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  • Using ADO.NET Entities LINQ Provider to model complex SQL Queries?

    - by Ivan Zlatanov
    What I find really powerful in ADO.NET Entities or LINQ to SQL, is the ability to model complex queries. I really don't need the mappings that Entities or LINQ to SQL are doing for me - I just need the ability to model complex expressions that can be translated into T-SQL. My question is - am I abusing too much? Can I use the Entity Framework for modeling queries and just that? Should I? I know I can write my own custom LINQ to SQL provider, but that is just not possible to handle in the time spans I have. What is the best approach to model complex T-SQL queries? How do you handle conditional group byes, orders, joins, unions etc in the OOP world? Using StringBuilders for this kind of job feels too ugly and harder to maintain given the possibilities we have with Expression Trees. When I use StringBuilder to model a complex SQL Query I feel kind of guilty! I feel the same way as when I have to hard code any number into my code that is different than 0 or 1. Feeling that makes you ask yourself if there is a better and cleaner way of doing it... I must mention that I am using C# 4.0, but I am not specifically looking for an answer in this language, but rather in the domain of CLR 4.

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  • [EF + Oracle] Entities

    - by JTorrecilla
    Prologue Following with the Serie I started yesterday about Entity Framework with Oracle, Today I am going to start talking about Entities. What is an Entity? A Entity is an object of the EF model corresponding to a record in a DB table. For example, let’s see, in Image 1 we can see one Entity from our model, and in the second one we can see the mapping done with the DB. (Image 1) (Image 2) More in depth a Entity is a Class inherited from the abstract class “EntityObject”, contained by the “System.Data.Objects.DataClasses” namespace. At the same time, this class inherits from the following Class and interfaces: StructuralObject: It is an Abstract class that inherits from INotifyPropertyChanging and INotifyPropertyChanged interfaces, and it exposes the events that manage the Changes of the class, and the functions related to check the data types of the Properties from our Entity.  IEntityWithKey: Interface which exposes the Key of the entity. IEntityWithChangeTracker: Interface which lets indicate the state of the entity (Detached, Modified, Added…) IEntityWithRelationships: Interface which indicates the relations about the entity. Which is the Content of a Entity? A Entity is composed by: Properties, Navigation Properties and Methods. What is a Property? A Entity Property is an object that represents a column from the mapped table from DB. It has a data type equivalent in .Net Framework to the DB Type. When we create the EF model, VS, internally, create the code for each Entity selected in the Tables step, such all methods that we will see in next steps. For each property, VS creates a structure similar to: · Private variable with the mapped Data type. · Function with a name like On{Property_Name}Changing({dataType} value): It manages the event which happens when we try to change the value. · Function with a name like On{Property_Name}Change: It manages the event raised when the property has changed successfully. · Property with Get and Set methods: The Set Method manages the private variable and do the following steps: Raise Changing event. Report the Entity is Changing. Set the prívate variable. For it, Use the SetValidValue function of the StructuralObject. There is a function for each datatype, and the functions takes 2 params: the value, and if the prop allow nulls. Invoke that the entity has been successfully changed. Invoke the Changed event of the Prop. ReportPropertyChanging and ReportPropertyChanged events, let, respectively, indicate that there is pending changes in the Entity, and the changes have success correctly. While the ReportPropertyChanged is raised, the Track State of the Entity will be changed. What is a Navigation Property? Navigation Properties are a kind of property of the type: EntityCollection<TEntity>, where TEntity is an Entity type from the model related with the current one, it is said, is a set of record from a related table in the DB. The EntityCollection class inherits from: · RelatedEnd: There is an abstract class that give the functions needed to obtein the related objects. · ICollection<TEntity> · IEnumerable<TEntity> · IEnumerable · IListSource For the previous interfaces, I wish recommend the following post from Jose Miguel Torres. Navigation properties allow us, to get and query easily objects related with the Entity. Methods? There is only one method in the Entity object. “Create{Entity}”, that allow us to create an object of the Entity by sending the parameters needed to create it. Finally After this chapter, we know what is an Entity, how is related to the DB and the relation to other Entities. In following chapters, we will se CRUD operations(Create, Read, Update, Delete).

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  • How do I unescape HTML entities in a string in Python 3.1?

