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  • Implementing a generic repository for WCF data services

    - by cibrax
    The repository implementation I am going to discuss here is not exactly what someone would call repository in terms of DDD, but it is an abstraction layer that becomes handy at the moment of unit testing the code around this repository. In other words, you can easily create a mock to replace the real repository implementation. The WCF Data Services update for .NET 3.5 introduced a nice feature to support two way data bindings, which is very helpful for developing WPF or Silverlight based application but also for implementing the repository I am going to talk about. As part of this feature, the WCF Data Services Client library introduced a new collection DataServiceCollection<T> that implements INotifyPropertyChanged to notify the data context (DataServiceContext) about any change in the association links. This means that it is not longer necessary to manually set or remove the links in the data context when an item is added or removed from a collection. Before having this new collection, you basically used the following code to add a new item to a collection. Order order = new Order {   Name = "Foo" }; OrderItem item = new OrderItem {   Name = "bar",   UnitPrice = 10,   Qty = 1 }; var context = new OrderContext(); context.AddToOrders(order); context.AddToOrderItems(item); context.SetLink(item, "Order", order); context.SaveChanges(); Now, thanks to this new collection, everything is much simpler and similar to what you have in other ORMs like Entity Framework or L2S. Order order = new Order {   Name = "Foo" }; OrderItem item = new OrderItem {   Name = "bar",   UnitPrice = 10,   Qty = 1 }; order.Items.Add(item); var context = new OrderContext(); context.AddToOrders(order); context.SaveChanges(); In order to use this new feature, you first need to enable V2 in the data service, and then use some specific arguments in the datasvcutil tool (You can find more information about this new feature and how to use it in this post). DataSvcUtil /uri:"http://localhost:3655/MyDataService.svc/" /out:Reference.cs /dataservicecollection /version:2.0 Once you use those two arguments, the generated proxy classes will use DataServiceCollection<T> rather than a simple ObjectCollection<T>, which was the default collection in V1. There are some aspects that you need to know to use this feature correctly. 1. All the entities retrieved directly from the data context with a query track the changes and report those to the data context automatically. 2. A entity created with “new” does not track any change in the properties or associations. In order to enable change tracking in this entity, you need to do the following trick. public Order CreateOrder() {   var collection = new DataServiceCollection<Order>(this.context);   var order = new Order();   collection.Add(order);   return order; } You basically need to create a collection, and add the entity to that collection with the “Add” method to enable change tracking on that entity. 3. If you need to attach an existing entity (For example, if you created the entity with the “new” operator rather than retrieving it from the data context with a query) to a data context for tracking changes, you can use the “Load” method in the DataServiceCollection. var order = new Order {   Id = 1 }; var collection = new DataServiceCollection<Order>(this.context); collection.Load(order); In this case, the order with Id = 1 must exist on the data source exposed by the Data service. Otherwise, you will get an error because the entity did not exist. These cool extensions methods discussed by Stuart Leeks in this post to replace all the magic strings in the “Expand” operation with Expression Trees represent another feature I am going to use to implement this generic repository. Thanks to these extension methods, you could replace the following query with magic strings by a piece of code that only uses expressions. Magic strings, var customers = dataContext.Customers .Expand("Orders")         .Expand("Orders/Items") Expressions, var customers = dataContext.Customers .Expand(c => c.Orders.SubExpand(o => o.Items)) That query basically returns all the customers with their orders and order items. Ok, now that we have the automatic change tracking support and the expression support for explicitly loading entity associations, we are ready to create the repository. The interface for this repository looks like this,public interface IRepository { T Create<T>() where T : new(); void Update<T>(T entity); void Delete<T>(T entity); IQueryable<T> RetrieveAll<T>(params Expression<Func<T, object>>[] eagerProperties); IQueryable<T> Retrieve<T>(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] eagerProperties); void Attach<T>(T entity); void SaveChanges(); } The Retrieve and RetrieveAll methods are used to execute queries against the data service context. While both methods receive an array of expressions to load associations explicitly, only the Retrieve method receives a predicate representing the “where” clause. The following code represents the final implementation of this repository.public class DataServiceRepository: IRepository { ResourceRepositoryContext context; public DataServiceRepository() : this (new DataServiceContext()) { } public DataServiceRepository(DataServiceContext context) { this.context = context; } private static string ResolveEntitySet(Type type) { var entitySetAttribute = (EntitySetAttribute)type.GetCustomAttributes(typeof(EntitySetAttribute), true).FirstOrDefault(); if (entitySetAttribute != null) return entitySetAttribute.EntitySet; return null; } public T Create<T>() where T : new() { var collection = new DataServiceCollection<T>(this.context); var entity = new T(); collection.Add(entity); return entity; } public void Update<T>(T entity) { this.context.UpdateObject(entity); } public void Delete<T>(T entity) { this.context.DeleteObject(entity); } public void Attach<T>(T entity) { var collection = new DataServiceCollection<T>(this.context); collection.Load(entity); } public IQueryable<T> Retrieve<T>(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] eagerProperties) { var entitySet = ResolveEntitySet(typeof(T)); var query = context.CreateQuery<T>(entitySet); foreach (var e in eagerProperties) { query = query.Expand(e); } return query.Where(predicate); } public IQueryable<T> RetrieveAll<T>(params Expression<Func<T, object>>[] eagerProperties) { var entitySet = ResolveEntitySet(typeof(T)); var query = context.CreateQuery<T>(entitySet); foreach (var e in eagerProperties) { query = query.Expand(e); } return query; } public void SaveChanges() { this.context.SaveChanges(SaveChangesOptions.Batch); } } For instance, you can use the following code to retrieve customers with First name equal to “John”, and all their orders in a single call. repository.Retrieve<Customer>(    c => c.FirstName == “John”, //Where    c => c.Orders.SubExpand(o => o.Items)); In case, you want to have some pre-defined queries that you are going to use across several places, you can put them in an specific class. public static class CustomerQueries {   public static Expression<Func<Customer, bool>> LastNameEqualsTo(string lastName)   {     return c => c.LastName == lastName;   } } And then, use it with the repository. repository.Retrieve<Customer>(    CustomerQueries.LastNameEqualsTo("foo"),    c => c.Orders.SubExpand(o => o.Items));

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  • Inside the Concurrent Collections: ConcurrentBag

