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• How to update GUI thread/class from worker thread/class?

  - by user315182

  First question here so hello everyone. The requirement I'm working on is a small test application that communicates with an external device over a serial port. The communication can take a long time, and the device can return all sorts of errors. The device is nicely abstracted in its own class that the GUI thread starts to run in its own thread and has the usual open/close/read data/write data basic functions. The GUI is also pretty simple - choose COM port, open, close, show data read or errors from device, allow modification and write back etc. The question is simply how to update the GUI from the device class? There are several distinct types of data the device deals with so I need a relatively generic bridge between the GUI form/thread class and the working device class/thread. In the GUI to device direction everything works fine with [Begin]Invoke calls for open/close/read/write etc. on various GUI generated events. I've read the thread here (How to update GUI from another thread in C#?) where the assumption is made that the GUI and worker thread are in the same class. Google searches throw up how to create a delegate or how to create the classic background worker but that's not at all what I need, although they may be part of the solution. So, is there a simple but generic structure that can be used? My level of C# is moderate and I've been programming all my working life, given a clue I'll figure it out (and post back)... Thanks in advance for any help.

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• (500) Internal Server Error with C# and Web Dev 2008 Express

  - by user32848

  The code below is generic, found in a variety of places, including a book I have. I have used it as a base for a working program in VS 2005. Now I've resurrected it with my current Visual Web Developer 2008 Express Edition and I seem to have problems connecting it to my default development server (I don't have IIS on my XP). The error is: (500) Internal Server Error. Is this saying what I thought it did (above) or something else, and how do I solve this problem? using System; using System.Collections; using System.Collections.Generic; using System.Configuration; using System.IO; using System.Net; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using System.Text.RegularExpressions; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { string strResult = ""; string url = "http://weather.unisys.com"; WebResponse objResponse; WebRequest objRequest; try { objRequest = System.Net.HttpWebRequest.Create(url); } catch { objRequest = System.Net.HttpWebRequest.Create("http://"+ url); } objResponse = objRequest.GetResponse(); using (StreamReader sr = new StreamReader(objResponse.GetResponseStream())) { strResult = sr.ReadToEnd(); sr.Close(); } } }

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• How to display two ObservableCollections as a single list in WPF?

  - by nareshbhatia

  I have two ObservableCollections, say ObservableCollection<Cat> and ObservableCollections<Dog>. Cat and Dog both derive from class Pet. I want to display a list of all Pets. How do I do this? I prefer not want create a new ObservableCollection<Pet> by adding items from the two source lists because this list will become stale as more Cats and Dogs are added to the source lists. I can think of two approaches: 1) Create a "Decorator" ObservableCollection that keeps the two source collections as members and iterates over them every time. 2) Create an ObservableCollection<Pet> that does have the combined elements of the two source collections, but is also dependent on the source collections. Thus if a Cat is added to the Cat collection, this collection is notified and it adds the new Cat to itself. Is there a standard way to solve this issue? I don't want to reinvent the wheel!

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• How to refer to items in Dictionary<string, string> by integer index?

  - by Edward Tanguay

  I made a Dictionary<string, string> collection so that I can quickly reference the items by their string identifier. But I now also need to access this collective by index counter (foreach won't work in my real example). What do I have to do to the collection below so that I can access its items via integer index as well? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace TestDict92929 { class Program { static void Main(string[] args) { Dictionary<string, string> events = new Dictionary<string, string>(); events.Add("first", "this is the first one"); events.Add("second", "this is the second one"); events.Add("third", "this is the third one"); string description = events["second"]; Console.WriteLine(description); string description = events[1]; //error Console.WriteLine(description); } } }

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• How to convert many thousands of lines of VBScript to C#?

