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  • Problem with moving a winform using C#

    - by karthik
    My form doesn't have a title bar, so I am implementing the code to drag the entire form around the screen. I am using the below code to do it, which works fine. I have two panels in my form, PanelA and PanelB. During the startup I show PanelA where the dragging works perfectly. Later when the user clicks the button in PanelA, I need to make PanelA invisible and show PanelB However, the dragging does not work when PanelB is shown. What's the problem here? private void SerialPortScanner_MouseUp(object sender, MouseEventArgs e) { this.drag = false; } private void SerialPortScanner_MouseDown(object sender, MouseEventArgs e) { this.drag = true; this.start_point = new Point(e.X, e.Y); } private void SerialPortScanner_MouseMove(object sender, MouseEventArgs e) { if (this.drag) { Point p1 = new Point(e.X, e.Y); Point p2 = this.PointToScreen(p1); Point p3 = new Point(p2.X - this.start_point.X, p2.Y - this.start_point.Y); this.Location = p3; } }

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  • Link Button on asp.net user control not firing

    - by andyriome
    Hi I have a user control, which is added to another user control. The nested user control is built up of a gridview, an image button and a link button. The nested user control is added to the outer control as a collection object based upon the results bound to the gridview. The problem that I have is that my link button doesn't work. I click on it and the event doesn't fire. Even adding a break point was not reached. As the nested user control is added a number of times, I have set image button to have unique ids and also the link button. Whilst image button works correctly with its java script. The link button needs to fire an event in the code behind, but despite all my efforts, I can't make it work. I am adding the link button to the control dynamically. Below is the relevant code that I am using: public partial class ucCustomerDetails : System.Web.UI.UserControl { protected override void CreateChildControls( ) { base.CreateChildControls( ); string strUniqueID = lnkShowAllCust.UniqueID; strUniqueID = strUniqueID.Replace('$','_'); this.lnkShowAllCust.ID = strUniqueID; this.lnkShowAllCust.Click += new EventHandler(this.lnkShowAllCust_Click); this.Controls.Add(lnkShowAllCust); } protected override void OnInit (EventArgs e) { CreateChildControls( ); base.OnInit(e); } protected override void OnLoad(EventArgs e) { base.EnsureChildControls( ); } protected void Page_Load(object sender, EventArgs e) { if (IsPostBack) { CreateChildControls( ); } } protected void lnkShowAllCust_Click(object sender, EventArgs e) { this.OnCustShowAllClicked(new EventArgs ( )); } protected virtual void OnCustShowAllClicked(EventArgs args) { if (this.ViewAllClicked != null) { this.ViewAllClicked(this, args); } } public event EventHandler ViewAllClicked; } I have been stuggling with this problem for the last 3 days and have had no success with it, and I really do need some help. Can anyone please help me?

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  • Async task ASP.net HttpContext.Current.Items is empty - How do handle this?

    - by GuruC
    We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions. So I started investigating it from the dumps and event viewer. My understanding was as follows: We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values. Task<Articles>.Factory.StartNew(() => { System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context; var service = new ArticlesService(page); return service.GetArticles(); }).ContinueWith(t => SetResult(t, "articles")); So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex: public class SomeClass { internal static int StreamID { get { if (HttpContext.Current != null) { return (int)HttpContext.Current.Items["StreamID"]; } else { return DEFAULT_STREAM_ID; } } } This runs fine as long as number of parallel requests are optimal. My questions are as follows: 1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions. 2. How do we make sure it is not null ? Any workaround if present ? NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.

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  • binding image with 2 values with convertor

    - by prince23
    hi, is it possiable to set 2 data field for an image control whiling binding **<Image Source="{Binding ItemID, Converter={StaticResource IDToImageConverter}}" Height="50" />** now here i need to add one more value Price now. need to send even price as an paramter for IDToImageConverter function how can i do it? now i need to check first price value there are 3 condition i neeed to check in my IDToImageConverter function if( price> 5o) { // then get the ItemID based on the value bind image here if(ItemID >20) { // bind image1 } if(ItemID >50) { // bind image2 } } if( price> 100) { // as above codition we do here } now how can i add these above functionality in IDToImageConverter ? any idea how i can solve it <Image Source="{Binding ItemID, Converter={StaticResource IDToImageConverter}}" Height="50" /> </DataTemplate> </data:DataGridTemplateColumn.CellTemplate> </data:DataGridTemplateColumn> </data:DataGrid.Columns> </data:DataGrid> public class IDToImageConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { Uri uri = new Uri("~/Images/" + value.ToString()+ ".jpg", UriKind.Relative); return new BitmapImage(uri); } thanks in advance. for anyhelp you provide prince

