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• Still Confused About Identifying vs. Non-Identifying Relationships

  - by Jason

  So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking at: What's the Difference Between Identifying and Non-Identifying Relationships Trouble Deciding on Identifying or Non-Identifying Relationship Looking at the top answers from each question, I appear to get two different ideas of what an identifying relationship is. The first question's response says that an identifying relationship "describes a situation in which the existence of a row in the child table depends on a row in the parent table." An example of this that is given is, "An author can write many books (1-to-n relationship), but a book cannot exist without an author." That makes sense to me. However, when I read the response to question two, I get confused as it says, "if a child identifies its parent, it is an identifying relationship." The answer then goes on to give examples such as SSN (is identifying of a Person), but an address is not (because many people can live at an address). To me, this sounds more like a case of the decision between primary key and non-primary key. My own gut feeling (and additional research on other sites) points to the first question and its response being correct. However, I wanted to verify before I continued forward as I don't want to learn something wrong as I am working to understand database design. Thanks in advance.

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• How to mock a String using mockito?

  - by Alceu Costa

  I need to simulate a test scenario in which I call the getBytes() method of a String object and I get an UnsupportedEncodingException. I have tried to achieve that using the following code: String nonEncodedString = mock(String.class); when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error.")); The problem is that when I run my test case I get a MockitoException that says that I can't mock a java.lang.String class. Is there a way to mock a String object using mockito or, alternatively, a way to make my String object throw an UnsupportedEncodingException when I call the getBytes method? Here are more details to illustrate the problem: This is the class that I want to test: public final class A{ public static String f(String str){ try{ return new String(str.getBytes("UTF-8")); } catch (UnsupportedEncodingException e) { // This is the catch block that I want to exercise. ... } } } This is my testing class (I'm using JUnit 4 and mockito): public class TestA { @Test(expected=UnsupportedEncodingException.class) public void test(){ String aString = mock(String.class); when(nonEncodedString.getBytes(anyString())).thenThrow(new UnsupportedEncodingException("Parsing error.")); A.f(aString); } }

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• How can I execute an ANTLR parser action for each item in a rule that can match more than one item?

  - by Chris Farmer

  I am trying to write an ANTLR parser rule that matches a list of things, and I want to write a parser action that can deal with each item in the list independently. Some example input for these rules is: $(A1 A2 A3) I'd like this to result in an evaluator that contains a list of three MyIdentEvaluator objects -- one for each of A1, A2, and A3. Here's a snippet of my grammar: my_list returns [IEvaluator e] : { $e = new MyListEvaluator(); } '$' LPAREN op=my_ident+ { /* want to do something here for each 'my_ident'. */ /* the following seems to see only the 'A3' my_ident */ $e.Add($op.e); } RPAREN ; my_ident returns [IEvaluator e] : IDENT { $e = new MyIdentEvaluator($IDENT.text); } ; I think my_ident is defined correctly, because I can see the three MyIdentEvaluators getting created as expected for my input string, but only the last my_ident ever gets added to the list (A3 in my example input). How can I best treat each of these elements independently, either through a grammar change or a parser action change? It also occurred to me that my vocabulary for these concepts is not what it should be, so if it looks like I'm misusing a term, I probably am. EDIT in response to Wayne's comment: I tried to use op+=my_ident+. In that case, the $op in my action becomes an IList (in C#) that contains Antlr.Runtime.Tree.CommonTree instances. It does give me one entry per matched token in $op, so I see my three matches, but I don't have the MyIdentEvaluator instances that I really want. I was hoping I could then find a rule attribute in the ANTLR docs that might help with this, but nothing seemed to help me get rid of this IList. Result... Based on chollida's answer, I ended up with this which works well: my_list returns [IEvaluator e] : { $e = new MyListEvaluator(); } '$' LPAREN (op=my_ident { $e.Add($op.e); } )+ RPAREN ; The Add method gets called for each match of my_ident.