    - by Simon Cooper
    Unlike the other concurrent collections, ConcurrentBag does not really have a non-concurrent analogy. As stated in the MSDN documentation, ConcurrentBag is optimised for the situation where the same thread is both producing and consuming items from the collection. We'll see how this is the case as we take a closer look. Again, I recommend you have ConcurrentBag open in a decompiler for reference. Thread Statics ConcurrentBag makes heavy use of thread statics - static variables marked with ThreadStaticAttribute. This is a special attribute that instructs the CLR to scope any values assigned to or read from the variable to the executing thread, not globally within the AppDomain. This means that if two different threads assign two different values to the same thread static variable, one value will not overwrite the other, and each thread will see the value they assigned to the variable, separately to any other thread. This is a very useful function that allows for ConcurrentBag's concurrency properties. You can think of a thread static variable: [ThreadStatic] private static int m_Value; as doing the same as: private static Dictionary<Thread, int> m_Values; where the executing thread's identity is used to automatically set and retrieve the corresponding value in the dictionary. In .NET 4, this usage of ThreadStaticAttribute is encapsulated in the ThreadLocal class. Lists of lists ConcurrentBag, at its core, operates as a linked list of linked lists: Each outer list node is an instance of ThreadLocalList, and each inner list node is an instance of Node. Each outer ThreadLocalList is owned by a particular thread, accessible through the thread local m_locals variable: private ThreadLocal<ThreadLocalList<T>> m_locals It is important to note that, although the m_locals variable is thread-local, that only applies to accesses through that variable. The objects referenced by the thread (each instance of the ThreadLocalList object) are normal heap objects that are not specific to any thread. Thinking back to the Dictionary analogy above, if each value stored in the dictionary could be accessed by other means, then any thread could access the value belonging to other threads using that mechanism. Only reads and writes to the variable defined as thread-local are re-routed by the CLR according to the executing thread's identity. So, although m_locals is defined as thread-local, the m_headList, m_nextList and m_tailList variables aren't. This means that any thread can access all the thread local lists in the collection by doing a linear search through the outer linked list defined by these variables. Adding items So, onto the collection operations. First, adding items. This one's pretty simple. If the current thread doesn't already own an instance of ThreadLocalList, then one is created (or, if there are lists owned by threads that have stopped, it takes control of one of those). Then the item is added to the head of that thread's list. That's it. Don't worry, it'll get more complicated when we account for the other operations on the list! Taking & Peeking items This is where it gets tricky. If the current thread's list has items in it, then it peeks or removes the head item (not the tail item) from the local list and returns that. However, if the local list is empty, it has to go and steal another item from another list, belonging to a different thread. It iterates through all the thread local lists in the collection using the m_headList and m_nextList variables until it finds one that has items in it, and it steals one item from that list. Up to this point, the two threads had been operating completely independently. To steal an item from another thread's list, the stealing thread has to do it in such a way as to not step on the owning thread's toes. Recall how adding and removing items both operate on the head of the thread's linked list? That gives us an easy way out - a thread trying to steal items from another thread can pop in round the back of another thread's list using the m_tail variable, and steal an item from the back without the owning thread knowing anything about it. The owning thread can carry on completely independently, unaware that one of its items has been nicked. However, this only works when there are at least 3 items in the list, as that guarantees there will be at least one node between the owning thread performing operations on the list head and the thread stealing items from the tail - there's no chance of the two threads operating on the same node at the same time and causing a race condition. If there's less than three items in the list, then there does need to be some synchronization between the two threads. In this case, the lock on the ThreadLocalList object is used to mediate access to a thread's list when there's the possibility of contention. Thread synchronization In ConcurrentBag, this is done using several mechanisms: Operations performed by the owner thread only take out the lock when there are less than three items in the collection. With three or greater items, there won't be any conflict with a stealing thread operating on the tail of the list. If a lock isn't taken out, the owning thread sets the list's m_currentOp variable to a non-zero value for the duration of the operation. This indicates to all other threads that there is a non-locked operation currently occuring on that list. The stealing thread always takes out the lock, to prevent two threads trying to steal from the same list at the same time. After taking out the lock, the stealing thread spinwaits until m_currentOp has been set to zero before actually performing the steal. This ensures there won't be a conflict with the owning thread when the number of items in the list is on the 2-3 item borderline. If any add or remove operations are started in the meantime, and the list is below 3 items, those operations try to take out the list's lock and are blocked until the stealing thread has finished. This allows a thread to steal an item from another thread's list without corrupting it. What about synchronization in the collection as a whole? Collection synchronization Any thread that operates on the collection's global structure (accessing anything outside the thread local lists) has to take out the collection's global lock - m_globalListsLock. This single lock is sufficient when adding a new thread local list, as the items inside each thread's list are unaffected. However, what about operations (such as Count or ToArray) that need to access every item in the collection? In order to ensure a consistent view, all operations on the collection are stopped while the count or ToArray is performed. This is done by freezing the bag at the start, performing the global operation, and unfreezing at the end: The global lock is taken out, to prevent structural alterations to the collection. m_needSync is set to true. This notifies all the threads that they need to take out their list's lock irregardless of what operation they're doing. All the list locks are taken out in order. This blocks all locking operations on the lists. The freezing thread waits for all current lockless operations to finish by spinwaiting on each m_currentOp field. The global operation can then be performed while the bag is frozen, but no other operations can take place at the same time, as all other threads are blocked on a list's lock. Then, once the global operation has finished, the locks are released, m_needSync is unset, and normal concurrent operation resumes. Concurrent principles That's the essence of how ConcurrentBag operates. Each thread operates independently on its own local list, except when they have to steal items from another list. When stealing, only the stealing thread is forced to take out the lock; the owning thread only has to when there is the possibility of contention. And a global lock controls accesses to the structure of the collection outside the thread lists. Operations affecting the entire collection take out all locks in the collection to freeze the contents at a single point in time. So, what principles can we extract here? Threads operate independently Thread-static variables and ThreadLocal makes this easy. Threads operate entirely concurrently on their own structures; only when they need to grab data from another thread is there any thread contention. Minimised lock-taking Even when two threads need to operate on the same data structures (one thread stealing from another), they do so in such a way such that the probability of actually blocking on a lock is minimised; the owning thread always operates on the head of the list, and the stealing thread always operates on the tail. Management of lockless operations Any operations that don't take out a lock still have a 'hook' to force them to lock when necessary. This allows all operations on the collection to be stopped temporarily while a global snapshot is taken. Hopefully, such operations will be short-lived and infrequent. That's all the concurrent collections covered. I hope you've found it as informative and interesting as I have. Next, I'll be taking a closer look at ThreadLocal, which I came across while analyzing ConcurrentBag. As you'll see, the operation of this class deserves a much closer look.

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  • Client-server application design issue

    - by user2547823
    I have a collection of clients on server's side. And there are some objects that need to work with that collection - adding and removing clients, sending message to them, updating connection settings and so on. They should perform these actions simultaneously, so mutex or another synchronization primitive is required. I want to share one instance of collection between these objects, but all of them require access to private fields of collection. I hope that code sample makes it more clear[C++]: class Collection { std::vector< Client* > clients; Mutex mLock; ... } class ClientNotifier { void sendMessage() { mLock.lock(); // loop over clients and send message to each of them } } class ConnectionSettingsUpdater { void changeSettings( const std::string& name ) { mLock.lock(); // if client with this name is inside collection, change its settings } } As you can see, all these classes require direct access to Collection's private fields. Can you give me an advice about how to implement such behaviour correctly, i.e. keeping Collection's interface simple without it knowing about its users?

