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• Handling undo and edit flag on window with several model objects

  - by Rui Pacheco

  Hi, I've a window that will hold several instances of a model object, listed in a table. The model object is updated using a text view. What is the best way to keep the edit flag and undo manager in synch with the content of the different model objects? I'm thinking creating an instance of the undo manager on the model object and manually set the undo manager for the text view every time the user choses a new model object. Does the undo manager also handle the edited flag?

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• Delphi / MySql : Problems escaping strings

  - by mawg

  N00b here, having problems escaping strings. I used the QuotedStr() function - shouldn't that be enough. Unfortunately, the string that I am trying to quote is rather messy, but I will post it here in case anyone wants to paste it into WinMerge or KDiff3, etc. I am trying to store an entire Delphi form into the database, rather than into a .DFM file. It has only one field, a TEdit edit box. The debugger shows the form as text as 'object Form1: TScriptForm'#$D#$A' Left = 0'#$D#$A' Top = 0'#$D#$A' Align = alClient'#$D#$A' BorderStyle = bsNone'#$D#$A' ClientHeight = 517'#$D#$A' ClientWidth = 993'#$D#$A' Color = clBtnFace'#$D#$A' Font.Charset = DEFAULT_CHARSET'#$D#$A' Font.Color = clWindowText'#$D#$A' Font.Height = -11'#$D#$A' Font.Name = 'MS Sans Serif''#$D#$A' Font.Style = []'#$D#$A' OldCreateOrder = False'#$D#$A' SaveProps.Strings = ('#$D#$A' 'Visible=False')'#$D#$A' PixelsPerInch = 96'#$D#$A' TextHeight = 13'#$D#$A' object Edit1: TEdit'#$D#$A' Left = 192'#$D#$A' Top = 64'#$D#$A' Width = 121'#$D#$A' Height = 21'#$D#$A' TabOrder = 8'#$D#$A' end'#$D#$A'end'#$D#$A before calling QuotedStr() and ''object Form1: TScriptForm'#$D#$A' Left = 0'#$D#$A' Top = 0'#$D#$A' Align = alClient'#$D#$A' BorderStyle = bsNone'#$D#$A' ClientHeight = 517'#$D#$A' ClientWidth = 993'#$D#$A' Color = clBtnFace'#$D#$A' Font.Charset = DEFAULT_CHARSET'#$D#$A' Font.Color = clWindowText'#$D#$A' Font.Height = -11'#$D#$A' Font.Name = ''MS Sans Serif'''#$D#$A' Font.Style = []'#$D#$A' OldCreateOrder = False'#$D#$A' SaveProps.Strings = ('#$D#$A' ''Visible=False'')'#$D#$A' PixelsPerInch = 96'#$D#$A' TextHeight = 13'#$D#$A' object Edit1: TEdit'#$D#$A' Left = 192'#$D#$A' Top = 64'#$D#$A' Width = 121'#$D#$A' Height = 21'#$D#$A' TabOrder = 8'#$D#$A' end'#$D#$A'end'#$D#$A''' afterwards. The strange thing is that my complete command 'INSERT INTO designerFormDfm(designerFormDfmText) VALUES ("'object Form1: TScriptForm'#$D#$A' Left = 0'#$D#$A' Top = 0'#$D#$A' Align = alClient'#$D#$A' BorderStyle = bsNone'#$D#$A' ClientHeight = 517'#$D#$A' ClientWidth = 993'#$D#$A' Color = clBtnFace'#$D#$A' Font.Charset = DEFAULT_CHARSET'#$D#$A' Font.Color = clWindowText'#$D#$A' Font.Height = -11'#$D#$A' Font.Name = ''MS Sans Serif'''#$D#$A' Font.Style = []'#$D#$A' OldCreateOrder = False'#$D#$A' SaveProps.Strings = ('#$D#$A' ''Visible=False'')'#$D#$A' PixelsPerInch = 96'#$D#$A' TextHeight = 13'#$D#$A' object Edit1: TEdit'#$D#$A' Left = 192'#$D#$A' Top = 64'#$D#$A' Width = 121'#$D#$A' Height = 21'#$D#$A' TabOrder = 8'#$D#$A' end'#$D#$A'end'#$D#$A''");' executes in a MySql console, but not from Delphi, where I pass that command as parameter command to a function which ADOCommand.CommandText := command; ADOCommand.CommandType := cmdText; ADOCommand.Execute(); I can only assume that I am having problems escpaing sequences which contain single quotes (and QuotedStr() doesn't seem to escape backslahes(?!)) What am I doing that is obviously, glaringly wrong?

