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• How to "upgrade" the database in real world?

  - by Tattat

  My company have develop a web application using php + mysql. The system can display a product's original price and discount price to the user. If you haven't logined, you get the original price, if you loginned , you get the discount price. It is pretty easy to understand. But my company want more features in the system, it want to display different prices base on different user. For example, user A is a golden parnter, he can get 50% off. User B is a silver parnter, only have 30 % off. But this logic is not prepare in the original system, so I need to add some attribute in the database, at least a user type in this example. Is there any recommendation on how to merge current database to my new version of database. Also, all the data should preserver, and the server should works 24/7. (within stop the database) Is it possible to do so? Also , any recommend for future maintaince advice? Thz u.

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• Differences in accessing resources between Simulator and Device?

  - by Tony

  Is there some difference between the way that bundle resources can be accessed on the iPhone simulator versus a device (in my case, an iPad)? I am able to access a file on the former, but not the latter. NSString *filePath = [NSString stringWithFormat:@"%@%@",[[NSBundle mainBundle] bundlePath], @"/AppResources/html/pages/quickHelp.html"]; BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:filePath]; // fileExists == YES in the debugger on both the simulator and the device NSString *path = [NSString stringWithFormat:@"AppResources/html/pages/%@", contentsFileName]; NSString *pathForURL = [[NSBundle mainBundle] pathForResource:path ofType:@"html"]; NSURL *url = [NSURL fileURLWithPath:pathForURL isDirectory:NO]; The code above works fine in the simulator, but on the device pathForResource:path returns nil, so the last line throws a 'nil string parameter' exception. Am I missing something obvious? edit: Of course, in the above @"quickHelp" is being passed in the contentsFileName var. edit2: if it makes any difference, in my build settings "Base SDK" is set to "iPhone Device 4.0", and "iPhone OS Deployment Target" is set to "iPhone OS 3.1.3". Any other settings that might have an influence?

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• `enable_shared_from_this` has a non-virtual destructor

  - by Shtééf

  I have a pet project with which I experiment with new features of the upcoming C++0x standard. While I have experience with C, I'm fairly new to C++. To train myself into best practices, (besides reading a lot), I have enabled some strict compiler parameters (using GCC 4.4.1): -std=c++0x -Werror -Wall -Winline -Weffc++ -pedantic-errors This has worked fine for me. Until now, I have been able to resolve all obstacles. However, I have a need for enable_shared_from_this, and this is causing me problems. I get the following warning (error, in my case) when compiling my code (probably triggered by -Weffc++): base class ‘class std::enable_shared_from_this<Package>’ has a non-virtual destructor So basically, I'm a bit bugged by this implementation of enable_shared_from_this, because: A destructor of a class that is intended for subclassing should always be virtual, IMHO. The destructor is empty, why have it at all? I can't imagine anyone would want to delete their instance by reference to enable_shared_from_this. But I'm looking for ways to deal with this, so my question is really, is there a proper way to deal with this? And: am I correct in thinking that this destructor is bogus, or is there a real purpose to it?

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• Magento layout related basic Questions ?

  - by user197992

  Here is what I think about Magento (plz correct me if I am wrong ) 1)Each module has its own layout.xml stored in /interface/theme/layouts/ folder. 2)Magento loads all these layouts for current theme and creates a big xml file. Now what I am confused at . a)If magento loads /default/default/ (interface & theme) then why all the templates & layouts are inside base/default/ ?? b)what if I create my module name “page” inside my namespace “Jason” i.e Jason_Page , now what will happen to blocks in layout files which are named c)Since all the layouts are loaded and merged into one big xml file , then what happen to all those reference blocks which have same name attribute and are inside “Default” handle tag ? e.g d)what is Local.xml layout for and its use ?? e)wats the relation ship between a module name foo , and its layout name foo.xml ? What will happen to layout.xml if two modules with same name exist in diff namespace ? Thanks in advance .

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• Why `is_base_of` works with private inheritance?

  - by Alexey Malistov

  Why the following code works? typedef char (&yes)[1]; typedef char (&no)[2]; template <typename B, typename D> struct Host { operator B*() const; operator D*(); }; template <typename B, typename D> struct is_base_of { template <typename T> static yes check(D*, T); static no check(B*, int); static const bool value = sizeof(check(Host<B,D>(), int())) == sizeof(yes); }; //Test sample class B {}; class D : private B {}; //Exspression is true. int test[is_base_of<B,D>::value && !is_base_of<D,B>::value]; Note that B is private base. Note that operator B*() is const. How does this work? Why this works? Why static yes check(D*, T); is better than static yes check(B*, int); ?

