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  • Undo/Redo using Memento: Stack, Queue or just LinkedList?

    - by serhio
    What is the best having when implementing Memento pattern (for Undo/Redo) in witch collection to Keep Mementos? Basically, I need this(c = change, u = undo, r = redo): 0 *c -1 0 *c -2 -1 0 *c -3 -2 -1 0 <u -2 -1 0 1 *c -3 -2 -1 0 Variants: LinkedList - possible in principle, maybe not optimized. Queue - not adapted for this task, IMO. Stack - not adapted for undo AND redo; Double Stack - maybe optimal, but can't control the undo maximum size.

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  • Java - Calling all methods of a class

    - by Thomas Eschemann
    I'm currently working on an application that has to render several Freemarker templates. So far I have a Generator class that handles the rendering. The class looks more or less like this: public class Generator { public static void generate(…) { renderTemplate1(); renderTemplate2(); renderTemplate3(); } private static void render(…) { // renders the template } private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; private static void renderTemplate1() { // Create config object for the rendering // and calls render(); }; … } This works, but it doesn't really feel right. What I would like to do is create a class that holds all the renderTemplate...() methods and then call them dynamically from my Generator class. This would make it cleaner and easier to extend. I was thinking about using something like reflection, but it doesn't really feel like a good solution either. Any idea on how to implement this properly ?

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  • Is the a pattern for iterating over lists held by a class (dynamicly typed OO languages)

    - by Roman A. Taycher
    If I have a class that holds one or several lists is it better to allow other classes to fetch those lists(with a getter) or to implement a doXList/eachXList type method for that list that take a function and call that function on each element of the list contained by that object. I wrote a program that did a ton of this and I hated passing around all these lists sometimes with method in class a calling method in class B to return lists contained in class C, B contains a C or multiple C's (note question is about dynamically typed OO languages languages like ruby or smalltalk) ex. (that came up in my program) on a Person class containing scheduling preferences and a scheduler class needing to access them.

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  • Process for beginning a Ruby on Rails project

    - by Daniel Beardsley
    I'm about to begin a Ruby on Rails project and I'd love to hear how others go through the process of starting an application design. I have quite a bit of experience with RoR, but don't have that many starting from scratch with only a vision experiences and would appreciate the wisdom of others who've been there. I'm looking for an order of events, reasons for the order, and maybe why each part is important. I can think of a few starting points, but I'm not sure where it's best to begin Model design and relationships (entities, how they relate, and their attributes) Think of user use-cases (or story-boards) and implement the minimum to get these done Create Model unit-tests then create the necessary migrations and AR models to get the tests to pass Hack out the most basic version of the simplest part of your application and go from there Start with a template for a rails app (like http://github.com/thoughtbot/suspenders) Do the boring gruntwork first (User auth, session management, ...) ...

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  • Explain "Leader/Follower" Pattern

    - by Alex B
    I can't seem to find a good explanation of "Leader/Follower" pattern. All explanations either simply refer to it in the context of some problem, or are completely meaningless. Can anyone explain to the the mechanics of how this pattern works, and why and how it improves performance over more traditional asynchronous IO models? Examples and links to diagrams are appreciated too.

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  • .Net - Whats the difference between a Session Facade and Business Delegate?

    - by KP65
    What I understand so far: Business Delegate - In the presentation tier, as an ASP component, provides an interface for ASP views to access business components without exposing their API, therefore reducing coupling between the two. Session Facade - In the business tier, as a com+ component, encapsulates business objects, provides a course grain interface for views to access business components. Reduces coupling, hides complex business component interaction from views. So what is the actual difference? They seem pretty similar to me..