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• How to read from a method that returns a filehandle in perl?

  - by Ryan Thompson

  I have an object with a method that returns a filehandle, and I want to read from that handle. The following doesn't work, because the right angle bracket of the method call is interpreted as the closing angle bracket of the input reader: my $input = <$object->get_handle()>; That gets parsed as: my $input = ( < $object- > ) get_handle() >; which is obviously a syntax error. Is there any way I can perform a method call within an angle operator, or do I need to break it into two steps like this? my $handle = $object->get_handle(); my $input = <$handle>;

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• nhibernate fluent repository pattern insert problem

  - by voam

  I am trying to use Fluent NHibernate and the repository pattern. I would like my business layer to not be knowledgeable of the data persistence layer. Ideally I would pass in an initialized domain object to the insert method of the repository and all would be well. Where I run into problems is if the object being passed in has a child object. For example say I want to insert an a new order for a customer, and the customer is a property of the order object. I would like to do something like this: Customer c = new Customer; c.CustomerId = 1; Order o = new Order; o.Customer = c; repository.InsertOrder(o); The problem is that using NHiberate the CustomerId field is only privately settable so I can not set it directly like this. so what I have ended up doing is have my repository have an interface of Order InsertOrder(int customerId) where all the foreign keys get passed in as parameters. Somehow this just doesn't seem right. The other approach was to use the NHibernate session variable to load a customer object in my business model and then have the order passed in to the repository but this defeats my persistence ignorance ideal. Should I throw this persistence ignorance out the window or am I missing something here? Thanks

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• Looking for an elegant way to store one-to-many relationship in coredata when order is important

  - by Eric Schweichler

  I've been trying to come up with a way to solve my problem, but every solution I can think of is messy and makes me want to retch. I have a one-to-many relationship, consisting of a Team object that can have many Member objects. When I built my data model using Xcode, I was given the default NSSet in which to store the member objects, Unfortunately Sets are not ordered and I need to preserve the order of the Member objects and I need to know if there are empty spaces between Members. I thought of Using an NSArray in place of the NSSet and creating a dummy Member object in my data store that I could use to mark vacant a spot between to Member objects, but that solution really feels like too much of a hack to me. Since I'll always have to filter out this dummy Member from any queries. An NSDictionary would be perfect as I could store the Member object references and their positions as Object-Key pairs, (taking care of both order and vacancies) but apparently CoreData does not support NSDictionary. Has anyone had a similar need, and devised a simple solution?

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• maths: motion depending on time

  - by clamp

  hello, i have a mathematical problem: i have a function where the only parameter is the current time. the return should be a position which is used to place an object on a certain place. int position(int time) { int x = 0; //TODO implement x depending on time return x; } so basically the function is called every frame to put the object in motion. the motion should look like this (this is the actual question): a linear motion for time A, the object moves at constant speed no motion for time B, the object is stopped repeat at 1. thanks!

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• Correct way to make datasources/resources a deploy-time setting

