solid state - Page 435 - Developer IT

How expensive is a context switch? Is it better to implement a manual task switch than to rely on OS

- by Vilx-

The title says it all. Imagine I have two (three, four, whatever) tasks that have to run in parallel. Now, the easy way to do this would be to create separate threads and forget about it. But on a plain old single-core CPU that would mean a lot of context switching - and we all know that context switching is big, bad, slow, and generally simply Evil. It should be avoided, right? On that note, if I'm writing the software from ground up anyway, I could go the extra mile and implement my own task-switching. Split each task in parts, save the state inbetween, and then switch among them within a single thread. Or, if I detect that there are multiple CPU cores, I could just give each task to a separate thread and all would be well. The second solution does have the advantage of adapting to the number of available CPU cores, but will the manual task-switch really be faster than the one in the OS core? Especially if I'm trying to make the whole thing generic with a TaskManager and an ITask, etc?

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Slow query. Wrong database structure?

- by Tin

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Is encrypting session id (or other authenticate value) in cookie useful at all?

- by Ji

In web development, when session state is enabled, a session id is stored in cookie(in cookieless mode, query string will be used instead). In asp.net, the session id is encrypted automatically. There are plenty of topics on the internet regarding how you should encrypt your cookie, including session id. I can understand why you want to encrypt private info such as DOB, but any private info should not be stored in cookie at first place. So for other cookie values such as session id, what is the purpose encryption? Does it add security at all? no matter how you secure it, it will be sent back to server for decryption. Be be more specific, For authentication purpose, turn off session, i don't want to deal with session time out any more store some sort of id value in the cookie, on the server side, check if the id value exists and matches, if it is, authenticate user. let the cookie value expire when browser session is ended, this way. vs Asp.net form authentication mechanism (it relies on session or session id, i think) does latter one offer better security?

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Should we retire the term "Context"?

- by MrGumbe

I'm not sure if there is a more abused term in the world of programming than "Context." A word that has a very clear meaning in the English language has somehow morphed into a hot mess in software development, where the definition where the connotation can be completely different based on what library you happen to be developing in. Tomcat uses the word context to mean the configuration of a web application. Java applets, on the other hand, use an AppletContext to define attributes of the browser and HTML tag that launched it, but the BeanContext is defined as a container. ASP.NET uses the HttpContext object as a grab bag of state - containing information about the current request / response, session, user, server, and application objects. Context Oriented Programming defines the term as "Any information which is computationally accessible may form part of the context upon which behavioral variations depend," which I translate as "anything in the world." The innards of the Windows OS uses the CONTEXT structure to define properties about the hardware environment. The .NET installation classes, however, use the InstallContext property to represent the command line arguments entered to the installation class. The above doesn't even touch how all of us non-framework developers have used the term. I've seen plenty of developers fall into the subconscious trap of "I can't think of anything else to call this class, so I'll name it 'WidgetContext.'" Do you all agree that before naming our class a "Context," we may want to first consider some more descriptive terms? "Environment", "Configuraton", and "ExecutionState" come readily to mind.

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Unit Testing - Algorithm or Sample based ?

- by ohadsc

Say I'm trying to test a simple Set class public IntSet : IEnumerable<int> { Add(int i) {...} //IEnumerable implementation... } And suppose I'm trying to test that no duplicate values can exist in the set. My first option is to insert some sample data into the set, and test for duplicates using my knowledge of the data I used, for example: //OPTION 1 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //3 will be added 3 times var values = new List<int> {1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I know 3 is the only candidate to appear multiple times int counter = 0; foreach (int i in set) if (i == 3) counter++; Assert.AreEqual(1, counter); } My second option is to test for my condition generically: //OPTION 2 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //The following could even be a list of random numbers with a duplicate var values = new List<int> { 1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I am not using my prior knowledge of the sample data //the following line would work for any data CollectionAssert.AreEquivalent(new HashSet<int>(values), set); } Of course, in this example, I conveniently have a set implementation to check against, as well as code to compare collections (CollectionAssert). But what if I didn't have either ? This is the situation when you are testing your real life custom business logic. Granted, testing for expected conditions generically covers more cases - but it becomes very similar to implementing the logic again (which is both tedious and useless - you can't use the same code to check itself!). Basically I'm asking whether my tests should look like "insert 1, 2, 3 then check something about 3" or "insert 1, 2, 3 and check for something in general" EDIT - To help me understand, please state in your answer if you prefer OPTION 1 or OPTION 2 (or neither, or that it depends on the case, etc )