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• Inefficient 'ANY' LINQ clause

  - by Focus

  I have a query that pulls back a user's "feed" which is essentially all of their activity. If the user is logged in the query will be filtered so that the feed not only includes all of the specified user's data, but also any of their friends. The database structure includes an Actions table that holds the user that created the action and a UserFriends table which holds any pairing of friends using a FrienderId and FriendeeId column which map to UserIds. I have set up my LINQ query and it works fine to pull back the data I want, however, I noticed that the query gets turned into X number of CASE clauses in profiler where X is the number of total Actions in the database. This will obviously be horrible when the database has a user base larger than just me and 3 test users. Here's the SQL query I'm trying to achieve: select * from [Action] a where a.UserId = 'GUID' OR a.UserId in (SELECT FriendeeId from UserFriends uf where uf.FrienderId = 'GUID') OR a.UserId in (SELECT FrienderId from UserFriends uf where uf.FriendeeId = 'GUID') This is what I currently have as my LINQ query. feed = feed.Where(o => o.User.UserKey == user.UserKey || db.Users.Any(u => u.UserFriends.Any(ufr => ufr.Friender.UserKey == user.UserKey && ufr.isApproved) || db.Users.Any(u2 => u2.UserFriends.Any(ufr => ufr.Friendee.UserKey == user.UserKey && ufr.isApproved) ))); This query creates this: http://pastebin.com/UQhT90wh That shows up X times in the profile trace, once for each Action in the table. What am I doing wrong? Is there any way to clean this up?

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• How to manage feeds with subclassed object in Django 1.2?

  - by Matteo

  Hi, I'm trying to generate a feed rss from a model like this one, selecting all the Entry objects: from django.db import models from django.contrib.sites.models import Site from django.contrib.auth.models import User from imagekit.models import ImageModel import datetime class Entry(ImageModel): date_pub = models.DateTimeField(default=datetime.datetime.now) author = models.ForeignKey(User) via = models.URLField(blank=True) comments_allowed = models.BooleanField(default=True) icon = models.ImageField(upload_to='icon/',blank=True) class IKOptions: spec_module = 'journal.icon_specs' cache_dir = 'icon/resized' image_field = 'icon' class Post(Entry): title = models.CharField(max_length=200) description = models.TextField() slug = models.SlugField(unique=True) def __unicode__(self): return self.title class Photo(Entry): alt = models.CharField(max_length=200) description = models.TextField(blank=True) original = models.ImageField(upload_to='photo/') class IKOptions: spec_module = 'journal.photo_specs' cache_dir = 'photo/resized' image_field = 'original' def __unicode__(self): return self.alt class Quote(Entry): blockquote = models.TextField() cite = models.TextField(blank=True) def __unicode__(self): return self.blockquote When I use the render_to_response in my views I simply call: def get_journal_entries(request): entries = Entry.objects.all().order_by('-date_pub') return render_to_response('journal/entries.html', {'entries':entries}) And then I use a conditional template to render the right snippets of html: {% extends "base.html" %} {% block main %} <hr> {% for entry in entries %} {% if entry.post %}[...]{% endif %}[...] But I cannot do the same with the Feed Framework in django 1.2... Any suggestion, please?

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• Intercept creation of activities when the application is restored

  - by Johan Bilien

  Most of our activities access a user-specific model. All these activities inherit from a ModelActivity base class, which provides a getModel() call. When one of these activities detect that the user has signed out (through the AccountManager callback), it sticks to its existing model, but prepares to exit back to the root activity (which is not user-specific) by starting its intent with FLAG_ACTIVITY_CLEAR_TOP. If however the user deletes an account while the app is not running, we run into trouble when the activity is restored. Now the activity needs to handle there not being a model, which makes the code more complicated and bug-prone. Ideally we would intercept the application restore process before the activity is created. Then we would check whether we have an account and a model, and if not clear up the saved stack of activities, and restart from our root activity instead of the last saved activity. But as far as I can tell the first place where we can run code is in the onCreate callback of the activity. Is there a way to run some code when the application is restored from background-saving, but before the saved activity is created?

