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  • How do I check if a SQL Server 2005 TEXT column is not null or empty using LINQ To Entities?

    - by emzero
    Hi there guys I'm new to LINQ and I'm trying to check whether a TEXT column is null or empty (as String.IsNullOrEmpty). from c in ... ... select new { c.Id, HasBio = !String.IsNullOrEmpty(c.bio) } Trying to use the above query produces an SqlException: Argument data type text is invalid for argument 1 of len function. The SQL generated is similar to the following: CASE WHEN ( NOT (([Extent2].[bio] IS NULL) OR (( CAST(LEN([Extent2].[bio]) AS int)) = 0))) THEN cast(1 as bit) WHEN (([Extent2].[bio] IS NULL) OR (( CAST(LEN([Extent2].[bio]) AS int)) = 0)) THEN cast(0 as bit) END AS [C1] LEN is not applicable to TEXT columns. I know DATALENGTH should be used for them... How can I force LINQ to produce such thing? Or any other workaround to test if a text column is null or empty??? Thanks!

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  • Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures?

    - by BritishDeveloper
    How would you rate each of them in terms of: Performance Speed of development Neat, intuitive, maintainable code Flexibility Overall I like my SQL and so have always been a die-hard fan of ADO.NET and stored procedures but I recently had a play with Linq to SQL and was blown away by how quickly I was writing out my DataAccess layer and have decided to spend some time really understanding either Linq to SQL or EF... or neither? I just want to check, that there isn't a great flaw in any of these technologies that would render my research time useless. E.g. performance is terrible, it's cool for simple apps but can only take you so far

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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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  • How to use LINQ To Entities for filtering when many methods are not supported?

    - by Kinderchocolate
    Hi, I have a table in SQL database: ID Data Value 1 1 0.1 1 2 0.4 2 10 0.3 2 11 0.2 3 10 0.5 3 11 0.6 For each unique value in Data, I want to filter out the row with the largest ID. For example: In the table above, I want to filter out the third and fourth row because the fifth and sixth rows have the same Data values but their IDs (3) are larger (2 in the third and fourth row). I tried this in Linq to Entities: IQueryable<DerivedRate> test = ObjectContext.DerivedRates.OrderBy(d => d.Data).ThenBy(d => d.ID).SkipWhile((d, index) => (index == size - 1) || (d.ID != ObjectContext.DerivedRates.ElementAt(index + 1).ID)); Basically, I am sorting the list and removing the duplicates by checking if the next element has an identical ID. However, this doesn't work because SkipWhile(index) and ElementAt(index) aren't supported in Linq to Entities. I don't want to pull the entire gigantic table into an array before sorting it. Is there a way?

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  • Uncaught TypeError: Object [object Object] has no method 'onAdded'

    - by user3604227
    I am using ExtJS4 with Java servlets. I am following the MVC architecture for ExtJS. I am trying a simple example of displaying a border layout but it doesnt work and I get the following error in ext-all.js in the javascript console: Uncaught TypeError: Object [object Object] has no method 'onAdded' Here is my code: app.js Ext.Loader.setConfig({ enabled : true }); Ext.application({ name : 'IN', appFolder : 'app', controllers : [ 'Items' ], launch : function() { console.log('in LAUNCH-appjs'); Ext.create('Ext.container.Viewport', { items : [ { xtype : 'borderlyt' } ] }); } }); Items.js (controller) Ext.define('IN.controller.Items', { extend : 'Ext.app.Controller', views : [ 'item.Border' ], init : function() { this.control({ 'viewport > panel' : { render : this.onPanelRendered } }); }, onPanelRendered : function() { console.log('The panel was rendered'); } }); Border.js (view) Ext.define('IN.view.item.Border',{extend : 'Ext.layout.container.Border', alias : 'widget.borderlyt', title : 'Border layout' , autoShow : true, renderTo : Ext.getBody(), defaults : { split : true, layout : 'border', autoScroll : true, height : 800, width : 500 }, items : [ { region : 'north', html : "Header here..", id : 'mainHeader' }, { region : 'west', width : 140, html : "Its West..", }, { region : 'south', html : "This is my temp footer content", height : 30, margins : '0 5 5 5', bodyPadding : 2, id : 'mainFooter' }, { id : 'mainContent', collapsible : false, region : 'center', margins : '5', border : true, } ] }); The folder structure for the Webcontent is as follows: WebContent app controller Items.js model store view item Border.js ext_js resources src ext_all.js index.html app.js Can someone help me resolve this error? Thanks in advance

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  • How to write this Linq SQL as a Dynamic Query (using strings)?