  - by Ross Patterson

  I have a collection of about 10,000 small VBScript programs (50-100 lines each) and a small collection of larger ones, and I'm looking for a way to convert them to C# without resorting to by-hand transliteration. The programs are automated test cases for a web application, written for HP/Mercury's QuickTest Pro, and I'm trying to turn them into test cases for Selenium. Luckily, the tests appear to be well-written, using a library of building blocks and idioms (the larger programs), so the test cases actually resemble a domain-specific language more than they do VBScript, and the QTP-ness is well-buried inside the libraries. Ideally, what I'm searching for is a tool that can do the syntactic transformation from VBScript to C# for both the dsl-ish test cases and also the more complicated building-block libraries. That would leave me with a manual cleanup of the libraries, and probably very little work on the test cases. If I could find a VBScript-to-VB.NET translator, I'd take that also, as I suspect I could compile the VB.NET and then de-compile to C# using .NET Relector or something similar. Plan B is to write a translator of my own for the test cases, since they're in a very straight-line style, but it wouldn't help with the libraries. Any suyggestions? I haven't written a compiler in at least 15 years, and while I haven't forgotten how, I'm not looking forward to it - least of all for VBScript!

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• Fluent NHibernate Repository with subclasses

  - by reallyJim

  Having some difficulty understanding the best way to implement subclasses with a generic repository using Fluent NHibernate. I have a base class and two subclasses, say: public abstract class Person { public virtual int PersonId { get; set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } } public class Student : Person { public virtual decimal GPA { get; set; } } public class Teacher : Person { public virtual decimal Salary { get; set; } } My Mappings are as follows: public class PersonMap : ClassMap { public PersonMap() { Table("Persons"); Id(x => x.PersonId).GeneratedBy.Identity(); Map(x => x.FirstName); Map(x => x.LastName); } } public class StudentMap : SubclassMap<Student> { public StudentMap() { Table("Students"); KeyColumn("PersonId"); Map(x => x.GPA); } } public class TeacherMap : SubclassMap<Teacher> { public TeacherMap() { Table("Teachers"); KeyColumn("PersonId"); Map(x => x.Salary); } } I use a generic repository to save/retreive/update the entities, and it works great--provided I'm working with Repository--where I already know that I'm working with students or working with teachers. The problem I run into is this: What happens when I have an ID, and need to determine the TYPE of person? If a user comes to my site as PersonId = 23, how do I go about figuring out which type of person it is?

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• Using LINQ on observable with GroupBy and Sum aggregate

  - by Mark Oates

  I have the following block of code which works fine; var boughtItemsToday = (from DBControl.MoneySpent bought in BoughtItemDB.BoughtItems select bought); BoughtItems = new ObservableCollection<DBControl.MoneySpent>(boughtItemsToday); It returns data from my MoneySpent table which includes ItemCategory, ItemAmount, ItemDateTime. I want to change it to group by ItemCategory and ItemAmount so I can see where I am spending most of my money, so I created a GroupBy query, and ended up with this; var finalQuery = boughtItemsToday.AsQueryable().GroupBy(category => category.ItemCategory); BoughtItems = new ObservableCollection<DBControl.MoneySpent>(finalQuery); Which gives me 2 errors; Error 1 The best overloaded method match for 'System.Collections.ObjectModel.ObservableCollection.ObservableCollection(System.Collections.Generic.List)' has some invalid arguments Error 2 Argument 1: cannot convert from 'System.Linq.IQueryable' to 'System.Collections.Generic.List' And this is where I'm stuck! How can I use the GroupBy and Sum aggregate function to get a list of my categories and the associated spend in 1 LINQ query?! Any help/suggestions gratefully received. Mark

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• KODO: how set up fetch plan for bidirectional relationships?