    - by Sho Minamimoto
    I have looked all around and only found solutions for python 2.6 and earlier, NOTHING on how to do this in python 3.X. (I only have access to Win7 box.) I HAVE to be able to do this in 3.1 and preferably without external libraries. Currently, I have httplib2 installed and access to command-prompt curl (that's how I'm getting the source code for pages). Unfortunately, curl does not decode html entities, as far as I know, I couldn't find a command to decode it in the documentation. YES, I've tried to get Beautiful Soup to work, MANY TIMES without success in 3.X. If you could provide EXPLICIT instructions on how to get it to work in python 3 in MS Windows environment, I would be very grateful. So, to be clear, I need to turn strings like this: Suzy &amp; John into a string like this: "Suzy & John".

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  • Entity LINQ on many-to-many got error "LINQ to Entities does not recognize the method 'Boolean Conta

    - by user300992
    I have 2 tables (Users and Roles) they are mapped as Many-to-Many in relational db. When I imported to Entity Data Content, they are still staying as the same relationship. Since they are mapped as Many-To-Many in Entity, I can access Users.RoleCollection or Roles.UserCollection However, when I execute this LINQ query, I got "LINQ to Entities does not recognize the method 'Boolean Contains... method, and this method cannot be translated into a store expression." var result (from a in Users from b in Roles where a.RoleCollection.Contains(b) select a); I think I must did something wrong... please help.

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  • Turning HTML character entities to 'regular' letters... why is it only partially working?

    - by Jack W-H
    I'm using all of the below to take a field called 'code' from my database, get rid of all the HTML entities, and print it 'as usual' to the site: <?php $code = preg_replace('~&#x([0-9a-f]+);~ei', 'chr(hexdec("\\1"))', $code); $code = preg_replace('~&#([0-9]+);~e', 'chr("\\1")', $code); $code = html_entity_decode($code); ?> However the exported code still looks like this: progid:DXImageTransform.Microsoft.AlphaImageLoader(src=’img/the_image.png’); See what's going on there? How many other things can I run on the string to turn them into darn regular characters?! Thanks! Jack

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  • How to make Nokogiri transparently return un/encoded Html entities untouched?

    - by svenfuchs
    How can I use Nokogiri with having html entities (like German umlauts) untouched? I.e.: # this is fine node = Nokogiri::HTML.fragment('<p>&ouml;</p>') node.to_s # => '<p>&ouml;</p>' # this is not node = Nokogiri::HTML.fragment('<p>ö</p>') node.to_s # => '<p>&ouml;</p>' # this is what I need node = Nokogiri::HTML.fragment('<p>ö</p>') node.to_s # => '<p>ö</p>' I've tried to mess with both PARSE_OPTIONS and :save_with options but could not come up with a way to have Nokogiri just transparently behave like above. Any pointers?

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  • GQL: I'm storing JSON in the DataStore. All json is getting converted to html entities, how to avoid

    - by fmsf
    The tittle says most: I'm storing JSON in the DataStore. All json is getting converted to html entities, how can I avoid this? Original I had myJson = db.StringProperty() it complained the json i had was to long and StringProperty had a limit of around 500 chars. Sugesting to use TextProperty instead. It inserted without problems but now myJson looks like this when i fetch it from the database: { &quot;timeUnit&quot;: &quot;14&quot;, &quot;taskCounter&quot;: &quot;0&quot;, &quot;dependencyCounter&quot;: &quot;0&quot;, &quot;tasks&quot;: [], &quot;dependencies&quot;: []} Any sugestions?

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  • How can I read malformed XML (unencoded entities) with Perl?

    - by Mrouge
    I'm trying to parse an XML file I get from an external source but am having problems because there are unencoded XML entities in the text nodes. Essentially, I'm asking the same question as this, but for Perl instead of PHP. <report> <company>A & W</company> <company>Some Other Company with a < in Inc.</company> </report>

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  • How to deal with large result sets with Linq to Entities?