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In jQuery datepicker beforeShowDay if fails

- by michalzuber

HI. I'm having problem to highlight more days. Somehow the if statement in beforeShowDay isn't true when it should be :( dateString typeof is string and an example is available in the screenshot at http://mikaelz.host.sk/datepicker.png Pasted code: var dates = new Array(); function addDate(date) {if (jQuery.inArray(date, dates) < 0) dates.push(date);} function removeDate(index) {dates.splice(index, 1);} function addOrRemoveDate(date) { var index = jQuery.inArray(date, dates); if (index >= 0) removeDate(index); else addDate(date); } function padNumber(number) { var ret = new String(number); if (ret.length == 1) ret = "0" + ret; return ret; } jQuery(document).ready(function(){ jQuery("#pick-date").datepicker({ onSelect: function(dateText, inst) { addOrRemoveDate(dateText); }, beforeShowDay: function (date){ var year = date.getFullYear(); var month = padNumber(date.getMonth()); var day = padNumber(date.getDate()); var dateString = day + "." + month + "." + year; if (dates.indexOf(dateString) >= 0) { return [true,"ui-state-highlight"]; } return [true, ""]; } }); }); Big thanks for any good ideas what could be wrong.

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CSV is actually .... Semicolon Separated Values ... (Excel export on AZERTY)

- by Bugz R us

I'm a bit confused here. When I use Excel 2003 to export a sheet to CSV, it actually uses semicolons ... Col1;Col2;Col3 shfdh;dfhdsfhd;fdhsdfh dgsgsd;hdfhd;hdsfhdfsh Now when I read the csv using Microsoft drivers, it expects comma's and sees the list as one big column ??? I suspect Excel is exporting with semicolons because I have a AZERTY keyboard. However, doesn't the CSV reader then also have to take in account the different delimiter ? How can I know the appropriate delimiter, and/or read the csv properly ?? public static DataSet ReadCsv(string fileName) { DataSet ds = new DataSet(); string pathName = System.IO.Path.GetDirectoryName(fileName); string file = System.IO.Path.GetFileName(fileName); OleDbConnection excelConnection = new OleDbConnection (@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + pathName + ";Extended Properties=Text;"); try { OleDbCommand excelCommand = new OleDbCommand(@"SELECT * FROM " + file, excelConnection); OleDbDataAdapter excelAdapter = new OleDbDataAdapter(excelCommand); excelConnection.Open(); excelAdapter.Fill(ds); } catch (Exception exc) { throw exc; } finally { if(excelConnection.State != ConnectionState.Closed ) excelConnection.Close(); } return ds; }

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How to write a "thread safe" function in C ?

- by Andrei Ciobanu

Hello I am writing some data structures in C, and I've realized that their associated functions aren't thread safe. The i am writing code uses only standard C, and I want to achieve some sort of 'synchronization'. I was thinking to do something like this: enum sync_e { TRUE, FALSE }; typedef enum sync_e sync; struct list_s { //Other stuff struct list_node_s *head; struct list_node_s *tail; enum sync_e locked; }; typedef struct list_s list; , to include a "boolean" field in the list structure that indicates the structures state: locked, unlocked. For example an insertion function will be rewritten this way: int list_insert_next(list* l, list_node *e, int x){ while(l->locked == TRUE){ /* Wait */ } l->locked = TRUE; /* Insert element */ /* -------------- */ l->locked = FALSE; return (0); } While operating on the list the 'locked' field will be set to TRUE, not allowing any other alterations. After operation completes the 'locked' field will be again set to 'TRUE'. Is this approach good ? Do you know other approaches (using only standard C).