  - by BestPractices

  Running KODO 4.2 and having an issue inefficient queries being generated by KODO. This happens when fetching an object that contains a collection where that collection has a bidrectional relationship back to the first object. Class Classroom { List<Student> _students; } Class Student { Classroom _classroom; } If we create a fetch plan to get a list of Classrooms and their corresponding Students by setting up the following fetch plan: fetchPlan.addField(Classroom.class,”_students”); This will result in two queries (get the classrooms and then get all students that are in those classrooms), which is what we would expect. However, if we include the reference back to the classroom in our fetch plan in order for the _classroom field to get populated by doing fetchPlan.addField(Student.class, “_classroom”), this will result in X number of additional queries where X is the number of students in each classroom. Can anyone explain how to fix this? KODO already has the original Classroom objects at the point that it's executing the queries to retrieve the Classroom objects and set them in each Student object's _classroom field. So I would expect KODO to simply set those objects in the _classroom field on each Student object accordingly and not go back to the database. Once again, the documentation is sorely lacking with Kodo/JDO/OpenJPA but from what I've read it should be able to do this more efficiently. Note-- EAGER_FETCH.PARALLEL is turned on and I have tried this with caching (query and data caches) turned on and off and there is no difference in the resultant queries.

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• Java Generics Class Parameter Type Inference

  - by Pindatjuh

  Given the interface: public interface BasedOnOther<T, U extends BasedList<T>> { public T getOther(); public void staticStatisfied(final U list); } The BasedOnOther<T, U extends BasedList<T>> looks very ugly in my use-cases. It is because the T type parameter is already defined in the BasedList<T> part, so the "uglyness" comes from that T needs to be typed twice. Problem: is it possible to let the Java compiler infer the generic T type from BasedList<T> in a generic class/interface definition? Ultimately, I'd like to use the interface like: class X implements BasedOnOther<BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } } // Does not compile, due to invalid parameter count. Instead: class X implements BasedOnOther<SomeType, BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } }

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• How to determine one to many column name from entity type

  - by snicker

  I need a way to determine the name of the column used by NHibernate to join one-to-many collections from the collected entity's type. I need to be able to determine this at runtime. Here is an example: I have some entities: namespace Entities { public class Stable { public virtual int Id {get; set;} public virtual string StableName {get; set;} public virtual IList<Pony> Ponies { get; set; } } public class Dude { public virtual int Id { get; set; } public virtual string DudesName { get; set; } public virtual IList<Pony> PoniesThatBelongToDude { get; set; } } public class Pony { public virtual int Id {get; set;} public virtual string Name {get; set;} public virtual string Color { get; set; } } } I am using NHibernate to generate the database schema, which comes out looking like this: create table "Stable" (Id integer, StableName TEXT, primary key (Id)) create table "Dude" (Id integer, DudesName TEXT, primary key (Id)) create table "Pony" (Id integer, Name TEXT, Color TEXT, Stable_id INTEGER, Dude_id INTEGER, primary key (Id)) Given that I have a Pony entity in my code, I need to be able to find out: A. Does Pony even belong to a collection in the mapping? B. If it does, what are the column names in the database table that pertain to collections In the above instance, I would like to see that Pony has two collection columns, Stable_id and Dude_id.

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• Slow performance with MVC2 DisplayFor

  - by PretzelSteelersFan

  I'm iterating through a collection on my view model. The collection contains HealthLifeDentalRates which implement IBeginsEnds. I have a Display Template BeginsEnds that displays the date range. This results in very slow performance. If I simply the date range (see commented code), it's fine. I think how I'm defining the lambda is the problem but not sure how to change it. <% foreach (var item in Model.Data.OrderBy(x=x.HealthLifeDentalRateCode)) { % <tr> <td> <%= Html.Encode(item.FiscalPeriodString()) %> </td> <td> <%= Html.Encode(item.HealthLifeDentalRateCode) %> </td> <td> <%= Html.Encode(item.Rate) %> </td> <td> <%= Html.Encode(item.IsDental.YesNo()) %> </td> <td> <%= Html.DisplayFor(i = item, "BeginsEnds") % - <%= Html.Encode(item.Ends.ToDateString()) % -- <%= Html.Encode(String.Format("{0:g}", item.Loaded)) % - <%= Html.Encode(item.LoadedBy) % <% } %>

