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• Making a DateTime field in a database automatic?

  - by Mike

  I'm putting together a simple test database to learn MVC with. I want to add a DateTime field to show when the record was CREATED. ID = int Name = Char DateCreated = (dateTime, DateTime2..?) I have a feeling that this type of DateTime capture can be done automatically - but that's all I have, a feeling. Can it be done? And if so how? While we're on the subject: if I wanted to include another field that captured the DateTime of when the record was LAST UPDATED how would I do that. I'm hoping to not do this manually. Many thanks Mike

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• Web App for smartphones in ASPX

  - by Ryan Knoll

  I have been looking around recently to try and find a good place to learn how to start making my website more smartphone friendly when it is visited by an iPhone, android, or blackberry. This is something like what Digg.com does when it is visited by a smartphone. I have found a few tutorials for PHP but none for ASPX, and all I have is windows servers. Could anyone point me in the right direction, and show me were to find a quick run through on how to do something like this? I am a bit lost. :(

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• How to store a numeric value which can have other statuses in a database?

  - by Jiho Han

  I need to store a set of numbers in a database which are imported from a spreadsheet. Sometimes a number is just a number. But in other times, a value can be "missing", "N/A", or blank and these all represent different things. What would be a good approach to store these numbers in the database? Originally I only had to account for N/A. So I made it -1 as I imported them (this only works if the number can never be negative obviously). I could use other negative numbers for other statuses. However, that seems clunky to me. Should I store the numbers as string then apply conversion at use time? Should I create a matching table that stores different statuses of each value?

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• Extend base type and automatically update audit information on Entity

  - by Nix

  I have an entity model that has audit information on every table (50+ tables) CreateDate CreateUser UpdateDate UpdateUser Currently we are programatically updating audit information. Ex: if(changed){ entity.UpdatedOn = DateTime.Now; entity.UpdatedBy = Environment.UserName; context.SaveChanges(); } But I am looking for a more automated solution. During save changes, if an entity is created/updated I would like to automatically update these fields before sending them to the database for storage. Any suggestion on how i could do this? I would prefer to not do any reflection, so using a text template is not out of the question. A solution has been proposed to override SaveChanges and do it there, but in order to achieve this i would either have to use reflection (in which I don't want to do ) or derive a base class. Assuming i go down this route how would I achieve this? For example EXAMPLE_DB_TABLE CODE NAME --Audit Tables CREATE_DATE CREATE_USER UPDATE_DATE UPDATE_USER And if i create a base class public abstract class IUpdatable{ public virtual DateTime CreateDate {set;} public virtual string CreateUser { set;} public virtual DateTime UpdateDate { set;} public virtual string UpdateUser { set;} } The end goal is to be able to do something like... public overrride void SaveChanges(){ //Go through state manager and update audit infromation //FOREACH changed entity in state manager if(entity is IUpdatable){ //If state is created... update create audit. //if state is updated... update update audit } } But I am not sure how I go about generating the code that would extend the interface.

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• DDD: Can I have my persistence layer object implement an interface that uses enum, with implicit con

  - by Maslow

  I have a domain interface public interface ITicket { ... TicketWorkflowStatus StatusId{get;set;} // Enum } but the linq-to-sql persistance layer on the database wants to use int, can I change it in the dbml so that the local type is TicketWorkflowStatus? What are my options?

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• Java language philosophy question

  - by BlessedKey

  Why was java defined such that methods may take as input multiple parameters, but may only return a single object (or void)? Did it make the language somehow easier to implement or use?

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• How do I load SciLexer.dll in Visual Studio 2008 Designer, on Windows 7 64-bit?

  - by Filini

  We develop a WinForm application using Scintilla.NET (1.7) component, which uses SciLexer.dll (unamnaged). At run-time, we distribute both 32bit and 64bit SciLexer.dll, and we load the correct one when the application starts (everything works fine). On our new development environments (Windows 7 64-bit), all our solutions build and run just fine, but the WinForm visual designer does not load our forms/controls which use Scintilla.NET, because it cannot load the correct SciLexer.dll: Window class name is not valid. at System.Windows.Forms.NativeWindow.WindowClass.RegisterClass() at System.Windows.Forms.NativeWindow.WindowClass.Create(String className, Int32 classStyle) at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp) at System.Windows.Forms.Control.CreateHandle() at System.Windows.Forms.Control.get_Handle() at Scintilla.ScintillaControl.SendMessageDirect(UInt32 msg, IntPtr wParam, IntPtr lParam) at Scintilla.ScintillaControl.SendMessageDirect(UInt32 msg) at Scintilla.ScintillaControl.get_CodePage() at Scintilla.ScintillaControl..ctor(String sciLexerDllName) at Scintilla.ScintillaControl..ctor() Where does Visual Studio 2008 look for unmanaged libraries? I tried putting the 64-bit SciLexer.dll in SysWOW64, in the folder where ScintillaNET.dll is referenced, adding a folder in PATH system variable, adding a folder reference in the project, but I keep getting this error. Any help is appreciated.