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  • Issue with class design to model user preferences for different classes

    - by Mulone
    Hi all, I'm not sure how to design a couple of classes in my app. Basically that's a situation: each user can have many preferences each preference can be referred to an object of different classes (e.g. album, film, book etc) the preference is expressed as a set of values (e.g. score, etc). The problem is that many users can have preferences on the same objects, e.g.: John: score=5 for filmid=apocalypsenow Paul: score=3 for filmid=apocalypsenow And naturally I don't want to duplicate the object film in each user. So I could create a class called "preference" holding a score and then a target object, something like: User{ hasMany preferences } Preference{ belongsTo User double score Film target Album target //etc } and then define just one target. Then I would create an interface for the target Classes (album, film etc): Interface canBePreferred{ hasMany preferences } And implement all of those classes. This could work, but it looks pretty ugly and it would requires a lot of joins to work. Do you have some patterns I could use to model this nicely? Cheers, Mulone

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  • What are the original reasons for ToString() in Java and .NET?

    - by d.
    I've used ToString() modestly in the past and I've found it very useful in many circumstances. However, my usage of this method would hardly justify to put this method in none other than System.Object. My wild guess is that, at some point during the work carried out and meetings held to come up with the initial design of the .NET framework, it was decided that it was necessary - or at least extremely useful - to include a ToString() method that would be implemented by everything in the .NET framework. Does anyone know what the exact reasons were? Am I missing a ton of situations where ToString() proves useful enough as to be part of System.Object? What were the original reasons for ToString()? Thanks a lot! PS - Again: I'm not questioning the method or implying that it's not useful, I'm just curious to know what makes it SO useful as to be placed in System.Object. Side note - Imagine this: AnyDotNetNativeClass someInitialObject = new AnyDotNetNativeClass([some constructor parameters]); AnyDotNetNativeClass initialObjectFullCopy = AnyDotNetNativeClass.FromString(someInitialObject.ToString()); Wouldn't this be cool? EDIT(1): (A) - Based on some answers, it seems that .NET languages inherited this from Java. So, I'm adding "Java" to the subject and to the tags as well. If someone knows the reasons why this was implemented in Java then please shed some light! (B) - Static hypothetical FromString vs Serialization: sure, but that's quite a different story, right?

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  • Hibernate: fetching multiple bags efficiently

    - by Jens Jansson
    Hi! I'm developing a multilingual application. For this reason many objects have in their name and description fields collections of something I call LocalizedStrings instead of plain strings. Every LocalizedString is basically a pair of a locale and a string localized to that locale. Let's take an example an entity, let's say a book -object. public class Book{ @OneToMany private List<LocalizedString> names; @OneToMany private List<LocalizedString> description; //and so on... } When a user asks for a list of books, it does a query to get all the books, fetches the name and description of every book in the locale the user has selected to run the app in, and displays it back to the user. This works but it is a major performance issue. For the moment hibernate makes one query to fetch all the books, and after that it goes through every single object and asks hibernate for the localized strings for that specific object, resulting in a "n+1 select problem". Fetching a list of 50 entities produces about 6000 rows of sql commands in my server log. I tried making the collections eager but that lead me to the "cannot simultaneously fetch multiple bags"-issue. Then I tried setting the fetch strategy on the collections to subselect, hoping that it would do one query for all books, and after that do one query that fetches all LocalizedStrings for all the books. Subselects didn't work in this case how i would have hoped and it basically just did exactly the same as my first case. I'm starting to run out of ideas on how to optimize this. So in short, what fetching strategy alternatives are there when you are fetching a collection and every element in that collection has one or multiple collections in itself, which has to be fetch simultaneously.

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  • Can Haskell's monads be thought of as using and returning a hidden state parameter?