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  • Static vs. dynamic memory allocation - lots of constant objects, only small part of them used at runtime

    - by k29
    Here are two options: Option 1: enum QuizCategory { CATEGORY_1(new MyCollection<Question>() .add(Question.QUESTION_A) .add(Question.QUESTION_B) .add...), CATEGORY_2(new MyCollection<Question>() .add(Question.QUESTION_B) .add(Question.QUESTION_C) .add...), ... ; public MyCollection<Question> collection; private QuizCategory(MyCollection<Question> collection) { this.collection = collection; } public Question getRandom() { return collection.getRandomQuestion(); } } Option 2: enum QuizCategory2 { CATEGORY_1 { @Override protected MyCollection<Question> populateWithQuestions() { return new MyCollection<Question>() .add(Question.QUESTION_A) .add(Question.QUESTION_B) .add...; } }, CATEGORY_2 { @Override protected MyCollection<Question> populateWithQuestions() { return new MyCollection<Question>() .add(Question.QUESTION_B) .add(Question.QUESTION_C) .add...; } }; public Question getRandom() { MyCollection<Question> collection = populateWithQuestions(); return collection.getRandomQuestion(); } protected abstract MyCollection<Question> populateWithQuestions(); } There will be around 1000 categories, each containing 10 - 300 questions (100 on average). At runtime typically only 10 categories and 30 questions will be used. Each question is itself an enum constant (with its fields and methods). I'm trying to decide between those two options in the mobile application context. I haven't done any measurements since I have yet to write the questions and would like to gather more information before committing to one or another option. As far as I understand: (a) Option 1 will perform better since there will be no need to populate the collection and then garbage-collect the questions; (b) Option 1 will require extra memory: 1000 categories x 100 questions x 4 bytes for each reference = 400 Kb, which is not significant. So I'm leaning to Option 1, but just wondered if I'm correct in my assumptions and not missing something important? Perhaps someone has faced a similar dilemma? Or perhaps it doesn't actually matter that much?

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  • I am trying to figure out the best way to understand how to cache domain objects

    - by Brett Ryan
    I've always done this wrong, I'm sure a lot of others have too, hold a reference via a map and write through to DB etc.. I need to do this right, and I just don't know how to go about it. I know how I want my objects to be cached but not sure on how to achieve it. What complicates things is that I need to do this for a legacy system where the DB can change without notice to my application. So in the context of a web application, let's say I have a WidgetService which has several methods: Widget getWidget(); Collection<Widget> getAllWidgets(); Collection<Widget> getWidgetsByCategory(String categoryCode); Collection<Widget> getWidgetsByContainer(Integer parentContainer); Collection<Widget> getWidgetsByStatus(String status); Given this, I could decide to cache by method signature, i.e. getWidgetsByCategory("AA") would have a single cache entry, or I could cache widgets individually, which would be difficult I believe; OR, a call to any method would then first cache ALL widgets with a call to getAllWidgets() but getAllWidgets() would produce caches that match all the keys for the other method invocations. For example, take the following untested theoretical code. Collection<Widget> getAllWidgets() { Entity entity = cache.get("ALL_WIDGETS"); Collection<Widget> res; if (entity == null) { res = loadCache(); } else { res = (Collection<Widget>) entity.getValue(); } return res } Collection<Widget> loadCache() { // Get widgets from underlying DB Collection<Widget> res = db.getAllWidgets(); cache.put("ALL_WIDGETS", res); Map<String, List<Widget>> byCat = new HashMap<>(); for (Widget w : res) { // cache by different types of method calls, i.e. by category if (!byCat.containsKey(widget.getCategory()) { byCat.put(widget.getCategory(), new ArrayList<Widget>); } byCat.get(widget.getCatgory(), widget); } cacheCategories(byCat); return res; } Collection<Widget> getWidgetsByCategory(String categoryCode) { CategoryCacheKey key = new CategoryCacheKey(categoryCode); Entity ent = cache.get(key); if (entity == null) { loadCache(); } ent = cache.get(key); return ent == null ? Collections.emptyList() : (Collection<Widget>)ent.getValue(); } NOTE: I have not worked with a cache manager, the above code illustrates cache as some object that may hold caches by key/value pairs, though it's not modelled on any specific implementation. Using this I have the benefit of being able to cache all objects in the different ways they will be called with only single objects on the heap, whereas if I were to cache the method call invocation via say Spring It would (I believe) cache multiple copies of the objects. I really wish to try and understand the best ways to cache domain objects before I go down the wrong path and make it harder for myself later. I have read the documentation on the Ehcache website and found various articles of interest, but nothing to give a good solid technique. Since I'm working with an ERP system, some DB calls are very complicated, not that the DB is slow, but the business representation of the domain objects makes it very clumsy, coupled with the fact that there are actually 11 different DB's where information can be contained that this application is consolidating in a single view, this makes caching quite important.

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  • How can a collection class instantiate many objects with one database call?

    - by Buttle Butkus
    I have a baseClass where I do not want public setters. I have a load($id) method that will retrieve the data for that object from the db. I have been using static class methods like getBy($property,$values) to return multiple class objects using a single database call. But some people say that static methods are not OOP. So now I'm trying to create a baseClassCollection that can do the same thing. But it can't, because it cannot access protected setters. I don't want everyone to be able to set the object's data. But it seems that it is an all-or-nothing proposition. I cannot give just the collection class access to the setters. I've seen a solution using debug_backtrace() but that seems inelegant. I'm moving toward just making the setters public. Are there any other solutions? Or should I even be looking for other solutions?

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  • Where can I find a collection of photorealistic scenes? [on hold]

    - by emchristiansen
    Where can I find a collection of 10-100 3D scenes with photorealistic levels of detail? For example, the scene rendered here contains photorealistic detail. Note I want the underlying object models, textures, etc, not final renderings. I'll be using these scenes to test a computer vision idea. BTW, this is a reposting of this question. I wasn't able to find a Stack Exchange site that is perfectly suited to the question, but as this is a modeling and rendering question, I'm hoping it is a good enough match for the venue.