  - by Draemon

  I have a web-app that requires two settings: A JDBC datasource A string token I desperately want to be able to deploy one .war to various different containers (jetty,tomcat,gf3 minimum) and configure these settings at application level within the container. My code does this: InitialContext ctx = new InitialContext(); Context envCtx = (javax.naming.Context) ctx.lookup("java:comp/env"); token = (String)envCtx.lookup("token"); ds = (DataSource)envCtx.lookup("jdbc/datasource") Let's assume I've used the glassfish management interface to create two jdbc resources: jdbc/test-datasource and jdbc/live-datasource which connect to different copies of the same schema, on different servers, different credentials etc. Say I want to deploy this to glassfish with and point it at the test datasource, I might have this in my sun-web.xml: ... <resource-ref> <res-ref-name>jdbc/datasource</res-ref-name> <jndi-name>jdbc/test-datasource</jndi-name> </resource-ref> ... but sun-web.xml goes inside my war, right? surely there must be a way to do this through the management interface Am I even trying to do the right thing? Do other containers make this any easier? I'd be particularly interested in how jetty 7 handles this since I use it for development. EDIT Tomcat has a reasonable way to do this: Create $TOMCAT_HOME/conf/Catalina/localhost/webapp.xml with: <?xml version="1.0" encoding="UTF-8"?> <Context antiResourceLocking="false" privileged="true"> <!-- String resource --> <Environment name="token" value="value of token" type="java.lang.String" override="false" /> <!-- Linking to a global resource --> <ResourceLink name="jdbc/datasource1" global="jdbc/test" type="javax.sql.DataSource" /> <!-- Derby --> <Resource name="jdbc/datasource2" type="javax.sql.DataSource" auth="Container" driverClassName="org.apache.derby.jdbc.EmbeddedDataSource" url="jdbc:derby:test;create=true" /> <!-- H2 --> <Resource name="jdbc/datasource3" type="javax.sql.DataSource" auth="Container" driverClassName="org.h2.jdbcx.JdbcDataSource" url="jdbc:h2:~/test" username="sa" password="" /> </Context> Note that override="false" means the opposite. It means that this setting can't be overriden by web.xml. I like this approach because the file is part of the container configuration not the war, but it's not part of the global configuration; it's webapp specific. I guess I expect a bit more from glassfish since it is supposed to have a full web admin interface, but I would be happy enough with something equivalent to the above.

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• How can I avoid the overflow when wheel scolling WPF DataGrid

  - by Jan Bannister

  When I use the mouse wheel to scroll the WPF Toolkit DataGrid on a Vista 64 Machine I get a cryptic low level error: at System.IntPtr.op_Explicit(IntPtr value) at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler) I logged an issue on CodePlex. But has anyone found a way to resolve this already?

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• Please help with iPhone Memory & Images, memory usage crashing app

  - by Andrew Gray

  I have an issue with memory usage relating to images and I've searched the docs and watched the videos from cs193p and the iphone dev site on memory mgmt and performance. I've searched online and posted on forums, but I still can't figure it out. The app uses core data and simply lets the user associate text with a picture and stores the list of items in a table view that lets you add and delete items. Clicking on a row shows the image and related text. that's it. Everything runs fine on the simulator and on the device as well. I ran the analyzer and it looked good, so i then starting looking at performance. I ran leaks and everything looked good. My issue is when running Object Allocations as every time i select a row and the view with the image is shown, the live bytes jumps up a few MB and never goes down and my app eventually crashes due to memory usage. Sorting the live bytes column, i see 2 2.72MB mallocs (5.45Mb total), 14 CFDatas (3.58MB total), 1 2.74MB malloc and everything else is real small. the problem is all the related info in instruments is really technical and all the problem solving examples i've seen are just missing a release and nothing complicated. Instruments shows Core Data as the responsible library for all but one (libsqlite3.dylib the other) with [NSSQLCore _prepareResultsFromResultSet:usingFetchPlan:withMatchingRows:] as the caller for all but one (fetchResultSetReallocCurrentRow the other) and im just not sure how to track down what the problem is. i've looked at the stack traces and opened the last instance of my code and found 2 culprits (below). I havent been able to get any responses at all on this, so if anyone has any tips or pointers, I'd really appreciate it!!!! //this is from view controller that shows the title and image - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.title = item.title; self.itemTitleTextField.text = item.title; if ([item.notes length] == 0) { self.itemNotesTextView.hidden = YES; } else { self.itemNotesTextView.text = item.notes; } //this is the line instruments points to UIImage *image = item.photo.image; itemPhoto.image = image; } - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the managed object for the given index path NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; // Save the context. NSError *error = nil; if (![context save:&error]) //this is the line instruments points to { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); exit(-1); } } }

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• In Ruby, how can I initialize instance variables in new objects of core classes created from literal

  - by Ollie Saunders

  class Object attr_reader :foo def initialize @foo = 'bar' end end Object.new.foo # => 'bar' ''.foo # => nil //.foo # => nil [].foo # => nil I want them all to return 'bar' Am aware that you can do this already: class Object def foo 'bar' end end But I specifically want to initialize a state variable. Also note that this doesn't work. class String alias_method :old_init, :initialize def initialize(*args) super old_init(*args) end end class Object attr_reader :foo def initialize @foo = 'bar' super end end ''.foo # => nil Nor does this: class String attr_reader :foo def initialize @foo = 'bar' end end ''.instance_variables # => [] I'm beginning to think that this isn't actually possible.

