have this same argument? What is the standard or traditionally accepted option in a programming area? Are there any good reasons for one way or the other outside of preference? How can we decide fairly? EDIT Just a little more info... We do not have clients/visitors come into our office. We do have windows and hall lights that make our environment plenty bearable with the lights off. It kind of resembles a meeting room that has the lights off during a powerpoint presentation.

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• Where should a programmer explain the extended logic behind the code?

  - by SRKX

  I have developed a few quantitative libraries in C# where it is important to understand not only the classic information that goes with the XMLDoc comments (which contains basic information with the method signature) but also the mathematical formulas being use within the methods. Hence I would like to be able to include extended documentation with the code, which could contain, for example Latex formulas, graphs, and so on. Do you think such information should be included in the API documentation? Or should it be included in a dev blog for examples? Are there common tools that are usually used for this kind of purposes?

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• what is the task of a coach in acm programming contests?

  - by Layla

  In the university that I am working they have decided to participate in the ACM regionals for the first time, they would like to appoint me like a coach. I have never been into that situation before and have not found so much information about it, so what is the real work of a coach in those contests? Sometimes I have found experienced programmers like coaches, but others are just people with no so good programming skills; so what is all about?

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• Store image as logic file (in db by using binary format) or physical file (in the server)

  - by Michel Ayres

  In those study cases of image storage, An image that change only once in a while, if it changes at all (like an image for an article) The image case from above is not only one image but over 10, that link to the same article An image that have changes very often (like a banner image for a website) The image above is huge What is the best approach for each case? What is the "right/faster" way to do this task in each scenario ?

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• Is there a quick and practical (hands on) way to learn another programming language?

  - by Tamsin

  Due to rather strange circumstances, I only have until Monday to learn (at least) the basics of PHP and .NET programming. I'm already fairly competent (though there is a lot of room for improvement) in C++ so I feel I have some of the concepts nailed already, but I need to get into the two languages in a bit more depth in a very short time frame. Unfortunately I won't have time to get any books so will need to exclusively use online resources, I'm more of a 'do-er' so any way to test my skills in a practical way would be a huge bonus :-)

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• C# calendar needs Business Logic for real-time reminders? [on hold]

  - by lazfish

  I am not a super experienced C# user, though I have some experience in .Net and VB.Net. Just got this new job and my first assignment is a mission critical part of the business. It is pretty important I get it right so I was hoping for some sage advice. We have created a calendar using jQuery, C#, .Net & SQL Server 08. The calendar works but now we are wanting to add email, SMS and voice-call reminders. We are a small company and can do whatever we need to do with no restrictions on our IT environment. I have some base-line experience with Unix servers but would prefer to stay in the Micro$oft universe if it is prudent to do so. I know how to add the API calls and services to initiate these reminders (using built in email services for email and Twilio.com for SMS). I am asking for advice about how to approach a reliable and timely listener service that knows when to call the service or API for the reminder before an appointment. EG. SMS: "You have a conference call in 30 minutes." I have done some research, but it is hard to know what is a proven reliable approach. What I am looking for is an experienced opinion on a good (or the best) strategy for implementing a solution that will reliably listen for appointments and dispatch the reminders when needed.

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• How to add correct cancellation when downloading a file with the example in the samples of the new P