    - by Dr. Zim
    Skip to the "specific question" as needed. Some background: The scenario: I have a set of products with a "drill down" filter (Query Object) populated with DDLs. Each progressive DDL selection will further limit the product list as well as what options are left for the DDLs. For example, selecting a hammer out of tools limits the Product Sizes to only show hammer sizes. Current setup: I created a query object, sent it to a repository, and fed each option to a SQL "table valued function" where null values represent "get all products". I consider this a good effort, but far from DDD acceptable. I want to avoid any "programming" in SQL, hopefully doing everything with a repository. Comments on this topic would be appreciated. Specific question: How would I rewrite this query as a Dynamic Query? A link to something like 101 Linq Examples would be fantastic, but with a Dynamic Query scope. I really want to pass to this method the field in quotes "" for which I want a list of options and how many products have that option. from p in db.Products group p by p.ProductSize into g select new Category { PropertyType = g.Key, Count = g.Count() } Each DDL option will have "The selection (21)" where the (21) is the quantity of products that have that attribute. Upon selecting an option, all other remaining DDLs will update with the remaining options and counts. Edit: Additional notes: .OrderBy("it.City") // "it" refers to the entire record .GroupBy("City", "new(City)") // This produces a unique list of City .Select("it.Count()") //This gives a list of counts... getting closer .Select("key") // Selects a list of unique City .Select("new (key, count() as string)") // +1 to me LOL. key is a row of group .GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by .GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it.count() as string)")// GroupBy new makes key an object Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it as object)")// the it object is the result of GroupBy var a = Product .Where("ProductType == @0", "Maps") .GroupBy("@0", "it", "City") // This fails to group Product at all .Select("new ( Key, it as Product )"); // "it" is property cast though What I have learned so far is LinqPad is fantastic, but still looking for an answer. Eventually, completely random research like this will prevail I guess. LOL. Edit:

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  • wcf web service in post method, object properties are null, although the object is not null

    - by Abdalhadi Kolayb
    i have this problem in post method when i send object parameter to the method, then the object is not null, but all its properties have the default values. here is data module: [DataContract] public class Products { [DataMember(Order = 1)] public int ProdID { get; set; } [DataMember(Order = 2)] public string ProdName { get; set; } [DataMember(Order = 3)] public float PrpdPrice { get; set; } } and here is the interface: [OperationContract] [WebInvoke( Method = "POST", UriTemplate = "AddProduct", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.WrappedRequest, RequestFormat = WebMessageFormat.Json)] string AddProduct([MessageParameter(Name = "prod")]Products prod); public string AddProduct(Products prod) { ProductsList.Add(prod); return "return string"; } here is the json request: Content-type:application/json {"prod":[{"ProdID": 111,"ProdName": "P111","PrpdPrice": 111}]} but in the server the object received: {"prod":[{"ProdID": 0,"ProdName": NULL,"PrpdPrice": 0}]}

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  • Returning a mock object from a mock object

    - by Songo
    I'm trying to return an object when mocking a parser class. This is the test code using PHPUnit 3.7 //set up the result object that I want to be returned from the call to parse method $parserResult= new ParserResult(); $parserResult->setSegment('some string'); //set up the stub Parser object $stubParser=$this->getMock('Parser'); $stubParser->expects($this->any()) ->method('parse') ->will($this->returnValue($parserResult)); //injecting the stub to my client class $fileHeaderParser= new FileWriter($stubParser); $output=$fileParser->writeStringToFile(); Inside my writeStringToFile() method I'm using $parserResult like this: writeStringToFile(){ //Some code... $parserResult=$parser->parse(); $segment=$parserResult->getSegment();//that's why I set the segment in the test. } Should I mock ParserResult in the first place, so that the mock returns a mock? Is it good design for mocks to return mocks? Is there a better approach to do this all?!