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• NHibernate class referencing discriminator based subclass

  - by Rich

  I have a generic class Lookup which contains code/value properties. The table PK is category/code. There are subclasses for each category of lookup, and I've set the discriminator column in the base class and its value in the subclass. See example below (only key pieces shown): public class Lookup { public string Category; public string Code; public string Description; } public class LookupClassMap { CompositeId() .KeyProperty(x = x.Category, "CATEGORY_ID") .KeyProperty(x = x.Code, "CODE_ID"); DiscriminateSubclassesBasedOnColumn("CATEGORY_ID"); } public class MaritalStatus: Lookup {} public class MartialStatusClassMap: SubclassMap { DiscriminatorValue(13); } This all works. Here's the problem. When a class has a property of type MaritalStatus, I create a reference based on the contained code ID column ("MARITAL_STATUS_CODE_ID"). NHibernate doesn't like it because I didn't map both primary key columns (Category ID & Code ID). But with the Reference being of type MaritalStatus, NHibernate should already know what the value of the category ID is going to be, because of the discriminator value. What am I missing?

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• Microsoft JScript runtime error Object doesn't support this property or method

  - by Darxval

  So i am trying to call this function in my javascript but it gives me the error of "Microsoft JScript runtime error Object doesn't support this property or method" and i cant figure out why. It is occuring when trying to call hmacObj.getHMAC. This is from the jsSHA website: http://jssha.sourceforge.net/ to use the hmac-sha1 algorithm encryption. Thank you! hmacObj = new jsSHA(signature_base_string,"HEX"); signature = hmacObj.getHMAC("hgkghk","HEX","SHA-1","HEX"); Above this i have copied the code from sha.js snippet: function jsSHA(srcString, inputFormat) { /* * Configurable variables. Defaults typically work */ jsSHA.charSize = 8; // Number of Bits Per character (8 for ASCII, 16 for Unicode) jsSHA.b64pad = ""; // base-64 pad character. "=" for strict RFC compliance jsSHA.hexCase = 0; // hex output format. 0 - lowercase; 1 - uppercase var sha1 = null; var sha224 = null; The function it is calling (inside of the jsSHA function) (snippet) this.getHMAC = function (key, inputFormat, variant, outputFormat) { var formatFunc = null; var keyToUse = null; var blockByteSize = null; var blockBitSize = null; var keyWithIPad = []; var keyWithOPad = []; var lastArrayIndex = null; var retVal = null; var keyBinLen = null; var hashBitSize = null; // Validate the output format selection switch (outputFormat) { case "HEX": formatFunc = binb2hex; break; case "B64": formatFunc = binb2b64; break; default: return "FORMAT NOT RECOGNIZED"; }

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• highlight listview items android

  - by user1752939

  I have listview with custom base adapter. When I populate the list I have to check a boolean in the object I'm populating the listview and if it is true to change the background color of that row. public View getView(int position, View convertView, ViewGroup parent) { LoginsList entry = listOfLoginsLists.get(position); if (convertView == null) { LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); convertView = inflater.inflate(R.layout.lists_row, null); } TextView ListName = (TextView) convertView.findViewById(R.id.tvListName); ListName.setText(entry.getListName()); TextView ListDescription = (TextView) convertView.findViewById(R.id.tvListDescription); ListDescription.setText(entry.getListDescription()); Button Send = (Button) convertView.findViewById(R.id.bSend); Send.setOnClickListener(this); Send.setTag(entry); RelativeLayout RelLayout = (RelativeLayout) convertView.findViewById(R.id.layoutListsRow); RelLayout.setFocusableInTouchMode(false); RelLayout.setFocusable(false); RelLayout.setOnClickListener(this); RelLayout.setTag(entry); if (entry.isSent()) { RelLayout.setBackgroundColor(Color.parseColor("#4400FF00")); } return convertView; } But this code doesn't work right. When I scroll the list view the rows colors get messed up.

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• WPF app startup problems

  - by Dave

  My brain is all over the map trying to fully understand Unity right now. So I decided to just dive in and start adding it in a branch to see where it takes me. Surprisingly enough (or maybe not), I am stuck just getting my darn Application to load properly. It seems like the right way to do this is to override OnStartup in App.cs. I've removed my StartupUri from App.xaml so it doesn't create my GUI XAML. My App.cs now looks something like this: public partial class App : Application { private IUnityContainer container { get; set; } protected override void OnStartup(StartupEventArgs e) { container = new UnityContainer(); GUI gui = new GUI(); gui.Show(); } protected override void OnExit(ExitEventArgs e) { container.Dispose(); base.OnExit(e); } } The problem is that nothing happens when I start the app! I put a breakpoint at the container assignment, and it never gets hit. What am I missing? App.xaml is currently set to ApplicationDefinition, but I'd expect this to work because some sample Unity + WPF code I'm looking at (from Codeplex) does the exact same thing, except that it works! I've also started the app by single-stepping, and it eventually hits the first line in App.xaml. When I step into this line, that's when the app just starts "running", but I don't see anything (and my breakpoint isn't hit). If I do the exact same thing in the sample application, stepping into App.xaml puts me right into OnStartup, which is what I'd expect to happen. Argh! Is it a Bad Thing to just put the Unity construction in my GUI's Window_Loaded event handler? Does it really need to be at the App level?

