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  • what is the Best way to learn object oriented principles

    - by Mike
    I am interesed in OOP principles and i found lots of documentations and books about it, for instance in C++, Java, .NET, PHP and so on, but if i only want to learn OOP principle, differences and not in language, what can i do? i want a good documentation, not just like a whole book about something except OOP :) specific answers, how it works, main features, pictures, or videos, or forum, or even stack... in every time I began studying i read a whole history of programming, computer science, software development and bla bla... i need specific answers, if it is possible i really need to learn, i need examples and exercises thanks in advance

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  • Simple moving object jitters every couple of seconds [on hold]

    - by Liam
    I'm trying to get smooth movement in my game, right now every couple of seconds the moving square jitters. I'm using C++ with SDL2. I made a very simple project to test different methods so all that's happening is a box moves across the screen. Here's a pastebin of the code http://pastebin.com/7YxxSw0D Here's a link to a dropbox folder containing the 'game' https://www.dropbox.com/sh/0ygntl140qv8iv0/AABVuuk6khArOJmdBi1OaFlua?dl=0 Any input would be greatly appreciated, and let me know if you need any more info. Thanks!

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  • Question on methods in Object Oriented Programming

    - by mal
    I’m learning Java at the minute (first language), and as a project I’m looking at developing a simple puzzle game. My question relates to the methods within a class. I have my Block type class; it has its many attributes, set methods, get methods and just plain methods. There are quite a few. Then I have my main board class. At the moment it does most of the logic, positioning of sprites collision detection and then draws the sprites etc... As I am learning to program as much as I’m learning to program games I’m curious to know how much code is typically acceptable within a given method. Is there such thing as having too many methods? All my draw functionality happens in one method, should I break this into a few ‘sub’ methods? My thinking is if I find at a later stage that the for loop I’m using to cycle through the array of sprites searching for collisions in the spriteCollision() method is inefficient I code a new method and just replace the old method calls with the new one, leaving the old code intact. Is it bad practice to have a method that contains one if statement, and place the call for that method in the for loop? I’m very much in the early stages of coding/designing and I need all the help I can get! I find it a little intimidating when people are talking about throwing together a prototype in a day too! Can’t wait until I’m that good!

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  • asp.net MVC ActionMethod causing null exception on parameter

    - by David Liddle
    I am trying to add filter functionality that sends a GET request to the same page to filter records in my table. The problem I am having is that the textbox complains about null object reference when a parameter is not passed. For example, when the person first views the page the url is '/mycontroller/myaction/'. Then when they apply a filter and submit the form it should be something like 'mycontroller/myaction?name=...' Obviously the problem stems from when the name value has not been passed (null) it is still trying to be bound to the 'name' textbox. Any suggestions on what I should do regarding this problem? UPDATE I have tried setting the DefaultValue attribute but I am assuming this is only for route values and not query string values ActionResult MyAction([DefaultValue("")] string name) //Action - /mycontroler/myaction ActionResult MyAction(string name) { ...do stuff } //View <div id="filter"> <% Html.BeginForm("myaction", "mycontroller", FormMethod.Get); %> Name: <%= Html.TextBox("name") %> .... </div> <table>...my list of filtered data

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  • SugarmCRM REST API always returns "null"

    - by TuomasR
    I'm trying to test out the SugarCRM REST API, running latest version of CE (6.0.1). It seems that whenever I do a query, the API returns "null", nothing else. If I omit the parameters, then the API returns the API description (which the documentation says it should). I'm trying to perform a login, passing as parameter the method (login), input_type and response_type (json) and rest_data (JSON encoded parameters). The following code does the query: $api_target = "http://example.com/sugarcrm/service/v2/rest.php"; $parameters = json_encode(array( "user_auth" => array( "user_name" => "admin", "password" => md5("adminpassword"), ), "application_name" => "Test", "name_value_list" => array(), )); $postData = http_build_query(array( "method" => "login", "input_type" => "json", "response_type" => "json", "rest_data" => $parameters )); echo $parameters . "\n"; echo $postData . "\n"; echo file_get_contents($api_target, false, stream_context_create(array( "http" => array( "method" => "POST", "header" => "Content-Type: application/x-www-form-urlencoded\r\n", "content" => $postData ) ))) . "\n"; I've tried different variations of parameters and using username instead of user_name, and all provide the same result, just a response "null" and that's it.