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  • WPF binding to a boolean on a control

    - by Jose
    I'm wondering if someone has a simple succinct solution to binding to a dependency property that needs to be the converse of the property. Here's an example I have a textbox that is disabled based on a property in the datacontext e.g.: <TextBox IsEnabled={Binding CanEdit} Text={Binding MyText}/> The requirement changes and I want to make it ReadOnly instead of disabled, so without changing my ViewModel I could do this: In the UserControl resources: <UserControl.Resources> <m:NotConverter x:Key="NotConverter"/> </UserControl.Resources> And then change the TextBox to: <TextBox IsReadOnly={Binding CanEdit,Converter={StaticResource NotConverter}} Text={Binding MyText}/> Which I personally think is EXTREMELY verbose I would love to be able to just do this(notice the !): <TextBox IsReadOnly={Binding !CanEdit} Text={Binding MyText}/> But alas, that is not an option that I know of. I can think of two options. Create an attached property IsNotReadOnly to FrameworkElement(?) and bind to that property If I change my ViewModel then I could add a property CanEdit and another CannotEdit which I would be kind of embarrassed of because I believe it adds an irrelevant property to a class, which I don't think is a good practice. The main reason for the question is that in my project the above isn't just for one control, so trying to keep my project as DRY as possible and readable I am throwing this out to anyone feeling my pain and has come up with a solution :)

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  • Managing libraries and imports in a programming language

    - by sub
    I've created an interpreter for a stupid programming language in C++ and the whole core structure is finished (Tokenizer, Parser, Interpreter including Symbol tables, core functions, etc.). Now I have a problem with creating and managing the function libraries for this interpreter (I'll explain what I mean with that later) So currently my core function handler is horrible: // Simplified version myLangResult SystemFunction( name, argc, argv ) { if ( name == "print" ) { if( argc < 1 ) { Error('blah'); } cout << argv[ 0 ]; } else if ( name == "input" ) { if( argc < 1 ) { Error('blah'); } string res; getline( cin, res ); SetVariable( argv[ 0 ], res ); } else if ( name == "exit ) { exit( 0 ); } And now think of each else if being 10 times more complicated and there being 25 more system functions. Unmaintainable, feels horrible, is horrible. So I thought: How to create some sort of libraries that contain all the functions and if they are imported initialize themselves and add their functions to the symbol table of the running interpreter. However this is the point where I don't really know how to go on. What I wanted to achieve is that there is e.g.: an (extern?) string library for my language, e.g.: string, and it is imported from within a program in that language, example: import string myString = "abcde" print string.at( myString, 2 ) # output: c My problems: How to separate the function libs from the core interpreter and load them? How to get all their functions into a list and add it to the symbol table when needed? What I was thinking to do: At the start of the interpreter, as all libraries are compiled with it, every single function calls something like RegisterFunction( string namespace, myLangResult (*functionPtr) ); which adds itself to a list. When import X is then called from within the language, the list built with RegisterFunction is then added to the symbol table. Disadvantages that spring to mind: All libraries are directly in the interpreter core, size grows and it will definitely slow it down.

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  • Free/open source code editor UI control for .Net

    - by Daniel I-S
    I'm looking for a free, syntax-highlighting, possibly autocompleting 'code editor's textbox' style control for use in a Visual Studio winforms or wpf project. It should work with C# and self-defined languages. There are pay-for solutions available - something like http://www.syncfusion.com/products/user-interface-edition/windows-forms/Edit would work fine - but I am looking for something simpler, and don't need to pay for unnecessary functionality. Any ideas?

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  • How many variables is to many when storing in _SESSION?

    - by steve
    Hi - I'm looking for an idea of best practices here. I have a web based application that has a number of hooks into other systems. Let's say 5, and each of these 5 systems has a number of flags to determine different settings the user has selected in said systems, lets say 5 settings per system (so 5*5). I am storing the status of these settings in the user sesion variables and was wondering is that a sufficient way of doing it? I'm learning php as I go along so not sure about any pitfalls that this could run me into!

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  • When are global variables acceptable?