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  • JGoodies HashMap

    - by JohnMcClane
    Hi, I'm trying to build a chart program using presentation model. Using JGoodies for data binding was relatively easy for simple types like strings or numbers. But I can't figure out how to use it on a hashmap. I'll try to explain how the chart works and what my problem is: A chart consists of DataSeries, a DataSeries consists of DataPoints. I want to have a data model and to be able to use different views on the same model (e.g. bar chart, pie chart,...). Each of them consists of three classes. For example: DataPointModel: holds the data model (value, label, category) DataPointViewModel: extends JGoodies PresentationModel. wraps around DataPointModel and holds view properties like font and color. DataPoint: abstract class, extends JComponent. Different Views must subclass and implement their own ui. Binding and creating the data model was easy, but i don't know how to bind my data series model. package at.onscreen.chart; import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; import java.beans.PropertyVetoException; import java.util.Collection; import java.util.HashMap; import java.util.Iterator; public class DataSeriesModel { public static String PROPERTY_DATAPOINT = "dataPoint"; public static String PROPERTY_DATAPOINTS = "dataPoints"; public static String PROPERTY_LABEL = "label"; public static String PROPERTY_MAXVALUE = "maxValue"; /** * holds the data points */ private HashMap dataPoints; /** * the label for the data series */ private String label; /** * the maximum data point value */ private Double maxValue; /** * the model supports property change notification */ private PropertyChangeSupport propertyChangeSupport; /** * default constructor */ public DataSeriesModel() { this.maxValue = Double.valueOf(0); this.dataPoints = new HashMap(); this.propertyChangeSupport = new PropertyChangeSupport(this); } /** * constructor * @param label - the series label */ public DataSeriesModel(String label) { this.dataPoints = new HashMap(); this.maxValue = Double.valueOf(0); this.label = label; this.propertyChangeSupport = new PropertyChangeSupport(this); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public DataSeriesModel(String label, DataPoint[] dataPoints) { this.dataPoints = new HashMap(); this.propertyChangeSupport = new PropertyChangeSupport(this); this.maxValue = Double.valueOf(0); this.label = label; for (int i = 0; i < dataPoints.length; i++) { this.addDataPoint(dataPoints[i]); } } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public DataSeriesModel(String label, Collection dataPoints) { this.dataPoints = new HashMap(); this.propertyChangeSupport = new PropertyChangeSupport(this); this.maxValue = Double.valueOf(0); this.label = label; for (Iterator it = dataPoints.iterator(); it.hasNext();) { this.addDataPoint(it.next()); } } /** * adds a new data point to the series. if the series contains a data point with same id, it will be replaced by the new one. * @param dataPoint - the data point */ public void addDataPoint(DataPoint dataPoint) { String category = dataPoint.getCategory(); DataPoint oldDataPoint = this.getDataPoint(category); this.dataPoints.put(category, dataPoint); this.setMaxValue(Math.max(this.maxValue, dataPoint.getValue())); this.propertyChangeSupport.firePropertyChange(PROPERTY_DATAPOINT, oldDataPoint, dataPoint); } /** * returns the data point with given id or null if not found * @param uid - the id of the data point * @return the data point or null if there is no such point in the table */ public DataPoint getDataPoint(String category) { return this.dataPoints.get(category); } /** * removes the data point with given id from the series, if present * @param category - the data point to remove */ public void removeDataPoint(String category) { DataPoint dataPoint = this.getDataPoint(category); this.dataPoints.remove(category); if (dataPoint != null) { if (dataPoint.getValue() == this.getMaxValue()) { Double maxValue = Double.valueOf(0); for (Iterator it = this.iterator(); it.hasNext();) { DataPoint itDataPoint = it.next(); maxValue = Math.max(itDataPoint.getValue(), maxValue); } this.setMaxValue(maxValue); } } this.propertyChangeSupport.firePropertyChange(PROPERTY_DATAPOINT, dataPoint, null); } /** * removes all data points from the series * @throws PropertyVetoException */ public void removeAll() { this.setMaxValue(Double.valueOf(0)); this.dataPoints.clear(); this.propertyChangeSupport.firePropertyChange(PROPERTY_DATAPOINTS, this.getDataPoints(), null); } /** * returns the maximum of all data point values * @return the maximum of all data points */ public Double getMaxValue() { return this.maxValue; } /** * sets the max value * @param maxValue - the max value */ protected void setMaxValue(Double maxValue) { Double oldMaxValue = this.getMaxValue(); this.maxValue = maxValue; this.propertyChangeSupport.firePropertyChange(PROPERTY_MAXVALUE, oldMaxValue, maxValue); } /** * returns true if there is a data point with given category * @param category - the data point category * @return true if there is a data point with given category, otherwise false */ public boolean contains(String category) { return this.dataPoints.containsKey(category); } /** * returns the label for the series * @return the label for the series */ public String getLabel() { return this.label; } /** * returns an iterator over the data points * @return an iterator over the data points */ public Iterator iterator() { return this.dataPoints.values().iterator(); } /** * returns a collection of the data points. the collection supports removal, but does not support adding of data points. * @return a collection of data points */ public Collection getDataPoints() { return this.dataPoints.values(); } /** * returns the number of data points in the series * @return the number of data points */ public int getSize() { return this.dataPoints.size(); } /** * adds a PropertyChangeListener * @param listener - the listener */ public void addPropertyChangeListener(PropertyChangeListener listener) { this.propertyChangeSupport.addPropertyChangeListener(listener); } /** * removes a PropertyChangeListener * @param listener - the listener */ public void removePropertyChangeListener(PropertyChangeListener listener) { this.propertyChangeSupport.removePropertyChangeListener(listener); } } package at.onscreen.chart; import java.beans.PropertyVetoException; import java.util.Collection; import java.util.Iterator; import com.jgoodies.binding.PresentationModel; public class DataSeriesViewModel extends PresentationModel { /** * default constructor */ public DataSeriesViewModel() { super(new DataSeriesModel()); } /** * constructor * @param label - the series label */ public DataSeriesViewModel(String label) { super(new DataSeriesModel(label)); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public DataSeriesViewModel(String label, DataPoint[] dataPoints) { super(new DataSeriesModel(label, dataPoints)); } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public DataSeriesViewModel(String label, Collection dataPoints) { super(new DataSeriesModel(label, dataPoints)); } /** * full constructor * @param model - the data series model */ public DataSeriesViewModel(DataSeriesModel model) { super(model); } /** * adds a data point to the series * @param dataPoint - the data point */ public void addDataPoint(DataPoint dataPoint) { this.getBean().addDataPoint(dataPoint); } /** * returns true if there is a data point with given category * @param category - the data point category * @return true if there is a data point with given category, otherwise false */ public boolean contains(String category) { return this.getBean().contains(category); } /** * returns the data point with given id or null if not found * @param uid - the id of the data point * @return the data point or null if there is no such point in the table */ public DataPoint getDataPoint(String category) { return