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  • Can I make an identity field span multiple tables in SQL Server?

    - by johnnycakes
    Can I have an "identity" (unique, non-repeating) column span multiple tables? For example, let's say I have two tables: Books and Authors. Authors AuthorID AuthorName Books BookID BookTitle The BookID column and the AuthorID column are identity columns. I want the identity part to span both columns. So, if there is an AuthorID with a value of 123, then there cannot be a BookID with a value of 123. And vice versa. I hope that makes sense. Is this possible? Thanks. Why do I want to do this? I am writing an APS.NET MVC app. I am creating a comment section. Authors can have comments. Books can have comments. I want to be able to pass an entity ID (a book ID or an author ID) to an action and have the action pull up all the corresponding comments. The action won't care if it's a book or an author or whatever. Sound reasonable?

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  • Refreshing a MKMapView when the user location is updated or using default values

    - by koichirose
    I'm trying to refresh my map view and load new data from the server when the device acquires the user location. Here's what I'm doing: - (void)viewDidLoad { CGRect bounds = self.view.bounds; mapView = [[MKMapView alloc] initWithFrame:bounds]; mapView.showsUserLocation=YES; mapView.delegate=self; [self.view insertSubview:mapView atIndex:0]; [self refreshMap]; } - (void)mapView:(MKMapView *)theMapView didUpdateUserLocation:(MKUserLocation *)userLocation { //this is to avoid frequent updates, I just need one position and don't need to continuously track the user's location if (userLocation.location.horizontalAccuracy > self.myUserLocation.location.horizontalAccuracy) { self.myUserLocation = userLocation; CLLocationCoordinate2D centerCoord = { userLocation.location.coordinate.latitude, userLocation.location.coordinate.longitude }; [theMapView setCenterCoordinate:centerCoord zoomLevel:10 animated:YES]; [self refreshMap]; } } - (void)refreshMap { [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES]; [self.mapView removeAnnotations:self.mapView.annotations]; //default position NSString *lat = @"45.464161"; NSString *lon = @"9.190336"; if (self.myUserLocation != nil) { lat = [[NSNumber numberWithDouble:myUserLocation.coordinate.latitude] stringValue]; lon = [[NSNumber numberWithDouble:myUserLocation.coordinate.longitude] stringValue]; } NSString *url = [[NSString alloc] initWithFormat:@"http://myserver/geo_search.json?lat=%@&lon=%@", lat, lon]; NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0]; [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; [url release]; [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO]; } I also have a - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data, to create and add the annotations. Here's what happens: sometimes I get the location after a while, so I already loaded data close to the default location. Then I get the location and it should remove the old annotations and add the new ones, instead I keep seeing the old annotations and the new ones are added anyway (let's say I receive 10 annotations each time, so it means that I have 20 on my map when I should have 10). What am I doing wrong?

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  • Using items in a list as arguments

    - by Travis Brown
    Suppose I have a function with the following type signature: g :: a -> a -> a -> b I also have a list of as—let's call it xs—that I know will contain at least three items. I'd like to apply g to the first three items of xs. I know I could define a combinator like the following: ($$$) :: (a -> a -> a -> b) -> [a] -> b f $$$ (x:y:z:_) = f x y z Then I could just use g $$$ xs. This makes $$$ a bit like uncurry, but for a function with three arguments of the same type and a list instead of a tuple. Is there a way to do this idiomatically using standard combinators? Or rather, what's the most idiomatic way to do this in Haskell? I thought trying pointfree on a non-infix version of $$$ might give me some idea of where to start, but the output was an abomination with 10 flips, a handful of heads and tails and aps, and 28 parentheses. (NB: I know this isn't a terribly Haskelly thing to do in the first place, but I've come across a couple of situations where it seems like a reasonable solution, especially when using Parsec. I'll certainly accept "don't ever do this in real code" if that's the best answer, but I'd prefer to see some clever trick involving the ((->) r) monad or whatever.)

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  • Is there a recommended way to communicate scientific/engineering programming to C developers?

    - by ggkmath
    Hi, I have a lot of MATLAB code that needs to get ported to C (execution speed is critical for this work) as part of a back-end process for a web application. When I attempt to outsource this code to a C developer, I assume (correct me if I'm wrong) few C developers also understand MATLAB code (things like indexing and memory management are different, etc.). I wonder if there are any C developers out there that can recommend a procedure for me to follow to best communicate what the code does? For example, should I provide the MATLAB code and explain what it's doing line by line? Or, should I just provide the math/algorithm, explain it in plain English, and let the C developer implement it with this understanding in his/her own way (e.g. can I assume the developer understands how to work with complex math (i.e. imaginary numbers), how to generate histograms, perform an FFT, etc.)? Or, is there a better method? I expect I'm not the first to need to do this, so I wonder if any C developers out there ran into this situation and can share any conventional wisdom how they'd like this task to be transferred? Thanks in advance for any comments.