    - by dsimcha
    Everyone here seems to hate global variables, but I see at least one very reasonable use for them: They are great for holding program parameters that are determined at program initialization and not modified afterwords. Do you agree that this is an exception to the "globals are evil" rule? Is there any other exception that you can think of, besides in quick and dirty throwaway code where basically anything goes? If not, why are globals so fundamentally evil that you do not believe that there are any exceptons?

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  • Should I create protected constructor for my singleton classes?

    - by Vijay Shanker
    By design, in Singleton pattern the constructor should be marked private and provide a creational method retuning the private static member of the same type instance. I have created my singleton classes like this only. public class SingletonPattern {// singleton class private static SingletonPattern pattern = new SingletonPattern(); private SingletonPattern() { } public static SingletonPattern getInstance() { return pattern; } } Now, I have got to extend a singleton class to add new behaviors. But the private constructor is not letting be define the child class. I was thinking to change the default constructor to protected constructor for the singleton base class. What can be problems, if I define my constructors to be protected? Looking for expert views....

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  • Best practices for displaying large number of images as thumbnails in c#

    - by andySF
    I got to a point where it's very difficult to get answers by debugging and tracing object, so i need some help. What I'm trying to do: A history form for my screen capture pet project. The history must list all images as thumbnails (ex: picasa). What I've done: I created a HistoryItem:UserControl. This history item has a few buttons, a check box, a label and a picture box. The buttons are for delete/edit/copy image. The check box is used for selecting one or more images and the label is for some info text. The picture box is getting the image from a public property that is a path and a method creates a proportional thumbnail to display it when the control has been loaded. This user control has two public events. One for deleting the image and one for bubbling the events for mouse enter and mouse leave trough all controls. For this I use EventBroadcastProvider. The bubbling is useful because wherever I move the mouse over the control, the buttons appear. The dispose method has been extended and I manually remove the events. All images are loaded by looping a xml file that contains the path of all images. For each image in this XML I create a new HitoryItem that is added (after a little coding to sort and limit the amount of images loaded) to a flow layout panel. The problem: When I lunch the history form, and the flow layout panel is populated with my HistoryItem custom control, my memory usage increases drastically.From 14Mb to around 100MB with 100 images loaded. By closing the history form and disposing whatever I could dispose and even trying to call GC.Collect() the memory increase remain. I search for any object that could not be disposed properly like an image or event but wherever I used them they are disposed. The problem seams to be from multiple sources. One is that the events for bubbling are not disposing properly, and the other is from the picture box itself. All of this i could see by commenting all the code to a limited version when only the custom control without any image processing and even events is loaded. Without the events the memory consumption is reduced by axiomatically 20%. So my real question is if this logic, flow layout panels and custom controls with picture boxes, is the best solution for displaying large amounts of images as thumbnails. Thank you!

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  • Design pattern for extending Android's activities?

    - by Carl
    While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

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  • Design pattern to integrate Rails with a Comet server

    - by empire29
    I have a Ruby on Rails (2.3.5) application and an APE (Ajax Push Engine) server. When records are created within the Rails application, i need to push the new record out on applicable channels to the APE server. Records can be created in the rails app by the traditional path through the controller's create action, or it can be created by several event machines that are constantly monitoring various inputstream and creating records when they see data that meets a certain criteria. It seems to me that the best/right place to put the code that pushes the data out to the APE server (which in turn pushes it out to the clients) is in the Model's after_create hook (since not all record creations will flow through the controller's create action). The final caveat is I want to push a piece of formatted HTML out to the APE server (rather than a JSON representation of the data). The reason I want to do this is 1) I already have logic to produce the desired layout in existing partials 2) I don't want to create a javascript implementation of the partials (javascript that takes a JSON object and creates all the HTML around it for presentation). This would quickly become a maintenance nightmare. The problem with this is it would require "rendering" partials from within the Model (which im having trouble doing anyhow because they don't seem to have access to Helpers when they're rendered in this manner). Anyhow - Just wondering what the right way to go about organizing all of this is. Thanks