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• Should business objects be able to create their own DTOs?

  - by Sam

  Suppose I have the following class: class Camera { public Camera( double exposure, double brightness, double contrast, RegionOfInterest regionOfInterest) { this.exposure = exposure; this.brightness = brightness; this.contrast = contrast; this.regionOfInterest = regionOfInterest; } public void ConfigureAcquisitionFifo(IAcquisitionFifo acquisitionFifo) { // do stuff to the acquisition FIFO } readonly double exposure; readonly double brightness; readonly double contrast; readonly RegionOfInterest regionOfInterest; } ... and a DTO to transport the camera info across a service boundary (WCF), say, for viewing in a WinForms/WPF/Web app: using System.Runtime.Serialization; [DataContract] public class CameraData { [DataMember] public double Exposure { get; set; } [DataMember] public double Brightness { get; set; } [DataMember] public double Contrast { get; set; } [DataMember] public RegionOfInterestData RegionOfInterest { get; set; } } Now I can add a method to Camera to expose its data: class Camera { // blah blah public CameraData ToData() { var regionOfInterestData = regionOfInterest.ToData(); return new CameraData() { Exposure = exposure, Brightness = brightness, Contrast = contrast, RegionOfInterestData = regionOfInterestData }; } } or, I can create a method that requires a special IReporter to be passed in for the Camera to expose its data to. This removes the dependency on the Contracts layer (Camera no longer has to know about CameraData): class Camera { // beep beep I'm a jeep public void ExposeToReporter(IReporter reporter) { reporter.GetCameraInfo(exposure, brightness, contrast, regionOfInterest); } } So which should I do? I prefer the second, but it requires the IReporter to have a CameraData field (which gets changed by GetCameraInfo()), which feels weird. Also, if there is any even better solution, please share with me! I'm still an object-oriented newb.

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• How you would you describe the Observer pattern in beginner language?

  - by Sheldon

  Currently, my level of understanding is below all the coding examples on the web about the Observer Pattern. I understand it simply as being almost a subscription that updates all other events when a change is made that the delegate registers. However, I'm very unstable in my true comprehension of the benefits and uses. I've done some googling, but most are above my level of understanding. I'm trying to implement this pattern with my current homework assignment, and to truly make sense on my project need a better understanding of the pattern itself and perhaps an example to see what its use. I don't want to force this pattern into something just to submit, I need to understand the purpose and develop my methods accordingly so that it actually serves a good purpose. My text doesn't really go into it, just mentions it in one sentence. MSDN was hard for me to understand, as I'm a beginner on this, and it seems more of an advanced topic. How would you describe this Observer pattern and its uses in C# to a beginner? For an example, please keep code very simple so I can understand the purpose more than complex code snippets. I'm trying to use it effectively with some simple textbox string manipulations and using delegates for my assignment, so a pointer would help!

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• where to enlist transaction with parent child delete (repository or bll)?

  - by Caroline Showden

  My app uses a business layer which calls a repository which uses linq to sql. I have an Item class that has an enum type property and an ItemDetail property. I need to implement a delete method that: (1) always delete the Item (2) if the item.type is XYZ and the ItemDetail is not null, delete the ItemDetail as well. My question is where should this logic be housed? If I have it in my business logic which I would prefer, this involves two separate repository calls, each of which uses a separate datacontext. I would have to wrap both calls is a System.Transaction which (in sql 2005) get promoted to a distributed transaction which is not ideal. I can move it all to a single repository call and the transaction will be handled implicitly by the datacontext but feel that this is really business logic so does not belong in the repository. Thoughts? Carrie

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• inner class within Interface

  - by harigm

  is that possible to create a inner class within an interface? If yes, why do we create like that? Anyways we are not going to create any interface objects? Do they help in any Development process?

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• Allocation algorithm help, using Python.

