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  • Copying a Polymorphic object in C++

    - by doron
    I have base-class Base from which is derived Derived1, Derived2 and Derived3. I have constructed an instance for one of the the derived classes which I store as Base* a. I now need to make a deep copy of the object which I will store as Base* b. As far as I know, the normal way of copying a class is to use copy constructors and to overload operator=. However since I don't know whether a is of type Derived1, Derived2 or Derived3, I cannot think of a way of using either the copy constructor or operator=. The only way I can think of to cleanly make this work is to implement something like: class Base { public: virtual Base* Clone() = 0; }; and the implement Clone in in the derived class as in: class Derivedn : public Base { public: Base* Clone() { Derived1* ret = new Derived1; copy all the data members } }; Java tends to use Clone quite a bit is there more of a C++ way of doing this?

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  • Is a base class with shared fields and functions good design

    - by eych
    I've got a BaseDataClass with shared fields and functions Protected Shared dbase as SqlDatabase Protected Shared dbCommand as DBCommand ... //also have a sync object used by the derived classes for Synclock'ing Protected Shared ReadOnly syncObj As Object = New Object() Protected Shared Sub Init() //initializes fields, sets connections Protected Shared Sub CleanAll() //closes connections, disposes, etc. I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results. So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes. Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?

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  • How can I make a read only version of a class?

    - by Eric
    I have a class with various public properties which I allow users to edit through a property grid. For persistence this class is also serialized/deserialized to/from an XML file through DataContractSerializer. Sometimes I want to user to be able to save (serialize) changes they've made to an instance of the class. Yet at other times I don't want to allow the user to save their changes, and should instead see all the properties in the property grid as read only. I don't want to allow users to make changes that they'll never be able to save later. Similar to how MS Word will allow users to open documents that are currently opened by someone else but only as read only. My class has a boolean property that determines if the class should be read-only, but is it possible to use this property to somehow dynamically add a read-only attributes to the class properties at run-time? If not what is an alternative solution? Should I wrap my class in a read-only wrapper class?

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  • Scale image to completely fill bounding box

    - by Larsenal
    For instance, if I need to fill a bounding box that is 100px wide by 50px tall, the following input images would have the following behavior: 200w x 200h gets scaled down 50% and 25% gets chopped off the top and bottom. 200w x 100h gets scaled down 50% with no cropping. 100w x 200h gets is not scaled, but 75px get chopped off top and bottom. This seems like it'd be a common resizing function, but I haven't been able to track down an example of the algorithm. Will accept answer in any language including pseudo code. A link to a page with the answer is great too!

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  • Data truncation when retrieving data from MySQL database with prepared statements

    - by KSiimson
    I have a script that retrieves multiple products using prepared statements. Like putting loops into loops, I have prepared statements in prepared statements - so there is a prepared statement for retrieving all products, a prepared statement to retrieve all images for that product, a prepared statement to get all attributes for that products, and so on. This does not work with one MySQLi instance, so I use multiple MySQLi objects that are opened and closed when needed. It usually works fine, but sometimes, especially when displaying multiple products, some data is truncated. For example - MicoLoans becomes MicoLoa. There was an actual spelling mistake here - now when I changed MicoLoans to MicroLoans, the same page displayed MicroLoa... So the same number of characters was truncated from the end. It is sort of consistent where it appears - for example there can be descriptions for 8 products, and description of 1 product is heavily truncated. When I add 9th product, the short description is still truncated for that same product as before. Any ideas?