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  • Regarding the ViewModel

    - by mizipzor
    Im struggling to understand the ViewModel part of the MVVM pattern. My current approach is to have a class, with no logic whatsoever (important), except that it implements INotifyPropertyChanged. The class is just a collection of properties, a struct if you like, describing an as small part of the data as possible. I consider this my Model. Most of the WPF code I write are settings dialogs that configure said Model. The code-behind of the dialog exposes a property which returns an instance of the Model. In the XAML code I bind to subproperties of that property, thereby binding directly to the Model's properties. Which works quite well since it implements the INotifyPropertyChanged. I consider this settings dialog the View. However, I havent really been able to figure out what in all this is the ViewModel. The articles Ive read suggests that the ViewModel should tie the View and the Model together, providing the logic the Model lacks but is still to complex to go directly into the View. Is this correct? Would, in my example, the code-behind of the settings dialog be considered the ViewModel? I just feel a bit lost and would like my peers to debunk some of my assumptions. Am I completely off track here?

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  • DI with disposable objects

    - by sunnychaganty
    Suppose my repository class looks like this: class myRepository : IDisposable{ private DataContext _context; public myRepository(DataContext context){ _context = context; } public void Dispose(){ // to do: implement dispose of DataContext } } now, I am using Unity to control the lifetime of my repository & the data context & configured the lifetimes as: DataContext - singleton myRepository - create a new instance each time Does this mean that I should not be implementing the IDisposable on the repository to clean up the DataContext? Any guidance on such items?

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  • how to use TinyMCE(rich text editor) in google-maps info window..

    - by zjm1126
    this is the demo rar file:http://omploader.org/vM3U1bA when i drag the red block to the google-maps ,it will be changed to a marker, and it will has TinyMCE when you click the info window, but my program is : it can not be written when i click it the second time, the first time: the second time(can not be written): and my code is : <!DOCTYPE html PUBLIC "-//WAPFORUM//DTD XHTML Mobile 1.0//EN" "http://www.wapforum.org/DTD/xhtml-mobile10.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <meta name="viewport" content="width=device-width,minimum-scale=0.3,maximum-scale=5.0,user-scalable=yes"> </head> <body onload="initialize()" onunload="GUnload()"> <style type="text/css"> *{ margin:0; padding:0; } </style> <!--<div style="width:100px;height:100px;background:blue;"> </div>--> <div id="map_canvas" style="width: 500px; height: 300px;"></div> <div class=b style="width: 20px; height: 20px;background:red;position:absolute;left:700px;top:200px;"></div> <div class=b style="width: 20px; height: 20px;background:red;position:absolute;left:700px;top:200px;"></div> <script src="jquery-1.4.2.js" type="text/javascript"></script> <script type="text/javascript" src="tiny_mce.js"></script> <script src="jquery-ui-1.8rc3.custom.min.js" type="text/javascript"></script> <script src="http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAA-7cuV3vqp7w6zUNiN_F4uBRi_j0U6kJrkFvY4-OX2XYmEAa76BSNz0ifabgugotzJgrxyodPDmheRA&sensor=false"type="text/javascript"></script> <script type="text/javascript"> var aFn; //********** function initialize() { if (GBrowserIsCompatible()) { var map = new GMap2(document.getElementById("map_canvas")); var center=new GLatLng(39.9493, 116.3975); map.setCenter(center, 13); aFn=function(x,y){ var point =new GPoint(x,y) point = map.fromContainerPixelToLatLng(point); //console.log(point.x+" "+point.y) var marker = new GMarker(point,{draggable:true}); var a=$( '<form method="post" action="" style="height:100px;overflow:hidden;width:220px;">'+ '<textarea id="" class="mce" name="content" cols="22" rows="5" style="border:none">sss</textarea>'+ '</form>') a.click(function(){ // }) GEvent.addListener(marker, "click", function() { marker.openInfoWindowHtml(a[0]); }); /****************** GEvent.addListener(marker, 'click', function() { marker.openInfoWindowHtml('<div contentEditable="true" ' + 'style="height: 100px; overflow: auto;">' + 'wwww</div>'); }); ***************/ map.addOverlay(marker); /********** var marker = new GMarker(point, {draggable: true}); GEvent.addListener(marker, "dragstart", function() { map.closeInfoWindow(); }); GEvent.addListener(marker, "dragend", function() { marker.openInfoWindowHtml("????..."); }); map.addOverlay(marker); //*/ } $(".b").draggable({ revert: true, revertDuration: 0 }); $("#map_canvas").droppable({ drop: function(event,ui) { //console.log(ui.offset.left+' '+ui.offset.top) aFn(event.pageX-$("#map_canvas").offset().left,event.pageY-$("#map_canvas").offset().top); } }); } } //********** $(".mce").live("click", function(){ var once=0; mce(); }); function mce(once){ if(once)return; tinyMCE.init({ // General options mode : "textareas", theme : "advanced", plugins : "safari,pagebreak,style,layer,table,save,advhr,advimage,advlink,emotions,iespell,inlinepopups,insertdatetime,preview,media,searchreplace,print,contextmenu,paste,directionality,fullscreen,noneditable,visualchars,nonbreaking,xhtmlxtras,template", // Theme options theme_advanced_buttons1 : "bold,forecolor,|,justifyleft,justifycenter,justifyright,|,fontsizeselect", theme_advanced_buttons2 : "", theme_advanced_buttons3 : "", theme_advanced_buttons4 : "", theme_advanced_toolbar_location : "top", theme_advanced_toolbar_align : "left", theme_advanced_statusbar_location : "bottom", theme_advanced_resizing : true, // Example content CSS (should be your site CSS) content_css : "css/example.css", // Drop lists for link/image/media/template dialogs template_external_list_url : "js/template_list.js", external_link_list_url : "js/link_list.js", external_image_list_url : "js/image_list.js", media_external_list_url : "js/media_list.js", // Replace values for the template plugin template_replace_values : { username : "Some User", staffid : "991234" } }); once=1; } //********** </script> </body> </html>