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• cmd.exe Command Line Parsing of Environment Variables

  - by Artefacto

  I can't figure how to have cmd.exe not interpret something like %PATH% as an environment variable. Given this program: #include<stdio.h> #include<windows.h> int main(int argc, char *argv[]) { int i; printf("cmd line: %s\n", GetCommandLine()); for (i = 0; i < argc; i++) { printf("%d: %s\n", i, argv[i]); } return 0; } I have these different outputs according to the position of the arguments: >args "k\" o" "^%PATH^%" cmd line: args "k\" o" "%PATH%" 0: args 1: k" o 2: %PATH% >args "^%PATH^%" "k\" o" cmd line: args "^%PATH^%" "k\" o" 0: args 1: ^%PATH^% 2: k" o I guess it's because cmd.exe doesn't recognize the escaped \" and sees the escaped double quote as closing the first, leaving in the first case %PATH% unquoted. I say this, because if I don't quote the argument, it always works: >args ^%PATH^% "k\" o" cmd line: args %PATH% "k\" o" 0: args 1: %PATH% 2: k" o but then I can have no spaces...

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• Hibernate mapping Problem

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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• PHP, MySQL prepared statements - can you use results of execute more than once by calling data_seek(

  - by Carvell Fenton

  Hello, I have a case where I want to use the results of a prepared statement more than once in a nested loop. The outer loop processes the results of another query, and the inner loop is the results of the prepared statement query. So the code would be something like this (just "pseudoish" to demonstrate the concept): // not showing the outer query, it is just a basic SELECT, not prepared statement // we'll call it $outer_query $obj_array = array(); // going to save objects in this $ids = array(18,19,20); // just example id numbers $query = "SELECT field1, field2 FROM table1 WHERE id=?"; $stmt = $db->prepare($query); foreach ($ids as $id) { $stmt->bind_param("i", $id); $stmt->execute(); $stmt->bind_result($var1, $var2); $stmt->store_result(); // I think I need this for data_seek while ($q1 = $outer_query->fetch_object()) { while ($stmt->fetch()) { if ($q1->field1 == $var1) { // looking for a match $obj = new stdClass(); $obj->var1 = $var1; $obj->var2 = $var2; $obj_array[] = $obj; $stmt->data_seek(0); // reset for outer loop break; // found match, so leave inner } } } } The problem I seem to be experiencing is that the values are not getting bound in the variables as I would expect after the first time I use fetch in the inner loop. Specifically, in one example I ran with 3 ids for the foreach, the first id was processed correctly, the second was processed incorrectly (matches were not found in the inner loop even though they existed), and then the third was processed correctly. Is there something wrong with the prepared statment function calls in the sequence I am doing above, or is this an invalid way to use the results of the prepared statement? Thanks.

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• Calling jQuery method from onClick attribute in HTML

  - by Russell

  I am relatively new to implementing JQuery throughout an entire system, and I am enjoying the opportunity. I have come across one issue I would love to find the correct resolve for. Here is a simple case example of what I want to do: I have a button on a page, and on the click event I want to call a jquery function I have defined. Here is the code I have used to define my method (Page.js): (function($) { $.fn.MessageBox = function(msg) { alert(msg); }; }); And here is my HTML page: <HTML> <head> <script type="text/javascript" src="C:\Sandpit\jQueryTest\jquery-1.3.2.js"></script> <script language="javascript" src="Page.js"></script> </head> <body> <div class="Title">Welcome!</div> <input type="button" value="ahaha" onclick="$().MessageBox('msg');" /> </body> </HTML> (The above code displays the button, but clicking does nothing.) I am aware I could add the click event in the document ready event, however it seems more maintainable to put events in the HTML element instead. However I have not found a way to do this. Is there a way to call a jquery function on a button element (or any input element)? Or is there a better way to do this? Thanks

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• php mailer attachments

  - by Matthew

  I have been using this script to send emails to certain staff but because of changes to my system i have to now send attachements with the email and i have tried multipul peices of code to accomplish this but have been unsuccessful... I still recive the email but without the attachement which is quite pointless in this case i have placed the script i am using bellow i have removed the real addresses i was using and smtp server require("PHPMailer/class.phpmailer.php"); $mail = new PHPMailer(); $mail->IsSMTP(); // set mailer to use SMTP $mail->Host = "SMTP.SErver.com"; $mail->From = "[email protected]"; $mail->FromName = "HCSC"; $mail->AddAddress("[email protected]", "Example"); $mail->AddReplyTo("[email protected]", "Hcsc"); $mail->WordWrap = 50; $mail->IsHTML(false); $mail->Subject = "AuthSMTP Test"; $mail->Body = "AuthSMTP Test Message!"; $mail->AddAttachment("matt.txt"); //this is basicly what i am trying to attach as a test but will be using excel spreadsheets in the production if(!$mail->Send()) { echo "Message could not be sent. <p>"; echo "Mailer Error: " . $mail->ErrorInfo; exit; } echo "Message has been sent"; i have also tried a few other emtods of attaching the file but none seem to work any help is greatly appricated