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• ASP.NET: Page HTML head rendering

  - by Fabian

  I've been trying to figure out the best way to custom render the <head> element of a pag to get rid of the extra line breaks which is caused by <head runat="server">, so its properly formatted. So far the only thing i've found which works is the following: protected override void Render(HtmlTextWriter writer) { StringWriter stringWriter = new StringWriter(); HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter); base.Render(htmlTextWriter); htmlTextWriter.Close(); string html = stringWriter.ToString(); string newHTML = html.Replace("\r\n\r\n<!DOCTYPE", "<!DOCTYPE") .Replace("\r\n<html", "<html") .Replace("<title>\r\n\t", "<title>") .Replace("\r\n</title>", "</title>") .Replace("</head>", "\n</head>"); writer.Write(newHTML); } I define my had tag like Now i have 2 questions: How does the above code affect the performance (so is this viable in an production environment)? Is there a better way to do this, for example a method which i can override to just custom render the <head>? Oh yeah ASP.NET MVC is not an option.

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• C ++ virtual function

  - by user2950788

  masters of C++. I am trying to implement polymorphism in C++. I want to write a base class with a virtual function and then redefine that function in the child class. then demonstrate dynamic binding in my driver program. But I just couldn't get it to work. I know how to do it in C#, so I figured that I might have made some syntactical mistakes where I had used C#'s syntax in my C++ code, but these mistakes are not obvious to me at all. So I'd greatly appreciate it if you would correct my mistakes. class polyTest { public: polyTest(); virtual void type(); virtual ~polyTest(); }; void polyTest::type() { cout << "first gen"; } class polyChild: public polyTest { public: void type(); }; void polyChild::type() { cout << "second gen"; } int main() { polyChild * ptr1; polyChild * ptr2; ptr1 = new polyTest(); ptr2 = new polyChild(); ptr1 -> type(); ptr2 -> type(); }

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• Using groovy ws with enum types?

  - by Jared

  I'm trying to use groovy ws to call a webservice. One of the properties of the generated class is it's self a class with an enum type. Although the debug messages show that the com.test.FinalActionType is created at runtime when the WSDL is read I can't create an instance of it using code like proxy.create("com.test.FinalActionType") When I try and assign a string to my class uin place of an instance of FinalActionType groovy is not able to do the conversion. How can I get an instance of this class to use in a webservice call? I've pasted the important part of the WSDL below. <xsd:simpleType name="FinalActionType"> <xsd:restriction base="xsd:string"> <xsd:enumeration value="stop"/> <xsd:enumeration value="quit"/> <xsd:enumeration value="continue"/> <xsd:whiteSpace value="collapse"/> </xsd:restriction> </xsd:simpleType>

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• Margically appearing margin in footer. Could use some fresh eye's on this.

  - by Banderdash

  Hi chaps! Got a nearly finished coded comp here: http://clients.pixelbleed.net/biodesign/ I realize it's not completely valid, what with my nesting of li's and ul's within A tags. Unfortunately that's the way it has to be. My issue is with the very bottom of the footer. It has a space showing the body's background color beneath it. Tried a number of things and this space after the black link bar on the very bottom is a resistant little bugger. Ideally the black box on the bottom should rest against the very base of the view-port, at least when the content is sufficiently long--which it is in this case. If someone would like to take a quick peak at my source and give me some ideas I'd be very grateful. The CSS can be found here: http://clients.pixelbleed.net/biodesign/css/core.css And, yes, I've tried removing the height:100%. Makes no difference it seems. I do believe the issue to be with the footer, as when I remove these Div's the content rests as it should. Just don't see anything in my CSS to cause the margin/spacing issue though. Thanks so much.