  - by Mike

  Hello everybody, I have downloaded the last samples of the Parallel Programming team, and I don't succeed in adding correctly the possibility to cancel the download of a file. Here is the code I ended to have: var wreq = (HttpWebRequest)WebRequest.Create(uri); // Fire start event DownloadStarted(this, new DownloadStartedEventArgs(remoteFilePath)); long totalBytes = 0; wreq.DownloadDataInFileAsync(tmpLocalFile, cancellationTokenSource.Token, allowResume, totalBytesAction => { totalBytes = totalBytesAction; }, readBytes => { Log.Debug("Progression : {0} / {1} => {2}%", readBytes, totalBytes, 100 * (double)readBytes / totalBytes); DownloadProgress(this, new DownloadProgressEventArgs(remoteFilePath, readBytes, totalBytes, (int)(100 * readBytes / totalBytes))); }) .ContinueWith( (antecedent ) => { if (antecedent.IsFaulted) Log.Debug(antecedent.Exception.Message); //Fire end event SetEndDownload(antecedent.IsCanceled, antecedent.Exception, tmpLocalFile, 0); }, cancellationTokenSource.Token); I want to fire an end event after the download is finished, hence the ContinueWith. I slightly changed the code of the samples to add the CancellationToken and the 2 delegates to get the size of the file to download, and the progression of the download: return webRequest.GetResponseAsync() .ContinueWith(response => { if (totalBytesAction != null) totalBytesAction(response.Result.ContentLength); response.Result.GetResponseStream().WriteAllBytesAsync(filePath, ct, resumeDownload, progressAction).Wait(ct); }, ct); I had to add the call to the Wait function, because if I don't, the method exits and the end event is fired too early. Here are the modified method extensions (lot of code, apologies :p) public static Task WriteAllBytesAsync(this Stream stream, string filePath, CancellationToken ct, bool resumeDownload = false, Action<long> progressAction = null) { if (stream == null) throw new ArgumentNullException("stream"); // Copy from the source stream to the memory stream and return the copied data return stream.CopyStreamToFileAsync(filePath, ct, resumeDownload, progressAction); } public static Task CopyStreamToFileAsync(this Stream source, string destinationPath, CancellationToken ct, bool resumeDownload = false, Action<long> progressAction = null) { if (source == null) throw new ArgumentNullException("source"); if (destinationPath == null) throw new ArgumentNullException("destinationPath"); // Open the output file for writing var destinationStream = FileAsync.OpenWrite(destinationPath); // Copy the source to the destination stream, then close the output file. return CopyStreamToStreamAsync(source, destinationStream, ct, progressAction).ContinueWith(t => { var e = t.Exception; destinationStream.Close(); if (e != null) throw e; }, ct, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Current); } public static Task CopyStreamToStreamAsync(this Stream source, Stream destination, CancellationToken ct, Action<long> progressAction = null) { if (source == null) throw new ArgumentNullException("source"); if (destination == null) throw new ArgumentNullException("destination"); return Task.Factory.Iterate(CopyStreamIterator(source, destination, ct, progressAction)); } private static IEnumerable<Task> CopyStreamIterator(Stream input, Stream output, CancellationToken ct, Action<long> progressAction = null) { // Create two buffers. One will be used for the current read operation and one for the current // write operation. We'll continually swap back and forth between them. byte[][] buffers = new byte[2][] { new byte[BUFFER_SIZE], new byte[BUFFER_SIZE] }; int filledBufferNum = 0; Task writeTask = null; int readBytes = 0; // Until there's no more data to be read or cancellation while (true) { ct.ThrowIfCancellationRequested(); // Read from the input asynchronously var readTask = input.ReadAsync(buffers[filledBufferNum], 0, buffers[filledBufferNum].Length); // If we have no pending write operations, just yield until the read operation has // completed. If we have both a pending read and a pending write, yield until both the read // and the write have completed. yield return writeTask == null ? readTask : Task.Factory.ContinueWhenAll(new[] { readTask, writeTask }, tasks => tasks.PropagateExceptions()); // If no data was read, nothing more to do. if (readTask.Result <= 0) break; readBytes += readTask.Result; if (progressAction != null) progressAction(readBytes); // Otherwise, write the written data out to the file writeTask = output.WriteAsync(buffers[filledBufferNum], 0, readTask.Result); // Swap buffers filledBufferNum ^= 1; } } So basically, at the end of the chain of called methods, I let the CancellationToken throw an OperationCanceledException if a Cancel has been requested. What I hoped was to get IsFaulted == true in the appealing code and to fire the end event with the canceled flags and the correct exception. But what I get is an unhandled exception on the line response.Result.GetResponseStream().WriteAllBytesAsync(filePath, ct, resumeDownload, progressAction).Wait(ct); telling me that I don't catch an AggregateException. I've tried various things, but I don't succeed to make the whole thing work properly. Does anyone of you have played enough with that library and may help me? Thanks in advance Mike

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• How would you go about tackling this problem? [SOLVED in C++]