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  • Delete object[i] from table or group in corona sdk

    - by Rober Dote
    i have a problem (obviusly :P) i'm create a mini game, and when i touch a Object-A , creates an Object-B. If i touch N times, this create N Object-B. (Object-B are Bubbles in my game) so, i try when I touch the bubble (object-B), that disappears or perform any actions. I try adding Object-B to Array local t = {} . . . bur = display.newImage("burbuja.png") table.insert(t,bur) and where i have my eventListeners i wrote: for i=1, #t do bur[i]:addEventListener("tap",reventar(i)) end and my function 'reventar' local function reventar (event,id) table.remove(t,id) end i'm lost, and only i want disappears the bubbles.

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  • Get selected object from TreeView

    - by GoGoDo
    I've been working on a minor (first time) app with quickly and hit a hurdle - how do I get the selected row (the data) from a TreeView? The data to the TreeView is passed from a list of files in a directory, and I need to know which rows were selected (and thus which files were). What is the best way to do that? Here's the current code: self.treeview = self.builder.get_object("treeview") select = self.treeview.get_selection() select.connect("changed", self.on_tree_selection_changed) def on_tree_selection_changed(selection): model, treeiter = self.treeview.selection-get() if treeiter != None: print "You selected", model[treeiter][0]

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  • C# Serialization Surrogate - Cannot access a disposed object

    - by crushhawk
    I have an image class (VisionImage) that is a black box to me. I'm attempting to serialize the image object to file using Serialization Surrogates as explained on this page. Below is my surrogate code. sealed class VisionImageSerializationSurrogate : ISerializationSurrogate { public void GetObjectData(Object obj, SerializationInfo info, StreamingContext context) { VisionImage image = (VisionImage)obj; byte[,] temp = image.ImageToArray().U8; info.AddValue("width", image.Width); info.AddValue("height", image.Height); info.AddValue("pixelvalues", temp, temp.GetType()); } public Object SetObjectData(Object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector) { VisionImage image = (VisionImage)obj; Int32 width = info.GetInt32("width"); Int32 height = info.GetInt32("height"); byte[,] temp = new byte[height, width]; temp = (byte[,])info.GetValue("pixelvalues", temp.GetType()); PixelValue2D tempPixels = new PixelValue2D(temp); image.ArrayToImage(tempPixels); return image; } } I've stepped through it to write to binary. It seems to be working fine (file is getting bigger as the images are captured). I tried to test it read the file back in. The values read back in are correct as far as the "info" object is concerned. When I get to the line image.ArrayToImage(tempPixels); It throws the "Cannot access a disposed object" exception. Upon further inspection, the object and the resulting image are both marked as disposed. My code behind the form spawns an "acquisitionWorker" and runs the following code. void acquisitionWorker_LoadImages(object sender, DoWorkEventArgs e) { // This is the main function of the acquisition background worker thread. // Perform image processing here instead of the UI thread to avoid a // sluggish or unresponsive UI. BackgroundWorker worker = (BackgroundWorker)sender; try { uint bufferNumber = 0; // Loop until we tell the thread to cancel or we get an error. When this // function completes the acquisitionWorker_RunWorkerCompleted method will // be called. while (!worker.CancellationPending) { VisionImage savedImage = (VisionImage) formatter.Deserialize(fs); CommonAlgorithms.Copy(savedImage, imageViewer.Image); // Update the UI by calling ReportProgress on the background worker. // This will call the acquisition_ProgressChanged method in the UI // thread, where it is safe to update UI elements. Do not update UI // elements directly in this thread as doing so could result in a // deadlock. worker.ReportProgress(0, bufferNumber); bufferNumber++; } } catch (ImaqException ex) { // If an error occurs and the background worker thread is not being // cancelled, then pass the exception along in the result so that // it can be handled in the acquisition_RunWorkerCompleted method. if (!worker.CancellationPending) e.Result = ex; } } What am I missing here? Why would the object be immediately disposed?

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  • Multiple operations depending on the type of the object passed

    - by mixm
    Assuming I create a method which is passed an object and that method would perform an action depending on the object passed. How should I identify the object? I thought of using the class name to identify the object, but that may be impractical since I could easily change the class name of objects, and generate headaches during future development. Am I right? edit: for example, i have objects ball and bomb. if i have another object called wall, and the wall has the method to resolve collisions with the wall (e.g. the coordinates of the colliding ball and bomb) but have different logic depending on the colliding object (i.e. ball and bomb)

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  • how can I change object look point?