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C# XNA: What can cause SpriteBatch.End() to throw a NRE?

- by Rosarch

I don't understand what I'm doing wrong here: public void Draw(GameTime gameTime) // in ScreenManager { SpriteBatch.Begin(SpriteBlendMode.AlphaBlend); for (int i = 0; i < Screens.Count; i++) { if (Screens[i].State == Screen.ScreenState.HIDDEN) continue; Screens[i].Draw(gameTime); } SpriteBatch.End(); // null ref exception } SpriteBatch itself is not null. Some more context: public class MasterEngine : Microsoft.Xna.Framework.Game { public MasterEngine() { graphicsDeviceManager = new GraphicsDeviceManager(this); Components.Add(new GamerServicesComponent(this)); // ... spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); screenManager = new ScreenManager(assets, gameEngine, graphicsDeviceManager.GraphicsDevice, spriteBatch); } //... protected override void Draw(GameTime gameTime) { screenManager.Draw(gameTime); // calls the problematic method base.Draw(gameTime); } } Am I failing to initialize something properly? UPDATE: As an experiment, I tried this to the constructor of MasterEngine: spriteBatch = new SpriteBatch(graphicsDeviceManager.GraphicsDevice); spriteBatch.Begin(); spriteBatch.DrawString(assets.GetAsset<SpriteFont>("calibri"), "ftw", new Vector2(), Color.White); spriteBatch.End(); This does not cause a NRE. hmm.... UPDATE 2: This does cause an NRE: protected override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.End(); // boned here //screenManager.Draw(gameTime); base.Draw(gameTime); }

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Segmentation fault on returning from main (very short and simple code, no arrays or pointers)

- by Gábor Kovács

I've been wondering why the following trivial code produces a segmentation fault when returning from main(): //Produces "Error while dumping state (probably corrupted stack); Segmentation fault" #include <iostream> #include <fstream> #include <vector> using namespace std; class Test { vector<int> numbers; }; int main() { Test a; ifstream infile; cout << "Last statement..." << endl; // this gets executed return 0; } Interestingly, 1) if only one of the two variables is declared, I don't get the error, 2) if I declare a vector variable instead of an object with a vector member, everything's fine, 3) if I declare an ofstream instead of an ifstream, again, everything works fine. Something appears to be wrong with this specific combination... Could this be a compiler bug? I use gcc version 3.4.4 with cygwin. Thanks for the tips in advance. Gábor

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.NET binary serialization conditionally without ISerializable

- by SillyWhy

I got 2 classes, for example: public class A { private B b; ... } public class B { ... } I need to serialize an object A using BinaryFormatter. When remoting it shall include the field b, but not when serialize to file. Here is what I added: [Serializable] public class A : MarshalByRefObject { private B b; [OnSerializing] private void OnSerializing(StreamingContext context) { if (context.State == StreamingContextStates.File) { this.b = null; } } ... } [Serializable] public class B : MarshalByRefObject { ... } I think this is a bad design because if another class C also contains B, in class C we must add the duplicate OnSerializing() logic as in A. Class B should decide what to do, not class A or C. I don't want to use ISerializable interface because there are too many variables in class B have to be added to SerializationInfo. I can create a SerializationSurrogate for class B, which perform nothing in GetObjectData() & SetObjectData(), then use it when serializing to file. However the same maintenance issue because whoever modify class B can't notice what going to happen during serialization & the existence of SerializationSurrogate. Is there a better alternative?