  - by incrediman

  Intro: EDIT: See solution at the bottom of this question (c++) I have a programming contest coming up in about half a week, and I've been prepping :) I found a bunch of questions from this canadian competition, they're great practice: http://cemc.math.uwaterloo.ca/contests/computing/2009/stage2/day1.pdf I'm looking at problem B ("Dinner"). Any idea where to start? I can't really think of anything besides the naive approach (ie. trying all permutations) which would take too long to be a valid answer. Btw, the language there says c++ and pascal I think, but i don't care what language you use - I mean really all I want is a hint as to the direction I should proceed in, and perhpas a short explanation to go along with it. It feels like I'm missing something obvious... Of course extended speculation is more than welcome, but I just wanted to clarify that I'm not looking for a full solution here :) Short version of the question: You have a binary string N of length 1-100 (in the question they use H's and G's instead of one's and 0's). You must remove all of the digits from it, in the least number of steps possible. In each step you may remove any number of adjacent digits so long as they are the same. That is, in each step you can remove any number of adjacent G's, or any number of adjacent H's, but you can't remove H's and G's in one step. Example: HHHGHHGHH Solution to the example: 1. HHGGHH (remove middle Hs) 2. HHHH (remove middle Gs) 3. Done (remove Hs) -->Would return '3' as the answer. Note that there can also be a limit placed on how large adjacent groups have to be when you remove them. For example it might say '2', and then you can't remove single digits (you'd have to remove pairs or larger groups at a time). Solution I took Mark Harrison's main algorithm, and Paradigm's grouping idea and used them to create the solution below. You can try it out on the official test cases if you want. //B.cpp //include debug messages? #define DEBUG false #include <iostream> #include <stdio.h> #include <vector> using namespace std; #define FOR(i,n) for (int i=0;i<n;i++) #define FROM(i,s,n) for (int i=s;i<n;i++) #define H 'H' #define G 'G' class String{ public: int num; char type; String(){ type=H; num=0; } String(char type){ this->type=type; num=1; } }; //n is the number of bits originally in the line //k is the minimum number of people you can remove at a time //moves is the counter used to determine how many moves we've made so far int n, k, moves; int main(){ /*Input from File*/ scanf("%d %d",&n,&k); char * buffer = new char[200]; scanf("%s",buffer); /*Process input into a vector*/ //the 'line' is a vector of 'String's (essentially contigious groups of identical 'bits') vector<String> line; line.push_back(String()); FOR(i,n){ //if the last String is of the correct type, simply increment its count if (line.back().type==buffer[i]) line.back().num++; //if the last String is of the wrong type but has a 0 count, correct its type and set its count to 1 else if (line.back().num==0){ line.back().type=buffer[i]; line.back().num=1; } //otherwise this is the beginning of a new group, so create the new group at the back with the correct type, and a count of 1 else{ line.push_back(String(buffer[i])); } } /*Geedily remove groups until there are at most two groups left*/ moves=0; int I;//the position of the best group to remove int bestNum;//the size of the newly connected group the removal of group I will create while (line.size()>2){ /*START DEBUG*/ if (DEBUG){ cout<<"\n"<<moves<<"\n----\n"; FOR(i,line.size()) printf("%d %c \n",line[i].num,line[i].type); cout<<"----\n"; } /*END DEBUG*/ I=1; bestNum=-1; FROM(i,1,line.size()-1){ if (line[i-1].num+line[i+1].num>bestNum && line[i].num>=k){ bestNum=line[i-1].num+line[i+1].num; I=i; } } //remove the chosen group, thus merging the two adjacent groups line[I-1].num+=line[I+1].num; line.erase(line.begin()+I);line.erase(line.begin()+I); moves++; } /*START DEBUG*/ if (DEBUG){ cout<<"\n"<<moves<<"\n----\n"; FOR(i,line.size()) printf("%d %c \n",line[i].num,line[i].type); cout<<"----\n"; cout<<"\n\nFinal Answer: "; } /*END DEBUG*/ /*Attempt the removal of the last two groups, and output the final result*/ if (line.size()==2 && line[0].num>=k && line[1].num>=k) cout<<moves+2;//success else if (line.size()==1 && line[0].num>=k) cout<<moves+1;//success else cout<<-1;//not everyone could dine. /*START DEBUG*/ if (DEBUG){ cout<<" moves."; } /*END DEBUG*/ }

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• Problem with my whiteboard application