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• jquery - detect if selector returns null

  - by peirix

  What is the best way to detect if a jQuery-selector returns an empty object. If you do: alert($('#notAnElement')); you get [object Object], so the way I do it now is: alert($('#notAnElement').get(0)); which will write "undefined", and so you can do a check for that. But it seems very bad. What other way is there?

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• django blog - post- reply system display replies

  - by dana

  I have a mini blog app, and a reply system. I want to list all mini blog entries, and their replies, if there are any. i have in views.py def profile_view(request, id): u = UserProfile.objects.get(pk=id) paginator = New.objects.filter(created_by = request.user) replies = Reply.objects.filter(reply_to = paginator) return render_to_response('profile/publicProfile.html', { 'object_list': u, 'list':paginator, 'replies':replies }, context_instance=RequestContext(request)) and in the template: <h3>Recent Entries:</h3> {% for object in list %} <li>{{ object.post }} <br /> {% for object in replies %} {{ object.reply }} <br /> {% endfor %} mention : reply_to is a ForeignKey to New, and New is the name of the 'mini blog' table But it only shows all the replies for each blog entry, not the reply for every entry, if there is one thanks

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• WITH_OBJECT_HEADERS enabled GC from Dalvik?

  - by Wonil

  Hello, As I know Dalvik VM does not support generational GC as default. But, I found "WITH_OBJECT_HEADERS" compilation flag which could be related with generational GC from HeapInternal.h file. typedef struct DvmHeapChunk { #if WITH_OBJECT_HEADERS u4 header; const Object *parent; const Object *parentOld; const Object *markFinger; const Object *markFingerOld; u2 birthGeneration; u2 markCount; u2 scanCount; u2 oldMarkGeneration; u2 markGeneration; u2 oldScanGeneration; u2 scanGeneration; #endif Does anyone try to build Dalvik with this option enabled? Do you know anything about generational GC support from Dalvik? Regards, Wonil.

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• Why are virtual methods considered early bound?

  - by AspOnMyNet

  One definition of binding is that it is the act of replacing function names with memory addresses. a) Thus I assume early binding means function calls are replaced with memory addresses during compilation process, while with late binding this replacement happens during runtime? b) Why are virtual methods also considered early bound (thus the target method is found at compile time, and code is created that will call this method)? As far as I know, with virtual methods the call to actual method is resolved only during runtime and not compile time?! thanx EDIT: 1) A a=new A(); a.M(); As far as I know, it is not known at compile time where on the heap (thus at which memory address ) will instance a be created during runtime. Now, with early binding the function calls are replaced with memory addresses during compilation process. But how can compiler replace function call with memory address, if it doesn’t know where on the heap will object a be created during runtime ( here I’m assuming the address of method a.M will also be at same memory location as a )? 2) v-table calls are neither early nor late bound. Instead there's an offset into a table of function pointers. The offset is fixed at compile time, but which table the function pointer is chosen from depends on the runtime type of the object (the object contains a hidden pointer to its v-table), so the final function address is found at runtime. But assuming the object of type T is created via reflection ( thus app doesn’t even know of existence of type T ), then how can at compile time exist an entry point for that type of object?

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• What is the best way get and hold property reference by name in c#