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  • Exception Error in c#

    - by Kumu
    using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Runtime.Serialization.Formatters.Binary; namespace FoolballLeague { public partial class MainMenu : Form { FootballLeagueDatabase footballLeagueDatabase; Game game; Login login; public MainMenu() { InitializeComponent(); changePanel(1); } public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn) { InitializeComponent(); footballLeagueDatabase = footballLeagueDatabaseIn; } private void Form_Loaded(object sender, EventArgs e) { } private void gameButton_Click(object sender, EventArgs e) { int option = 0; changePanel(option); } private void scoreboardButton_Click(object sender, EventArgs e) { int option = 1; changePanel(option); } private void changePanel(int optionIn) { gamePanel.Hide(); scoreboardPanel.Hide(); string title = "Football League System"; switch (optionIn) { case 0: gamePanel.Show(); this.Text = title + " - Game Menu"; break; case 1: scoreboardPanel.Show(); this.Text = title + " - Display Menu"; break; } } private void logoutButton_Click(object sender, EventArgs e) { login = new Login(); login.Show(); this.Hide(); } private void addGameButton_Click(object sender, EventArgs e) { if ((homeTeamTxt.Text.Length) == 0) MessageBox.Show("You must enter a Home Team"); else if (homeScoreUpDown.Value > 9 || homeScoreUpDown.Minimum < 0) MessageBox.Show("You must enter one digit between 0 and 9"); else if ((awayTeamTxt.Text.Length) == 0) MessageBox.Show("You must enter a Away Team"); else if (homeScoreUpDown.Value > 9 || homeScoreUpDown.Value < 0) MessageBox.Show("You must enter one digit between 0 to 9"); else { //checkGameInputFields(); game = new Game(homeTeamTxt.Text, int.Parse(homeScoreUpDown.Value.ToString()), awayTeamTxt.Text, int.Parse(awayScoreUpDown.Value.ToString())); MessageBox.Show("Home Team -" + '\t' + homeTeamTxt.Text + '\t' + "and" + '\r' + "Away Team -" + '\t' + awayTeamTxt.Text + '\t' + "created"); footballLeagueDatabase.AddGame(game); //clearCreateStudentInputFields(); } } private void timer1_Tick(object sender, EventArgs e) { displayDateAndTime(); } private void displayDateAndTime() { dateLabel.Text = DateTime.Today.ToLongDateString(); timeLabel.Text = DateTime.Now.ToShortTimeString(); } private void displayResultsButton_Click(object sender, EventArgs e) { Game game = new Game(homeTeamTxt.Text, int.Parse(homeScoreUpDown.Value.ToString()), awayTeamTxt.Text, int.Parse(awayScoreUpDown.Value.ToString())); gameResultsListView.Items.Clear(); gameResultsListView.View = View.Details; ListViewItem row = new ListViewItem(); row.SubItems.Add(game.HomeTeam.ToString()); row.SubItems.Add(game.HomeScore.ToString()); row.SubItems.Add(game.AwayTeam.ToString()); row.SubItems.Add(game.AwayScore.ToString()); gameResultsListView.Items.Add(row); } private void displayGamesButton_Click(object sender, EventArgs e) { Game game = new Game("Home", 2, "Away", 4);//homeTeamTxt.Text, int.Parse(homeScoreUpDown.Value.ToString()), awayTeamTxt.Text, int.Parse(awayScoreUpDown.Value.ToString())); modifyGamesListView.Items.Clear(); modifyGamesListView.View = View.Details; ListViewItem row = new ListViewItem(); row.SubItems.Add(game.HomeTeam.ToString()); row.SubItems.Add(game.HomeScore.ToString()); row.SubItems.Add(game.AwayTeam.ToString()); row.SubItems.Add(game.AwayScore.ToString()); modifyGamesListView.Items.Add(row); } } } This is the whole code and I got same error like previous question. Unhandled Exception has occurred in you application.If you click...............click Quit.the application will close immediately. Object reference not set to an instance of an object. And the following details are in the error message. ***** Exception Text ******* System.NullReferenceException: Object reference not set to an instance of an object. at FoolballLeague.MainMenu.addGameButton_Click(Object sender, EventArgs e) in C:\Users\achini\Desktop\FootballLeague\FootballLeague\MainMenu.cs:line 91 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) I need to add the games to using the addGameButton and the save those added games and display them in the list view (gameResultsListView). Now I can add a game and display in the list view.But when I pressed the button addGameButton I got the above error message. If you can please give me a solution to this problem.

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  • Why doesn't a LinkButton work with a table as it's content?

    - by Telos
    Using ASP.NET 3.5, you can create a LinkButton then define content inside of it. It works fine if I have div tags or any kind of text or anything, but if I use a table the click doesn't actually post back for some reason. This should take you to google (you'll get an error there but it should still go) for instance: <asp:LinkButton ID="lbTest" PostBackUrl="http://www.google.com" runat="server"> <table> <tr> <td>Test</td> <td>col2</td> <td>col3</td> </tr> </table> </asp:LinkButton> I could work around it by building a "table" with divs I guess, but I hate formatting with divs.