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• LDAP/AD Integrated Group/Membership Management Package suitable for embedding in an application

  - by Ernest

  In several web applications, it is often necessary to define groups of users for purposes of membership as well as role management. For example, in one of our applications we would like to user a group of "Network Engineers" and another group that consists of "Managers" of such Network Engineers. The information we need is contact details of members of each group. So far, we have written our own tools to allow the administrator of the application to add/delete/move groups and their memberships and either store them in a XML file or a database. Increasingly, companies already have the groups we want defined in LDAP/AD, so it would be best to create a pointer in our application to the correspoding group in LDAP. Although there are a number of LDAP libraries and LDAP browsers available and we could code this and provide a web front end to get a list of available groups and their members, we are wondering if there is already a "component framework" available that would readily provide this LDAP browsing functionality that we could just embed this into our application. Something between a library and a full LDAP browser product ? (To clarify, the use case is for an admin of our web application to create a locally relevant group name and then map it to an exiting LDAP group. To enable this in the UI, we would like to present a way for the admin to browse available groups in the company LDAP server, view their membership, and select the LDAP group they would like to map to the locally relevant group name. In a second step, we would then synchronize the members of that LDAP group and their contact details to a store in our application ) Appreciate any pointers.

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• Are game engines developed in the USA?

  - by numerical25

  I just finished talking to a Flashpoint Academy recruiter about their curriculum. I told him that after I graduate, I would like to go more in-depth with learning game engines and how to make games. So I asked him did their school teach anything in regards to learning any graphics API such as DirectX. He asked me to elaborate a little more as if he was not sure what I was talking about. So I asked did their school teach on how to build game engines. He said "no we only teach with the tools at hand, such as XNA, or the Unreal engine". He further said "most jobs that deal with building game engines go overseas and most of creative work is done in the United States." To be honest, I really had no intentions of going to this school. I just wanted to learn more about the school in case I had second thoughts somewhere down the line. To me I thought it was a bunch of BS, but my question is to you guys, "is it" ??

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• MS Office Excel Ribbon - Cannot change/hide Editing group in Home tab

  - by A9S6

  I have a .net addin for Excel. The addin creates the Ribbon UI for Excel 2007 and re-purposes some existing commands such as Cut, Copy, Paste, Sort etc. For Cut, Copy and Paste I am just overriding their OnAction value to call my own procedure when the buttons are clicked. But for Sort, Sort Asc and Sort Desc commands the case is a little different. When either of the Sort, Sort Asc or Sort Desc buttons are clicked, I want to get notified and then call the default functionality. This was possible in Excel 2003 commandsbars by calling the Execute() method on the CommandBarControl. In Excel 2007, there is a ExecuteMso() method to programmatically click a ribbon element but when the OnAction is overridden, this ExecuteMso() method just executes my own procedure and not the default functionality of that button. So I thought that I will HIDE the Sort buttons in the "Editing" group in Home tab and add my own Sort, Sort Asc and Sort Desc buttons to it. The buttons will call into my procedure first from where I will call the default behavior. Now the problem is that I am unable to change/hide the Editing group (idMso="GroupEditing"). Is this built-in group not editable? I can however HIDE the Clipboard and other groups(but can't add buttons to them). <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui"> <ribbon> <tabs> <tab idMso="TabHome"> <group idMso="GroupEditing" visible="false" /> </tab> </tabs> </ribbon> </customUI>

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• Is it a good idea to use MySQL and Neo4j together?