  - by Jeff Weber

  I want to know if there is a better way (than what I'm currently doing) to obtain and hold a reference to a property in another object using only the object and property string names. Particularly, is there a better way to do this with the new dynamic functionality of .Net 4.0? Here is what I have right now. I have a "PropertyReference<T>" object that takes an object name and property name in the constructor. An Initialize() method uses reflection to find the object and property and stores the property Getter as an Action<T> and the property Setter as an Func<T>. When I want to actually call the property I do something like this: int x = _propertyReference.Get(); or _propertyReference.Set(2); Here is my PropertyReference<T> code. Please dissect and make suggestions for improvement. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Reflection; using System.Xml; namespace WindowsFormsApplication2 { public class PropertyReference<T> : IPropertyReference { public string ComponentName { get; set; } public string PropertyName { get; set; } public bool IsInitialized { get { return (_action != null && _func != null); } } Action<T> _action; Func<T> _func; public PropertyReference() { } public PropertyReference(string componentName, string propertyName) { ComponentName = componentName; PropertyName = propertyName; } public void Initialize(IEntity e) { Object component = e.GetByName(ComponentName); if (component == null) return; Type t = e.GetByName(ComponentName).GetType(); PropertyInfo pi = t.GetProperty(PropertyName); _action = (T a) => pi.SetValue(component, a, null); _func = () => (T)pi.GetValue(component, null); } public void Reset() { _action = null; _func = null; } public void Set(T value) { _action.Invoke(value); } public T Get() { return _func(); } } } Note: I can't use the "Emit" functionality as I need this code to work on the new Windows Phone 7 and that does not support Emit.

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• Should I call Dispose() within a function after Return?

  - by Camilo Martin

  Should I call .Dispose() after returning an object that implements IDisposable? myDisposableObject Gimme() { //Code return disposableResult; disposableResult.Dispose(); } In other words, is the object I return a copy, or is it the object itself? Thanks :)

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• Bing Map on Windows Phone - add click events to pushpins; display more details

  - by Will Gill

  I have a WP Phone app using a Bing Map control. I have an array of objects, and each object has a location. I iterate the array to place the pins on the map (see below). I have a touch event bound to each pin to allow the user to tap the pin to start an action. Now - I would like, on tap, to show information from the object that relates to that pin to be shown in a textbox. How can I retrieve the object from the array that corresponds to the pushpin that was tapped/clicked? foreach (wikiResult result in arrayResults) { double lat = double.Parse(result.Latitude, CultureInfo.InvariantCulture); double lng = double.Parse(result.Longitude, CultureInfo.InvariantCulture); statusTextBlock.Text = result.Latitude + " " + result.Longitude + " " + lat + " " + lng; GeoCoordinate d = new GeoCoordinate(lat, lng); Pushpin pin; pin = new Pushpin(); pin.Location = d; pin.Content = result.Name; pin.MouseLeftButtonUp += new MouseButtonEventHandler(pin1_MouseLeftButtonUp); myMap.Children.Add(pin); } void pin1_MouseLeftButtonUp(object sender, MouseButtonEventArgs e) { //display the content from the object in a text box } Many thanks in advance!

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• Case Insensitive Ternary Search Tree

  - by Yan Cheng CHEOK

  I had been using Ternary Search Tree for a while, as the data structure to implement a auto complete drop down combo box. Which means, when user type "fo", the drop down combo box will display foo food football The problem is, my current used of Ternary Search Tree is case sensitive. My implementation is as follow. It had been used by real world for around 1++ yeas. Hence, I consider it as quite reliable. My Ternary Search Tree code However, I am looking for a case insensitive Ternary Search Tree, which means, when I type "fo", the drop down combo box will show me foO Food fooTBall Here are some key interface for TST, where I hope the new case insentive TST may have similar interface too. /** * Stores value in the TernarySearchTree. The value may be retrieved using key. * @param key A string that indexes the object to be stored. * @param value The object to be stored in the tree. */ public void put(String key, E value) { getOrCreateNode(key).data = value; } /** * Retrieve the object indexed by key. * @param key A String index. * @return Object The object retrieved from the TernarySearchTree. */ public E get(String key) { TSTNode<E> node = getNode(key); if(node==null) return null; return node.data; } An example of usage is as follow. TSTSearchEngine is using TernarySearchTree as the core backbone. Example usage of Ternary Search Tree // There is stock named microsoft and MICROChip inside stocks ArrayList. TSTSearchEngine<Stock> engine = TSTSearchEngine<Stock>(stocks); // I wish it would return microsoft and MICROCHIP. Currently, it just return microsoft. List<Stock> results = engine.searchAll("micro");

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• Hos to group the complex list objects by using Linq

  - by Daoming Yang

  I want to select and group the products, and rank them by the number of times they occur. For example, I have an OrderList each of order object has a OrderProductVariantList(OrderLineList), and each of OrderProductVariant object has ProductVariant, and then the ProductVariant object will have a Product object which contains product information. A friend helped me with the following code. It could be compiled, but it did not return any value/result. I used the watch window for the query and it gave me "The name 'query' does not exist in the current context". Can anyone help me? Many thanks. var query = orderList.SelectMany( o => o.OrderLineList ) // results in IEnumerable<OrderProductVariant> .Select( opv => opv.ProductVariant ) .Select( pv => p.Product ) .GroupBy( p => p ) .Select( g => new { Product = g.Key, Count = g.Count() });