  - by swift

  I have to develop a whiteboard application in which both the local user and the remote user should be able to draw simultaneously, is this possible? If possible then any logic? I have already developed a code but in which i am not able to do this, when the remote user starts drawing the shape which i am drawing is being replaced by his shape and co-ordinates. This problem is only when both draw simultaneously. any idea guys? Here is my code class Paper extends JPanel implements MouseListener,MouseMotionListener,ActionListener { static BufferedImage image; int bpressed; Color color; Point start; Point end; Point mp; Button elipse=new Button("elipse"); Button rectangle=new Button("rect"); Button line=new Button("line"); Button empty=new Button(""); JButton save=new JButton("Save"); JButton erase=new JButton("Erase"); String selected; int ex,ey;//eraser DatagramSocket dataSocket; JButton button = new JButton("test"); Client client; Point p=new Point(); int w,h; public Paper(DatagramSocket dataSocket) { this.dataSocket=dataSocket; client=new Client(dataSocket); System.out.println("paper"); setBackground(Color.white); addMouseListener(this); addMouseMotionListener(this); color = Color.black; setBorder(BorderFactory.createLineBorder(Color.black)); //save.setPreferredSize(new Dimension(100,20)); save.setMaximumSize(new Dimension(75,27)); erase.setMaximumSize(new Dimension(75,27)); } public void paintComponent(Graphics g) { try { g.drawImage(image, 0, 0, this); Graphics2D g2 = (Graphics2D)g; g2.setPaint(Color.black); if(selected==("elipse")) g2.drawOval(start.x, start.y,(end.x-start.x),(end.y-start.y)); else if(selected==("rect")) g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y)); else if(selected==("line")) g2.drawLine(start.x,start.y,end.x,end.y); } catch(Exception e) {} } //Function to draw the shape on image public void draw() { Graphics2D g2 = image.createGraphics(); g2.setPaint(color); if(selected=="line") g2.drawLine(start.x, start.y, end.x, end.y); if(selected=="elipse") g2.drawOval(start.x, start.y, (end.x-start.x),(end.y-start.y)); if(selected=="rect") g2.drawRect(start.x, start.y, (end.x-start.x),(end.y-start.y)); repaint(); g2.dispose(); start=null; } //To add the point to the board which is broadcasted by the server public synchronized void addPoint(Point ps,String varname,String shape,String event) { try { if(end==null) end = new Point(); if(start==null) start = new Point(); if(shape.equals("elipse")) selected="elipse"; else if(shape.equals("line")) selected="line"; else if(shape.equals("rect")) selected="rect"; else if(shape.equals("erase")) { selected="erase"; erase(); } if(end!=null && start!=null) { if(varname.equals("end")) end=ps; if(varname.equals("mp")) mp=ps; if(varname.equals("start")) start=ps; if(event.equals("drag")) repaint(); else if(event.equals("release")) draw(); } } catch(Exception e) { e.printStackTrace(); } } //To set the size of the image public void setWidth(int x,int y) { System.out.println("("+x+","+y+")"); w=x; h=y; image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB); Graphics2D g2 = image.createGraphics(); g2.setPaint(Color.white); g2.fillRect(0,0,w,h); g2.dispose(); } //Function which provides the erase functionality public void erase() { Graphics2D pic=(Graphics2D) image.getGraphics(); pic.setPaint(Color.white); pic.fillRect(start.x, start.y, 10, 10); } //Function to add buttons into the panel, calling this function returns a panel public JPanel addButtons() { JPanel buttonpanel=new JPanel(); JPanel row1=new JPanel(); JPanel row2=new JPanel(); JPanel row3=new JPanel(); JPanel row4=new JPanel(); buttonpanel.setPreferredSize(new Dimension(80,80)); //buttonpanel.setMinimumSize(new Dimension(150,150)); row1.setLayout(new BoxLayout(row1,BoxLayout.X_AXIS)); row1.setPreferredSize(new Dimension(150,150)); row2.setLayout(new BoxLayout(row2,BoxLayout.X_AXIS)); row3.setLayout(new BoxLayout(row3,BoxLayout.X_AXIS)); row4.setLayout(new BoxLayout(row4,BoxLayout.X_AXIS)); buttonpanel.setLayout(new BoxLayout(buttonpanel,BoxLayout.Y_AXIS)); elipse.addActionListener(this); rectangle.addActionListener(this); line.addActionListener( this); save.addActionListener( this); erase.addActionListener( this); buttonpanel.add(Box.createRigidArea(new Dimension(10,10))); row1.add(elipse); row1.add(Box.createRigidArea(new Dimension(5,0))); row1.add(rectangle); buttonpanel.add(row1); buttonpanel.add(Box.createRigidArea(new Dimension(10,10))); row2.add(line); row2.add(Box.createRigidArea(new Dimension(5,0))); row2.add(empty); buttonpanel.add(row2); buttonpanel.add(Box.createRigidArea(new Dimension(10,10))); row3.add(save); buttonpanel.add(row3); buttonpanel.add(Box.createRigidArea(new Dimension(10,10))); row4.add(erase); buttonpanel.add(row4); return buttonpanel; } //To save the image drawn public void save() { try { ByteArrayOutputStream bos = new ByteArrayOutputStream(); JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos); JFileChooser fc = new JFileChooser(); fc.showSaveDialog(this); encoder.encode(image); byte[] jpgData = bos.toByteArray(); FileOutputStream fos = new FileOutputStream(fc.getSelectedFile()+".jpeg"); fos.write(jpgData); fos.close(); //add replce confirmation here } catch (IOException e) { System.out.println(e); } } public void mouseClicked(MouseEvent arg0) { // TODO Auto-generated method stub } @Override public void mouseEntered(MouseEvent arg0) { } public void mouseExited(MouseEvent arg0) { // TODO Auto-generated method stub } public void mousePressed(MouseEvent e) { if(selected=="line"||selected=="erase") { start=e.getPoint(); client.broadcast(start,"start", selected,"press"); } else if(selected=="elipse"||selected=="rect") { mp = e.getPoint(); client.broadcast(mp,"mp", selected,"press"); } } public void mouseReleased(MouseEvent e) { if(start!=null) { if(selected=="line") { end=e.getPoint(); client.broadcast(end,"end", selected,"release"); } else if(selected=="elipse"||selected=="rect") { end.x = Math.max(mp.x,e.getX()); end.y = Math.max(mp.y,e.getY()); client.broadcast(end,"end", selected,"release"); } draw(); } //start=null; } public void mouseDragged(MouseEvent e) { if(end==null) end = new Point(); if(start==null) start = new Point(); if(selected=="line") { end=e.getPoint(); client.broadcast(end,"end", selected,"drag"); } else if(selected=="erase") { start=e.getPoint(); erase(); client.broadcast(start,"start", selected,"drag"); } else if(selected=="elipse"||selected=="rect") { start.x = Math.min(mp.x,e.getX()); start.y = Math.min(mp.y,e.getY()); end.x = Math.max(mp.x,e.getX()); end.y = Math.max(mp.y,e.getY()); client.broadcast(start,"start", selected,"drag"); client.broadcast(end,"end", selected,"drag"); } repaint(); } @Override public void mouseMoved(MouseEvent arg0) { // TODO Auto-generated method stub } public void actionPerformed(ActionEvent e) { if(e.getSource()==elipse) selected="elipse"; if(e.getSource()==line) selected="line"; if(e.getSource()==rectangle) selected="rect"; if(e.getSource()==save) save(); if(e.getSource()==erase) { selected="erase"; erase(); } } } class Button extends JButton { String name; public Button(String name) { this.name=name; Dimension buttonSize = new Dimension(35,35); setMaximumSize(buttonSize); } public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D)g; g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); //g2.setStroke(new BasicStroke(1.2f)); if (name == "line") g.drawLine(5,5,30,30); if (name == "elipse") g.drawOval(5,7,25,20); if (name== "rect") g.drawRect(5,5,25,23); } }

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• How much business logic belongs in RIA services layer?