  - by Sanoj

  I will make an application with a lot of similar items (millions), and I would like to store them in a MySQL database, because I would like to do a lot of statistics and search on specific values for specific columns. But at the same time, I will store relations between all the items, that are related in many connected binary-tree-like structures (transitive closure), and relation databases are not good at that kind of structures, so I would like to store all relations in Neo4j which have good performance for this kind of data. My plan is to have all data except the relations in the MySQL database and all relations with item_id stored in the Neo4j database. When I want to lookup a tree, I first search the Neo4j for all the item_id:s in the tree, then I search the MySQL-database for all the specified items in a query that would look like: SELECT * FROM items WHERE item_id = 45 OR item_id = 345435 OR item_id = 343 OR item_id = 78 OR item_id = 4522 OR item_id = 676 OR item_id = 443 OR item_id = 4255 OR item_id = 4345 Is this a good idea, or am I very wrong? I haven't used graph-databases before. Are there any better approaches to my problem? How would the MySQL-query perform in this case?

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• Getting list of states/events from a model that AASM's

  - by Jason Nerer

  Hi, I successfully integrated the most recent AASM gem into an application, using it for the creation of a wizard. In my case I have a model order class Order < ActiveRecord::Base belongs_to :user has_one :billing_plan, :dependent => :destroy named_scope :with_user, ..... <snip> include AASM aasm_column :aasm_state aasm_initial_state :unauthenticated_user aasm_state :unauthenticated_user, :after_exit => [:set_state_completed] aasm_state : <snip> <and following the event definitions> end Now I would like to give an administrator the possibility to create his own graphs through the AASM states. Therefore I created two additional models called OrderFlow and Transition where there order_flow has many transitions and order belongs_to order_flow. No problem so far. Now I would like to give my admin the possibility to dynamically add existing transitions / events to an order_flow graph. The problem now is, that I do not find any possibility to get a list of all events / transitions out of my order model. aasm_states_for_select seems to be the correct candidate, but I cannot call it on my order model. Can anyone help? Thx in advance. J.

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• When should we use Views, Temporary Tables and Direct Queries ? What are the Performance issues in a

  - by Shantanu Gupta

  I want to know the performance of using Views, Temp Tables and Direct Queries Usage in a Stored Procedure. I have a table that gets created every time when a trigger gets fired. I know this trigger will be fired very rare and only once at the time of setup. Now I have to use that created table from triggers at many places for fetching data and I confirms it that no one make any changes in that table. i.e ReadOnly Table. I have to use this tables data along with multiple tables to join and fetch result for further queries say select * from triggertable By Using temp table select ... into #tx from triggertable join t2 join t3 and so on select a,b, c from #tx --do something select d,e,f from #tx ---do somethign --and so on --around 6-7 queries in a row in a stored procedure. By Using Views create view viewname ( select ... from triggertable join t2 join t3 and so on ) select a,b, c from viewname --do something select d,e,f from viewname ---do somethign --and so on --around 6-7 queries in a row in a stored procedure. This View can be used in other places as well. So I will be creating at database rather than at sp By Using Direct Query select a,b, c from select ... into #tx from triggertable join t2 join t3 join ... --do something select a,b, c from select ... into #tx from triggertable join t2 join t3 join ... --do something . . --and so on --around 6-7 queries in a row in a stored procedure. Now I can create a view/temporary table/ directly query usage in all upcoming queries. What would be the best to use in this case.

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• Prove correctness of unit test

  - by Timo Willemsen

  I'm creating a graph framework for learning purposes. I'm using a TDD approach, so I'm writing a lot of unit tests. However, I'm still figuring out how to prove the correctness of my unit tests For example, I have this class (not including the implementation, and I have simplified it) public class SimpleGraph(){ //Returns true on success public boolean addEdge(Vertex v1, Vertex v2) { ... } //Returns true on sucess public boolean addVertex(Vertex v1) { ... } } I also have created this unit tests @Test public void SimpleGraph_addVertex_noSelfLoopsAllowed(){ SimpleGraph g = new SimpleGraph(); Vertex v1 = new Vertex('Vertex 1'); actual = g.addVertex(v1); boolean expected = false; boolean actual = g.addEdge(v1,v1); Assert.assertEquals(expected,actual); } Okay, awesome it works. There is only one crux here, I have proved that the functions work for this case only. However, in my graph theory courses, all I'm doing is proving theorems mathematically (induction, contradiction etc. etc.). So I was wondering is there a way I can prove my unit tests mathematically for correctness? So is there a good practice for this. So we're testing the unit for correctness, instead of testing it for one certain outcome.