    - by user169867
    I have a fairly complex linq to entities query that I display on a website. It uses paging so I never pull down more than 50 records at a time for display. But I also want to give the user the option to export the full results to Excel or some other file format. My concern is that there could potentially be a large # of records all being loaded into memory at one time to do this. Is there a way to process a linq result set 1 record at a time like you could w/ a datareader so only 1 record is really being kept in memory at a time? I'd appreciate any help. Thanks

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  • Entity Framework Code First: Get Entities From Local Cache or the Database

    - by Ricardo Peres
    Entity Framework Code First makes it very easy to access local (first level) cache: you just access the DbSet<T>.Local property. This way, no query is sent to the database, only performed in already loaded entities. If you want to first search local cache, then the database, if no entries are found, you can use this extension method: 1: public static class DbContextExtensions 2: { 3: public static IQueryable<T> LocalOrDatabase<T>(this DbContext context, Expression<Func<T, Boolean>> expression) where T : class 4: { 5: IEnumerable<T> localResults = context.Set<T>().Local.Where(expression.Compile()); 6:  7: if (localResults.Any() == true) 8: { 9: return (localResults.AsQueryable()); 10: } 11:  12: IQueryable<T> databaseResults = context.Set<T>().Where(expression); 13:  14: return (databaseResults); 15: } 16: }

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  • General visual effects to meshes/entities

    - by Pacha
    I am trying to add some visual effects to some entities, meshes, or whatever you want to call them as they are looking pretty dull in my game right now. What I want to achieve is this: http://youtu.be/zox8935PLw0?t=36s (the "texture" gets disintegrated and then goes back to normal, covering the whole mesh.) Also I would like to know what is the best way to add effects like the one in the video to my game (for example, thunder effects, shattering, etc.) I know that I can do some things with shaders, but I haven't learned them too well and I am still in a beginner level. I am using Ogre3D, and GLSL for shaders. Thanks! Note: this is a screen-shot of my game, I want to apply the effect in the video to my main character):

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  • Local Entities with NHibernate

    - by Ricardo Peres
    You may know that Entity Framework Code First has a nice property called Local which lets you iterate through all the entities loaded by the current context (first level cache). This comes handy at times, so I decided to check if it would be difficult to have it on NHibernate. It turned out it is not, so here it is! Another nice addition to an NHibernate toolbox! public static class SessionExtensions { public static IEnumerable<T> Local<T>(this ISession session) { ISessionImplementor impl = session.GetSessionImplementation(); IPersistenceContext pc = impl.PersistenceContext; foreach (Object key in pc.EntityEntries.Keys) { if (key is T) { yield return ((T) key); } } } } //simple usage IEnumerable<Post> localPosts = session.Local<Post>(); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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  • How to profile LINQ to Entities queries in your asp.net applications - part 1

    - by nikolaosk
    I have been teaching ASP.Net and EF in one of my classes and I have been asked on the various ways we can profile database activity. Everyone that I know that uses EF as its data access layer has the same question. "How can I see the T-SQL code that the LINQ to Entities engine generates on the fly?" I know a lot of people use VS studio built-in visualisers but that is not enough. A lot of developers use SQL Server Profiler. That is also a good solution since we can see the queries(generated from...(read more)

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  • Can the following Domain Entity contain logic for creating/deleting other entities?

    - by user702769
    a) As far as I understand it, in most cases Domain Model DM doesn't contain code for creating/deleting domain entities, but instead it is the job of layers ( ie service layer or UI layer ) on top of DM to create/delete domain entities? b) Domain entities are modelled after real world entities. Assuming particular real world entity being abstracted does have the functionality of creating/deleting other real world entities, then I assume the domain entity abstracting this real world entity could also contain logic for creating/deleting other entities? class RobotDestroyerCreator { ... void heavyThinking() { ... if(...) unitOfWork.registerDelete(robot); ... if(...) { var robotNew = new Robot(...); unitOfWork.registerNew(robotNew); { ... } } Thank you

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  • Track updated/inserted entities in LINQ to SQL applications

    - by nikolaosk
    In this post I would like to discuss in further detail the issue of track changing of entities in LINQ to SQL applications. I would like to show you how the DataContext object keeps track of all the items that are updated,deleted or inserted in the underlying data store. If you want to have a look at my other post about LINQ to SQL and transactions click here . I am going to demonstrate this with a hands on example. I assume that you have access to a version of SQL Server and Northwind database....(read more)

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  • EF 4 Self Tracking Entities does not work as expected.