  - by Az

  Hi there, I've been working on this general allocation algorithm for students. The pseudocode for it (a Python implementation) is: for a student in a dictionary of students: for student's preference in a set of preferences (ordered from 1 to 10): let temp_project be the first preferred project check if temp_project is available if so, allocate it to them and make the project UNavailable to others Quite simply this will try to allocate projects by starting from their most preferred. The way it works, out of a set of say 100 projects, you list 10 you would want to do. So the 10th project wouldn't be the "least preferred overall" but rather the least preferred in their chosen set, which isn't so bad. Obviously if it can't allocate a project, a student just reverts to the base case which is an allocation of None, with a rank of 11. What I'm doing is calculating the allocation "quality" based on a weighted sum of the ranks. So the lower the numbers (i.e. more highly preferred projects), the better the allocation quality (i.e. more students have highly preferred projects). That's basically what I've currently got. Simple and it works. Now I'm working on this algorithm that tries to minimise the allocation weight locally (this pseudocode is a bit messy, sorry). The only reason this will probably work is because my "search space" as it is, isn't particularly large (just a very general, anecdotal observation, mind you). Since the project is only specific to my Department, we have their own limits imposed. So the number of students can't exceed 100 and the number of preferences won't exceed 10. for student in a dictionary/list/whatever of students: where i = 0 take the (i)st student, (i+1)nd student for their ranks: allocate the projects and set local_weighting to be sum(student_i.alloc_proj_rank, student_i+1.alloc_proj_rank) these are the cases: if local_weighting is 2 (i.e. both ranks are 1): then i += 1 and and continue above if local weighting is = N>2 (i.e. one or more ranks are greater than 1): let temp_local_weighting be N: pick student with lowest rank and then move him to his next rank and pick the other student and reallocate his project after this if temp_local_weighting is < N: then allocate those projects to the students move student with lowest rank to the next rank and reallocate other if temp_local_weighting < previous_temp_allocation: let these be the new allocated projects try moving for the lowest rank and reallocate other else: if this weighting => previous_weighting let these be the allocated projects i += 1 and move on for the rest of the students So, questions: This is sort of a modification of simulated annealing, but any sort of comments on this would be appreciated. How would I keep track of which student is (i) and which student is (i+1) If my overall list of students is 100, then the thing would mess up on (i+1) = 101 since there is none. How can I circumvent that? Any immediate flaws that can be spotted? Extra info: My students dictionary is designed as such: students[student_id] = Student(student_id, student_name, alloc_proj, alloc_proj_rank, preferences) where preferences is in the form of a dictionary such that preferences[rank] = {project_id}

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• how to aviod infinite loop in observer pattern?

  - by joseph

  Hello. I have only one class with many instances. Every instance is observer of couple of other instances. As well every instance can be observable by couple of another instances. How to avoid infinite loop of calling update() in observers?

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• What makes a bad programming language bad?

  - by sub

  We have all seen things like the typing system of JavaScript (There is a funny post including a truth table somewhere around here). I consider this one of the main things that makes a programming language bad. Other things that spring to mind: Bad Error messages (Either obfuscated so you can't figure out whats wrong, not existing or simply too long and red) The language wasn't planned and just grew uncontrolled in all directions (PHP?) The language encourages bad programm(er/ing) habits such as: Global variables everywhere, bad variable names Inconsistent naming conventions inside the language I can't come up with any more at the moment and would be very happy to read what you think about this. What shouldn't be missing in a language created to be as bad (from the perspectives of the programmer, the company that hires to programmer, the team leader and the customer) as possible? (I ask this because I'm designing a bad, experimental language at the moment)

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• Clear all class variables between instances

  - by ensnare

  This is probably a stupid question, but what's the best way to clear class variables between instances? I know I could reset each variable individually in the constructor; but is there a way to do this in bulk? Or am I doing something totally wrong that requires a different approach? Thanks for helping ... class User(): def __init__(self): #RESET ALL CLASS VARIABLES def commit(self): #Commit variables to database >>u = User() >>u.name = 'Jason' >>u.email = '[email protected]' >>u.commit() So that each time User is called the variables are fresh. Thanks.

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• Proper reconstitution of Aggregate objects in the Repository?