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• Enum exeeding the 65535 bytes limit of static initializer... what's best to do?

  - by Daniel Bleisteiner

  I've started a rather large Enum of so called Descriptors that I've wanted to use as a reference list in my model. But now I've come across a compiler/VM limit the first time and so I'm looking for the best solution to handle this. Here is my error : The code for the static initializer is exceeding the 65535 bytes limit It is clear where this comes from - my Enum simply has far to much elements. But I need those elements - there is no way to reduce that set. Initialy I've planed to use a single Enum because I want to make sure that all elements within the Enum are unique. It is used in a Hibernate persistence context where the reference to the Enum is stored as String value in the database. So this must be unique! The content of my Enum can be devided into several groups of elements belonging together. But splitting the Enum would remove the unique safety I get during compile time. Or can this be achieved with multiple Enums in some way? My only current idea is to define some Interface called Descriptor and code several Enums implementing it. This way I hope to be able to use the Hibernate Enum mapping as if it were a single Enum. But I'm not even sure if this will work. And I loose unique safety. Any ideas how to handle that case?

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• Android: SurfaceView and Z-Level Question

  - by JimBadger

  I have a FrameLayout containint first a SurfaceView, and second a RelativeLayout which in turn contians various Buttons and TextViews. Upon the canvas of the SurfaceView I am drawing numerous Bitmaps, and, via Touch and Motion Events am allowing the user to drag them around. These Bitmaps, when dragged around pass underneath the Buttons etc that are inside the RelativeLayout. Now, it's my (possibly mistaken) understanding that the "Z-level" of the SurfaceView, or whatever it has that passes for it, is entirely unrelated to the actual Z-level of the rest of the Layout. Is this the case? If so, how may I get around it, so that dragged Bitmaps are drawn ontop of other Views? Or what other way can I implement a full-screen canvas and yet not have my buttons etc act like the controls of an overlay. I guess what I actually need is an underlay, where touch events can still be picked up by the Buttons etc underneath. But I don't know how to achieve this, as, when redrawing my Canvas, I have to also redraw the background. Can I swap the order of the RelativeLayout and the SurfaceView inside the FrameLayout, and then make the background of the Canvas transparent? If so how? Will touch events still "fall through" to the buttons underneath? Thanks for bearing with me, I know I'm a bit of a waffler.

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• Objective-C properties are not being recognized in header file?

  - by Greg

  Hey folks, I wonder if I'm doing something completely stupid here... I'm clearly missing something. I've gotten used to the pattern of defining properties of a custom class, however I seem to be hitting a point where extended classes do not recognize new properties. Case of point, here's my header file: import import "MyTableViewController.h" @interface MyRootController : MyTableViewController { NSMutableArray *sectionList; } @property (nonatomic, retain) NSMutableArray *sectionList; @end Now, for some reason that "sectionList" property is not turning green within my interface file (ie: it's not being recognized as custom property it seems). As a result, I'm getting all kinds of errors down in my implementation. The first is right at the top of my implementation where I try to synthesize the property: import "MyRootController.h" @implementation MyRootController @synthesize sectionList; That synthesize line throws the error "No declaration of property 'sectionList' found in the interface". So, this is really confusing. I'm clearly doing something wrong, although I can't put my finger on what. One thought: I am extending another custom class of my own. Do I need to specify some kind of super-class declaration to keep the architecture from getting sealed one level up? Thanks!

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• Error handling in C++, constructors vs. regular methods

  - by Dennis Ritchie

  I have a cheesesales.txt CSV file with all of my recent cheese sales. I want to create a class CheeseSales that can do things like these: CheeseSales sales("cheesesales.txt"); //has no default constructor cout << sales.totalSales() << endl; sales.outputPieChart("piechart.pdf"); The above code assumes that no failures will happen. In reality, failures will take place. In this case, two kinds of failures could occur: Failure in the constructor: The file may not exist, may not have read-permissions, contain invalid/unparsable data, etc. Failure in the regular method: The file may already exist, there may not be write access, too little sales data available to create a pie chart, etc. My question is simply: How would you design this code to handle failures? One idea: Return a bool from the regular method indicating failure. Not sure how to deal with the constructor. How would seasoned C++ coders do these kinds of things?