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  • Understanding run time code interpretation and execution

    - by Bob
    I'm creating a game in XNA and was thinking of creating my own scripting language (extremely simple mind you). I know there's better ways to go about this (and that I'm reinventing the wheel), but I want the learning experience more than to be productive and fast. When confronted with code at run time, from what I understand, the usual approach is to parse into a machine code or byte code or something else that is actually executable and then execute that, right? But, for instance, when Chrome first came out they said their JavaScript engine was fast because it compiles the JavaScript into machine code. This implies other engines weren't compiling into machine code. I'd prefer not compiling to a lower language, so are there any known modern techniques for parsing and executing code without compiling to low level? Perhaps something like parsing the code into some sort of tree, branching through the tree, and comparing each symbol and calling some function that handles that symbol? (Wild guessing and stabbing in the dark)

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  • Java Spring 3.0 MVC Annotation vs COC. Whats the preferred method in the Java community?

    - by Athens
    I am using Spring's MVC framework for an application I'm hosting on Google's App Engine. So far, my controllers are registered via the @Controller annotation; however, prior to getting into Spring, I evaluated ASP.net MVC 2 which requires no configuration and is based on convention. Is convention over configuration (COC) the current and preferred method in the Java community to implement MVC with Spring. Also, this may be a result of my limited knowledge so far but i noticed that i could only instantiate my Controllers the required constuctor injection if i use the COC method via the ControllerClassNameHandlerMapping. For instance the following controller bean config will fail if i use the defaultannotationhandlermapping. <bean id="c" class="com.domain.TestController"> <constructor-arg ref="service" /> </bean> <bean id="service" class="com.domain.Service" /> My com.domain.TestController controller works fine if i use ControllerClassNameHandlerMapping/COC but it results in an error when i use defaultannotationhandlermapping/Annotations.

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  • How do I set sys.excepthook to invoke pdb globally in python?

    - by saffsd
    From Python docs: sys.excepthook(type, value, traceback)¶ This function prints out a given traceback and exception to sys.stderr. When an exception is raised and uncaught, the interpreter calls sys.excepthook with three arguments, the exception class, exception instance, and a traceback object. In an interactive session this happens just before control is returned to the prompt; in a Python program this happens just before the program exits. The handling of such top-level exceptions can be customized by assigning another three-argument function to sys.excepthook. http://docs.python.org/library/sys.html How do I modify this globally so the default action is to always invoke pdb? Is there a configuration file I can change? I don't want to wrap my code to do this.

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  • My object becomes NSCFArray when running on iPhone

    - by cagreen
    I'm really scratching my head on this one: I have an object (MyObject) which I instantiate, and this object has an NSArray member variable. The following simple code working in the sim: MyObject *myObj = [[MyObject alloc] init]; NSArray *arr = [myObj myMemberArray]; When I hover over myObj in XCode the tooltip reads "MyObject". Good! But when I debug it on the device (OS 3.1.3) I get: "[NSCFArray myMemberArray]: unrecognized selector sent to instance ... " When I hover over myObj, sure enough it reads "NSCFArray". Can anyone give me some pointers on where to go next with this? Thanks.

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  • Retrieve part of a MySQL column with PHP

    - by Gerardo Marset
    For instance, if I have the following table: +----+---+----------+ | id | a | position | +----+---+----------+ | 0 | 0 | 0 | | 1 | 0 | 1 | | 2 | 1 | 4 | | 3 | 1 | 9 | | 4 | 1 | 6 | | 5 | 1 | 1 | +----+---+----------+ and I want to get an array that contains the first 100 values from position where a is 1 in ascending order, what would I do? Im guessing something like this: $col = mysql_fetch_array( mysql_query(' SELECT `position` FROM `table` WHERE `a`="1" ORDER BY `position` ASC LIMIT 100 ')); I'd expect to get the following array: +-------+-------+ | index | value | +-------+-------+ | 0 | 1 | | 1 | 4 | | 2 | 6 | | 3 | 9 | +-------+-------+ but it doesn't work. ¿What should I do to make it work? Thanks

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  • Android WebViewClient problem

    - by deSelby
    I've defined a private class that extends WebViewClient and set my WebView's client to an instance of that class (webView01.setWebViewClient(new Callback());). The class definition is as follows: private class Callback extends WebViewClient { public void onLoadResource (WebView view, String url) { } public void onPageStarted (WebView view, String url, Bitmap favicon) { } public void onPageFinished (WebView view, String url) { Animation anim = AnimationUtils.loadAnimation(MyNews.this, R.anim.webviewanim); view.startAnimation(anim); } public void onReceivedError (WebView view, int errorCode, String description, String failingUrl) { } public boolean shouldOverrideUrlLoading (WebView view, String url) { Log.e("loading url", url); return false; } } My problem is that onPageFinished is definitely getting called, but shouldOverrideUrlLoading is never being called. What am I doing wrong here?