  - by jkohlhepp

  I have been experimenting recently with Silverlight, RIA Services, and Entity Framework using .NET 4.0. I'm trying to figure out if that stack makes sense for use in any of my upcoming projects. It certainly seems like these technologies can be very productive for developing applications, but I'm struggling to decide how an application on top of this stack should be architected. The main issue I have is that in most of the demos I've seen most of the business logic ends up as DataAnnotations and custom validations in the RIA Services domain service class. This seems inappropriate to me. I view the domain service as basically a glorified web service that happens to make it easy to push information to the client. But most of what I've seen seems to orient the domain service as the main source of business logic in the application. So, my questions: What is the best location for business logic (rules, validations, behaviors, authorization) in an application using this stack? Are there any guidelines published at an architectural level for using this stack? My questions pertain to large, complex, and long-lived applications. Obviously for an application of only a few screens this is less of a concern. Edit: Another thing I meant to mention is that obviously you can make the domain service class stupid, but then you lose a lot of the automagic entity information (e.g. validations) being pushed to the client. And then if you lose that is there any point to using RIA services?

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• Logic in the db for maintaining a points system relationship?

  - by MarcusBooster

  I'm making a little web based game and need to determine where to put logic that checks the integrity of some underlying data in the sql database. Each user keeps track of points assigned to him, and points are awarded by various tasks. I keep a record of each task transaction to make sure they're not repeated, and to keep track of the value of the task at the time of completion, since an individual award level my fluctuate over time. My schema looks like this so far: create table player ( player_ID serial primary key, player_Points int not null default 0 ); create table task ( task_ID serial primary key, task_PointsAwarded int not null ); create table task_list ( player_ID int references player(player_ID), task_ID int references task(task_ID), when_completed timestamp default current_timestamp, point_value int not null, --not fk because task value may change later constraint pk_player_task_id primary key (player_ID, task_ID) ); So, the player.player_Points should be the total of all his cumulative task points in the task_list. Now where do I put the logic to enforce this? Should I do away with player.player_Points altogether and do queries every time I want to know the total score? Which seems wasteful since I'll be doing that query a lot over the course of a game. Or, put a trigger in the task_list that automatically updates the player.player_Points? Is that too much logic to have in the database and should just maintain this relationship in the application? Thanks.

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• Should the program logic reside inside the gui object class or be external to the class?

  - by hd112

  I have a question about how to structure code in relation to GUI objects. Suppose I have a dialog that has a list control that has a bunch of names obtained from a database. The user can edit the names. Does the logic reside inside that dialog class or should it be from the outside. To illustrate what I mean, here’s some pseudo code showing the structure of the code when the logic is handled outside the dialog class: NamesDialog : wxDialog { Private: ..stuff.. Public: ... SetNames(wxStringArray names); wxStringArray GetNames(); ..stuff.. } So the user of the class would do something like: wxStringArray names = DatabaseManager::Get()->GetNames(); names.Sort(); NamesDialogObject.SetNames(names); NamesDialogObject.ShowModal(); wxStringArray modified_names = NamesDialogObject.GetNames(); AddToDatabase(modified_names); //or something like this. On the other hand, the database logic can reside inside the NamesDialog class itself. In the show method I can query the database for the names and as the user interacts with the controls (list control in this case), the database can be updated from the event handlers. As a result the NamesDialog class only has the Show() method as there is no need to use SetNames or GetNames() etc. Which method is generally preferred? I don’t have much work experience so I’m not sure which is the proper way to handle it. Sometimes it's easier to handle everything in the class but getting access to objects it interacts with can be challenging. Generally can do it by having the relevant objects be singletons like the database manager in the above example.

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• [C++] A minimalistic smart array (container) class template