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• Validations for a has_many/belongs_to relationship

  - by Craig Walker

  I have a Recipe model which has_many Ingredients (which in turn belongs_to Recipe). I want Ingredient to be existent dependent on Recipe; an Ingredient should never exist without a Recipe. I'm trying to enforce the presence of a valid Recipe ID in the Ingredient. I've been doing this with a validates :recipe, :presence => true (Rails 3) statement in Ingredient. This works fine if I save the Recipe before adding an Ingredient to it's ingredients collection. However, if I don't have explicit control over the saving (such as when I'm creating a Recipe and its Ingredients from a nested form) then I get an error: Ingredients recipe can't be blank I can get around this simply by dropping the presence validation on Ingredient.recipe. However, I don't particularly like this, as it means I'm working without a safety net. What is the best way to enforce existence-dependence in Rails? Things I'm considering (please comment on the wisdom of each): Adding a not-null constraint on the ingredients.recipe_id database column, and letting the database do the checking for me. A custom validation that somehow checks whether the Ingredient is in an unsaved recipe's ingredient collection (and thus can't have a recipe_id but is still considered valid).

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• Componentizing complex functionality in an MVC web app

  - by NXT

  Hi Everyone, This is question about MVC web-app architecture, and how it can be extended to handle componentizing moderately complex units of functionality. I have an MVC style web-app with a customer facing credit card charge page. I've been asked to allow the admins to enter credit card payments as well, for times when credit cards are taken over the phone. The customer facing credit card charge section of the website is currently it's own controller, with approximately 3 pages and a login. That controller is responsible for: Customer login credential authentication Credit card data collection Calling a library to do the actual charge. reporting the results to the user. I would like to extract the card data collection pages into a component of some kind so that I can easily reuse the code on the admin side of the app. Right now my components are limited to single "view" pages with PHP style embedded Perl code. This is a simple, custom MVC framework written in Perl. Right now, controllers are called directly from the framework to service web requests. My idea is to allow controllers to be called from other controllers, so that I can componentize more complex functionality. For simplicity I think I prefer composition over inheritance, even though it will require writing a bunch of pass-through methods (actions). Being Perl, I could in theory do multiple inheritance. I'm wondering if anyone with experience in other MVC web frameworks can comment on how this sort of thing is usually done. Thank you.

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• Dealing with multiple generics in a method call

  - by thaBadDawg

  I've been dealing a lot lately with abstract classes that use generics. This is all good and fine because I get a lot of utility out of these classes but now it's making for some rather ugly code down the line. For example: abstract class ClassBase<T> { T Property { get; set; } } class MyClass : ClassBase<string> { OtherClass PropertyDetail { get; set; } } This implementation isn't all that crazy, except when I want to reference the abstract class from a helper class and then I have to make a list of generics just to make reference to the implemented class, like this below. class Helper { void HelpMe<C, T>(object Value) where C : ClassBase<T>, new() { DoWork(); } } This is just a tame example, because I have some method calls where the list of where clauses end up being 5 or 6 lines long to handle all of the generic data. What I'd really like to do is class Helper { void HelpMe<C>(object Value) where C : ClassBase, new() { DoWork(); } } but it obviously won't compile. I want to reference ClassBase without having to pass it a whole array of generic classes to get the function to work, but I don't want to reference the higher level classes because there are a dozen of those. Am I the victim of my own cleverness or is there an avenue that I haven't considered yet?