this.getBean().getDataPoint(category); } /** * returns a collection of the data points. the collection supports removal, but does not support adding of data points. * @return a collection of data points */ public Collection getDataPoints() { return this.getBean().getDataPoints(); } /** * returns the label for the series * @return the label for the series */ public String getLabel() { return this.getBean().getLabel(); } /** * sets the max value * @param maxValue - the max value */ public Double getMaxValue() { return this.getBean().getMaxValue(); } /** * returns the number of data points in the series * @return the number of data points */ public int getSize() { return this.getBean().getSize(); } /** * returns an iterator over the data points * @return an iterator over the data points */ public Iterator iterator() { return this.getBean().iterator(); } /** * removes all data points from the series * @throws PropertyVetoException */ public void removeAll() { this.getBean().removeAll(); } /** * removes the data point with given id from the series, if present * @param category - the data point to remove */ public void removeDataPoint(String category) { this.getBean().removeDataPoint(category); } } package at.onscreen.chart; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.beans.PropertyVetoException; import java.util.Collection; import java.util.Iterator; import javax.swing.JComponent; public abstract class DataSeries extends JComponent implements PropertyChangeListener { /** * the model */ private DataSeriesViewModel model; /** * default constructor */ public DataSeries() { this.model = new DataSeriesViewModel(); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * constructor * @param label - the series label */ public DataSeries(String label) { this.model = new DataSeriesViewModel(label); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public DataSeries(String label, DataPoint[] dataPoints) { this.model = new DataSeriesViewModel(label, dataPoints); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public DataSeries(String label, Collection dataPoints) { this.model = new DataSeriesViewModel(label, dataPoints); this.model.addPropertyChangeListener(this); this.createComponents(); } /** * full constructor * @param model - the model */ public DataSeries(DataSeriesViewModel model) { this.model = model; this.model.addPropertyChangeListener(this); this.createComponents(); } /** * creates, binds and configures UI components. * data point properties can be created here as components or be painted in paintComponent. */ protected abstract void createComponents(); @Override public void propertyChange(PropertyChangeEvent evt) { this.repaint(); } /** * adds a data point to the series * @param dataPoint - the data point */ public void addDataPoint(DataPoint dataPoint) { this.model.addDataPoint(dataPoint); } /** * returns true if there is a data point with given category * @param category - the data point category * @return true if there is a data point with given category, otherwise false */ public boolean contains(String category) { return this.model.contains(category); } /** * returns the data point with given id or null if not found * @param uid - the id of the data point * @return the data point or null if there is no such point in the table */ public DataPoint getDataPoint(String category) { return this.model.getDataPoint(category); } /** * returns a collection of the data points. the collection supports removal, but does not support adding of data points. * @return a collection of data points */ public Collection getDataPoints() { return this.model.getDataPoints(); } /** * returns the label for the series * @return the label for the series */ public String getLabel() { return this.model.getLabel(); } /** * sets the max value * @param maxValue - the max value */ public Double getMaxValue() { return this.model.getMaxValue(); } /** * returns the number of data points in the series * @return the number of data points */ public int getDataPointCount() { return this.model.getSize(); } /** * returns an iterator over the data points * @return an iterator over the data points */ public Iterator iterator() { return this.model.iterator(); } /** * removes all data points from the series * @throws PropertyVetoException */ public void removeAll() { this.model.removeAll(); } /** * removes the data point with given id from the series, if present * @param category - the data point to remove */ public void removeDataPoint(String category) { this.model.removeDataPoint(category); } /** * returns the data series view model * @return - the data series view model */ public DataSeriesViewModel getViewModel() { return this.model; } /** * returns the data series model * @return - the data series model */ public DataSeriesModel getModel() { return this.model.getBean(); } } package at.onscreen.chart.builder; import java.util.Collection; import net.miginfocom.swing.MigLayout; import at.onscreen.chart.DataPoint; import at.onscreen.chart.DataSeries; import at.onscreen.chart.DataSeriesViewModel; public class BuilderDataSeries extends DataSeries { /** * default constructor */ public BuilderDataSeries() { super(); } /** * constructor * @param label - the series label */ public BuilderDataSeries(String label) { super(label); } /** * full constructor * @param label - the series label * @param dataPoints - an array of data points */ public BuilderDataSeries(String label, DataPoint[] dataPoints) { super(label, dataPoints); } /** * full constructor * @param label - the series label * @param dataPoints - a collection of data points */ public BuilderDataSeries(String label, Collection dataPoints) { super(label, dataPoints); } /** * full constructor * @param model - the model */ public BuilderDataSeries(DataSeriesViewModel model) { super(model); } @Override protected void createComponents() { this.setLayout(new MigLayout()); /* * * I want to add a new BuilderDataPoint for each data point in the model. * I want the BuilderDataPoints to be synchronized with the model. * e.g. when a data point is removed from the model, the BuilderDataPoint shall be removed * from the BuilderDataSeries * */ } } package at.onscreen.chart.builder; import javax.swing.JFormattedTextField; import javax.swing.JTextField; import at.onscreen.chart.DataPoint; import at.onscreen.chart.DataPointModel; import at.onscreen.chart.DataPointViewModel; import at.onscreen.chart.ValueFormat; import com.jgoodies.binding.adapter.BasicComponentFactory; import com.jgoodies.binding.beans.BeanAdapter; public class BuilderDataPoint extends DataPoint { /** * default constructor */ public BuilderDataPoint() { super(); } /** * constructor * @param category - the category */ public BuilderDataPoint(String category) { super(category); } /** * constructor * @param value - the value * @param label - the label * @param category - the category */ public BuilderDataPoint(Double value, String label, String category) { super(value, label, category); } /** * full constructor * @param model - the model */ public BuilderDataPoint(DataPointViewModel model) { super(model); } @Override protected void createComponents() { BeanAdapter beanAdapter = new BeanAdapter(this.getModel(), true); ValueFormat format = new ValueFormat(); JFormattedTextField value = BasicComponentFactory.createFormattedTextField(beanAdapter.getValueModel(DataPointModel.PROPERTY_VALUE), format); this.add(value, "w 80, growx, wrap"); JTextField label = BasicComponentFactory.createTextField(beanAdapter.getValueModel(DataPointModel.PROPERTY_LABEL)); this.add(label, "growx, wrap"); JTextField category = BasicComponentFactory.createTextField(beanAdapter.getValueModel(DataPointModel.PROPERTY_CATEGORY)); this.add(category, "growx, wrap"); } } To sum it up: I need to know how to bind a hash map property to JComponent.components property. JGoodies is in my opinion not very well documented, I spent a long time searching through the internet, but I did not find any solution to my problem. Hope you can help me.