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Passing models between controllers in MVC4

- by wtfsven

I'm in the middle of my first foray into web development with MVC4, and I've run into a problem that I just know is one of the core issues in web development in general, but can't seem to wrap my mind around it. So I have two models: Employee and Company. Employee has a Company, therefore /Employee/Create contains a field that is either a dropdown list for selecting an existing Company, or an ActionLink to /Company/Create if none exists. But here's the issue: If a user has to create a Company, I need to preserve the existing Employee model across both Views--over to /Company/Create, then back to /Employee/Create. So my first approach was to pass the Employee model to /Company/Create with a @Html.ActionLink("Add...", "Create", "Organization", Model , null), but then when I get to Company's Create(Employee emp), all of emp's values are null. The second problem is that if I try to come back to /Employee/Create, I'd be passing back an Employee, which would resolve to the POST Action. Basically, the whole idea is to save the state of the /Employee/Create page, jump over to /Company/Create to create a Company record, then back to /Employee/Create to finish creating the Employee. I know there is a well understood solution to this because , but I can't seem to phase it well enough to get a good Google result out of it. I've though about using Session, but it seems like doing so would be a bit of a kludge. I'd really like an elegant solution to this.

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design pattern for related inputs

- by curiousMo

My question is a design question : let's say i have a data entry web page with 4 drop down lists, each depending on the previous one, and a bunch of text boxes. ddlCountry (DropDownList) ddlState (DropDownList) ddlCity (DropDownList) ddlBoro (DropDownList) txtAddress (TxtBox) txtZipcode(TxtBox) and an object that represents a datarow with a value for each: countrySeqid stateSeqid citySeqid boroSeqid address zipCode naturally the country, state, city and boro values will be values of primary keys of some lookup tables. when the user chooses to edits that record, i would load it from database and load it into the page. the issue that I have is how to streamline loading the DropDownLists. i have some code that would grab the object,look thru its values and move them to their corresponding input controls in one shot. but in this case i will have to load the ddlCountry with possible values, then assign values, then do the same thing for the rest of the ddls. I guess i am looking for an elegant solution. i am using asp.net, but i think it is irrelevant to the question. i am looking more into a design pattern.

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WPF bound object update notification

- by Carlo

I have a TreeView with a few objects bound to it, let's say something like this: public class House { public List<Room> Rooms { get; set; } public List<Person> People { get; set; } public House() { this.Rooms = new List<Room>(); this.People = new List<Person>(); } public void BuildRoom(string name) { this.Rooms.Add(new Room() { Name = name }); } public void DestroyRoom(string name) { this.Rooms.Remove(new Room() { Name = name }); } public void PersonEnter(string name) { this.People.Add(new Person() { Name = name }); } public void PersonLeave(string name) { this.People.Remove(new Person() { Name = name }); } } public class Room { public string Name { get; set; } } public class Person { public string Name { get; set; } } The TreeView is watching over the House object, whenever a room is built / destroyed or a person enters / leaves, my tree view updates itself to show the new state of the house (I omitted some implementation details for simplicity). What I want is to know the exact moment when this update finishes, so I can do something right there, the thing is that I created an indicator of the selected item, and when something moves, I need to update said indicator's position, that's the reason I need it exactly when the tree view updates. Let me know if you know a solution to this. Also, the code is not perfect (DestroyRoom and PersonLeave), but you get the idea. Thanks!

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iphone viewWillAppear not firing

- by chzk

I've read numerous posts about people having problems with viewWillAppear when you do not create your view heirarchy JUST right. My problem is I can't figure out what that means. If I create a RootViewController and call addSubView on that controller, I would expect the added view(s) to be wired up for viewWillAppear events. Does anyone have an example of a complex programmatic view heirarchy that successfully recieves viewWillAppear events at every level? Apple Docs state: Warning: If the view belonging to a view controller is added to a view hierarchy directly, the view controller will not receive this message. If you insert or add a view to the view hierarchy, and it has a view controller, you should send the associated view controller this message directly. Failing to send the view controller this message will prevent any associated animation from being displayed. The problem is that they don't describe how to do this. What the hell does "directly" mean. How do you "indirectly" add a view. I am fairly new to Cocoa and iPhone so it would be nice if there were useful examples from Apple besides the basic Hello World crap. Any help is greatly appreciated...