  - by Jebb

  Assuming that no ORM (e.g. Doctrine) is used inside the Repository, my question is what is the proper way of instantiating the Aggregate objects? Is it instantiating the child objects directly inside the Repository and just assign it to the Aggregate Root through its setters or the Aggregate Root is responsible of constructing its child entities/objects? Example 1: class UserRepository { // Create user domain entity. $user = new User(); $user->setName('Juan'); // Create child object orders entity. $orders = new Orders($orders); $user->setOrders($orders); } Example 2: class UserRepository { // Create user domain entity. $user = new User(); $user->setName('Juan'); // Get orders. $orders = $ordersDao->findByUser(1); $user->setOrders($orders); } whereas in example 2, instantiation of orders are taken care inside the user entity.

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• How does a compiler initially compile itself?

  - by jdk

  I recently read the Mono C# compiler is able to compile itself. Cool. In the past I've heard of other languages doing the same. It twists my mind - seems like a chicken and egg problem. What comes first, second and third, etc?...

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• CQRS - The query side

  - by mattcodes

  A lot of the blogsphere articles related to CQRS (command query repsonsibility) seperation seem to imply that all screens/viewmodels are flat. e.g. Name, Age, Location Of Birth etc.. and thus the suggestion that implementation wise we stick them into fast read source etc.. single table per view mySQL etc.. and pull them out with something like primitive SqlDataReader, kick that nasty nhibernate ORM etc.. However, whilst I agree that domain models dont mapped well to most screens, many of the screens that I work with are more dimensional, and Im sure this is pretty common in LOB apps. So my question is how are people handling screen where by for example it displays a summary of customer details and then a list of their orders with a [more detail] link etc.... I thought about keeping with the straight forward SQL query to the Query Database breaking off the outer join so can build a suitable ViewModel to View but it seems like overkill? Alternatively (this is starting to feel yuck) in CustomerSummaryView table have a text/big (whatever the type is in your DB) column called Orders, and the columns for the Order summary screen grid are seperated by , and rows by |. Even with XML datatype it still feeel dirty. Any thoughts on an optimal practice?

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• log in as a proxy for a certain user

  - by Samuel

  We have a requirement, wherein the administrative user needs to proxy in as a certain user in an environment where several users (Role: User) are managed by an administrator (Role: Admin). e.g If we have the following users in the database (admin, user1, user2, user3), we would want the admin to proxy as 'user2' and use the system in certain scenarios. Authentication in our web application is based username / password credentials, what mechanisms are available for the admin to proxy as 'user2' when he doesn't have the password for 'user2'. How can the application track such access for audit purposes to mention that 'admin' had proxied for 'user2' and performed certain actions. I am looking for suggestions on supporting this in our j2ee (jboss seam) web application.

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• Hibernate : Opinions in Composite PK vs Surrogate PK

  - by Albert Kam

  As i understand it, whenever i use @Id and @GeneratedValue on a Long field inside JPA/Hibernate entity, i'm actually using a surrogate key, and i think this is a very nice way to define a primary key considering my not-so-good experiences in using composite primary keys, where : there are more than 1 business-value-columns combination that become a unique PK the composite pk values get duplicated across the table details cannot change the business value inside that composite PK I know hibernate can support both types of PK, but im left wondering by my previous chats with experienced colleagues where they said that composite PK is easier to deal with when doing complex SQL queries and stored procedure processes. They went on saying that when using surrogate keys will complicate things when doing joining and there are several condition when it's impossible to do some stuffs when using surrogate keys. Although im sorry i cant explain the detail here since i was not clear enough when they explain it. Maybe i'll put more details next time. Im currently trying to do a project, and want to try out surrogate keys, since it's not getting duplicated across tables, and we can change the business-column values. And when the need for some business value combination uniqueness, i can use something like : @Table(name="MY_TABLE", uniqueConstraints={ @UniqueConstraint(columnNames={"FIRST_NAME", "LAST_NAME"}) // name + lastName combination must be unique But im still in doubt because of the previous discussion about the composite key. Could you share your experiences in this matter ? Thank you !

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• Most Astonishing Violation of the Principle of Least Astonishment

  - by Adam Liss

  The Principle of Least Astonishment suggests that a system should operate as a user would expect it to, as much as possible. In other words, it should never "astonish" the user with unexpected behavior. In your experience as the "astonishee," what types of systems are the worst offenders, and if you were the project manager, how would you correct the problem? Bonus if your answer describes how you'd retrain the developers!