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• Mono Text Based Web Browser

  - by powerbox

  Hi guys, is there any public text based web browser implementation for C# or on mono base api that I can use to fill up web forms automatically? I'll be using it to automate some web task that does not require any image authentication. I'm currently using a web browser control available on .Net Framework and waits for the event WebBrowserDocumentCompletedEventHandler to fire after a page is successfully loaded and invoke some actions like Submit or simulating a mouse click on some links. It actually does the job but I can't process bulk transactions since I needed to wait for the whole page to be loaded together with the images and other stuff. It is easy to use HttpWebRequest to fill up some forms , provide some data and then submit. But on some occasions I only need to simulate a mouse click to a certain link which I don't know how to do with HttpWebRequest. By the way using HttpWebRequest will still download all the images of a web page that I see pointless since I only need to provide correct data back to the server. I hope someone can pinpoint me the correct way of doing this kind of automation and thanks in advance!

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• Spring annotation-based container configuration context:include & exclude filters

  - by lisak

  Hey, first off I point to the similar question. I spent more than an hour to set this up, but PathMatchingResourcePatternResolver still scans everything. I have one common.xml (that is imported from specific.xml) and a specific.xml bean definition file. The context is loaded from specific.xml. In common.xml there is this element: <context:component-scan base-package="cz.instance.transl"> <context:exclude-filter type="aspectj" expression="cz.instance.transl.model..* &amp;&amp; cz.instance.transl.service..* &amp;&amp; cz.instance.transl.hooks..*"/> </context:component-scan> Where classes in packages like cz.instance.transl.service.* should not be subject of scanning, but everything else in here cz.instance.transl.* should be scanned through. But PathMatchingResourcePatternResolver marks everything as matching resources. It is the same with regex. BTW: in xml style configuration, one can have many components that share a common.xml beans via "import resource" when loading context. How this is done when Annotation-based container configuration is used ?

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• Trapping messages in .NET

  - by user350632

  How can i trap a Windows system message (like WM_SETTEXT) that was sent by some window (VLC player window in my case)? I've tried to inherit NativeWindow class and override WndProc like this: class VLCFilter : NativeWindow { System.IntPtr iHandle; const int WM_SETTEXT = 0x000C; public VLCFilter() { Process p = Process.GetProcessesByName("vlc")[0]; iHandle = p.MainWindowHandle; } protected override void WndProc(ref Message aMessage) { base.WndProc(ref aMessage); if (aMessage.HWnd != iHandle) return false; if (aMessage.Msg == WM_SETTEXT) { MessageBox.Show("VLC window text changed!"); } } } I have checked with Microsoft Spy++ that WM_SETTEXT message is sent by VLC player but my code doesn't seem to get the work done. I've refered mainly to: http://www.codeproject.com/kb/dotnet/devicevolumemonitor.aspx I'm trying to make this work for some time with no success. What am I doing wrong? What I am not doing? Maybe there is easier way to do this? My initial goal is to catch when VLC player (that could be playing somewhere in the background and is not emmbed in my application) repeats its playback (have noticed that WM_SETTEXT message is sent then and I'm trying to find it out like this).

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• Constructor and Destructors in C++ work?

  - by Jack

  I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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• Centralizing Messagebox handling for application

  - by DRapp

  I'm wondering how others deal with trying to centralize MessageBox function calling. Instead of having long text embedded all over the place in code, in the past (non .net language), I would put system and application base "messagebox" type of messages into a database file which would be "burned" into the executable, much like a resource file in .Net. When a prompting condition would arise, I would just do call something like MBAnswer = MyApplication.CallMsgBox( IDUserCantDoThat ) then check the MBAnswer upon return, such as a yes/no/cancel or whatever. In the database table, I would have things like what the messagebox title would be, the buttons that would be shown, the actual message, a special flag that automatically tacked on a subsequent standard comment like "Please contact help desk if this happens.". The function would call the messagebox with all applicable settings and just return back the answer. The big benefits of this was, one location to have all the "context" of messages, and via constants, easier to read what message was going to be presented to the user. Does anyone have a similar system in .Net to do a similar approach, or is this just a bad idea in the .Net environment.

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• Fluent NHibernate: Example of a one-to-many relationship on an abstract class of a table-per-subclas

  - by BigTommy79

  Hi All, I've been trying for ages to find an example (because I can't get it to work myself) of the correct mapping for a one-to-many relationship on an abstract class of a table-per-subclass implementation, in fluent nHibernate. An example below: I'm looking to map the list of Fines on the Debt abstract base class to the Fine class. if anyone knows of any tutorial or example they've come across before please let me know. Thanks, Tim public abstract class Entity { public int Id { get; set; } } public abstract class Debt : Entity { public decimal Balance { get; set; } public IList<Fine> Fines { get; set; } public Debt() { Fines = new List<Fine>(); } } public class CarLoan : Debt { } public class CreditCard : Debt { } public class LoanApplication : Entity { public IList<Debt> ExistingDebts { get; set; } public LoanApplication() { ExistingDebts = new List<Debt>(); } } public class Fine { public Int64 Cash { get; set; } }

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• Problems with binding to Window Height and Width

  - by D.H.