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  • Memory Allocation - Arduino

    - by Joey Arnold Andres
    I'm new to this low level stuff. I'm currently learning arduino. I'm currently using an Arduino Mega 2560 and in our course we are practicing memory management. I'm a pro at memory management in pc but somehow I'm having crazy problems here in arduino. For instance: The arduino have 8192B, I'm trying to overflow it with uint_16 so I made an array of 8192/16 which is 512. so I did uint16_t A[512+1]; Well I expected that to cause an overflow. What is wrong with my concept?

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  • Zend Dd Rowset getting parent row

    - by simple
    I am wondering about using the abstraction in Zend Db RowSet instead of joins, is it possible for instance I am able to get some info from parent table as in here /** * Get default photo info (path , description) */ public function getDefaultPhotoInfo($userdId){ $select = $this->select($this) ->where('id=?', $userdId); $rowset = $this->fetchAll($select); $current = $rowset->current(); $res = $current->findParentRow('UserPhotos', 'Avatar'); if(isset($res)){ return $res->toArray(); } } How can I use Rowset abstraction to get this logic working table( id, pic_path,) table_translation(id, table_id, lang_id, pic_title); the above is representation of two tables , the idea is to get the info from both table specifying the lang_id , it is easy with joins but can I do it with the abstraction of Db Rowset ?

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  • Are concurrency issues possible when using the WCF Service Behavoir attribute set to ConcurrencyMode

    - by Brandon Linton
    We have a WCF service that makes a good deal of transactional NHibernate calls. Occasionally we were seeing SQL timeouts, even though the calls were updating different rows and the tables were set to row level locking. After digging into the logs, it looks like different threads were entering the same point in the code (our transaction using block), and an update was hanging on commit. It didn't make sense, though, because we believed that the following service class attribute was forcing a unique execution thread per service call: [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.PerCall)] We recently changed the concurrency mode to ConcurrencyMode.Single and haven't yet run into any issues, but the bug was very difficult to reproduce (if anyone has any thoughts on flushing a bug like that out, let me know!). Anyway, that all brings me to my question: shouldn't an InstanceContextMode of PerCall enforce thread-safety within the service, even if the ConcurrencyMode is set to multiple? How would it be possible for two calls to be serviced by the same service instance? Thanks!

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  • Get C# Templates For VS 2008 Shell

    - by Onorio Catenacci
    I've got VS 2008 Shell Integrated mode; I've got F# 2.0 on that installation. Till now this has worked fine for me because I've been hacking at F# code. Now though, I want to install Intellifactory's WebSharper. It looks like the Intellifactory templates assume that C# templates will be available because while it will create the F# portion of the solution it will not create the Web project in the solution with the complaint A problem was encountered creating the sub project 'Web Application'. The template specified cannot be found. Is there any place where I can get the C# stuff to add to this instance of VS 2008 Shell? Apologies in advance if this is a dup question but I've googled without much luck and I don't seem to find this here either. I've seen that about devenv /installvstemplates but that also fails with a message about needing to elevate privileges (which is odd since I try it under an admin user).

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  • gcc problem with explicit template instantiation?

    - by steve jaffe
    It is my understanding that either a declaration or typedef of a specialization ought to cause a template class to be instantiated, but this does not appear to be happening with gcc. E.g. I have a template class, template class Foo {}; I write class Foo<double>; or typedef Foo<double> DoubleFoo; but after compilation the symbol table of the resulting object file does not contain the members of Foo. If I create an instance: Foo<double> aFoo; then of course the symbols are all generated. Has anyone else experienced this and/or have an explanation?

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  • F# Interactive bug?

    - by John Reynolds
    I've tried the following code in VS2010: open System.Security.Cryptography let rsaTest1 = let ecKey = [|0uy..143uy|] // junk data for testing let ecKeyMod = ecKey.[8..8+128-1] let ecKeyExp = ecKey.[136..136+8-1] let rsa = RSAParameters(Modulus = ecKeyMod, Exponent = ecKeyExp) rsa let rsaTest2 = let ecKey = [|0uy..143uy|] // junk data for testing let rsa = RSAParameters(Modulus = ecKey.[8..8+128-1], Exponent = ecKey.[136..136+8-1]) rsa If I highlight all code and send it to F# Interactive (Alt+Enter), then rsaTest1 works, but rsaTest2 gives an error message, System.NullReferenceException: Object reference not set to an instance of an object. at <StartupCode$FSI_0004>.$FSI_0004.main@() in P:\proj\Tachograph\Project\CompuTachTest\CompuTachTest\rsaTest.fsx:line 16 However, if I change rsaTest2 from a value into a function and call it, let rsaTest2 () = let ecKey = [|0uy..143uy|] // junk data for testing let rsa = RSAParameters(Modulus = ecKey.[8..8+128-1], Exponent = ecKey.[136..136+8-1]) rsa let x = rsaTest2 () then there is no error. F# bug or my mistake?