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  • Monitoring / metric collection for system collectives that change a lot in time (a.k.a. cloud)

    - by Florin Andrei
    When your server fleet doesn't change a lot in time, like when you're using bare-metal hosting, classic monitoring and metric collection solutions (Nagios, Munin) work well. But if the number of systems varies a lot in time, and may in fact vary rapidly, classic software is more difficult to setup and use. E.g., trying to make Nagios (monitoring) keep up with a rapidly evolving cloud infrastructure can be cumbersome. Same for Munin (metric collection). It's not just the configuration, but the way the information is conveyed to the user, or displayed, is inadequate for the cloud. What are some possible alternatives that work well with the cloud? The goals are to collect and display metrics (analog to Munin), and generate alerts when certain metrics go out of bounds or when certain services are unavailable (analog to Nagios), and do everything in a cloud-friendly manner. Some cloud providers offer monitoring / metric collection as services, but not always, and if you use more than one provider you don't want to become too dependent of just one vendor. So provider-independent solutions are required. EDIT: I am asking this question in a general fashion - not limited to any given cloud infrastructure (like OpenStack), but in the general case of using arbitrary cloud providers.

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  • Upgrading Team Foundation Server 2008 to 2010

    - by Martin Hinshelwood
    I am sure you will have seen my posts on upgrading our internal Team Foundation Server from TFS2008 to TFS2010 Beta 2, RC and RTM, but what about a fresh upgrade of TFS2008 to TFS2010 using the RTM version of TFS. One of our clients is taking the plunge with TFS2010, so I have the job of doing the upgrade. It is sometimes very useful to have a team member that starts work when most of the Sydney workers are heading home as I can do the upgrade without impacting them. The down side is that if you have any blockers then you can be pretty sure that everyone that can deal with your problem is asleep I am starting with an existing blank installation of TFS 2010, but Adam Cogan let slip that he was the one that did the install so I thought it prudent to make sure that it was OK. Verifying Team Foundation Server 2010 We need to check that TFS 2010 has been installed correctly. First, check the Admin console and have a root about for any errors. Figure: Even the SQL Setup looks good. I don’t know how Adam did it! Backing up the Team Foundation Server 2008 Databases As we are moving from one server to another (recommended method) we will be taking a backup of our TFS2008 databases and resorting them to the SQL Server for the new TFS2010 Server. Do not just detach and reattach. This will cause problems with the version of the database. If you are running a test migration you just need to create a backup of the TFS 2008 databases, but if you are doing the live migration then you should stop IIS on the TFS 2008 server before you backup the databases. This will stop any inadvertent check-ins or changes to TFS 2008. Figure: Stop IIS before you take a backup to prevent any TFS 2008 changes being written to the database. It is good to leave a little time between taking the TFS 2008 server offline and commencing the upgrade as there is always one developer who has not finished and starts screaming. This time it was John Liu that needed 10 more minutes to make his changes and check-in, so I always give it 30 minutes and see if anyone screams. John Liu [SSW] said:   are you doing something to TFS :-O MrHinsh [SSW UK][VS ALM MVP] said:   I have stopped TFS 2008 as per my emails John Liu [SSW] said:   haven't finish check in @_@   can we have it for 10mins? :) MrHinsh [SSW UK][VS ALM MVP] said:   TFS 2008 has been started John Liu [SSW] said:   I love you! -IM conversation at TFS Upgrade +25 minutes After John confirmed that he had everything done I turned IIS off again and made a cup of tea. There were no more screams so the upgrade can continue. Figure: Backup all of the databases for TFS and include the Reporting Services, just in case.   Figure: Check that all the backups have been taken Once you have your backups, you need to copy them to your new TFS2010 server and restore them. This is a good way to proceed as if we have any problems, or just plain run out of time, then you just turn the TFS 2008 server back on and all you have lost is one upgrade day, and not 10 developer days. As per the rules, you should record the number of files and the total number of areas and iterations before the upgrade so you have something to compare to: TFS2008 File count: Type Count 1 1845 2 15770 Areas & Iterations: 139 You can use this to verify that the upgrade was successful. it should however be noted that the numbers in TFS 2010 will be bigger. This is due to some of the sorting out that TFS does during the upgrade process. Restore Team Foundation Server 2008 Databases Restoring the databases is much more time consuming than just attaching them as you need to do them one at a time. But you may be taking a backup of an operational database and need to restore all your databases to a particular point in time instead of to the latest. I am doing latest unless I encounter any problems. Figure: Restore each of the databases to either a latest or specific point in time.     Figure: Restore all of the required databases Now that all of your databases are restored you now need to upgrade them to Team Foundation Server 2010. Upgrade Team Foundation Server 2008 Databases This is probably the easiest part of the process. You need to call a fire and forget command that will go off to the database specified, find the TFS 2008 databases and upgrade them to 2010. During this process all of the 6 main TFS 2008 databases are merged into the TfsVersionControl database, upgraded and then the database is renamed to TFS_[CollectionName]. The rename is only the database and not the physical files, so it is worth going back and renaming the physical file as well. This keeps everything neat and tidy. If you plan to keep the old TFS 2008 server around, for example if you are doing a test migration first, then you will need to change the TFS GUID. This GUID is unique to each TFS instance and is preserved when you upgrade. This GUID is used by the clients and they can get a little confused if there are two servers with the same one. To kick of the upgrade you need to open a command prompt and change the path to “C:\Program Files\Microsoft Team Foundation Server 2010\Tools” and run the “import” command in  “tfsconfig”. TfsConfig import /sqlinstance:<Previous TFS Data Tier>                  /collectionName:<Collection Name>                  /confirmed Imports a TFS 2005 or 2008 data tier as a new project collection. Important: This command should only be executed after adequate backups have been performed. After you import, you will need to configure portal and reporting settings via the administration console. EXAMPLES -------- TfsConfig import /sqlinstance:tfs2008sql /collectionName:imported /confirmed TfsConfig import /sqlinstance:tfs2008sql\Instance /collectionName:imported /confirmed OPTIONS: -------- sqlinstance         The sql instance of the TFS 2005 or 2008 data tier. The TFS databases at that location will be modified directly and will no longer be usable as previous version databases.  Ensure you have back-ups. collectionName      The name of the new Team Project Collection. confirmed           Confirm that you have backed-up databases before importing. This command will automatically look for the TfsIntegration database and verify that all the other required databases exist. In this case it took around 5 minutes to complete the upgrade as the total database size was under 700MB. This was unlike the upgrade of SSW’s production database with over 17GB of data which took a few hours. At the end of the process you should get no errors and no warnings. The Upgrade operation on the ApplicationTier feature has completed. There were 0 errors and 0 warnings. As this is a new server and not a pure upgrade there should not be a problem with the GUID. If you think at any point you will be doing this more than once, for example doing a test migration, or merging many TFS 2008 instances into a single one, then you should go back and rename the physical TfsVersionControl.mdf file to the same as the new collection. This will avoid confusion later down the line. To do this, detach the new collection from the server and rename the physical files. Then reattach and change the physical file locations to match the new name. You can follow http://www.mssqltips.com/tip.asp?tip=1122 for a more detailed explanation of how to do this. Figure: Stop the collection so TFS does not take a wobbly when we detach the database. When you try to start the new collection again you will get a conflict with project names and will require to remove the Test Upgrade collection. This is fine and it just needs detached. Figure: Detaching the test upgrade from the new Team Foundation Server 2010 so we can start the new Collection again. You will now be able to start the new upgraded collection and you are ready for testing. Do you remember the stats we took off the TFS 2008 server? TFS2008 File count: Type Count 1 1845 2 15770 Areas & Iterations: 139 Well, now we need to compare them to the TFS 2010 stats, remembering that there will probably be more files under source control. TFS2010 File count: Type Count 1 19288 Areas & Iterations: 139 Lovely, the number of iterations are the same, and the number of files is bigger. Just what we were looking for. Testing the upgraded Team Foundation Server 2010 Project Collection Can we connect to the new collection and project? Figure: We can connect to the new collection and project.   Figure: make sure you can connect to The upgraded projects and that you can see all of the files. Figure: Team Web Access is there and working. Note that for Team Web Access you now use the same port and URL as for TFS 2010. So in this case as I am running on the local box you need to use http://localhost:8080/tfs which will redirect you to http://localhost:8080/tfs/web for the web access. If you need to connect with a Visual Studio 2008 client you will need to use the full path of the new collection, http://[servername]/tfs/[collectionname] and this will work with all of your collections. With Visual Studio 2005 you will only be able to connect to the Default collection and in both VS2008 and VS2005 you will need to install the forward compatibility updates. Visual Studio Team System 2005 Service Pack 1 Forward Compatibility Update for Team Foundation Server 2010 Visual Studio Team System 2008 Service Pack 1 Forward Compatibility Update for Team Foundation Server 2010 To make sure that you have everything up to date, make sure that you run SSW Diagnostics and get all green ticks. Upgrade Done! At this point you can send out a notice to everyone that the upgrade is complete and and give them the connection details. You need to remember that at this stage we have 2008 project upgraded to run under TFS 2010 but it is still running under that same process template that it was running before. You can only “enable” 2010 features in a process template you can’t upgrade. So what to do? Well, you need to create a new project and migrate things you want to keep across. Souse code is easy, you can move or Branch, but Work Items are more difficult as you can’t move them between projects. This instance is complicated more as the old project uses the Conchango/EMC Scrum for Team System template and I will need to write a script/application to get the work items across with their attachments in tact. That is my next task! Technorati Tags: TFS 2010,TFS 2008,VS ALM

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  • Creating an anonymous site in SharePoint 2010

    - by shehan
    Here’s how: Open up the Central Administration site and click on “Manage Web Applications” under the “Application Management” section From the ribbon click on “New” (Note: if its an existing web app, then click on “Extend”) Fill in the fields with appropriate values. Under “Security Configurations” make sure to select “Yes” for “Allow Anonymous” Click OK Once the web application has been created, a site collection would need to be created. Navigate to “Application Management” –> “Create Site Collection” Fill in the fields with the appropriate values and create the site collection Next sign into the newly created site collection as the Site Collection Administrator. From the “Site Actions” menu, select “Site Permissions” In the permissions page that loads, click on the Anonymous Access button appearing on the ribbon. A modal dialog would popup. Select the appropriate option and click OK. If you selected “Entire Web Site” its advisable to restart the browser to test anonymous access Technorati Tags: SharePoint 2010,anonymous,site collection,web application

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  • JNI cached jclass global reference variables being garbage collected?