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• Flex 3 - Image cache

  - by BS_C3

  Hello Community. I'm doing an Image Cache following this method: http://www.brandondement.com/blog/2009/08/18/creating-an-image-cache-with-actionscript-3/ I copied the two as classes, renaming them CachedImage and CachedImageMap. The thing is that I don't want to store the image after being loaded a first time, but while the application is being loaded. For that, I've created a function that is called by the application pre-initialize event. This is how it looks: private function loadImages():void { var im:CachedImage = new CachedImage; var sources:ArrayCollection = new ArrayCollection; for each(var cs in divisionData.division.collections.collection.collectionSelection) { sources.addItem(cs.toString()); } for each(var se in divisionData.division.collections.collection.searchEngine) { sources.addItem(se.toString()); } for each( var source:String in sources) { im.source = source; im.load(source); } } The sources are properly retrieved. However, even if I use the load method, I do not get the "complete" event... As if the image is not being loaded... How is that? Any help would be appreciated. Thanks in advance. Regards, BS_C3

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• How to customize the process employed by WCF when serializing contract method arguments?

  - by mark

  Dear ladies and sirs. I would like to formulate a contrived scenario, which nevertheless has firm actual basis. Imagine a collection type COuter, which is a wrapper around an instance of another collection type CInner. Both implement IList (never mind the T). Furthermore, a COuter instance is buried inside some object graph, the root of which (let us refer to it as R) is returned from a WCF service method. My question is how can I customize the WCF serialization process, so that when R is returned, the request to serialize the COuter instance will be routed through my code, which will extract CInner and pass it to the serializer instead. Thus the receiving end still gets R, only no COuter instance is found in the object graph. I hoped that http://stackoverflow.com/questions/2220516/how-does-wcf-serialize-the-method-call will contain the answer, unfortunately the article mentioned there (http://msdn.microsoft.com/en-us/magazine/cc163569.aspx) only barely mentions that advanced serialization scenarios are possible using IDataContractSurrogate interface, but no details are given. I am, on the other hand, would really like to see a working example. Thank you very much in advance.

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• using STI and ActiveRecordBase<> with full FindAll

  - by oillio

  Is it possible to use generic support with single table inheritance, and still be able to FindAll of the base class? As a bonus question, will I be able to use ActiveRecordLinqBase< as well? I do love those queries. More detail: Say I have the following classes defined: public interface ICompany { int ID { get; set; } string Name { get; set; } } [ActiveRecord("companies", DiscriminatorColumn="type", DiscriminatorType="String", DiscriminatorValue="NA")] public abstract class Company<T> : ActiveRecordBase<T>, ICompany { [PrimaryKey] private int Id { get; set; } [Property] public String Name { get; set; } } [ActiveRecord(DiscriminatorValue="firm")] public class Firm : Company<Firm> { [Property] public string Description { get; set; } } [ActiveRecord(DiscriminatorValue="client")] public class Client : Company<Client> { [Property] public int ChargeRate { get; set; } } This works fine for most cases. I can do things like: var x = Client.FindAll(); But sometimes I want all of the companies. If I was not using generics I could do: var x = (Company[]) FindAll(Company); Client a = (Client)x[0]; Firm b = (Firm)x[1]; Is there a way to write a FindAll that returns an array of ICompany's that can then be typecast into their respective types? Something like: var x = (ICompany[]) FindAll(Company<ICompany>); Client a = (Client)x[0]; Or maybe I am going about implementing the generic support all wrong?

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• JS/CSS include section replacement, Debug vs Release

  - by Bayard Randel

  I'd be interested to hear how people handle conditional markup, specifically in their masterpages between release and debug builds. The particular scenario this is applicable to is handling concatenated js and css files. I'm currently using the .Net port of YUI compress to produce a single site.css and site.js from a large collection of separate files. One thought that occurred to me was to place the js and css include section in a user control or collection of panels and conditionally display the <link> and <script> markup based on the Debug or Release state of the assembly. Something along the lines of: #if DEBUG pnlDebugIncludes.visible = true #else pnlReleaseIncludes.visible = true #endif The panel is really not very nice semantically - wrapping <script> tags in a <div> is a bit gross; there must be a better approach. I would also think that a block level element like a <div> within <head> would be invalid html. Another idea was this could possibly be handled using web.config section replacements, but I'm not sure how I would go about doing that.