    - by jques
    I have tried to load image but system does not give permission. Please look image http://www.rps.net/gunslinger/scrnshot/gunslinger33.jpg I have two arm with two gun, I want to rotate these arm with mouse. For example, if I move mouse position to the left, arms with guns should be move also. Since this is hoby project, I am a bit confort to ask below question ; What should I do to achieve my wish ? some explanation: perspective view gun in viewing direction left click = trigger left gun perspective Feel free to change the title Thanks

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  • Hibernate object equality checking

    - by Sujee
    As far as I understand(correct me if I am wrong) Hibernate uses object reference to check the object equality. When Hibernate identifies that there are more than one objects attached to same DB record, it throws following exception. "a different object with the same identifier value was already associated with the session" My question is, does Hibernate use equal() method to check the object equality (The default equal method uses object reference)? If it is true, will overridden equal() method change the Hibernate behavior? Note: My question is not about the issues of implementing equal() or hashCode() methods in a Hibernate persisted object. Thank you.

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  • Declarative Data Load for Object Properties & .NET UI Controls

    This article details a new practice to prepare the .NET Business Objects using the data retrieved from the Database and binding them to .NET UI Controls dynamically using Reflection through centralized mapping between a typess Properties Vs Data-Columns Vs UI-Controls....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Object-C: initWithContentsOfURL returning null

    - by AragornSG
    Hey! I'm working on an app that would display a remote html and use local images, so what I'm trying to do is download the HTML of the website and display it as a "local" page, that would have access to images in my bundle. For some reason I can't get initWithContentsOfURL to work. I checked all manuals and examples I could find and it seems that I'm doing it correctly, but the thing just won't work, returns null all the time. The same page loaded with NSURLRequest requestWithURL works fine. Appreciate your help! Here is the code: - (void)awakeFromNib { appURL = @"http://dragontest.fantasy-fan.org"; notConnectedHTML = @"Could not connect."; NSString *seedString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:@"%@/seed.php", appURL]]]; NSString *HTMLdata = @""; if (seedString = @"(null)") { NSLog(@"Can't connect on awakeFromNib."); HTMLdata = notConnectedHTML; }else { HTMLdata = [NSString stringWithFormat:@"<body style='padding:0px;margin:0px;'>%@%@</body>", seedString, @"<br><img src='images/Default.png'>"]; } [homeView loadHTMLString:HTMLdata baseURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] resourcePath]]]; }

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  • Query Parameter Value Is Null When Enum Item 0 is Cast with Int32

    - by Timothy
    When I use the first item in a zero-based Enum cast to Int32 as a query parameter, the parameter value is null. I've worked around it by simply setting the first item to a value of 1, but I was wondering though what's really going on here? This one has me scratching my head. Why is the parameter value regarded as null, instead of 0? Enum LogEventType : int { SignIn, SignInFailure, SignOut, ... } private static DataTable QueryEventLogSession(DateTime start, DateTime stop) { DataTable entries = new DataTable(); using (FbConnection conn = new FbConnection(DSN)) { using (FbDataAdapter adapter = new FbDataAdapter( "SELECT event_type, event_timestamp, event_details FROM event_log " + "WHERE event_timestamp BETWEEN @start AND @stop " + "AND event_type IN (@signIn, @signInFailure, @signOut) " + "ORDER BY event_timestamp ASC", conn)) { adapter.SelectCommand.Parameters.AddRange(new Object[] { new FbParameter("@start", start), new FbParameter("@stop", stop), new FbParameter("@signIn", (Int32)LogEventType.SignIn), new FbParameter("@signInFailure", (Int32)LogEventType.SignInFailure), new FbParameter("@signOut", (Int32)LogEventType.SignOut)}); Trace.WriteLine(adapter.SelectCommand.CommandText); foreach (FbParameter p in adapter.SelectCommand.Parameters) { Trace.WriteLine(p.Value.ToString()); } adapter.Fill(entries); } } return entries; }

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  • Is it reasonable to null guard every single dereferenced pointer?

    - by evadeflow
    At a new job, I've been getting flagged in code reviews for code like this: PowerManager::PowerManager(IMsgSender* msgSender) : msgSender_(msgSender) { } void PowerManager::SignalShutdown() { msgSender_->sendMsg("shutdown()"); } I'm told that last method should read: void PowerManager::SignalShutdown() { if (msgSender_) { msgSender_->sendMsg("shutdown()"); } } i.e., I must put a NULL guard around the msgSender_ variable, even though it is a private data member. It's difficult for me to restrain myself from using expletives to describe how I feel about this piece of 'wisdom'. When I ask for an explanation, I get a litany of horror stories about how some junior programmer, some-year, got confused about how a class was supposed to work and accidentally deleted a member he shouldn't have (and set it to NULL afterwards, apparently), and things blew up in the field right after a product release, and we've "learned the hard way, trust us" that it's better to just NULL check everything. To me, this feels like cargo cult programming, plain and simple. A few well-meaning colleagues are earnestly trying to help me 'get it' and see how this will help me write more robust code, but... I can't help feeling like they're the ones who don't get it. Is it reasonable for a coding standard to require that every single pointer dereferenced in a function be checked for NULL first—even private data members? (Note: To give some context, we make a consumer electronics device, not an air traffic control system or some other 'failure-equals-people-die' product.) EDIT: In the above example, the msgSender_ collaborator isn't optional. If it's ever NULL, it indicates a bug. The only reason it is passed into the constructor is so PowerManager can be tested with a mock IMsgSender subclass.