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  • Object-Oriented Operating System

    - by nmagerko
    As I thought about writing an operating system, I came across a point that I really couldn't figure out on my own: Can an operating system truly be written in an Object-Oriented Programming (OOP) Language? Being that these types of languages do not allow for direct accessing of memory, wouldn't this make it impossible for a developer to write an entire operating system using only an OOP Language? Take, for example, the Android Operating System that runs many phones and some tablets in use around the world. I believe that this operating system uses only Java, an Object-Oriented language. In Java, I have been unsuccessful in trying to point at and manipulate a specific memory address that the run-time environment (JRE) has not assigned to my program implicitly. In C, C++, and other non-OOP languages, I can do this in a few lines. So this makes me question whether or not an operating system can be written in an OOP, especially Java. Any counterexamples or other information is appreciated.

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  • Object Oriented programming on 8-bit MCU Case Study

    - by Calvin Grier
    I see that there's a lot of questions related to OO Programming here. I'm actually trying to find a specific resource related to embedded OO approaches for an 8 bit MCU. Several years back (maybe 6) I was looking for material related to Object Oriented programming for resource constrained 8051 microprocessors. I found an article/website with a case history of a design group that used a very small RAM part, and implemented many Object based constructs during their C design and development. I believe it was an 8051. The project was a success, and managed to stay inside the very small ROM/RAM they had available. I'm attempting to find it again, but Google can't locate it. The article was well written, and recommended a "mixed" approach using C methods for inheritance and encapsulation - if I recall correctly. Can anyone help me locate this article?

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  • What is Object Oriented Programming ill-suited for?

    - by Richard JP Le Guen
    In Martin Fowler's book Refactoring, Fowler speaks of how when developers learn something new, they don't consider when it's inappropriate for the job: Ten years ago it was like that with objects. If someone asked me when not to use objects, it was hard to answer. [...] It was just that I didn't know what those limitations were, although I knew what the benefits were. Reading this, it occurred to me I don't know what the limitations or potential disadvantages of Object-Oriented Programming are. What are the limitations of Object Oriented Programming? When should one look at a project and think "OOP is not best suited for this"?

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  • Is there really Object-relational impedance mismatch?

    - by user52763
    It is always stated that it is hard to store applications objects in relational databases - the object-relational impedance mismatch - and that is why Document databases are better. However, is there really an impedance mismatch? And object has a key (albeit it may be hidden away by the runtime as a pointer to memory), a set of values, and foreign keys to other objects. Objects are as much made up of tables as it is a document. Neither really fit. I can see a use for databases to model the data into specific shapes for scenarios in the application - e.g. to speed up database lookup and avoid joins, etc., but won't it be better to keep the data as normalized as possible at the core, and transform as required?

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  • In which object should I implement wait()/notify()?

    - by Christopher Francisco
    I'm working in an Android project with multithreading. Basically I have to wait to the server to respond before sending more data. The data sending task is delimited by the flag boolean hasServerResponded so the Thread will loop infinitely without doing anything until the flag becomes true. Since this boolean isn't declared as volatile (yet), and also looping without doing anything wastes resources, I thought maybe I should use AtomicBoolean and also implement wait() / notify() mechanism. Should I use the AtomicBoolean object notify() and wait() methods or should I create a lock Object?