  I have some problems when I try to bind the height and width of a window to properties in my view model. Here is a small sample app to illustrate the problem. This is the code in app.xaml.xs public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { base.OnStartup(e); MainWindow mainWindow = new MainWindow(); MainWindowViewModel mainWindowViewModel = new MainWindowViewModel(); mainWindow.DataContext = mainWindowViewModel; mainWindow.Show(); } } This is MainWindow.xaml: <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="{Binding WindowHeight}" Width="{Binding WindowWidth}" BorderThickness="{Binding WindowBorderThickness}"> </Window> And this is the view model: public class MainWindowViewModel { public int WindowWidth { get { return 100; } } public int WindowHeight { get { return 200; } } public int WindowBorderThickness { get { return 8; } } } When the program is started the getters of WindowHeight and WindowBorderThickness (but not WindowWidth) are called, so the height and the border of the window is set properly, but not the width. I then add button that will trigger PropertyChanged for all properties, so that the view model now looks like this: public class MainWindowViewModel : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public void TriggerPropertyChanges() { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs("WindowWidth")); PropertyChanged(this, new PropertyChangedEventArgs("WindowHeight")); PropertyChanged(this, new PropertyChangedEventArgs("WindowBorderThickness")); } } public ICommand ButtonCommand { get { return new RelayCommand(delegate { TriggerPropertyChanges(); }); } } public int WindowWidth { get { return 100; } } public int WindowHeight { get { return 200; } } public int WindowBorderThickness { get { return 8; } } } Now, when I click the button, the getter of WindowBorderThickness is called, but not the ones for WindowWidth and WindowHeight. It all just seems very weird and inconsistent to me. What am I missing?

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• Storing large numbers of varying size objects on disk

  - by Foredecker

  I need to develop a system for storing large numbers (10's to 100's of thousands) of objects. Each object is email-like - there is a main text body, and several ancillary text fields of limited size. A body will be from a few bytes, to several KB in size. Each item will have a single unique ID (probably a GUID) that identifies it. The store will only be written to when an object is added to it. It will be read often. Deletions will be rare. The data is almost all human readable text so it will be readily compressible. A system that lets me issue the I/Os and mange the memory and caching would be ideal. I'm going to keep the indexes in memory, using it to map indexes to the single (and primary) key for the objects. Once I have the key, then I'll load it from disk, or the cache. The data management system needs to be part of my application - I do not want to depend on OS services. Or separately installed packages. Native (C++) would be best, but a manged (C#) thing would be ok. I believe that a database is an obvious choice, but this needs to be super-fast for look up and loading into memory of an object. I am not experienced with data base tech and I'm concerned that general relational systems will not handle all this variable sized data efficiently. (Note, this has nothing to do with my job - its a personal project.) In your experience, what are the viable alternatives to a traditional relational DB? Or would a DB work well for this?

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• Inheritance of TCollectionItem

  - by JamesB

  I'm planning to have collection of items stored in a TCollection. Each item will derive from TBaseItem which in turn derives from TCollectionItem, With this in mind the Collection will return TBaseItem when an item is requested. Now each TBaseItem will have a Calculate function, in the the TBaseItem this will just return an internal variable, but in each of the derivations of TBaseItem the Calculate function requires a different set of parameters. The Collection will have a Calculate All function which iterates through the collection items and calls each Calculate function, obviously it would need to pass the correct parameters to each function I can think of three ways of doing this: Create a virtual/abstract method for each calculate function in the base class and override it in the derrived class, This would mean no type casting was required when using the object but it would also mean I have to create lots of virtual methods and have a large if...else statement detecting the type and calling the correct "calculate" method, it also means that calling the calculate method is prone to error as you would have to know when writing the code which one to call for which type with the correct parameters to avoid an Error/EAbstractError. Create a record structure with all the possible parameters in and use this as the parameter for the "calculate" function. This has the added benefit of passing this to the "calculate all" function as it can contain all the parameters required and avoid a potentially very long parameter list. Just type casting the TBaseItem to access the correct calculate method. This would tidy up the TBaseItem quite alot compared to the first method. What would be the best way to handle this collection?

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