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Domain validates but won't save

- by marko

I have the following setup. Class, say, Car that has a CarPart (belongsTo=[car:Car]). When I'm creating a Car I also want to create som default CarParts, so I do def car = new Car(bla bla bla) def part = new CarPart(car:car) Now, when I do car.validate() or part.validate() it seems fine. But when I do if(car.save && part.save() I get this exception: 2012-03-24 14:02:21,943 [http-8080-4] ERROR util.JDBCExceptionReporter - Batch entry 0 insert into car_part (version, car_id, id) values ('0', '297', '298') was aborted. Call getNextException to see the cause. 2012-03-24 14:02:21,943 [http-8080-4] ERROR util.JDBCExceptionReporter - ERROR: value too long for type character varying(6) 2012-03-24 14:02:21,943 [http-8080-4] ERROR events.PatchedDefaultFlushEventListener - Could not synchronize database state with session org.hibernate.exception.DataException: Could not execute JDBC batch update Stacktrace follows: java.sql.BatchUpdateException: Batch entry 0 insert into car_part (version, deal_id, id) values ('0', '297', '298') was aborted. Call getNextException to see the cause. at org.postgresql.jdbc2.AbstractJdbc2Statement$BatchResultHandler.handleError(AbstractJdbc2Statement.java:2621) at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1837) at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:407) at org.postgresql.jdbc2.AbstractJdbc2Statement.executeBatch(AbstractJdbc2Statement.java:2754) at $Proxy20.flush(Unknown Source) at ristretto.DealController$_closure5.doCall(DealController.groovy:109) at ristretto.DealController$_closure5.doCall(DealController.groovy) at java.lang.Thread.run(Thread.java:722) Any ideas?

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Git: HEAD has disappeared, want to merge it into master.

- by samgoody

The top image is the output of: git reflog. The bottom is what GITK in GIT GUI (msysgit) shows me when I look at all branch history. The last few commits do not show on GIT GUI. Why do they not show on GITK (at least as a branch or something)? How do I merge them into master? I gather this happened when I checked out tag 0.42. Why is that not the same as master? (I had tagged the master in its latest state) When I click push, why does the remote repo claim to be up to date.. shouldn't it try to update these commits into whatever branch they are in? The first of the questions is important - I would like to begin to understand what GIT is thinking. It's more oracle than logic at this point. If it makes a difference to see the earlier history, the project is a [pretty powerful] JS color picker that can be viewed here in its entirety.

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Cross-platform HTML application options

- by Charles

I'd like to develop a stand-alone desktop application targeting Windows (XP through 7) and Mac (Tiger through Snow Leopard), and if possible iPhone and Android. In order to make it all work with as much common code as possible (and because it's the only thing I'm good at), I'd like to handle the main logic with HTML and JS. Using Adobe AIR is a possibility. And I think I can do this with various application wrappers, using .NET for Windows XP, Objective C for iPhone, Java for Android and native "widget" platform support for Mac and Windows Vista & 7 (though I'd like to keep the widget in the foreground, so the Mac dashboard isn't ideal). Does anyone have any suggestions on where to start? The two sticking points are: I'll certainly need some form of persistent storage (cookies perhaps) to keep state between sessions I'll also probably need access to remote data files, so if I use AJAX and the hosting HTML file resides on the device, it will need to be able to do cross-domain requests. I've done this on the iPhone without any problems, but I'd be surprised if this were possible on other platforms. For me, Android and iPhone will be the easiest to handle, and it looks like I can use Adobe AIR to handle the rest. But I wanted to know if there are any other alternatives. Does anyone have any suggesions?

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Does anyone still believe in the Capability Maturity Model for Software?