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  • Getting an object from a 2d array inside of a class

    - by user36324
    I am have a class file that contains two classes, platform and platforms. platform holds the single platform information, and platforms has an 2d array of platforms. Im trying to render all of them in a for loop but it is not working. If you could kindly help me i would greatly appreciate. void Platforms::setUp() { for(int x = 0; x < tilesW; x++){ for(int y = 0; y < tilesH; y++){ Platform tempPlat(x,y,true,renderer,filename,tileSize/scaleW,tileSize/scaleH); platArray[x][y] = tempPlat; } } } void Platforms::show() { for(int x = 0; x < tilesW; x++){ for(int y = 0; y < tilesH; y++){ platArray[x][y].show(renderer,scaleW,scaleH); } } }

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  • GUnload is null or undefined using Directions Service

    - by user1677756
    I'm getting an error using Google Maps API V3 that I don't understand. My initial map displays just fine, but when I try to get directions, I get the following two errors: Error: The value of the property 'GUnload' is null or undefined, not a Function object Error: Unable to get value of the property 'setDirections': object is null or undefined I'm not using GUnload anywhere, so I don't understand why I'm getting that error. As far as the second error is concerned, it's as if something is wrong with the Directions service. Here is my code: var directionsDisplay; var directionsService = new google.maps.DirectionsService(); var map; function initialize(address) { directionsDisplay = new google.maps.DirectionsRenderer(); var geocoder = new google.maps.Geocoder(); var latlng = new google.maps.LatLng(42.733963, -84.565501); var mapOptions = { center: latlng, zoom: 15, mapTypeId: google.maps.MapTypeId.ROADMAP }; map = new google.maps.Map(document.getElementById("map_canvas"), mapOptions); geocoder.geocode({ 'address': address }, function (results, status) { if (status == google.maps.GeocoderStatus.OK) { map.setCenter(results[0].geometry.location); var marker = new google.maps.Marker({ map: map, position: results[0].geometry.location }); } else { alert("Geocode was not successful for the following reason: " + status); } }); directionsDisplay.setMap(map); } function getDirections(start, end) { var request = { origin:start, destination:end, travelMode: google.maps.TravelMode.DRIVING }; directionsService.route(request, function(result, status) { if (status == google.maps.DirectionsStatus.OK) { directionsDisplay.setDirections(result); } else { alert("Directions cannot be displayed for the following reason: " + status); } }); } I'm not very savvy with javascript, so I could have made some sort of error there. I appreciate any help I can get.

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  • Why are controls (null) in awakeFromNib?

    - by fuzzygoat
    This is a follow on from another question regarding why I could not set UIControls in awakeFromNib. The answer to that is that as you can see below the controls are nil in the awakeFromNib, although they are initialised to the correct objects by the time we get to viewDidLoad. I setup the view the same as I always do, should I be doing something different to access them here, the xib(nib) was designed and saved with the current version of Image Builder. CODE: @interface iPhone_TEST_AwakeFromNibViewController : UIViewController { UILabel *myLabel; UIImageView *myView; } @property(nonatomic, retain)IBOutlet UILabel *myLabel; @property(nonatomic, retain)IBOutlet UIImageView *myView; @end . @synthesize myLabel; @synthesize myView; -(void)awakeFromNib { NSLog(@"awakeFromNib ..."); NSLog(@"myLabel: %@", [myLabel class]); NSLog(@"myView : %@", [myView class]); //[myLabel setText:@"AWAKE"]; [super awakeFromNib]; } -(void)viewDidLoad { NSLog(@"viewDidLoad ..."); NSLog(@"myLabel: %@", [myLabel class]); NSLog(@"myView : %@", [myView class]); //[myLabel setText:@"VIEW"]; [super viewDidLoad]; } OUTPUT: awakeFromNib ... myLabel: (null) myView : (null) viewDidLoad ... myLabel: UILabel myLabel: UIImageView Much appreciated ... gary

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  • T4MVC Optional Parameter Inferred From Current Context