    - by bubbadoughball
    I'm working in the JNI Invocation API, calling into Java from C. I have some upfront initialization to cache 30+ Java classes into global references. The results of FindClass are passed into NewGlobalRef to acquire a global reference to the class. I'm caching these class variables to reuse them later. I have 30+ global references to classes (and 30+ global methodIDs for the class constructors). In the following sample, I've removed exception handling as well as JNI invocation for the purpose of shortening the code snippet. My working code has exception checks after every JNI call and I'm running with -Xcheck:jni. Here's the snippet: jclass aClass; jclass bClass; jmethodID aCtor; jmethodID bCtor; void getGlobalRef(const char* clazz, jclass* globalClass) { jclass local = (*jenv)->FindClass(jenv,clazz); if (local) { *globalClass = (jclass) (*jenv)->NewGlobalRef(jenv,local); (*jenv)->DeleteLocalRef(jenv,local); } } methodID getMethodID(jclass clazz, const char* method, const char* sig) { return (*jenv)->GetMethodID(jenv,clazz,method,sig); } void initializeJNI() { getGlobalRef("MyProj/Testclass1", &aclass); getGlobalRef("MyProj/Testclass2", &bclass); . . aCtor = getMethodID(aclass,"<init>","()V"); bCtor = getMethodID(bclass,"<init>","(I)V"); } The initializeJNI() function sets the global references for jclasses and method IDs for constructors as well as some jfieldID's and some initialization of C data structures. After initialization, when I call into a JNI function using some of the cached jclasses and ctor jmethodIDs, I get a bad global or local reference calling reported from the -Xcheck:jni. In gdb, I break at the last line of initializeJNI(), and print all jclasses and jmethodIDs and the ones causing problems look to have been turned into garbage or garbage-collected (i.e. 0x00 or 0x06). Is it possible for global references to be gc'ed? Any suggestions?

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  • Most efficient way to store this collection of moduli and remainders?

    - by Bryan
    I have a huge collection of different moduli and associated with each modulus a fairly large list of remainders. I want to store these values so that I can efficiently determine whether an integer is equivalent to any one of the remainders with respect to any of the moduli (it doesn't matter which, I just want a true/false return). I thought about storing these values as a linked-list of balanced binary trees, but I was wondering if there is a better way? EDIT Perhaps a little more detail would be helpful. As for the size of this structure, it will be holding about 10s of thousands of (prime-1) moduli and associated to each modulus will be a variable amount of remainders. Most moduli will only have one or two remainders associated to it, but a very rare few will have a couple hundred associated to it. This is part of a larger program which handles numbers with a couple thousand (decimal) digits. This program will benefit more from this table being as large as possible and being able to be searched quickly. Here's a small part of the dataset where the moduli are in parentheses and the remainders are comma separated: (46) k = 20 (58) k = 15, 44 (70) k = 57 (102) k = 36, 87 (106) k = 66 (156) k = 20, 59, 98, 137 (190) k = 11, 30, 68, 87, 125, 144, 182 (430) k = 234 (520) k = 152, 282 (576) k = 2, 11, 20, 29, 38, 47, 56, 65, 74, ...(add 9 each time), 569 I had said that the moduli were prime, but I was wrong they are each one below a prime.

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  • Top 10 collection completion - a monster in-query formula in MySQL?

    - by Andrew Heath
    I've got the following tables: User Basic Data (unique) [userid] [name] [etc] User Collection (one to one) [userid] [game] User Recorded Plays (many to many) [userid] [game] [scenario] [etc] Game Basic Data (unique) [game] [total_scenarios] I would like to output a table that shows the collection play completion percentage for the Top 10 users in descending order of %: Output Table [userid] [collection_completion] 3 95% 1 81% 24 68% etc etc In my mind, the calculation sequence for ONE USER is: grab user's total owned scenarios from User Collection joined with Game Basic Data and COUNT(gbd.total_scenarios) grab all recorded plays by COUNT(DISTINCT scenario) for that user Divide all recorded plays by total owned scenarios So that's 2 queries and a little PHP massage at the end. For a list of users sorted by completion percentage things get a little more complicated. I figure I could grab all users' collection totals in one query, and all users recorded plays in another, and then do the calcs and sort the final array in PHP, but it seems like overkill to potentially be doing all that for 1000+ users when I only ever want the Top 10. Is there a wicked monster query in MySQL that could do all that and LIMIT 10? Or is sticking with PHP handling the bulk of the work the way to go in this case?

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  • How do I implement a collection in Scala 2.8?

    - by Simon Reinhardt
    In trying to write an API I'm struggling with Scala's collections in 2.8(.0-beta1). Basically what I need is to write something that: adds functionality to immutable sets of a certain type where all methods like filter and map return a collection of the same type without having to override everything (which is why I went for 2.8 in the first place) where all collections you gain through those methods are constructed with the same parameters the original collection had (similar to how SortedSet hands through an ordering via implicits) which is still a trait in itself, independent of any set implementations. Additionally I want to define a default implementation, for example based on a HashSet. The companion object of the trait might use this default implementation. I'm not sure yet if I need the full power of builder factories to map my collection type to other collection types. I read the paper on the redesign of the collections API but it seems like things have changed a bit since then and I'm missing some details in there. I've also digged through the collections source code but I'm not sure it's very consistent yet. Ideally what I'd like to see is either a hands-on tutorial that tells me step-by-step just the bits that I need or an extensive description of all the details so I can judge myself which bits I need. I liked the chapter on object equality in "Programming in Scala". :-) But I appreciate any pointers to documentation or examples that help me understand the new collections design better.

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  • How to take a collection of bytes and pull typed values out of it?

    - by Pat
    Say I have a collection of bytes var bytes = new byte[] {0, 1, 2, 3, 4, 5, 6, 7}; and I want to pull out a defined value from the bytes as a managed type, e.g. a ushort. What is a simple way to define what types reside at what location in the collection and pull out those values? One (ugly) way is to use System.BitConverter and a Queue or byte[] with an index and simply iterate through, e.g.: int index = 0; ushort first = System.BitConverter.ToUint16(bytes, index); index += 2; // size of a ushort int second = System.BitConverter.ToInt32(bytes, index); index += 4; ... This method gets very, very tedious when you deal with a lot of these structures! I know that there is the System.Runtime.InteropServices.StructLayoutAttribute which allows me to define the locations of types inside a struct or class, but there doesn't seem to be a way to import the collection of bytes into that struct. If I could somehow overlay the struct on the collection of bytes and pull out the values, that would be ideal. E.g. Foo foo = (Foo)bytes; // doesn't work because I'd need to implement the implicit operator ushort first = foo.first; int second = foo.second; ... [StructLayout(LayoutKind.Explicit, Size=FOO_SIZE)] public struct Foo { [FieldOffset(0)] public ushort first; [FieldOffset(2)] public int second; } Any thoughts on how to achieve this?