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  • Representing complex object dependencies

    - by max
    I have several classes with a reasonably complex (but acyclic) dependency graph. All the dependencies are of the form: class X instance contains an attribute of class Y. All such attributes are set during initialization and never changed again. Each class' constructor has just a couple parameters, and each object knows the proper parameters to pass to the constructors of the objects it contains. class Outer is at the top of the dependency hierarchy, i.e., no class depends on it. Currently, the UI layer only creates an Outer instance; the parameters for Outer constructor are derived from the user input. Of course, Outer in the process of initialization, creates the objects it needs, which in turn create the objects they need, and so on. The new development is that the a user who knows the dependency graph may want to reach deep into it, and set the values of some of the arguments passed to constructors of the inner classes (essentially overriding the values used currently). How should I change the design to support this? I could keep the current approach where all the inner classes are created by the classes that need them. In this case, the information about "user overrides" would need to be passed to Outer class' constructor in some complex user_overrides structure. Perhaps user_overrides could be the full logical representation of the dependency graph, with the overrides attached to the appropriate edges. Outer class would pass user_overrides to every object it creates, and they would do the same. Each object, before initializing lower level objects, will find its location in that graph and check if the user requested an override to any of the constructor arguments. Alternatively, I could rewrite all the objects' constructors to take as parameters the full objects they require. Thus, the creation of all the inner objects would be moved outside the whole hierarchy, into a new controller layer that lies between Outer and UI layer. The controller layer would essentially traverse the dependency graph from the bottom, creating all the objects as it goes. The controller layer would have to ask the higher-level objects for parameter values for the lower-level objects whenever the relevant parameter isn't provided by the user. Neither approach looks terribly simple. Is there any other approach? Has this problem come up enough in the past to have a pattern that I can read about? I'm using Python, but I don't think it matters much at the design level.

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  • Passing functions into other functions as parameters, bad practice?

    - by BlueHat
    We've been in the process of changing how our AS3 application talks to our back end and we're in the process of implementing a REST system to replace our old one. Sadly the developer who started the work is now on long term sick leave and it's been handed over to me. I've been working with it for the past week or so now and I understand the system, but there's one thing that's been worrying me. There seems to be a lot of passing of functions into functions. For example our class that makes the call to our servers takes in a function that it will then call and pass an object to when the process is complete and errors have been handled etc. It's giving me that "bad feeling" where I feel like it's horrible practice and I can think of some reasons why but I want some confirmation before I propose a re-work to system. I was wondering if anyone had any experience with this possible problem?

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  • What kind of programs/solutions can only be written with OOP or are too hard to achieve without it?

    - by user1598390
    Paraphrasing a recent question: What is Object Oriented Programming ill-suited for? I would like to ask the opposite question: What kind of programs cannot be written unless you use OOP? What kind of programs are not recommended to be written using non-OOP techniques? What kind of programs need OOP in order to even be written? What kind of programs would be too hard to write without OOP ? The answer to this question can help sell the idea of OOP to project leaders that have no special interest in code quality. At least they could buy the idea if one shows them the kind of things that are not even possible unless you use OOP.

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  • Sharing object between 2 classes

    - by Justin
    I am struggling to wrap my head around being able to share an object between two classes. I want to be able to create only one instance of the object, commonlib in my main class and then have the classes, foo1 and foo2, to be able to mutually share the properties of the commonlib. commonlib is a 3rd party class which has a property Queries that will be added to in each child class of bar. This is why it is vital that only one instance is created. I create two separate queries in foo1 and foo2. This is my setup: abstract class bar{ //common methods } class foo1 extends bar{ //add query to commonlib } class foo2 extends bar{ //add query to commonlib } class main { public $commonlib = new commonlib(); public function start(){ //goal is to share one instance of $this->commonlib between foo1 and foo2 //so that they can both add to the properites of $this->commonlib (global //between the two) //now execute all of the queries after foo1 and foo2 add their query $this->commonlib->RunQueries(); } }

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  • Any tips/tricks/resources on actually TEACHING a class on OOP? [closed]

    - by Sempus
    I may slowly be getting into teaching an Object-Orientated Programming class at my school in a year or two. I just graduated and work at my school as an Application Programmer. I'd first start off as a TA/grader and then slowly move into the Professor role. The class would be in Java. I always see resources on this fine site about HOW to program, but does anyone know any tips/tricks/resources on how to TEACH a programming class? It would be full of all different skills levels(but still semi-technical) so it would have to be a little more understandable than if it was just CS kids.