  - by legends2k

  I've written a (array) container class template (lets call it smart array) for using it in the BREW platform (which doesn't allow many C++ constructs like STD library, exceptions, etc. It has a very minimal C++ runtime support); while writing this my friend said that something like this already exists in Boost called MultiArray, I tried it but the ARM compiler (RVCT) cries with 100s of errors. I've not seen Boost.MultiArray's source, I've just started learning template only lately; template meta programming interests me a lot, although am not sure if this is strictly one, which can be categorised thus. So I want all my fellow C++ aficionados to review it ~ point out flaws, potential bugs, suggestions, optimisations, etc.; somthing like "you've not written your own Big Three which might lead to...". Possibly any criticism that'll help me improve this class and thereby my C++ skills. smart_array.h #include <vector> using std::vector; template <typename T, size_t N> class smart_array { vector < smart_array<T, N - 1> > vec; public: explicit smart_array(vector <size_t> &dimensions) { assert(N == dimensions.size()); vector <size_t>::iterator it = ++dimensions.begin(); vector <size_t> dimensions_remaining(it, dimensions.end()); smart_array <T, N - 1> temp_smart_array(dimensions_remaining); vec.assign(dimensions[0], temp_smart_array); } explicit smart_array(size_t dimension_1 = 1, ...) { static_assert(N > 0, "Error: smart_array expects 1 or more dimension(s)"); assert(dimension_1 > 1); va_list dim_list; vector <size_t> dimensions_remaining(N - 1); va_start(dim_list, dimension_1); for(size_t i = 0; i < N - 1; ++i) { size_t dimension_n = va_arg(dim_list, size_t); assert(dimension_n > 0); dimensions_remaining[i] = dimension_n; } va_end(dim_list); smart_array <T, N - 1> temp_smart_array(dimensions_remaining); vec.assign(dimension_1, temp_smart_array); } smart_array<T, N - 1>& operator[](size_t index) { assert(index < vec.size() && index >= 0); return vec[index]; } size_t length() const { return vec.size(); } }; template<typename T> class smart_array<T, 1> { vector <T> vec; public: explicit smart_array(vector <size_t> &dimension) : vec(dimension[0]) { assert(dimension[0] > 0); } explicit smart_array(size_t dimension_1 = 1) : vec(dimension_1) { assert(dimension_1 > 0); } T& operator[](size_t index) { assert(index < vec.size() && index >= 0); return vec[index]; } size_t length() { return vec.size(); } }; Sample Usage: #include <iostream> using std::cout; using std::endl; int main() { // testing 1 dimension smart_array <int, 1> x(3); x[0] = 0, x[1] = 1, x[2] = 2; cout << "x.length(): " << x.length() << endl; // testing 2 dimensions smart_array <float, 2> y(2, 3); y[0][0] = y[0][1] = y[0][2] = 0; y[1][0] = y[1][1] = y[1][2] = 1; cout << "y.length(): " << y.length() << endl; cout << "y[0].length(): " << y[0].length() << endl; // testing 3 dimensions smart_array <char, 3> z(2, 4, 5); cout << "z.length(): " << z.length() << endl; cout << "z[0].length(): " << z[0].length() << endl; cout << "z[0][0].length(): " << z[0][0].length() << endl; z[0][0][4] = 'c'; cout << z[0][0][4] << endl; // testing 4 dimensions smart_array <bool, 4> r(2, 3, 4, 5); cout << "z.length(): " << r.length() << endl; cout << "z[0].length(): " << r[0].length() << endl; cout << "z[0][0].length(): " << r[0][0].length() << endl; cout << "z[0][0][0].length(): " << r[0][0][0].length() << endl; // testing copy constructor smart_array <float, 2> copy_y(y); cout << "copy_y.length(): " << copy_y.length() << endl; cout << "copy_x[0].length(): " << copy_y[0].length() << endl; cout << copy_y[0][0] << "\t" << copy_y[1][0] << "\t" << copy_y[0][1] << "\t" << copy_y[1][1] << "\t" << copy_y[0][2] << "\t" << copy_y[1][2] << endl; return 0; }

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• A minimalistic smart array (container) class template