    - by AJM
    I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets modified, but a third list is created and returned. Is it therefore valid to think of monadic operations as implicitly taking an initial state object as a parameter and implicitly returning a final state object? These state objects would be hidden so that the programmer doesn't have to worry about them and to control how they gets accessed. So, the programmer would not try to copy the object representing the IO stream as it was ten minutes ago. In other words, if we have this code: main = do putStrLn "Enter your name:" name <- getLine putStrLn ( "Hello " ++ name ) ...is it OK to think of the IO monad and the "do" syntax as representing this style of code? putStrLn :: IOState -> String -> IOState getLine :: IOState -> (IOState, String) main :: IOState -> IOState -- main returns an IOState we can call "state3" main state0 = putStrLn state2 ("Hello " ++ name) where (state2, name) = getLine state1 state1 = putStrLn state0 "Enter your name:"

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  • How can I prevent double file uploading with Amazon S3?

    - by Tony
    I decided to use Amazon S3 for document storage for an app I am creating. One issue I run into is while I need to upload the files to S3, I need to create a document object in my app so my users can perform CRUD actions. One solution is to allow for a double upload. A user uploads a document to the server my Rails app lives on. I validate and create the object, then pass it on to S3. One issue with this is progress indicators become more complicated. Using most out-of-the-box plugins would show the client that file has finished uploading because it is on my server, but then there would be a decent delay when the file was going from my server to S3. This also introduces unnecessary bandwidth (at least it does not seem necessary) The other solution I am thinking about is to upload the file directly to S3 with one AJAX request, and when that is successful, make a second AJAX request to store the object in my database. One issue here is that I would have to validate the file after it is uploaded which means I have to run some clean up code in S3 if the validation fails. Both seem equally messy. Does anyone have something more elegant working that they would not mind sharing? I would imagine this is a common situation with "cloud storage" being quite popular today. Maybe I am looking at this wrong.

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  • Random number generation in MVC applications

    - by SlimShaggy
    What is the correct way of generating random numbers in an ASP.NET MVC application if I need exactly one number per request? According to MSDN, in order to get randomness of sufficient quality, it is necessary to generate multiple numbers using a single System.Random object, created once. Since a new instance of a controller class is created for each request in MVC, I cannot use a private field initialized in the controller's constructor for the Random object. So in what part of the MVC app should I create and store the Random object? Currently I store it in a static field of the controller class and lazily initialize it in the action method that uses it: public class HomeController : Controller { ... private static Random random; ... public ActionResult Download() { ... if (random == null) random = new Random(); ... } } Since the "random" field can be accessed by multiple instances of the controller class, is it possible for its value to become corrupted if two instances attempt to initialize it simultaneously? And one more question: I know that the lifetime of statics is the lifetime of the application, but in case of an MVC app what is it? Is it from IIS startup till IIS shutdown?

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  • List of Objects to be used on ascx view with Inherits data already loaded MVC...

    - by user54197
    I have an object list being loded from a database to a drop down list. The Model loads the data to the Controller. The aspx view includes an ascx view. The ascx view already inherits data from another Project. I cannot set my List object in the ascx page. Can this be done? Model ... string List = dr["example"].ToString().Trim(); int indicator = dr["ex"].ToString().Trim(); LossCauseList.Add(new LossCauses(indicator, List)); ... Controller LossCauses test = new LossCauses(); test.GetLossCauses(LossType); TempData["Select"] = test.LossCauseList; return View(myData); Partial View ... <select id="SelectedProperty"> <% List<string> selectProperty = new List<string>(); selectProperty = TempData["Select"] as List<string>; foreach(var item in selectProperty) { %> <option><%=item.ToString() %></option> <% } %> </select> ... Partial view's List should be an actual LossCauses object. HELP!!!

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  • .NET Web Serivce hydrate custom class

    - by row1
    I am consuming an external C# Web Service method which returns a simple calculation result object like this: [Serializable] public class CalculationResult { public string Name { get; set; } public string Unit { get; set; } public decimal? Value { get; set; } } When I add a Web Reference to this service in my ASP .NET project Visual Studio is kind enough to generate a matching class so I can easily consume and work with it. I am using Castle Windsor and I may want to plug in other method of getting a calculation result object, so I want a common class CalculationResult (or ICalculationResult) in my solution which all my objects can work with, this will always match the object returned from the external Web Service 1:1. Is there anyway I can tell my Web Service client to hydrate a particular class instead of its generated one? I would rather not do it manually: foreach(var fromService in calcuationResultsFromService) { ICalculationResult calculationResult = new CalculationResult() { Name = fromService.Name }; yield return calculationResult; } Edit: I am happy to use a Service Reference type instead of the older Web Reference.