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• Silverlight 4 XAML Collections

  - by mattduffield

  Hello, I have authored some custom classes that I would like to create using XAML: <Grid Width="300" Height="300"> <l:DashboardTable> <l:DashboardTable.DashboardTableQuery> <dq:DashboardTableQuery ConnectionString="Data Source=bunkerhill;Initial Catalog=emgov_data;User Id=emgovadmin;Password=p@$$word;" Query="select datename(month, cr_tb_DateDue) AS Month, sum(cr_tb_AmountTransaction) AS Total from cr_tb_transactionbill where Year(cr_tb_DateDue) = 2005 and Month(cr_tb_DateDue) IN (1,2,3,4) group by datename(month, cr_tb_DateDue)" > <dq:DashboardTableQuery.DataColumns> <dq:DataColumn ColumnName="Month" ColumnOrder="0" Label="Month" /> <dq:DataColumn ColumnName="Total" ColumnOrder="1" Label="Total" /> </dq:DashboardTableQuery.DataColumns> </dq:DashboardTableQuery> </l:DashboardTable.DashboardTableQuery> </l:DashboardTable> </Grid> The problem is that I get a XamlParseException when I try to run this XAML. I have determined it is when it gets to the dq:DataColumn element. It seems like this is only happening when I have a property that then has a collection and then several items in the collection that I am getting this issue. Has any encountered anything similar? I am try to achieve this all in XAML declaratively.

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• Query String to Object with strongly typed properties

  - by Kamar

  Let’s say we track 20 query string parameters in our site. Each request which comes will have only a subset of those 20 parameters. But we definitely look for all/most of the parameters which comes in each request. We do not want to loop through the collection each time we are looking for a particular parameter initially or somewhere down the pipeline in the code. So we loop once through the query string collection, convert string values to their respective types (enums, int, string etc.), populate to QueryString object which is added to the context. After that wherever its needed we will have a strongly typed properties in the QueryString object which is easy to use and we maintain a standard. public class QueryString { public int Key1{ get; private set; } public SomeType Key2{ get; private set; } private QueryString() { } public static QueryString GetQueryString() { QueryString l_QS = new QueryString(); foreach (string l_Key in HttpContext.Current.Request.QueryString.AllKeys) { switch (l_Key) { case "key1": l_QS.Key1= DoSomething(l_Key, HttpContext.Current.Request.QueryString[l_Key]); break; case "key2": l_QS.Key2 = DoAnotherThing(l_Key, HttpContext.Current.Request.QueryString[l_Key]); break; } } return l_QS; } } Any other solution to achieve this?

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• Intermittent Issue Writing to Google Appengine Datastore

  - by user242153

  Hi, I have a functioning app and recently have had intermittent problems writing to the datastore. I did not make any relevant code changes, however in the last few days my attempts to write to the datastore sometimes work and sometimes don't. I am trying to save an object that is in a many to one relationship with an existing persisted parent. So, the logic works like this: 1) Parent pulled from the datastore 2) Child created / instantiated using constructor 3) Parent.addSingleChild(child); // the "addSingleChild" method just adds the object argument to the collection of children 4) child.setParent(Parent); // sets the Parent object to the parent field I am using transactions as explained in the documentation ending with "finally {if (tx.isActive()) {tx.rollback(); } }" When the servlet is called, the parent is called from the datastore and the child object is created and added to the many to one mapping to the pre-existing parent. The child should automatically be persisted, since the parent is already persistent, and the child is added to the collection of children that map to the parent. And it worked this way in the past. However, to be sure, i did add a pm.makePersistent(child). Doesn't seem to help, still have the intermittent problem. Any suggestions would be appreciated, and if you need to see the actual code I can post. Thanks

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• Why doesn't the Java Collections API include a Graph implementation?