  - by legends2k

  I've written a (array) container class template (lets call it smart array) for using it in the BREW platform (which doesn't allow many C++ constructs like STD library, exceptions, etc. It has a very minimal C++ runtime support); while writing this my friend said that something like this already exists in Boost called MultiArray, I tried it but the ARM compiler (RVCT) cries with 100s of errors. I've not seen Boost.MultiArray's source, I've started learning templates only lately; template meta programming interests me a lot, although am not sure if this is strictly one that can be categorized thus. So I want all my fellow C++ aficionados to review it ~ point out flaws, potential bugs, suggestions, optimizations, etc.; something like "you've not written your own Big Three which might lead to...". Possibly any criticism that will help me improve this class and thereby my C++ skills. Edit: I've used std::vector since it's easily understood, later it will be replaced by a custom written vector class template made to work in the BREW platform. Also C++0x related syntax like static_assert will also be removed in the final code. smart_array.h #include <vector> #include <cassert> #include <cstdarg> using std::vector; template <typename T, size_t N> class smart_array { vector < smart_array<T, N - 1> > vec; public: explicit smart_array(vector <size_t> &dimensions) { assert(N == dimensions.size()); vector <size_t>::iterator it = ++dimensions.begin(); vector <size_t> dimensions_remaining(it, dimensions.end()); smart_array <T, N - 1> temp_smart_array(dimensions_remaining); vec.assign(dimensions[0], temp_smart_array); } explicit smart_array(size_t dimension_1 = 1, ...) { static_assert(N > 0, "Error: smart_array expects 1 or more dimension(s)"); assert(dimension_1 > 1); va_list dim_list; vector <size_t> dimensions_remaining(N - 1); va_start(dim_list, dimension_1); for(size_t i = 0; i < N - 1; ++i) { size_t dimension_n = va_arg(dim_list, size_t); assert(dimension_n > 0); dimensions_remaining[i] = dimension_n; } va_end(dim_list); smart_array <T, N - 1> temp_smart_array(dimensions_remaining); vec.assign(dimension_1, temp_smart_array); } smart_array<T, N - 1>& operator[](size_t index) { assert(index < vec.size() && index >= 0); return vec[index]; } size_t length() const { return vec.size(); } }; template<typename T> class smart_array<T, 1> { vector <T> vec; public: explicit smart_array(vector <size_t> &dimension) : vec(dimension[0]) { assert(dimension[0] > 0); } explicit smart_array(size_t dimension_1 = 1) : vec(dimension_1) { assert(dimension_1 > 0); } T& operator[](size_t index) { assert(index < vec.size() && index >= 0); return vec[index]; } size_t length() { return vec.size(); } }; Sample Usage: #include "smart_array.h" #include <iostream> using std::cout; using std::endl; int main() { // testing 1 dimension smart_array <int, 1> x(3); x[0] = 0, x[1] = 1, x[2] = 2; cout << "x.length(): " << x.length() << endl; // testing 2 dimensions smart_array <float, 2> y(2, 3); y[0][0] = y[0][1] = y[0][2] = 0; y[1][0] = y[1][1] = y[1][2] = 1; cout << "y.length(): " << y.length() << endl; cout << "y[0].length(): " << y[0].length() << endl; // testing 3 dimensions smart_array <char, 3> z(2, 4, 5); cout << "z.length(): " << z.length() << endl; cout << "z[0].length(): " << z[0].length() << endl; cout << "z[0][0].length(): " << z[0][0].length() << endl; z[0][0][4] = 'c'; cout << z[0][0][4] << endl; // testing 4 dimensions smart_array <bool, 4> r(2, 3, 4, 5); cout << "z.length(): " << r.length() << endl; cout << "z[0].length(): " << r[0].length() << endl; cout << "z[0][0].length(): " << r[0][0].length() << endl; cout << "z[0][0][0].length(): " << r[0][0][0].length() << endl; // testing copy constructor smart_array <float, 2> copy_y(y); cout << "copy_y.length(): " << copy_y.length() << endl; cout << "copy_x[0].length(): " << copy_y[0].length() << endl; cout << copy_y[0][0] << "\t" << copy_y[1][0] << "\t" << copy_y[0][1] << "\t" << copy_y[1][1] << "\t" << copy_y[0][2] << "\t" << copy_y[1][2] << endl; return 0; }

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• What is the logic behind IE7s Ctrl-Tab order?

  - by torbengb

  Using Ctrl+Tab in Internet Explorer 7 (on Windows XP) seems to follow no sequence that I can work out. Using Shift+Ctrl+Tab even jumps around with no clear logic in what tab order is being followed. It doesn't even work to the reverse as expected from using it in other programs, such as Firefox. Please explain to me how this key combo works in IE7 because I can't figure it out.

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• What's the logic behind the Ctrl-Tab order in Internet Explorer 7?

  - by torbengb

  Using Ctrl+Tab in Internet Explorer 7 (on Windows XP) seems to follow no sequence that I can work out. Using Shift+Ctrl+Tab even jumps around with no clear logic in what tab order is being followed. It doesn't even work to the reverse as expected from using it in other programs, such as Firefox. Please explain to me how this key combo works in IE7 because I can't figure it out.

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• How do we, as a community, help encourage programming in public schools? (Or state Schools for the U

  - by NoMoreZealots

  PRIMARY MOTIVATION My office gets involved with the "First Robotics" competitions and one thing that lingers year to year is the students typically have no preparation for doing even simple programming as part of the public schools system. While the science classes provide some basic grasp of mechanical and electrical concepts, by in large computer programming gets no coverage from the curriculum. (This my be different in other areas of the country/world.) What makes it worse is there is only a short period of time you have to prepare the student's and help them design the robot. Talking to some professors from local colleges, it's a problem because you can't assume even the most basic understanding for freshman CS majors. Languages like Python, Lua and BASIC are simple enough for at least high school level students, if not younger. SCOPE So how do you get public schools to support a programming, at least to the level of "Try it in BASIC" examples that used to be at the end of a chapter in my Algebra book? At least enough to prepare them for event's such as the FIRST Robotic competitions. Which the primary objectives are to teach problem solving and team work, and to possible foster an interest in Math, Science and Engineering in general. (Not force feed to them, as some people her seem to be implying.) Edit: Why teach kids: (Since 2000 CS enrollment in US colleges has decreased by 70% while college enrollment has increased, this is a PROBLEM.) Saying there is no value in teaching someone programming in Jr./High school because they might think "they know programming." Is like saying there's no value in teaching High school science and physics, because they might decide they "know physics." Leading to abuse like: "I passed a high school physics class, I'm going to develop a Unified Quantum Gravitational Theory." Better Prepared students are better students. Instead it would allows college programs to raise the bar on the entry level courses, allowing students to be weeded out based on their understanding of more advanced material. Plus people who did poorly in that in topic in High school aren't as likely to say "I think there's money in computer's so I'll computer science." Plus if people take it in high school and decide THEN that it's not for them, it's better than them wasting their money to PAY a college to figure that out. The result is that people who take the degree are more likely to succeed and be there for the RIGHT reasons. (i.e. It's what they REALLY want to do. And that's REALLY the key to being good at anything.) Programming is like anything else, the more practice and genuine interest you have the better you get. If you start them later, they get less practice. The earlier give them the opportunity to start, the more practice they will get. All other things equal, the more practice the better the programmer.