    - by Itakou
    I have read the other post about this at T4MVC OptionalParameter values implied from current context and I am using the latest T4MVC (2.11.1) which is suppose to have the fix in. I even checked checked to make sure that it's there -- and it is. I am still getting the optional parameters filled in based on the current context. For example: Let's say I have a list that is by default ordered by a person's last name. I have the option to order by first name instead with the URL http://localhost/list/stuff?orderby=firstname When I am in that page, I want to go back to order by first name with the code: @Html.ActionLink("order by last name", MVC.List.Stuff(null)) the link I wanted was simply http://localhost/list/stuff without any parameters to keep the URL simple and short - invoking default behaviors within the action. But instead the orderby is kept and the url is still http://localhost/list/stuff?orderby=firstname Any help would be great. I know that in the most general cases, this does remove the query parameter - maybe I do have a specific case where it was not removed. I find that it only happens when I have the URL inside a page that I included with RenderPartial. My actual code is <li>@Html.ActionLink("Recently Updated", MVC.Network.Ticket.List(Model.UI.AccountId, "LastModifiedDate", null, null, null, null, null))</li> <li>@Html.ActionLink("Recently Created", MVC.Network.Ticket.List(Model.UI.AccountId, "CreatedDate", null, null, null, null, null))</li> <li>@Html.ActionLink("Most Severe", MVC.Network.Ticket.List(Model.UI.AccountId, "MostSevere", null, null, null, null, null))</li> <li>@Html.ActionLink("Previously Closed", MVC.Network.Ticket.List(Model.UI.AccountId, "LastModifiedDate", null, "Closed", null, null, null))</li> the problem happens when someone clicks Previously Closed and and go to ?status=closed. When they click Recently Updated, which I want to the ?status so that it shows the active ones, the ?status=closed stays. Any insight would be greatly appreciated.

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

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

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  • model.matrix() with na.action=NULL?

    - by Vincent
    I have a formula and a data frame, and I want to extract the model.matrix(). However, I need the resulting matrix to include the NAs that were found in the original dataset. If I were to use model.frame() to do this, I would simply pass it na.action=NULL. However, the output I need is of the model.matrix() format. Specifically, I need only the right-hand side variables, I need the output to be a matrix (not a data frame), and I need factors to be converted to a series of dummy variables. I'm sure I could hack something together using loops or something, but I was wondering if anyone could suggest a cleaner and more efficient workaround. Thanks a lot for your time! And here's an example: dat <- data.frame(matrix(rnorm(20),5,4), gl(5,2)) dat[3,5] <- NA names(dat) <- c(letters[1:4], 'fact') ff <- a ~ b + fact # This omits the row with a missing observation on the factor model.matrix(ff, dat) # This keeps the NA, but it gives me a data frame and does not dichotomize the factor model.frame(ff, dat, na.action=NULL) Here is what I would like to obtain: (Intercept) b fact2 fact3 fact4 fact5 1 1 0.7266086 0 0 0 0 2 1 -0.6088697 0 0 0 0 3 NA 0.4643360 NA NA NA NA 4 1 -1.1666248 1 0 0 0 5 1 -0.7577394 0 1 0 0 6 1 0.7266086 0 1 0 0 7 1 -0.6088697 0 0 1 0 8 1 0.4643360 0 0 1 0 9 1 -1.1666248 0 0 0 1 10 1 -0.7577394 0 0 0 1

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  • What causes markup-controls to be null?

    - by Earlz
    Ok, I have a very strange problem. I have a regular UserControl with some controls in the markup. At Page_Load these controls are still null. And I have tried EnsureChildControls It is laid out like this: Masterpage - Page - mycontrol1 - mycontrol2 - problemcontrol ProblemControl is where the controls are null. MyControl1 contains MyControl2. MyControl2 is another UserControl which contains ProblemControl in it's markup. Masterpage is nothing special and Page contains MyControl1 in it's markup. The only oddity is that ProblemControl is created dynamically at Page_Init. Everything works fine until I get to ProblemControl where none of the controls are being created. ProblemControl has the proper things all set such as the Page and Parent property. I do not see any problems. The source code for all of these(except ProblemControl) is pretty extensive, so I'm hoping someone can just give me some troubleshooting tips for this problem and if anyone has encountered it before. Also, I can place ProblemControl on another Page control and it will work fine, it's something about mycontrol1 and/or mycontrol2. But we've never had any problems with mycontrol1 and mycontrol2 doesn't have anything I can see wrong with it. (which I've been tediously analyzing for the past few hours). Has anyone else had this same problem? Are there any common things to check for?

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