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• Linq2Sql: query - subquery optimisation

  - by Budda

  I have the following query: IList<InfrStadium> stadiums = (from sector in DbContext.sectors where sector.Type=typeValue select new InfrStadium(sector.TeamId) ).ToList(); and InfrStadium class constructor: private InfrStadium(int teamId) { IList<Sector> teamSectors = (from sector in DbContext.sectors where sector.TeamId==teamId select sector) .ToList<>(); ... work with data } Current implementation perform 1+n queries, where n - number of records fetched the 1st time. I want to optimize that. And another one I would love to do using 'group' operator in way like this: IList<InfrStadium> stadiums = (from sector in DbContext.sectors group sector by sector.TeamId into team_sectors select new InfrStadium(team_sectors.Key, team_sectors) ).ToList(); with appropriate constructor: private InfrStadium(int iTeamId, IEnumerable<InfrStadiumSector> eSectors) { IList<Sector> teamSectors = eSectors.ToList(); ... work with data } But attempt to launch query causes the following error: Expression of type 'System.Int32' cannot be used for constructor parameter of type 'System.Collections.Generic.IEnumerable`1[InfrStadiumSector]' Question 1: Could you please explain, what is wrong here, I don't understand why 'team_sectors' is applied as 'System.Int32'? I've tried to change query a little (replace IEnumerable with IQueryeable): IList<InfrStadium> stadiums = (from sector in DbContext.sectors group sector by sector.TeamId into team_sectors select new InfrStadium(team_sectors.Key, team_sectors.AsQueryable()) ).ToList(); with appropriate constructor: private InfrStadium(int iTeamId, IQueryeable<InfrStadiumSector> eSectors) { IList<Sector> teamSectors = eSectors.ToList(); ... work with data } In this case I've received another but similar error: Expression of type 'System.Int32' cannot be used for parameter of type 'System.Collections.Generic.IEnumerable1[InfrStadiumSector]' of method 'System.Linq.IQueryable1[InfrStadiumSector] AsQueryableInfrStadiumSector' Question 2: Actually, the same question: can't understand at all what is going on here... P.S. I have another to optimize query idea (describe here: Linq2Sql: query optimisation) but I would love to find a solution with 1 request to DB).

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• EF/LINQ: Where() against a property of a subtype

  - by ladenedge

  I have a set of POCOs, all of which implement the following simple interface: interface IIdObject { int Id { get; set; } } A subset of these POCOs implement this additional interface: interface IDeletableObject : IIdObject { bool IsDeleted { get; set; } } I have a repository hierarchy that looks something like this: IRepository<T <: BasicRepository<T <: ValidatingRepository<T (where T is IIdObject) I'm trying to add a FilteringRepository to the hierarchy such that all of the POCOs that implement IDeletableObject have a Where(p => p.IsDeleted == false) filter applied before any other queries take place. My goal is to avoid duplicating the hierarchy solely for IDeletableObjects. My first attempt looked like this: public override IQueryable<T> Query() { return base.Query().Where(t => ((IDeletableObject)t).IsDeleted == false); } This works well with LINQ to Objects, but when I switch to an EF backend I get: "LINQ to Entities only supports casting Entity Data Model primitive types." I went on to try some fancier parameterized solutions, but they ultimately failed because I couldn't make T covariant in the following case for some reason I don't quite understand: interface IQueryFilter<out T> // error { Expression<Func<T, bool>> GetFilter(); } I'd be happy to go into more detail on my more complicated solutions if it would help, but I think I'll stop here for now in hope that someone might have an idea for me to try. Thanks very much in advance!

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• How do the major C# DI/IoC frameworks compare?