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  • anti-if campaign

    - by Andrew Siemer
    I recently ran against a very interesting site that expresses a very interesting idea - the anti-if campaign. You can see this here at www.antiifcampaign.com. I have to agree that complex nested IF statements are an absolute pain in the rear. I am currently on a project that up until very recently had some crazy nested IFs that scrolled to the right for quite a ways. We cured our issues in two ways - we used Windows Workflow Foundation to address routing (or workflow) concerns. And we are in the process of implementing all of our business rules utilizing ILOG Rules for .NET (recently purchased by IBM!!). This for the most part has cured our nested IF pains...but I find myself wondering how many people cure their pains in the manner that the good folks at the AntiIfCampaign suggest (see an example here) by creating numerous amounts of abstract classes to represent a given scenario that was originally covered by the nested IF. I wonder if another way to address the removal of this complexity might also be in using an IoC container such as StructureMap to move in and out of different bits of functionality. Either way... Question: Given a scenario where I have a nested complex IF or SWITCH statement that is used to evaluate a given type of thing (say evaluating an Enum) to determine how I want to handle the processing of that thing by enum type - what are some ways to do the same form of processing without using the IF or SWITCH hierarchical structure? public enum WidgetTypes { Type1, Type2, Type3, Type4 } ... WidgetTypes _myType = WidgetTypes.Type1; ... switch(_myType) { case WidgetTypes.Type1: //do something break; case WidgetTypes.Type2: //do something break; //etc... }

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  • Make a Method of the Business Layer secure. best practice / best pattern [.net/c#]

    - by gsharp
    Hi We are using ASP.NET with a lot of AJAX "Page Method" calls. The WebServices defined in the Page invokes methods from our BusinessLayer. To prevent hackers to call the Page Methods, we want to implement some security in the BusinessLayer. We are struggling with two different issues. First one: public List<Employees> GetAllEmployees() { // do stuff } This Method should be called by Authorized Users with the Role "HR". Second one: public Order GetMyOrder(int orderId) { // do sutff } This Method should only be called by the owner of the Order. I know it's easy to implement the security for each method like: public List<Employees> GetAllEmployees() { // check if the user is in Role HR } or public Order GetMyOrder(int orderId) { // check if the order.Owner = user } What I'm looking for is some pattern/best practice to implement this kind of security in a generic way (without coding the the if then else every time) I hope you get what i mean :-) Thanks for you help.