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  • C# "Rename" Property in Derived Class

    - by Eric
    When you read this you'll be awfully tempted to give advice like "this is a bad idea for the following reason..." Bear with me. I know there are other ways to approach this. This question should be considered trivia. Lets say you have a class "Transaction" that has properties common to all transactions such as Invoice, Purchase Order, and Sales Receipt. Let's take the simple example of Transaction "Amount", which is the most important monetary amount for a given transaction. public class Transaction { public double Amount { get; set; } public TxnTypeEnum TransactionType { get; set; } } This Amount may have a more specific name in a derived type... at least in the real world. For example, the following values are all actually the same thing: Transaction - Amount Invoice - Subtotal PurchaseOrder - Total Sales Receipt - Amount So now I want a derived class "Invoice" that has a Subtotal rather than the generically-named Amount. Ideally both of the following would be true: In an instance of Transaction, the Amount property would be visible. In an instance of Invoice, the Amount property would be hidden, but the Subtotal property would refer to it internally. Invoice looks like this: public class Invoice : Transaction { new private double? Amount { get { return base.Amount; } set { base.Amount = value; } } // This property should hide the generic property "Amount" on Transaction public double? SubTotal { get { return Amount; } set { Amount = value; } } public double RemainingBalance { get; set; } } But of course Transaction.Amount is still visible on any instance of Invoice. Thanks for taking a look!

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  • Why is my code stopping and not returning an exception?

    - by BeckyLou
    I have some code that starts a couple of threads to let them execute, then uses a while loop to check for the current time passing a set timeout period, or for the correct number of results to have been processed (by checking an int on the class object) (with a Thread.Sleep() to wait between loops) Once the while loop is set to exit, it calls Abort() on the threads and should return data to the function that calls the method. When debugging and stepping through the code, I find there can be exceptions in the code running on the separate threads, and in some cases I handle these appropriately, and at other times I don't want to do anything specific. What I have been seeing is that my code goes into the while loop and the thread sleeps, then nothing is returned from my function, either data or an exception. Code execution just stops completely. Any ideas what could be happening? Code sample: System.Threading.Thread sendThread = new System.Threading.Thread(new System.Threading.ThreadStart(Send)); sendThread.Start(); System.Threading.Thread receiveThread = new System.Threading.Thread(new System.Threading.ThreadStart(Receive)); receiveThread.Start(); // timeout Int32 maxSecondsToProcess = this.searchTotalCount * timeout; DateTime timeoutTime = DateTime.Now.AddSeconds(maxSecondsToProcess); Log("Submit() Timeout time: " + timeoutTime.ToString("yyyyMMdd HHmmss")); // while we're still waiting to receive results & haven't hit the timeout, // keep the threads going while (resultInfos.Count < this.searchTotalCount && DateTime.Now < timeoutTime) { Log("Submit() Waiting..."); System.Threading.Thread.Sleep(10 * 1000); // 1 minute } Log("Submit() Aborting threads"); // <== this log doesn't show up sendThread.Abort(); receiveThread.Abort(); return new List<ResultInfo>(this.resultInfos.Values);

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  • Can I write a .NETCF Partial Class to extend System.Windows.Forms.UserControl?

    - by eidylon
    Okay... I'm writing a .NET CF (VBNET 2008 3.5 SP1) application, which has one master form, and it dynamically loads specific UserControls based on menu click, in a sort of framework idea. There are certain methods and properties these controls all need to work within the app. Right now I am doing this as an Interface, but this is aggravating as all get up, because some of the methods are optional, and yet I MUST implement them by the nature of interfaces. I would prefer to use inheritance, so that I can have certain code be inherited with overridability, but if I write a class which inherits System.Windows.Forms.UserControl and then inherit my control from that, it squiggles, and tells me that UserControls MUST inherit directly from System.Windows.Forms.UserControl. (Talk about a design flaw!) So next I thought, well, let me use a partial class to extend System.Windows.Forms.UserControl, but when I do that, even though it all seems to compile fine, none of my new properties/methods show up on my controls. Is there any way I can use partial classes to 'extend' System.Windows.Forms.UserControl? For example, can anyone give me a code sample of a partial class which simply adds a MyCount As Integer readonly property to the System.Windows.Forms.UserControl class? If I can just see how to get this going, I can take it from there and add the rest of my functionality. Thanks in advance! I've been searching google, but can't find anything that seems to work for UserControl extension on .NET CF. And the Interface method is driving me crazy as even a small change means updating ALL the controls whether they need to 'override' the method or not.