    - by ashraf
    I am using EF4 Self Tracking Entities (VS2010 Beta 2 CTP 2 plus new T4 generator). But when I try to update entity information it does not update to database as expected. I setup 2 service calls. one for GetResource(int id) which return a resource object. the second call is SaveResource(Resource res); here is the code. public Resource GetResource(int id) { using (var dc = new MyEntities()) { return dc.Resources.Where(d => d.ResourceId == id).SingleOrDefault(); } } public void SaveResource(Resource res) { using (var dc = new MyEntities()) { dc.Resources.ApplyChanges(res); dc.SaveChanges(); // Nothing save to database. } } //Windows Console Client Calls var res = service.GetResource(1); res.Description = "New Change"; // Not updating... service.SaveResource(res); // does not change anything. It seems to me that ChangeTracker.State is always show as "Unchanged". anything wrong in this code?

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  • Organizing MVC entities communication

    - by Stefano Borini
    I have the following situation. Imagine you have a MainWindow object who is layouting two different widgets, ListWidget and DisplayWidget. ListWidget is populated with data from the disk. DisplayWidget shows the details of the selection the user performs in the ListWidget. I am planning to do the following: in MainWindow I have the following objects: ListWidget ListView ListModel ListController ListView is initialized passing the ListWidget. ListViewController is initialized passing the View and the Model. Same happens for the DisplayWidget: DisplayWidget DisplayView DisplayModel DisplayController I initialize the DisplayView with the widget, and initialize the Model with the ListController. I do this because the DisplayModel wraps the ListController to get the information about the current selection, and the data to be displayed in the DisplayView. I am very rusty with MVC, being out of UI programming since a while. Is this the expected interaction layout for having different MVC triplets communicate ? In other words, MVC focus on the interaction of three objects. How do you put this interaction as a whole into a larger context of communication with other similar entities, MVC or not ?

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  • Nested Entities and calculation on leaf entity property - SQL or NoSQL approach

    - by Chandu
    I am working on a hobby project called Menu/Recipe Management. This is how my entities and their relations look like. A Nutrient has properties Code and Value An Ingredient has a collection of Nutrients A Recipe has a Collection of Ingredients and occasionally can have a collection of other recipes A Meal has a Collection of Recipes and Ingredients A Menu has a Collection of Meals The relations can be depicted as In one of the pages, for a selected menu I need to display the effective nutrients information calculated based on its constituents (Meals, Recipes, Ingredients and the corresponding nutrients). As of now am using SQL Server to store the data and I am navigating the chain from my C# code, starting from each meal of the menu and then aggregating the nutrient values. I think this is not an efficient way as this calculation is being done every time the page is requested and the constituents change occasionally. I was thinking about a having a background service that maintains a table called MenuNutrients ({MenuId, NutrientId, Value}) and will populate/update this table with the effective nutrients when any of the component (Meal, Recipe, Ingredient) changes. I feel that a GraphDB would be a good fit for this requirement, but my exposure to NoSQL is limited. I want to know what are the alternative solutions/approaches to this requirement of displaying the nutrients of a given menu. Hope my description of the scenario is clear.

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  • Loading Entities Dynamically with Entity Framework

    - by Ricardo Peres
    Sometimes we may be faced with the need to load entities dynamically, that is, knowing their Type and the value(s) for the property(ies) representing the primary key. One way to achieve this is by using the following extension methods for ObjectContext (which can be obtained from a DbContext, of course): 1: public static class ObjectContextExtensions 2: { 3: public static Object Load(this ObjectContext ctx, Type type, params Object [] ids) 4: { 5: Object p = null; 6:  7: EntityType ospaceType = ctx.MetadataWorkspace.GetItems<EntityType>(DataSpace.OSpace).SingleOrDefault(x => x.FullName == type.FullName); 8:  9: List<String> idProperties = ospaceType.KeyMembers.Select(k => k.Name).ToList(); 10:  11: List<EntityKeyMember> members = new List<EntityKeyMember>(); 12:  13: EntitySetBase collection = ctx.MetadataWorkspace.GetEntityContainer(ctx.DefaultContainerName, DataSpace.CSpace).BaseEntitySets.Where(x => x.ElementType.FullName == type.FullName).Single(); 14:  15: for (Int32 i = 0; i < ids.Length; ++i) 16: { 17: members.Add(new EntityKeyMember(idProperties[i], ids[i])); 18: } 19:  20: EntityKey key = new EntityKey(String.Concat(ctx.DefaultContainerName, ".", collection.Name), members); 21:  22: if (ctx.TryGetObjectByKey(key, out p) == true) 23: { 24: return (p); 25: } 26:  27: return (p); 28: } 29:  30: public static T Load<T>(this ObjectContext ctx, params Object[] ids) 31: { 32: return ((T)Load(ctx, typeof(T), ids)); 33: } 34: } This will work with both single-property primary keys or with multiple, but you will have to supply each of the corresponding values in the appropriate order. Hope you find this useful!