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  • Use LINQ, to Sort and Filter items in a List<ReturnItem> collection, based on the values within a Li

    - by Daniel McPherson
    This is tricky to explain. We have a DataTable that contains a user configurable selection of columns, which are not known at compile time. Every column in the DataTable is of type String. We need to convert this DataTable into a strongly typed Collection of "ReturnItem" objects so that we can then sort and filter using LINQ for use in our application. We have made some progress as follows: We started with the basic DataTable. We then process the DataTable, creating a new "ReturnItem" object for each row This "ReturnItem" object has just two properties: ID ( string ) and Columns( List(object) ). The properties collection contains one entry for each column, representing a single DataRow. Each property is made Strongly Typed (int, string, datetime, etc). For example it would add a new "DateTime" object to the "ReturnItem" Columns List containing the value of the "Created" Datatable Column. The result is a List(ReturnItem) that we would then like to be able to Sort and Filter using LINQ based on the value in one of the properties, for example, sort on "Created" date. We have been using the LINQ Dynamic Query Library, which gets us so far, but it doesn't look like the way forward because we are using it over a List Collection of objects. Basically, my question boils down to: How can I use LINQ, to Sort and Filter items in a List(ReturnItem) collection, based on the values within a List(object) property which is part of the ReturnItem class?

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  • How to stop XBox Music commercials while playing music in collection?

    - by bill weaver
    So i decided to give Xbox Music a try, and played a song in my collection. Then moved to another song and a commercial started playing. Huh? Searching revealed others with this problem, but i didn't see any answers. Yes, i know Xbox Music plays commercials when streaming free music that you don't own, but this is mp3 music i own, on my hard drive, in my collection. MS claims "You’ll never get ads when you’re playing MP3s that are on your PC or when you’re playing music you bought from Xbox Music." (FWIW, this is running on Windows 8.1 Pro, though the problem seems to have been reported last year too, so it's probably not a new issue.)

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  • How can I organize my video collection and update meta data?

    - by Pieter Breed
    I have a large collection of downloaded video files containing different movies, tv shows and music videos. I have a FreeNAS box set up that uses Fuppes as a UPnP media server. My media player on Windows correctly detects this UPnP collection and can stream from it fine. However, All of my music videos, tv shows and movies are all sorted under the same 'Videos' group. I would like to seperate the different types of video files so that they can correctly go under 'Recorded TV' or whatever the case may be. Any ideas? I guess I am looking for something like an MP3Tagger but for video files?

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  • Linq filtering an IQueryable<T> (System.Data.Linq.DataQuery) object by a List<T> (System.Collection.

    - by Klaptrap
    My IQueryable line is: // find all timesheets for this period - from db so System.Data.Linq.DataQuery var timesheets = _timesheetRepository.FindByPeriod(dte1, dte2); My List line is: // get my team from AD - from active directory so System.Collection.Generic.List var adUsers = _adUserRepository.GetMyTeam(User.Identity.Name); I wish to only show timesheets for those users in the timesheet collection that are present in the user collection. If I use a standard c# expression such as: var teamsheets = from t in timesheets join user in adUsers on t.User1.username equals user.fullname select t; I get the error "An IQueryable that returns a self-referencing Constant expression is not supported" Any recommendations?

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  • Which collection interface should I use in .NET for COM-interop?

    - by jhominal
    That is a followup from my previous question, but you don't need to read it to understand that one. I'm designing an interface in .NET that would be consumed from COM applications (mainly VB6, but Visual C++ 6 is also a possibility) and I would like to use Collection types as argument and return types for the methods in the interface. Questions: What happens to the VB6 built-in collection types (arrays, collections, dictionaries) when they go through interop? My current guess is that: arrays - System.Array collections - Microsoft.VisualBasic.Collection dictionaries - System.Collections.Hashtable Is that correct? Which interfaces should I use as return types? IEnumerable, ICollection, IList, IDictionary? Would I be able to do a For Each in VB6 to iterate over these interfaces? Should I use the generic or non-generic variants of the interfaces?

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  • How to use List<T>.Find() on a simple collection that does not implement Find()?

    - by Bilal
    Hi, I want to use List.Find() on a simple collection that does not implement Find(). The naive way I thought of, is to just wrap it with a list and execute .Find(), like this: ICollection myCows = GetAllCowsFromFarm(); // whatever the collection impl. is... var steak = new List<Cow>(myCows).Find(moo => moo.Name == "La Vache qui Rit"); Now, 1st of all I'd like to know, C#-wise, what is the cost of this wrapping? Is it still faster to 'for' this collection the traditional way? Second, is there a better straightforward way elegantly use that .Find()? Cheers!

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  • Can you open an SPSite object while being within a different site collection?

    - by Chris Stewart
    I'm working on creating a common navigation experience across two site collections in MOSS 2007. I've looked around for various solutions and haven't found anything that fits. Our navigation is dynamic and driven by a number of factors, including audience targeting. Most of what I've found relates to having static XML and that just won't work for our requirements. What I'm down to at the moment is just getting a navigation item from site collection A while in the context of site collection B. Are there reasons I shouldn't be able to just open a navigation item from site collection A and gets its audience? Certainly there could be permissions problems on my end, or code related issues, or things that are in my control. What I'm wondering is if there's something inherent to SharePoint that would not allow this. Something I don't have control over which would force me to travel a different path.

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  • C# Elegant way to handle checking for an item in a collection.

    - by JL
    I've posted a code sample below. Firstly let me explain termStore.Groups in the code below is a collection of Group Objects (The exact class is irrelevant). Checking for null : if (termStore.Groups[groupName] == null) seems like a logical (clean) approach, but if the Groups collection is empty then an exception is produced. using the termStore.Groups.Contains is not an option either because this expects a strong type i.e: .Contains(Group)... not .Contains(GroupName as string) Can someone recommend a clean / generic way I can check for if an item exists in collection . Thank you.... TermStore termStore = session.TermStores.Where(ts => ts.Name == termStoreName).FirstOrDefault(); if (termStore.Groups[groupName] == null) { termStore.CreateGroup(groupName); termStore.CommitAll(); } Update: The exact class Sharepoint Taxonomy Classes. http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.taxonomy.group.aspx

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  • how to add a variables which comes from dataset in for loop Collection array in c#?

    - by leventkalay1986
    I have a collection of RSS items protected Collection<Rss.Items> list = new Collection<Rss.Items>(); The class RSS.Items includes properties such as Link, Text, Description, etc. But when I try to read the XML and set these properties: for (int i = 0; i < dt.Rows.Count; i++) { row = dt.Rows[i]; list[i].Link.Equals(row[0].ToString()); list[i].Description.Equals( row[1].ToString()); list[i].Title.Equals( row[2].ToString()); list[i].Date.Equals( Convert.ToDateTime(row[3])); } I get a null reference exception on the line list[i].Link.Equals(row[0].ToString()); What am I doing wrong?

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