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  • Need a piece of advice about e-mail automation in ms exchange + ms office environment

    - by be here now
    Hi, guys. I need your help in the following simple situation. I've got an MS Exchange server and some client computers running on XP with Office 2003 installed. And I've got a process I need to automate. Twice a day a known list of people sends an e-mail to a certain mailbox (let's call it manager's mailbox) - basically, an accomplishment report. After recieving letters from all of these people the mailbox owner sends and e-mail to another mailbox, meaning that a certain process is done. What I need to do is to replace this manager's mailbox with a depersonalized mailbox that will accumulate all the reports and automatically send a message after collecting all of them. I am definitely not in a "oh my God, what shold I do?" situation, and currently my imagination shows me a couple of ways to solve this problem, which I'm going to try, and I'm not ascking for a ready solution. But since I'm not experienced in Office/VBA developement, I'd like to ask a corresponding pro's opinion. Can you point me to a right direction from the best practices' point of view?

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  • How can I make Access think there is a primary key

    - by user3692757
    I have a table and I'm trying to join it with another table, but it doesn't have a distinctive primary key. The two tables do share similarities, “Acct” and “Location”. If I could concatenate “Acct&Location” it would become a primary key, but Access won’t let me make a primary key from a calculation. I provided a small sample below. Each hospital has an “Acct”, but the “Acct” will show up once for each “Location”. How can I make join these in a relationship? I connected the two in a relationships and tried to “Enforce Referential Integrity”, but it indicated “No unique index found for the referenced field of the primary key”. Also, if I run a “Find UnMatched Query” it doesn’t find anything. I think its because I can’t make it realize that in combination “Acct” and “Location” can be perceived as primary keys when used in conjunction of each other. Acct 1 2 3 1 2 3 1 2 3| Location ABI ABI ABI NHO NHO NHO NTX NTX NTX I tried to load an image to illustrate it better, but I haven't made enough post.

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  • Ajax response takes time and status is 503

    - by Suresh S
    guys, i have a html page where onclick of a button a ajax request is sent to server , the request calls a jsp page which runs an oracle procedure.The procedure runs the logic and places it in a temp table . once procedure is completed , the values are returned to the client by selecting values from tmp table. as the response is too late . the data is not received at the client side. solution: i tried to run the procedure in a separate thread using a ajax call. when the procedure is completed a global flag is set to indicate that the data is generated. if the response is 500 , a second ajax call invoked by timeout function after 10000 ms . the second call checks the global flag ,if true then reads from table and sends the response. if not again a timeout is set at the client side. this solution is not mature enough. , as the procedure may take long time to respond. please let me know a good solution for this problenm?

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  • When is Googling it wrong?

    - by Drahcir
    I've been going through Stack Overflow for quite a bit now and noticed certain people (usually experienced programmers) frown upon Googling (researching) certain problems. Since I myself tend to use Google quite a bit to solve certain programming related issues I found certain comments rather demoralising. Now some of you may have come here trigger happy to delete this post but I needed some clarification. I usually Google things that usually syntax related that I would have never figured out on my own. For example I once wondered how to access the properties of a class that I didn't have a direct relationship to. So after a bit of research I discovered reflection and got what I wanted. Now in another scenario is learning a new language, in my case Silverlight were it differs in certain aspects of .NET compared to say ASP.NET. A few weeks ago I had no idea how to load another Silverlight page (usercontrol) and had to Google my way to the solution which I found wasn't as simple as I had imagined. In scenario three is were I myself frown up, that is just stealing a huge chunk of code to avoid doing the work yourself, for example paging a HTML table using JavaScript, where one just copies and pastes the JavasSript code without as much as trying to understand how it works. I do admit I have done this once or twice before for trivial tasks that had very little time limit and weren't all that important but most of the time still have to throw away what I found because it took too much time to adapt it and get what I wanted out of it. In the last scenario, I sometimes have a piece of code that I would be really unhappy about, as in I find it sloppy or too overcomplicated and try to look on the Internet to see other ways to tackle the same problem, let's say filtering through a table. With the knowledge I acquire I learned new coding practices that help me work more efficiently like "Do not repeat yourself" and such. Now in your opinion when do you find it wrong to use Google (or any other researching tool) to find a solution to your problem?