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  • .NET framework execution aborted while executing CLR stored procedure?

    - by Sean Ochoa
    I constructed a stored procedure that does the equivalent of FOR XML AUTO in SQL Server 2008. Now that I'm testing it, it gives me a really unhelpful error message. What does this error mean? Msg 10329, Level 16, State 49, Procedure ForXML, Line 0 .NET Framework execution was aborted. System.Threading.ThreadAbortException: Thread was being aborted. System.Threading.ThreadAbortException: at System.Runtime.InteropServices.Marshal.PtrToStringUni(IntPtr ptr, Int32 len) at System.Data.SqlServer.Internal.CXVariantBase.WSTRToString() at System.Data.SqlServer.Internal.SqlWSTRLimitedBuffer.GetString(SmiEventSink sink) at System.Data.SqlServer.Internal.RowData.GetString(SmiEventSink sink, Int32 i) at Microsoft.SqlServer.Server.ValueUtilsSmi.GetValue(SmiEventSink_Default sink, ITypedGettersV3 getters, Int32 ordinal, SmiMetaData metaData, SmiContext context) at Microsoft.SqlServer.Server.ValueUtilsSmi.GetValue200(SmiEventSink_Default sink, SmiTypedGetterSetter getters, Int32 ordinal, SmiMetaData metaData, SmiContext context) at System.Data.SqlClient.SqlDataReaderSmi.GetValue(Int32 ordinal) at System.Data.SqlClient.SqlDataReaderSmi.GetValues(Object[] values) at System.Data.ProviderBase.DataReaderContainer.CommonLanguageSubsetDataReader.GetValues(Object[] values) at System.Data.ProviderBase.SchemaMapping.LoadDataRow() at System.Data.Common.DataAdapter.FillLoadDataRow(SchemaMapping mapping) at System.Data.Common.DataAdapter.FillFromReader(DataSet dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) at System.Data.Common.DataAdapter.Fill(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) at ForXML.GetXML...

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  • Is it possible to De-Serialize a new Derived class using Old Binary?

    - by Anand
    In my project I have a class which I Serialize in Binary format to the disk. Due to some new requirement I need to create a new class which is derived from the original class. eg [Serializable] public class Sample { String someString; int someInt; public Sample() { } public Sample(String _someString, int _someInt) { this.someInt = _someInt; this.someString = _someString; } public String SomeString { get { return someString; } } public int SomeInt { get { return someInt; } } } [Serializable] public class DerivedSample : Sample { String someMoreString; int someMoreInt; public DerivedSample () : base() { } public DerivedSample (String _someString, int _someInt, String _someMoreString, int _someMoreInt) : base(_someString, _someInt) { this.someMoreString = _someMoreString; this.someMoreInt = _someMoreInt; } public String SomeMoreString { get { return someMoreString; } } public int SomeMoreInt { get { return someMoreInt; } } } When I try to De serialize an old file which contains only object of Sample it works fine, in the current assembly. That means backward compatibility is there. But when I try to deserialize the file which contains object of DerivedSample using the previous version of the assembly application crashes. Which means forward compatibilty needs to be taken care off... It it possible to say read only the base class part of the object from new version of the file?

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  • Unit Testing an Event Firing From a Thread

    - by Dougc
    I'm having a problem unit testing a class which fires events when a thread starts and finishes. A cut down version of the offending source is as follows: public class ThreadRunner { private bool keepRunning; public event EventHandler Started; public event EventHandler Finished; public void StartThreadTest() { this.keepRunning = true; var thread = new Thread(new ThreadStart(this.LongRunningMethod)); thread.Start(); } public void FinishThreadTest() { this.keepRunning = false; } protected void OnStarted() { if (this.Started != null) this.Started(this, new EventArgs()); } protected void OnFinished() { if (this.Finished != null) this.Finished(this, new EventArgs()); } private void LongRunningMethod() { this.OnStarted(); while (this.keepRunning) Thread.Sleep(100); this.OnFinished(); } } I then have a test to check that the Finished event fires after the LongRunningMethod has finished as follows: [TestClass] public class ThreadRunnerTests { [TestMethod] public void CheckFinishedEventFiresTest() { var threadTest = new ThreadRunner(); bool finished = false; object locker = new object(); threadTest.Finished += delegate(object sender, EventArgs e) { lock (locker) { finished = true; Monitor.Pulse(locker); } }; threadTest.StartThreadTest(); threadTest.FinishThreadTest(); lock (locker) { Monitor.Wait(locker, 1000); Assert.IsTrue(finished); } } } So the idea here being that the test will block for a maximum of one second - or until the Finish event is fired - before checking whether the finished flag is set. Clearly I've done something wrong as sometimes the test will pass, sometimes it won't. Debugging seems very difficult as well as the breakpoints I'd expect to be hit (the OnFinished method, for example) don't always seem to be. I'm assuming this is just my misunderstanding of the way threading works, so hopefully someone can enlighten me.