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  • What design pattern to use for one big method calling many private methods

    - by Jeune
    I have a class that has a big method that calls on a lot of private methods. I think I want to extract those private methods into their own classes for one because they contain business logic and I think they should be public so they can be unit tested. Here's a sample of the code: public void handleRow(Object arg0) { if (continueRunning){ hashData=(HashMap<String, Object>)arg0; Long stdReportId = null; Date effDate=null; if (stdReportIds!=null){ stdReportId = stdReportIds[index]; } if (effDates!=null){ effDate = effDates[index]; } initAndPutPriceBrackets(hashData, stdReportId, effDate); putBrand(hashData,stdReportId,formHandlerFor==0?true:useLiveForFirst); putMultiLangDescriptions(hashData,stdReportId); index++; if (stdReportIds!=null && stdReportIds[0].equals(stdReportIds[1])){ continueRunning=false; } if (formHandlerFor==REPORTS){ putBeginDate(hashData,effDate,custId); } //handle logic that is related to pricemaps. lstOfData.add(hashData); } } What design pattern should I apply to this problem?

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  • Exploring the Factory Design Pattern

    - by asksuperuser
    There was an article here: http://msdn.microsoft.com/en-us/library/Ee817667%28pandp.10%29.aspx The first part of tut implemented this pattern with abstract classes. The second part shows an example with Interface class. But nothing in this article discusses why this pattern would rather use abstract or interface. So what explanation (advantages of one over the other) would you give ? Not in general but for this precise pattern.

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  • SharePoint Web Part on Masterpage not displaying on SubSite

    - by madatanic
    Hi all, Scenario: - A out-of-the-box DataFormWebPart on masterpage connected to a top-level site List. - A subsite using that same masterpage from top-level site. - Error happens when accessing the sub site as below Stack Trace [InvalidOperationException: Operation is not valid due to the current state of the object.] Microsoft.SharePoint.SPFolder.get_ContentTypeOrder() +488 Microsoft.SharePoint.SPContext.get_ContentTypes() +898 Microsoft.SharePoint.SPContext.get_ContentType() +472 Microsoft.SharePoint.SPContext.get_Fields() +271 Microsoft.SharePoint.WebControls.FormComponent.get_Fields() +44 Microsoft.SharePoint.WebControls.FieldMetadata.get_Field() +419 Microsoft.SharePoint.WebControls.FormField.CreateChildControls() +596 System.Web.UI.Control.EnsureChildControls() +87 Microsoft.SharePoint.WebControls.BaseFieldControl.OnLoad(EventArgs e) +176 System.Web.UI.Control.LoadRecursive() +50 System.Web.UI.Control.LoadRecursive() +141 System.Web.UI.Control.AddedControl(Control control, Int32 index) +265 System.Web.UI.ControlCollection.Add(Control child) +80 System.Web.UI.Control.AddParsedSubObject(Object obj) +41 Microsoft.SharePoint.WebPartPages.WebPart.AddParsedSubObject(Object obj) +1149 Microsoft.SharePoint.WebPartPages.DataFormWebPart.CreateChildControls() +1267 System.Web.UI.Control.EnsureChildControls() +87 System.Web.UI.Control.PreRenderRecursiveInternal() +44 System.Web.UI.WebControls.WebParts.WebPart.PreRenderRecursiveInternal() +42 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842 I have tried the solution from this site to enable the subsite to access top level site list. Is this a bug? Any help would be appreciated.

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