- by Ed Guiness

Ten years ago when I first encountered the CMM for software I was, I suppose like many, struck by how accurately it seemed to describe the chaotic "level one" state of software development in many businesses, particularly with its reference to reliance on heroes. It also seemed to provide realistic guidance for an organisation to progress up the levels improving their processes. But while it seemed to provide a good model and realistic guidance for improvement, I never really witnessed an adherence to CMM having a significant positive impact on any organisation I have worked for, or with. I know of one large software consultancy that claims CMM level 5 - the highest level - when I can see first hand that their processes are as chaotic, and the quality of their software products as varied, as other, non-CMM businesses. So I'm wondering, has anyone seen a real, tangible benefit from adherence to process improvement according to CMM? And if you have seen improvement, do you think that the improvement was specifically attributable to CMM, or would an alternative approach (such as six-sigma) have been equally or more beneficial? Does anyone still believe? As an aside, for those who haven't yet seen it, check out this funny-because-its-true parody

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Parallel doseq for Clojure

- by andrew cooke

I haven't used multithreading in Clojure at all so am unsure where to start. I have a doseq whose body can run in parallel. What I'd like is for there always to be 3 threads running (leaving 1 core free) that evaluate the body in parallel until the range is exhausted. There's no shared state, nothing complicated - the equivalent of Python's multiprocessing would be just fine. So something like: (dopar 3 [i (range 100)] ; repeated 100 times in 3 parallel threads... ...) Where should I start looking? Is there a command for this? A standard package? A good reference? So far I have found pmap, and could use that (how do I restrict to 3 at a time? looks like it uses 32 at a time - no, source says 2 + number of processors), but it seems like this is a basic primitive that should already exist somewhere. clarification: I really would like to control the number of threads. I have processes that are long-running and use a fair amount of memory, so creating a large number and hoping things work out OK isn't a good approach (example which uses a significant chunk available mem). update: Starting to write a macro that does this, and I need a semaphore (or a mutex, or an atom i can wait on). Do semaphores exist in Clojure? Or should I use a ThreadPoolExecutor? It seems odd to have to pull so much in from Java - I thought parallel programming in Clojure was supposed to be easy... Maybe I am thinking about this completely the wrong way? Hmmm. Agents?

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Can knowing C actually hurt the code you write in higher level languages?

- by Jurily

The question seems settled, beaten to death even. Smart people have said smart things on the subject. To be a really good programmer, you need to know C. Or do you? I was enlightened twice this week. The first one made me realize that my assumptions don't go further than my knowledge behind them, and given the complexity of software running on my machine, that's almost non-existent. But what really drove it home was this Slashdot comment: The end result is that I notice the many naive ways in which traditional C "bare metal" programmers assume that higher level languages are implemented. They make bad "optimization" decisions in projects they influence, because they have no idea how a compiler works or how different a good runtime system may be from the naive macro-assembler model they understand. Then it hit me: C is just one more abstraction, like all others. Even the CPU itself is only an abstraction! I've just never seen it break, because I don't have the tools to measure it. I'm confused. Has my mind been mutilated beyond recovery, like Dijkstra said about BASIC? Am I living in a constant state of premature optimization? Is there hope for me, now that I realized I know nothing about anything? Is there anything to know, even? And why is it so fascinating, that everything I've written in the last five years might have been fundamentally wrong? To sum it up: is there any value in knowing more than the API docs tell me? EDIT: Made CW. Of course this also means now you must post examples of the interpreter/runtime optimizing better than we do :)

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Best practice for debug Asserts during Unit testing

- by Steve Steiner

Does heavy use of unit tests discourage the use of debug asserts? It seems like a debug assert firing in the code under test implies the unit test shouldn't exist or the debug assert shouldn't exist. "There can be only one" seems like a reasonable principle. Is this the common practice? Or do you disable your debug asserts when unit testing, so they can be around for integration testing? Edit: I updated 'Assert' to debug assert to distinguish an assert in the code under test from the lines in the unit test that check state after the test has run. Also here is an example that I believe shows the dilema: A unit test passes invalid inputs for a protected function that asserts it's inputs are valid. Should the unit test not exist? It's not a public function. Perhaps checking the inputs would kill perf? Or should the assert not exist? The function is protected not private so it should be checking it's inputs for safety.