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  • Recursive Enumeration in Java

    - by Harm De Weirdt
    Hello everyone. I still have a question about Enumerations. Here's a quick sketch of the situation. I have a class Backpack that has a Hashmap content with as keys a variable of type long, and as value an ArrayList with Items. I have to write an Enumeration that iterates over the content of a Backpack. But here's the catch: in a Backpack, there can also be another Backpack. And the Enumeration should also be able to iterate over the content of a backpack that is in the backpack. (I hope you can follow, I'm not really good at explaining..) Here is the code I have: public Enumeration<Object> getEnumeration() { return new Enumeration<Object>() { private int itemsDone = 0; //I make a new array with all the values of the HashMap, so I can use //them in nextElement() Collection<Long> keysCollection = getContent().keySet(); Long [] keys = keysCollection.toArray(new Long[keysCollection.size()]); public boolean hasMoreElements() { if(itemsDone < getContent().size()) { return true; }else { return false; } } public Object nextElement() { ArrayList<Item> temporaryList= getContent().get(keys[itemsDone]); for(int i = 0; i < temporaryList.size(); i++) { if(temporaryList.get(i) instanceof Backpack) { return temporaryList.get(i).getEnumeration(); }else { return getContent().get(keys[itemsDone++]); } } } }; Will this code work decently? It's just the "return temporaryList.get(i).getEnumeration();" I'm worried about. Will the users still be able to use just the hasMoreElemens() and nextElement() like he would normally do? Any help is appreciated, Harm De Weirdt

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  • Use cases of [ordered], the new PowerShell 3.0 feature

    - by Roman Kuzmin
    PowerShell 3.0 CTP1 introduces a new feature [ordered] which is somewhat a shortcut for OrderedDictionary. I cannot imagine practical use cases of it. Why is this feature really useful? Can somebody provide some useful examples? Example: this is, IMHO, rather demo case than practical: $a = [ordered]@{a=1;b=2;d=3;c=4} (I do not mind if it is still useful, then I am just looking for other useful cases). I am not looking for use cases of OrderedDictionary, it is useful, indeed. But we can use it directly in v2.0 (and I do a lot). I am trying to understand why is this new feature [ordered] needed in addition. Collected use cases from answers: $hash = [ordered]@{} is shorter than $hash = New-Object System.Collections.Specialized.OrderedDictionary N.B. ordered is not a real shortcut for the type. New-Object ordered does not work. N.B. 2: But this is still a good shortcut because (I think, cannot try) it creates typical for PowerShell case insensitive dictionary. The equivalent command in v2.0 is too long, indeed: New-Object System.Collections.Specialized.OrderedDictionary]([System.StringComparer]::OrdinalIgnoreCase)

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  • UpdatePanel reloads the whole page

    - by Emil D
    Hi.I'm building an asp.net cutom control inside which I have two dropdownlists: companyIdSelection and productFamilySelection.I populate the companyIdSelection at Page_Load and in order to populate the productFamilySelection depending on the selected item in companyIdSelection.I'm using UpdatePanels to achieve this, but for some reason every time I update companyIdSelection Page_Load is being called ( which as far as I know should happen only when the entire page is reloaded ), the list is being reloaded again and the item the user selected is lost( the selected item is always the top one ).Here's the code <asp:UpdatePanel ID="updateFamilies" runat="server" UpdateMode="Always"> <ContentTemplate> Company ID:<br> <br></br> <asp:DropDownList ID="companyIdSelection" runat="server" AutoPostBack="True" OnSelectedIndexChanged="companyIdSelection_SelectedIndexChanged"> </asp:DropDownList> <br></br> Product Family: <br></br> <asp:DropDownList ID="productFamilySelection" runat="server" AutoPostBack="True" onselectedindexchanged="productFamilySelection_SelectedIndexChanged"> </asp:DropDownList> <br> </ContentTemplate> </asp:UpdatePanel> protected void Page_Load(object sender, EventArgs e) { this.companyIdSelection.DataSource = companyIds(); //companyIds returns the object containing the initial data items this.companyIdSelection.DataBind(); } protected void companyIdSelection_SelectedIndexChanged(object sender, EventArgs e) { // Page_Load is called again for some reason before this method is called, so it // resets the companyIdSelection EngDbService s = new EngDbService(); productFamilySelection.DataSource = s.getProductFamilies(companyIdSelection.Text); productFamilySelection.DataBind(); } Also, I tried setting the UpdateMode of the UpdatePanel to "Conditional" and adding an asyncpostback trigger but the result was the same. What am I doing wrong? PS: I fixed the updating problem, by using Page.IsPostBack in the Page_Load method, but I would still want to avoid a full postback if possible