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• Suggest Cassandra data model for an existing schema

  - by Andriy Bohdan

  Hello guys! I hope there's someone who can help me suggest a suitable data model to be implemented using nosql database Apache Cassandra. More of than I need it to work under high loads and large amounts of data. Simplified I have 3 types of objects: Product Tag ProductTag Product: key - string key name - string .... - some other fields Tag: key - string key name - unique tag words ProductTag: product_key - foreign key referring to product tag_key - foreign key referring to tag rating - this is rating of tag for this product Each product may have 0 or many tags. Tag may be assigned to 1 or many products. Means relation between products and tags is many-to-many in terms of relational databases. Value of "rating" is updated "very" often. I need to be run the following queries Select objects by keys Select tags for product ordered by rating Select products by tag order by rating Update rating by product_key and tag_key The most important is to make these queries really fast on large amounts of data, considering that rating is constantly updated.

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• "Public" nested classes or not

  - by Frederick

  Suppose I have a class 'Application'. In order to be initialised it takes certain settings in the constructor. Let's also assume that the number of settings is so many that it's compelling to place them in a class of their own. Compare the following two implementations of this scenario. Implementation 1: class Application { Application(ApplicationSettings settings) { //Do initialisation here } } class ApplicationSettings { //Settings related methods and properties here } Implementation 2: class Application { Application(Application.Settings settings) { //Do initialisation here } class Settings { //Settings related methods and properties here } } To me, the second approach is very much preferable. It is more readable because it strongly emphasises the relation between the two classes. When I write code to instantiate Application class anywhere, the second approach is going to look prettier. Now just imagine the Settings class itself in turn had some similarly "related" class and that class in turn did so too. Go only three such levels and the class naming gets out out of hand in the 'non-nested' case. If you nest, however, things still stay elegant. Despite the above, I've read people saying on StackOverflow that nested classes are justified only if they're not visible to the outside world; that is if they are used only for the internal implementation of the containing class. The commonly cited objection is bloating the size of containing class's source file, but partial classes is the perfect solution for that problem. My question is, why are we wary of the "publicly exposed" use of nested classes? Are there any other arguments against such use?

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• Constructing human readable sentences based on a survey

  - by Joshua

  The following is a survey given to course attendees to assess an instructor at the end of the course. Communication Skills 1. The instructor communicated course material clearly and accurately. Yes No 2. The instructor explained course objectives and learning outcomes. Yes No 3. In the event of not understanding course materials the instructor was available outside of class. Yes No 4. Was instructor feedback and grading process clear and helpful? Yes No 5. Do you feel that your oral and written skills have improved while in this course? Yes No We would like to summarize each attendees selection based on the choices chosen by him. If the provided answers were [No, No, Yes, Yes, Yes]. Then we would summarize this as "The instructor was not able to summarize course objectives and learning outcomes clearly, but was available for usually helpful outside of class. The instructor feedback and grading process was clear and helpful and I feel that my oral and written skills have improved because of this course. Based on the selections chosen by the attendee the summary would be quite different. This leads to many answers based on the choices selected and the number of such questions in the survey. The questions are usually provided by the training organization. How do you come up with a generic solution so that this can be effectively translated into a human readable form. I am looking for tools or libraries (java based), suggestions which will help me create such human readable output. I would like to hide the complexity from the end users as much as possible.

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• Memcache key generation strategy

  - by Maxim Veksler

  Given function f1 which receives n String arguments, would be considered better random key generation strategy for memcache for the scenario described below ? Our Memcache client does internal md5sum hashing on the keys it gets public class MemcacheClient { public Object get(String key) { String md5 = Md5sum.md5(key) // Talk to memcached to get the Serialization... return memcached(md5); } } First option public static String f1(String s1, String s2, String s3, String s4) { String key = s1 + s2 + s3 + s4; return get(key); } Second option /** * Calculate hash from Strings * * @param objects vararg list of String's * * @return calculated md5sum hash */ public static String stringHash(Object... strings) { if(strings == null) throw new NullPointerException("D'oh! Can't calculate hash for null"); MD5 md5sum = new MD5(); // if(prevHash != null) // md5sum.Update(prevHash); for(int i = 0; i < strings.length; i++) { if(strings[i] != null) { md5sum.Update("_" + strings[i] + "_"); // Convert to String... } else { // If object is null, allow minimum entropy by hashing it's position md5sum.Update("_" + i + "_"); } } return md5sum.asHex(); } public static String f1(String s1, String s2, String s3, String s4) { String key = stringHash(s1, s2, s3, s4); return get(key); } Note that the possible problem with the second option is that we are doing second md5sum (in the memcache client) on an already md5sum'ed digest result. Thanks for reading, Maxim.

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