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• What are the best programming websites on the web?

  - by lajoo

  Ok,lets have a big list here,write about the best programming websites you have approached and a description of them and they'll be added here.i'll write some websites for now: UVA Online Judge a bunch of useful programming problems are there that you could use to improve your programming. Prgrammers Heven Resources for different programming languages. SourceForge This site Has lots of open source programs available for download,it's a must-go site for a programmer. W3Schools This Websites has all you need to learn about Web-designing Languages like Java Script,Css,PHP,HTML,.... Note:This is not an advertising topic,it's just a guide for programmers to find what they need.

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• What features would you like to see added to your favorite programming language?

  - by George Edison

  Are there any features you would like to see added to a programming language? Maybe... A programming construct An extra operator A built-in function you think would be useful I realize questions like this are frowned upon, but I think this one is a genuine programming question that can be answered and the answers will spawn valuable discussion. (And it's community wiki.) Here is one of mine: How come C++ has no exponent operator, like Python's **?

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• What effects has working in rotating shifts on programming teams?

  - by eKek0

  I work in a bank, and the boss now want's that we, the programming team, work on rotating shifts. He wants that sometimes we work from 7am to 3pm, and sometimes on 11.30am to 7.30pm. He says that we will be more productive working this way, because he has worked with teams just like that and he just knows that. Nobody of the team wants this change, but we don't know how to effectively reject this new rule. I was trying to find some empirical (or almost) evidence about how rotating shifts affects performance of programming teams, and I couldn't. I had read something about rotating shifts, but not exactly about the effect of this on programming teams. Do you know any research about rotating shifts on programming teams? Did you have any experience with this kind of work? EDIT: Other teams of the company, like the database administrators team, the help desk team, the communication team or the network administrators team are already working in rotating shifts, and they don't like this but they do it anyway. I think the boss want that we work on rotating shifts too because of them, but since only we do programming I think the effects of rotating shifts could be, at least, different for us.

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• Should uni provide "correct answer" after programming assignment is due?

  - by Michael Mao

  Hi all: This is my very first subjective question. And I think it is programming related - the assignment is to be written in a programming language. I am not for "getting the full marks out of a subject". I am actually not for a "correct answer", but for a "better solution", so that I can compare, and can improve. I reckon it is good that I practice programming first and check the solution later to pick up the things I've done wrong/bad. Without a "benchmark" to against, this would be much harder. Unfortunately as far as I know, not all programming subjects taught in uni would kindly provide the students with a "correct answer" in the end, after the assignment is due. One bad metaphor for this is like someone asks you a question which they don't have a clear answer themselves and hope to take advantage of your answer as the basis for their answer. Personally, I feel having a assignment solution provided by the academic staff is essential to students. I do appreciate this, and I feel I might not be the only one. I am a very proactive student in uni. I learn more, I practice more, an assignment for me is more like a challenge to achieve "the best solution I can come up with", not something "I have to pass"... The cause of this question is that for the past few days I have crafted 500+ lines of Perl code, for a tiny assignment. I feel pain when I look at my solution(not finished yet) and I feel like I am an idiot doing some crap code. I know there must be a much better solution. And I reckon it is better for the lecturer in this subject to get me one, rather than asking for an answer here, even I would shamelessly add the link to my solution apart from the assignment requirements. I know in SO, there are a lot of tutors/lecturers for programming subjects/courses. I'd like to hear your words on this question.

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• what do i need to do now that I want to take programming hobby to next level ?

  - by hohog

  i've always wanted to make games but did not start actively learning programming by myself until 1st year of university. i kept going throughout university learning new languages, showing off things i had made, while neglecting my major in Biology. Anyways, i've ended up with an Economics degree, with a portfolio of SaaS and web apps i had created so i could eat during my final year. So far, I'm getting a few interviews here and there in web programming positions. When I get a logic pretest, I fail miserably. or job requires comp sci degree. I mean I can easily design and code an entire app which I emphasize through my portfolio.... but i dont know why I am so slow at logic puzzles on prescreening interview... So what should I do now ? get certificates in languages ? go back to school and learn CS ? is it too late to get into windows programming jobs than web programming ?

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• I love programming but i also want to learn hardware. [closed]

  - by user167082

  I like programming so much, i did it since i was 10, and i believe that studying computer science will make a lot of money as well as i love it. However I also want to learn hardware. I don't only want to do programming all the time without knowing the architecture of device that i program. I asked my teacher, and she said that if I get into computer science, i won't learn anything about hardware, is it true?(She graduated from u-dub) In the other hand, my math teacher told me to get into electrical engineering, since it also contain programming. The thing is that i want to emphasize my study to programming while learning some about hardware. What is major that suits me the best? Can i take some hardware courses if I get into computer science major? Thanks a lot.

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