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How to post only a specific ASCX partial instead of the whole page

- by Hallaghan

I've got an ASPX page rendering a search ascx page which in turn will fill a grid on the main ASPX page. Aside that, I've also got an ascx page which uploads files, like this: <form method="post" action="<%= Url.Action("UploadFile") %>" enctype="multipart/form-data"> <fieldset> <input type="file" name="file" id="file" /> <%=Html.ButtonSubmit("Upload") %> </fieldset></form> Here's the problem: imagine I have searched for a single entry to be displayed on the grid. The grid displays this single entry and after wards, I upload a file and press the button "Upload". The whole page gets posted and the content in the grid is lost, now displaying all the results available. What could I do to prevent this from happening, maintaining the grid state (we're not using ViewState) or otherwise not posting back the whole page but only the ascx with the file upload? Note: I'm new to MVC.

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Why do we need Audit Columns in Database Tables?

- by Software Enthusiastic

Hi I have seen many database designs having following audit columns on all the tables... Created By Create DateTime Updated By Upldated DateTime From one perspective I see tables from the following view... Entity Tables: Good candidate for Audit columns) Reference Tables: Audit columns may or may not required. In some case last update information is not at all required because record is never going to be modified.) Reference Data Tables Like Country Names, Entity State etc... Audit columns may not required because these information is created only during system installation time, and never going to be changed. I have seen many designers blindly put all audit columns to all tables, is this practice good, if yes what could be the reason... I just want to know because to me it seems illogical. It is difficult for me to figure out why do they design their db this way? I am not saying they are wrong or right, just want to know the WHY? You can also suggest me, if there is an alternative auditing patter or solution available... Thanks and Regards

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ExecuteNonQuery: Connection property has not been initialized

- by 20151012

I get an error in my code: The error point at dbcom.ExecuteNonQuery();. Code(connection) public admin_addemp() { InitializeComponent(); con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\EMPS.accdb;Persist Security Info=True"); con.Open(); ds.Tables.Add(dt); ds.Tables.Add(dt2); } Code (Save button) private void save_btn_Click(object sender, EventArgs e) { OleDbCommand check = new OleDbCommand(); check.Connection = con; check.CommandText = "SELECT COUNT(*) FROM employeeDB WHERE ([EmployeeName]=?)"; check.Parameters.AddWithValue("@EmployeeName", tb_name.Text); if (Convert.ToInt32(check.ExecuteScalar()) == 0) { dbcom2 = new OleDbCommand("SELECT EmployeeID FROM employeeDB WHERE EmployeeID='" + tb_id.Text + "'", con); OleDbParameter param = new OleDbParameter(); param.ParameterName = tb_id.Text; dbcom.Parameters.Add(param); OleDbDataReader read = dbcom2.ExecuteReader(); if (read.HasRows) { MessageBox.Show("The Employee ID '" + tb_id.Text + "' already exist. Please choose another Employee ID."); read.Dispose(); read.Close(); } else { string q = "INSERT INTO employeeDB (EmployeeID, EmployeeName, IC, Address, State, " + " Postcode, DateHired, Phone, ManagerName) VALUES ('" + tb_id.Text + "', " + " '" + tb_name.Text + "', '" + tb_ic.Text + "', '" + tb_add1.Text + "', '" + cb_state.Text + "', " + " '" + tb_postcode.Text + "', '" + dateTimePicker1.Value + "', '" + tb_hp.Text + "', '" + cb_manager.Text + "')"; dbcom = new OleDbCommand(q, con); dbcom.ExecuteNonQuery(); MessageBox.Show("New Employee '" + tb_name.Text + "'- Successfuly Added."); } } else { MessageBox.Show("Employee name '" + tb_name.Text + "' already added into the database"); } ds.Dispose(); } I'm using Microsoft Access 2010 as my database and this is stand alone system. Please help me.

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- by Vilx-

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- by ohadsc

- by michalzuber

- by Bugz R us

- by Andrei Ciobanu

- by Rosarch

- by Gábor Kovács

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