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  • jaxb entity print out as xml

    - by Cristian Boariu
    Hi, I have a class, let's say User adnotated with @XmlRootElement, with some properties (name, surname etc). I use this class for REST operations, as application/xml. The client will POST User class so i want to keep the values in the log. Is there any method in jax-ws to prints out this object as xml? For instance: log.info("Customers sent a USER"+user.whichMethod()); Customer sent a User <user> <name>cristi</name> <surname>kevin</surname> </user> Thanks.

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  • What's a good way to create an Event Calendar

    - by iFloh
    Hi, I want to create an Event Calendar for my iPhone App. In a first instance the Event Calendar is supposed to list the Events and have a Details View with additional info. It is also supposed to contain an action to trasfer a specific event to the iPhone Calendar. First thoughts go towards using a UITableView where I make the event dates as sections. Since the Calendar is supposed to span many month I am unsure whether this really is the best way to go about it. Any suggestions? Do you probably know some sample code that I might use ? thanks in advance

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  • How to direct people to fill out a form

    - by Solmead
    What is the best way to get people to fill out a form correctly? For instance I originally had a "Name" field on a form and I want 1 person per form. People filled it out like this: "Mark & Becky Newsman". So I broke it into 2 fields, "First Name" and "Last Name", And people are still filling it out wrong, like "First Name" = "Mark & Becky", "Last Name" = "Newsman". Are there any recommendations on how better to get people to understand that only one person's name should go there? I currently have it on two lines, would it work better to put both fields on one line? If this is on the wrong site go ahead and move it to the correct site.

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  • Configuring DSVL to show camera images from Logitech9000 webcam

    - by curryage
    I am trying to view camera feed from a Logitech9000 camera using DSVL(DirectShow Video Library) http://sourceforge.net/projects/dsvideolib/. The xml file currently looks as below: <?xml version="1.0" encoding="UTF-8"?> <dsvl_input xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="C:\Documents and Settings\Thomas\My Documents\projects\ARToolKit &amp; DSVideoLib\ARVideoLib\DsVideoLib\DsVideoLib.xsd"> <camera show_format_dialog="false" friendly_name="Logitech Webcam Pro 9000"> <pixel_format> <RGB24 flip_v="false"/> </pixel_format> </camera> </dsvl_input> However, the image that comes up looks vertically inverted. I tried changing the flip_v value to true in the config above but it did not make any difference. Any suggestions?

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  • Override bits of a CSS class while inline?

    - by larryq
    I have an html img that is being styled by a CSS class. I would like to override the width and height values used in that class under some circumstances. I'm building this img tag using something called a TagBuilder class, provided by Microsoft for the .Net system, which allows developers to assign attributes to an html element. In this case a CSS class has been assigned to the img tag, and I can assign width and height attributes individually, but they're not taking precedence over the values set in the CSS class. My tag looks like this currently: <img alt="my link" class="static" height="240" id="StaticImage" src="http://imageserver.com/myImage.jpg" width="240"> The static CSS class has width and height values of 300 each, and as you can see I'm trying to override them with 240. It's not working in this instance but can I do it without a second CSS class?

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  • datatable works in C# winform but not ASP.NET

    - by Charles Gargent
    Hi I have created a class that returns a datatable, when I use the class in a c# winform the dataGridView is populted corectly using the following code dataGridView1.DataSource = dbLib.GetData(); However when I try the same thing with ASP.NET I get a Object reference not set to an instance of an object. using the following code GridView1.DataSource = dbLib.GetData(); GridView1.DataBind(); What am I doing wrong / missing Thanks EDIT for the curios here is the dbLib class public static DataTable GetData() { SQLiteConnection cnn = new SQLiteConnection("Data Source=c:\\test.db"); SQLiteCommand cmd = new SQLiteCommand("SELECT count(Message) AS Occurances, Message FROM evtlog GROUP BY Message ORDER BY Occurances DESC LIMIT 25", cnn); cnn.Open(); SQLiteDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection); DataTable dt = new DataTable(); dt.Load(dr); return dt; }

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