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  • Java extends classes - Share the extended class fields within the super class.

    - by Bastan
    Straight to the point... I have a class public class P_Gen{ protected String s; protected Object oP_Gen; public P_Gen(String str){ s = str; oP_Gen = new Myclass(this); } } Extended class: public class P extends P_Gen{ protected Object oP; public P(String str){ oP = new aClass(str); super(str); } } MyClass: public class MyClass{ protected Object oMC; public MyClass(P extendedObject){ oMc = oP.getSomething(); } } I came to realize that MyClass can only be instantiated with (P_Gen thisObject) as opposed to (P extendedObject). The situation is that I have code generated a bunch of classes like P_Gen. For each of them I have generated a class P which would contains my P specific custom methods and fields. When I'll regenerate my code in the future, P would not be overwritten as P_Gen would. ** So what happened in my case???!!!... I realized that MyClass would beneficiate from the info stored in P in addition to only P_Gen. Would that possible? I know it's not JAVA "realistic" since another class that extends P_Gen might not have the same fields... BY DESIGN, P_Gen will not be extended by anything but P.... And that's where it kinda make sens. :-) at least in other programming language ;-) In other programming language, it seems like P_Gen.this === P.this, in other word, "this" becomes a combination of P and P_Gen. Is there a way to achieve this knowing that P_Gen won't be extended by anything than P?

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  • Is there a design pattern that expresses objects (an their operations) in various states?

    - by darren
    Hi I have a design question about the evolution of an object (and its state) after some sequence of methods complete. I'm having trouble articulating what I mean so I may need to clean up the question based on feedback. Consider an object called Classifier. It has the following methods: void initialise() void populateTrainingSet(TrainingSet t) void pupulateTestingSet(TestingSet t) void train() void test() Result predict(Instance i) My problem is that these methods need to be called in a certain order. Futher, some methods are invalid until a previous method is called, and some methods are invalid after a method has been called. For example, it would be invalid to call predict() before test() was called, and it would be invalid to call train() after test() was called. My approach so far has been to maintain a private enum that represents the current stateof the object: private static enum STATE{ NEW, TRAINED, TESTED, READY}; But this seems a bit cloogy. Is there a design pattern for such a problem type? Maybe something related to the template method.

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  • Pattern for version-specific implementations of a Java class

    - by Mike Monkiewicz
    So here's my conundrum. I am programming a tool that needs to work on old versions of our application. I have the code to the application, but can not alter any of the classes. To pull information out of our database, I have a DTO of sorts that is populated by Hibernate. It consumes a data object for version 1.0 of our app, cleverly named DataObject. Below is the DTO class. public class MyDTO { private MyWrapperClass wrapper; public MyDTO(DataObject data) { wrapper = new MyWrapperClass(data); } } The DTO is instantiated through a Hibernate query as follows: select new com.foo.bar.MyDTO(t1.data) from mytable t1 Now, a little logic is needed on top of the data object, so I made a wrapper class for it. Note the DTO stores an instance of the wrapper class, not the original data object. public class MyWrapperClass { private DataObject data; public MyWrapperClass(DataObject data) { this.data = data; } public String doSomethingImportant() { ... version-specific logic ... } } This works well until I need to work on version 2.0 of our application. Now DataObject in the two versions are very similar, but not the same. This resulted in different sub classes of MyWrapperClass, which implement their own version-specific doSomethingImportant(). Still doing okay. But how does myDTO instantiate the appropriate version-specific MyWrapperClass? Hibernate is in turn instantiating MyDTO, so it's not like I can @Autowire a dependency in Spring. I would love to reuse MyDTO (and my dozens of other DTOs) for both versions of the tool, without having to duplicate the class. Don't repeat yourself, and all that. I'm sure there's a very simple pattern I'm missing that would help this. Any suggestions?