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• Using properties in web.xml

  - by Pich

  Hi, I would like to control the settings in web.xml and using different once for different environments. Is it possible to use a property, from a property file on classpath, in web.xml? Something like this: <context-param> <param-name>myparam</param-name> <param-value>classpath:mypropertyfile.properties['myproperty']</param-value> </context-param> Best regards P

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• LINQ to SQL: On load processing of lazy loaded associations

  - by Matt Holmes

  If I have an object that lazy loads an association with very large objects, is there a way I can do processing at the time the lazy load occurs? I thought I could use AssociateWith or LoadWith from DataLoadOptions, but there are very, very specific restrictions on what you can do in those. Basically I need to be notified when an EntitySet< decides it's time to load the associated object, so I can catch that event and do some processing on the loaded object. I don't want to simply walk through the EntitySet when I load the parent object, because that will force all the lazy loaded items to load (defeating the purpose of lazy loading entirely).

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• Linq to Sql get SqlCommand when stored procedure execution fails

  - by Tim Mahy

  Hi all, currently I'm assigning a TextWriter to the Log property of my Linq to Sql data context (per request instancing) and write this to my logging when an exception is thrown while executing a stored procedure (is strongly typed mapped in the context, so not executing a custom command) however when using ADO.NET we normally inspect the SqlCommand upon unhandled exception to read out the parameters and log them is it possible to access the SqlCommand that was used for executing a Stored Procedure in L2S so we can reuse that existing logging component? This would be far nicer than the current Log TextWriter solution.... greetings, Tim

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• Findbugs warning: Equals method should not assume anything about the type of its argument

  - by Uri

  When running FindBugs on my project, I got a few instances of the error described above. Namely, my overriding versions of equals cast the RHS object into the same type as the object in which the overriding version is defined. However, I'm not sure whether a better design is possible, since AFAIK Java does not allow variance in method parameters, so it is not possible to define any other type for the equals parameter. Am I doing something very wrong, or is FindBugs too eager? A different way to phrase this question is: what is the correct behavior if the object passed to equals is not the same type as an LHS: Is this a false, or should there be an exception? For example: public boolean equals(Object rhs) { MyType rhsMyType = (MyType)rhs; // Should throw exception if(this.field1().equals(rhsMyType.field1())... // Or whatever }

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• Recycle Freed Objects

  - by uray

  suppose I need to allocate and delete object on heap frequently (of arbitrary size), is there any performance benefit if instead of deleting those objects, I will return it back to some "pool" to be reused later? would it give benefit by reduce heap allocation/deallocation?, or it will be slower compared to memory allocator performance, since the "pool" need to manage a dynamic collection of pointers. my use case: suppose I create a queue container based on linked list, and each node of that list are allocated on the heap, so every call to push() and pop() will allocate and deallocate that node: ` template <typename T> struct QueueNode { QueueNode<T>* next; T object; } template <typename T> class Queue { void push(T object) { QueueNode<T>* newNode = QueueNodePool<T>::get(); //get recycled node if(!newNode) { newNode = new QueueNode<T>(object); } // push newNode routine here.. } T pop() { //pop routine here... QueueNodePool<T>::store(unusedNode); //recycle node return unusedNode->object; } } `

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• Copy constructor with more than one parameter

  - by Ravi Gupta

  I am learning C++ and was reading copy constructor from the C++: The Complete Reference. The books says that It is permissible for a copy constructor to have additional parameters as long as they have default arguments defined for them. However, in all cases the first parameter must be a reference to the object doing the initializing. But I am confused that how we are going to pass those additional parameters? I am sure there should be some way which is not given in the book and which I am unable to figure out. Can anyone help me out? EDIT: Also is it possible to pass these extra parameters in all three cases i.e. ¦ When one object explicitly initializes another, such as in a declaration ¦ When a copy of an object is made to be passed to a function ¦ When a temporary object is generated (most commonly, as a return value)

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