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  • Best Practices for serializing/persisting String Object Dictionary entities

    - by Mark Heath
    I'm noticing a trend towards using a dictionary of string to object (or sometimes string to string), instead of strongly typed objects. For example, the new Katana project makes heavy use of IDictionary<string,object>. This approach avoids the need to continually update your entity classes/DTOs and the database tables that persist them with new properties. It also avoids the need to create new derived entity types to support new types of entity, since the Dictionary is flexible enough to store any arbitrary properties. Here's a contrived example: class StorageDevice { public int Id { get; set; } public string Name { get; set; } } class NetworkShare : StorageDevice { public string Path { get; set; } public string LoginName { get; set; } public string Password { get; set; } } class CloudStorage : StorageDevice { public string ServerUri { get; set } public string ContainerName { get; set; } public int PortNumber { get; set; } public Guid ApiKey { get; set; } } versus: class StorageDevice { public IDictionary<string, object> Properties { get; set; } } Basically I'm on the lookout for any talks, books or articles on this approach, so I can pick up on any best practices / difficulties to avoid. Here's my main questions: Does this approach have a name? (only thing I've heard used so far is "self-describing objects") What are the best practices for persisting these dictionaries into a relational database? Especially the challenges of deserializing them successfully with strongly typed languages like C#. Does it change anything if some of the objects in the dictionary are themselves lists of strongly typed entities? Should a second dictionary be used if you want to temporarily store objects that are not to be persisted/serialized across a network, or should you use some kind of namespacing on the keys to indicate this?

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  • How can one prevent double encoding of html entities when they are allowed in the input

    - by Bob
    How can I prevent double encoding of html entities, or fix them programmatically? I am using the encode() function from the HTML::Entities perl module to encode HTML entities in user input. The problem here is that we also allow users to input HTML entities directly and these entities end up being double encoded. For example, a user may enter: Stackoverflow & Perl = Awesome&hellip; This ends up being encoded to Stackoverflow &amp; Perl = Awesome&amp;hellip; This renders in the browser as Stackoverflow & Perl = Awesome&hellip; We want this to render as Stackoverflow & Perl = Awesome... Is there a way to prevent this double encoding? Or is there a module or snippet of code that can easily correct these double encoding issues? Any help is greatly appreciated!

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  • Comparing multiple entity properties against list of entities

    - by roosteronacid
    Consider this snippet of code: var iList = new List<Entities.Ingredient> { new Entities.Ingredient { Name = "tomato", Amount = 2.0 }, new Entities.Ingredient { Name = "cheese", Amount = 100.0 } }; var matches = new DataContext().Ingredients.Where(i => Comparer(i, iList)); private Boolean Comparer(Entities.Ingredient i, List<Entities.Ingredient> iList) { foreach (var i in iList) { if (i.Name == iList.Name && i.Amount >= iList.Amount) return true; } return false; } Is there a more efficient way of doing this? Preferably without being too verbose; from x in y select z... If thats at all possible.

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  • Entities groups in transactions

    - by Joel
    In the context of "Keys and Entity Groups" article by google: http://code.google.com/appengine/docs/python/datastore/transactions.html 1) "Only use entity groups when they are needed for transactions" 2) "Every entity belongs to an entity group, a set of one or more entities that can be manipulated in a single transaction." It seems like entity groups exist only for the use of transactions, i.e. making one transaction possible between all entities in a group. My question is then why are there parent-child relations between entities and not just a simple declaration of entities to be in a single group (that is defining A,B,C to be in the same group as opposed to defining relations between them "A (parent of) B, B (parent of C)"). What is the benefit from using parent-child relation model when the only purpose is for entities to be in the same group to make transaction possible? Thanks Joel

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