  - by dvanaria

  I’m currently learning the Java Collections API and feel I have a good understanding of the basics, but I’ve never understood why this standard API doesn’t include a Graph implementation. The three base classes are easily understandable (List, Set, and Map) and all their implementations in the API are mostly straightforward and consistent. Considering how often graphs come up as a potential way to model a given problem, this just doesn’t make sense to me (it’s possible it does exist in the API and I’m not looking in the right place of course). Steve Yegge suggests in one of his blog posts that a programmer should consider graphs first when attacking a problem, and if the problem domain doesn’t fit naturally into this data structure, only then consider the alternative structures. My first guess is that there is no universal way to represent graphs, or that their interfaces may not be generic enough for an API implementation to be useful? But if you strip down a graph to its basic components (vertices and a set of edges that connect some or all of the vertices) and consider the ways that graphs are commonly constructed (methods like addVertex(v) and insertEdge(v1, v2)) it seems that a generic Graph implementation would be possible and useful. Thanks for helping me understand this better.

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• Is it better to use a relational database or document-based database for an app like Wufoo?

  - by mboyle

  I'm working on an application that's similar to Wufoo in that it allows our users to create their own databases and collect/present records with auto generated forms and views. Since every user is creating a different schema (one user might have a database of their baseball card collection, another might have a database of their recipes) our current approach is using MySQL to create separate databases for every user with its own tables. So in other words, the databases our MySQL server contains look like: main-web-app-db (our web app containing tables for users account info, billing, etc) user_1_db (baseball_cards_table) user_2_db (recipes_table) .... And so on. If a user wants to set up a new database to keep track of their DVD collection, we'd do a "create database ..." with "create table ...". If they enter some data in and then decide they want to change a column we'd do an "alter table ....". Now, the further along I get with building this out the more it seems like MySQL is poorly suited to handling this. 1) My first concern is that switching databases every request, first to our main app's database for authentication etc, and then to the user's personal database, is going to be inefficient. 2) The second concern I have is that there's going to be a limit to the number of databases a single MySQL server can host. Pretending for a moment this application had 500,000 user databases, is MySQL designed to operate this way? What if it were a million, or more? 3) Lastly, is this method going to be a nightmare to support and scale? I've never heard of MySQL being used in this way so I do worry about how this affects things like replication and other methods of scaling. To me, it seems like MySQL wasn't built to be used in this way but what do I know. I've been looking at document-based databases like MongoDB, CouchDB, and Redis as alternatives because it seems like a schema-less approach to this particular problem makes a lot of sense. Can anyone offer some advice on this?

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• Choosing design method for ladder-like word game.

  - by owca

  I'm trying to build a simple application, with the finished program looking like this : I will also have to implement two different GUI layouts for this. Now I'm trying to figure out the best method to perform this task. My professor told me to introduce Element class with 4 states : - empty - invisible (used in GridLayout) - first letter - other letter I've thought about following solutions (by List I mean any sort of Collection) : 1. Element is a single letter, and each line is Element[]. Game class will be array of arrays Element[]. I guess that's the dumbest way, and the validation might be troublesome. 2. Like previously but Line is a List of Element. Game is an array of Lines. 3. Like previously but Game is a List of Lines. Which one should I choose ? Or maybe do you have better ideas ? What collection would be best if to use one ?

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• Java Generics Class Type Parameter Inference

  - by Pindatjuh

  Given the interface: public interface BasedOnOther<T, U extends BasedList<T>> { public T getOther(); public void staticStatisfied(final U list); } The BasedOnOther<T, U extends BasedList<T>> looks very ugly in my use-cases. It is because the T type parameter is already defined in the BasedList<T> part, so the "uglyness" comes from that T needs to be typed twice. Problem: is it possible to let the Java compiler infer the generic T type from BasedList<T> in a generic class/interface definition? Ultimately, I'd like to use the interface like: class X extends BasedOnOther<BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } } Instead: class X extends BasedOnOther<SomeType, BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } }

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