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  • How can I stop an auto-generated Linq to SQL class from loading ALL data?

    - by Gary McGill
    I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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  • How to avoid geometric slowdown with large Linq transactions?

    - by Shaul
    I've written some really nice, funky libraries for use in LinqToSql. (Some day when I have time to think about it I might make it open source... :) ) Anyway, I'm not sure if this is related to my libraries or not, but I've discovered that when I have a large number of changed objects in one transaction, and then call DataContext.GetChangeSet(), things start getting reaalllly slooowwwww. When I break into the code, I find that my program is spinning its wheels doing an awful lot of Equals() comparisons between the objects in the change set. I can't guarantee this is true, but I suspect that if there are n objects in the change set, then the call to GetChangeSet() is causing every object to be compared to every other object for equivalence, i.e. at best (n^2-n)/2 calls to Equals()... Yes, of course I could commit each object separately, but that kinda defeats the purpose of transactions. And in the program I'm writing, I could have a batch job containing 100,000 separate items, that all need to be committed together. Around 5 billion comparisons there. So the question is: (1) is my assessment of the situation correct? Do you get this behavior in pure, textbook LinqToSql, or is this something my libraries are doing? And (2) is there a standard/reasonable workaround so that I can create my batch without making the program geometrically slower with every extra object in the change set?

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  • Add properties to stdClass object from another object

    - by Florin
    I would like to be able to do the following: $obj = new stdClass; $obj->status = "success"; $obj2 = new stdClass; $obj2->message = "OK"; How can I extend $obj so that it contains the properties of $obj2, eg: $obj->status //"success" $obj->message // "OK" I know I could use an array, add all properties to the array and then cast that back to object, but is there a more elegant way, something like this: extend($obj, $obj2); //adds all properties from $obj2 to $obj Thanks!

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  • What is the difference between "LINQ to Entities", "LINQ to SQL" and "LINQ to Dataset".

    - by Marcel
    I've been working for quite a while now with LINQ. However, it remains a bit of a mystery what the real differences are between the mentioned flavours of LINQ. The successful answer will contain a short differentiation between them. What is the main goal of each flavor, what is the benefit, and is there a performance impact... P.S. I know that there are a lot of information sources out there, but I'm looking for a kind of a "cheat sheet" which instructs a newbie where to head for a specific goal.

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  • What is the differnce between "LINQ to Entities", "LINQ to SQL" and "LINQ to Dataset".

    - by Marcel
    Hi all, I'm working for quite a while now with LINQ. However, it remained still a bit of a mystery what are the real differences between the mentioned flavours of LINQ. The successful answer will contain a short differentiation between them. What is the main goal if it, what is the benefit, and is there a performance impact... P.S. I know that there are a lot of information sources out there, but I look for a kind of a "cheat sheet" which instructs a newbie where to head to for a specific goal.

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  • Use decorator and factory together to extend objects?

    - by TheClue
    I'm new to OOP and design pattern. I've a simple app that handles the generation of Tables, Columns (that belong to Table), Rows (that belong to Column) and Values (that belong to Rows). Each of these object can have a collection of Property, which is in turn defined as an enum. They are all interfaces: I used factories to get concrete instances of these products, depending on circumnstances. Now I'm facing the problem of extending these classes. Let's say I need another product called "SpecialTable" which in turn has some special properties or new methods like 'getSomethingSpecial' or an extended set of Property. The only way is to extend/specialize all my elements (ie. build a SpecialTableFactory, a SpecialTable interface and a SpecialTableImpl concrete)? What to do if, let's say, I plan to use standard methods like addRow(Column column, String name) that doesn't need to be specialized? I don't like the idea to inherit factories and interfaces, but since SpecialTable has more methods than Table i guess it cannot share the same factory. Am I wrong? Another question: if I need to define product properties at run time (a Table that is upgraded to SpecialTable at runtime), i guess i should use a decorator. Is it possible (and how) to combine both factory and decorator design? Is it better to use a State or Strategy pattern, instead?

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