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  • How to force my method to accept objects from external software?

    - by Roman
    I have a method which needs to take a callback object as an argument and then (at the moment when it's needed) my method will call a specific method of the callback object. I wrote a class called Manager which has a method called addListener. As the argument for this method I need to use a callback object which is defined by the external software. So, I define the addListener in the following way: public void addListener(Listener listener). Of course Eclipse complains because it does not know what Listener is (because the Listener is defined by the external software). The only think that I know (should know) about the Listener is that it has a method called doSomething. So, to pleasure Eclipse I add an interface before my Manager class: interface Listener { void doSomething(); } public class CTManager { ... The problem seems to be solved but then I try to test my software. So, I create a class called test. In this class I create an instance of the Manager class and try to use addListener method of this instance. I also create a class Listener, instantiate it and give the instance to the addListener. And it's the place where the problem appears. Eclipse writes that addListener is not applicable to the given argument. I think it's because it expect something from my Listenr interface but gets something from the Listener class. How can I solve this problem?

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  • How can I refactor this to work without breaking the pattern horribly?

    - by SnOrfus
    I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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  • Strongly typed dynamic Linq sorting

    - by David
    I'm trying to build some code for dynamically sorting a Linq IQueryable<. The obvious way is here, which sorts a list using a string for the field name http://dvanderboom.wordpress.com/2008/12/19/dynamically-composing-linq-orderby-clauses/ However I want one change - compile time checking of field names, and the ability to use refactoring/Find All References to support later maintenance. That means I want to define the fields as f=f.Name, instead of as strings. For my specific use I want to encapsulate some code that would decide which of a list of named "OrderBy" expressions should be used based on user input, without writing different code every time. Here is the gist of what I've written: var list = from m Movies select m; // Get our list var sorter = list.GetSorter(...); // Pass in some global user settings object sorter.AddSort("NAME", m=m.Name); sorter.AddSort("YEAR", m=m.Year).ThenBy(m=m.Year); list = sorter.GetSortedList(); ... public class Sorter ... public static Sorter GetSorter(this IQueryable source, ...) The GetSortedList function determines which of the named sorts to use, which results in a List object, where each FieldData contains the MethodInfo and Type values of the fields passed in AddSort: public SorterItem AddSort(Func field) { MethodInfo ... = field.Method; Type ... = TypeOf(TKey); // Create item, add item to diction, add fields to item's List // The item has the ThenBy method, which just adds another field to the List } I'm not sure if there is a way to store the entire field object in a way that would allow it be returned later (it would be impossible to cast, since it is a generic type) Is there a way I could adapt the sample code, or come up with entirely new code, in order to sort using strongly typed field names after they have been stored in some container and retrieved (losing any generic type casting)

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  • I need help solving a rather weird error in a WCF service.

    - by Moulde
    Hi.. I have a solution that contains three projects. A main project with my MVC app, a silverlight application and a (silverlight enabled) WCF service project. In my silverlight project i have made a Service Reference to my WCF service. And i pretty much got that working. In my WCF service i have a method that returns an Book object, which got some random fields like title, date etc. In the book class, i have a ICollection field that contains a list of events. The book class is generated using entity framework 4.0, and Lazy Loading is enabled. If i in my getBook(int id) method return a book with the events field not initialized, it works as a charm. But if i initialize the field, i'm getting this error. The server did not provide a meaningful reply; this might be caused by a contract mismatch, a premature session shutdown or an internal server error. I have a few ideas why that is happening, and while writing this i just got another one. The wcf service somehow threw away the reference to the event class. That would be very weird since i have a reference between my main mvc app (with the models) and my WCF service. Since i have enabled lazy loading in EF 4.0, i suspect that it may be the thing generating the error. But i'm not sure why that would be, because i'm not in any way accessing that field. I could understand that i may not be able to access the events field after i recive the object in my silverlight application since the connection between the book object and the entity framework is like broken. Did i mention that Lazy Loading is enabled on my EF instance? And there is no inner exception in the thrown exception. Thanks in advance. Malte Baden Hansen

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