  - by Slomojo

  At the risk of stepping into holy war territory, What are the strengths and weaknesses of these popular DI/IoC frameworks, and could one easily be considered the best? ..: Ninject Unity Castle.Windsor Autofac StructureMap Are there any other DI/IoC Frameworks for C# that I haven't listed here? In context of my use case, I'm building a client WPF app, and a WCF/SQL services infrastructure, ease of use (especially in terms of clear and concise syntax), consistent documentation, good community support and performance are all important factors in my choice. Update: The resources and duplicate questions cited appear to be out of date, can someone with knowledge of all these frameworks come forward and provide some real insight? I realise that most opinion on this subject is likely to be biased, but I am hoping that someone has taken the time to study all these frameworks and have at least a generally objective comparison. I am quite willing to make my own investigations if this hasn't been done before, but I assumed this was something at least a few people had done already. Second Update: If you do have experience with more than one DI/IoC container, please rank and summarise the pros and cons of those, thank you. This isn't an exercise in discovering all the obscure little containers that people have made, I'm looking for comparisons between the popular (and active) frameworks.

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• Multi-Precision Arithmetic on MIPS

  - by Rob

  Hi, I am just trying to implement multi-precision arithmetic on native MIPS. Assume that one 64-bit integer is in register $12 and $13 and another is in registers $14 and $15. The sum is to be placed in registers $10 and $11. The most significant word of the 64-bit integer is found in the even-numbered registers, and the least significant word is found in the odd-numbered registers. On the internet, it said, this is the shortest possible implementation. addu $11, $13, $15 # add least significant word sltu $10, $11, $15 # set carry-in bit addu $10, $10, $12 # add in first most significant word addu $10, $10, $14 # add in second most significant word I just wanna double check that I understand correctly. The sltu checks if the sum of the two least significant words is smaller or equal than one of the operands. If this is the case, than did a carry occur, is this right? To check if there occured a carry when adding the two most significant words and store the result in $9 I have to do: sltu $9, $10, $12 # set carry-in bit Does this make any sense?

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• Is there a term for this concept, and does it exist in a static-typed language?

  - by Strilanc

  Recently I started noticing a repetition in some of my code. Of course, once you notice a repetition, it becomes grating. Which is why I'm asking this question. The idea is this: sometimes you write different versions of the same class: a raw version, a locked version, a read-only facade version, etc. These are common things to do to a class, but the translations are highly mechanical. Surround all the methods with lock acquires/releases, etc. In a dynamic language, you could write a function which did this to an instance of a class (eg. iterate over all the functions, replacing them with a version which acquires/releases a lock.). I think a good term for what I mean is 'reflected class'. You create a transformation which takes a class, and returns a modified-in-a-desired-way class. Synchronization is the easiest case, but there are others: make a class immutable [wrap methods so they clone, mutate the clone, and include it in the result], make a class readonly [assuming you can identify mutating methods], make a class appear to work with type A instead of type B, etc. The important part is that, in theory, these transformations make sense at compile-time. Even though an ActorModel<T> has methods which change depending on T, they depend on T in a specific way knowable at compile-time (ActorModel<T> methods would return a future of the original result type). I'm just wondering if this has been implemented in a language, and what it's called.

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• How to (kindly) ask your users to upgrade from IE6?

  - by nickf

  It's no secret at all that IE6 has been a major roadblock to the advancement of the web over the last few years. I couldn't count the number of hours I've spent bashing my head against a wall trying to fix or debug IE6 issues. The way I see it, there are two types of IE6 user. a) the poor corporate schmoe whose IT department doesn't want to upgrade in case something breaks, and b) the mums and dads of the world who think the internet is the blue E on their desktop (and I don't mean that in a nasty way). There's probably a couple of people who know about all the other browsers, but still choose to run IE6. They get what they deserve, IMO. Anyway, getting to the point, I'd say that 90% of my IE6-using visitors are in the the mums and dads category - they're not stupid, they just don't know WHY they should upgrade to IE7 or Firefox or whatever. How do I educate these people without pissing them off? Is there a nice and friendly website I can direct these people to, which explains the reasons for upgrading in plain language? Any mention of "security" or "web standards" I think would just come across as scary. I've just seen http://www.whatbrowser.org which seems to fit the bill nicely. It explains in very basic terms: what a web browser is why you'd want to upgrade it how old your current browser is (subtle hint to those with a 9 year old browser) ..aaaand it's in 22 languages. It's from Google but displays no bias (it links to Firefox, Chrome, Opera, Safari, Internet Explorer displayed in a random order).

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