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  • Exit and rollback everything in script on error

    - by Jan W.
    Hey guys ! I'm in a bit of a pickle here. I have a TSQL script that does a lot of database structure adjustments but it's not really safe to just let it go through when something fails. to make things clear: using MS SQL 2005 it's NOT a stored procedure, just a script file (.sql) what I have is something in the following order BEGIN TRANSACTION ALTER Stuff GO CREATE New Stuff GO DROP Old Stuff GO IF @@ERROR != 0 BEGIN PRINT 'Errors Found ... Rolling back' ROLLBACK TRANSACTION RETURN END ELSE PRINT 'No Errors ... Committing changes' COMMIT TRANSACTION just to illustrate what I'm working with ... can't go into specifics now, the problem ... When I introduce an error (to test if things get rolled back), I get a statement that the ROLLBACK TRANSACTION could not find a corresponding BEGIN TRANSACTION. This leads me to believe that something when REALLY wrong and the transaction was already killed. what I also noticed is that the script didn't fully quit on error and thus DID try to execute every statement after the error occured. (I noticed this when new tables showed up when I wasn't expecting them because it should have rollbacked) any help in this department is welcome if more speficics are needed, ask! greetz

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  • If attacker has original data, and encrypted data, can they determine the passphrase?

    - by Brad Cupit
    If an attacker has several distinct items (for example: e-mail addresses) and knows the encrypted value of each item, can the attacker more easily determine the secret passphrase used to encrypt those items? Meaning, can they determine the passphrase without resorting to brute force? This question may sound strange, so let me provide a use-case: User signs up to a site with their e-mail address Server sends that e-mail address a confirmation URL (for example: https://my.app.com/confirmEmailAddress/bill%40yahoo.com) Attacker can guess the confirmation URL and therefore can sign up with someone else's e-mail address, and 'confirm' it without ever having to sign in to that person's e-mail account and see the confirmation URL. This is a problem. Instead of sending the e-mail address plain text in the URL, we'll send it encrypted by a secret passphrase. (I know the attacker could still intercept the e-mail sent by the server, since e-mail are plain text, but bear with me here.) If an attacker then signs up with multiple free e-mail accounts and sees multiple URLs, each with the corresponding encrypted e-mail address, could the attacker more easily determine the passphrase used for encryption? Alternative Solution I could instead send a random number or one-way hash of their e-mail address (plus random salt). This eliminates storing the secret passphrase, but it means I need to store that random number/hash in the database. The original approach above does not require this extra table. I'm leaning towards the the one-way hash + extra table solution, but I still would like to know the answer: does having multiple unencrypted e-mail addresses and their encrypted counterparts make it easier to determine the passphrase used?

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  • How to use javascript to get information from the content of another page (same domain)?

    - by hlovdal
    Let's say I have a web page (/index.html) that contains the following <li> <div>item1</div> <a href="/details/item1.html">details</a> </li> and I would like to have some javascript on /index.html to load that /details/item1.html page and extract some information from that page. The page /details/item1.html might contain things like <div id="some_id"> <a href="/images/item1_picture.png">picture</a> <a href="/images/item1_map.png">map</a> </div> My task is to write a greasemonkey script, so changing anything serverside is not an option. To summarize, javascript is running on /index.html and I would like to have the javascript code to add some information on /index.html extracted from both /index.html and /details/item1.html. My question is how to fetch information from /details/item1.html. I currently have written code to extract the link (e.g. /details/item1.html) and pass this on to a method that should extract the wanted information (at first just .innerHTML from the some_id div is ok, I can process futher later). The following is my current attempt, but it does not work. Any suggestions? function get_information(link) { var obj = document.createElement('object'); obj.data = link; document.getElementsByTagName('body')[0].appendChild(obj) var some_id = document.getElementById('some_id'); if (! some_id) { alert("some_id == NULL"); return ""; } return some_id.innerHTML; }

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  • Maven + AspectJ - all steps to configure it

    - by Alice
    I have a problem with applying aspects to my maven project. Probably I am missing something, so I've made a list of steps. Could you please check if it is correct? Let say in projectA is an aspect class and in projectB classes, which should be changed by aspects. Create maven project ProjectA with AspectJ class add Aspectj plugin and dependency Add ProjectA as a dependency to projectB pom.xml Add to projectB pom.xml plugin " <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>aspectj-maven-plugin</artifactId> <version>1.4</version> <executions> <execution> <goals> <goal>compile</goal> <goal>test-compile</goal> </goals> </execution> </executions> <configuration> <source>${maven.compiler.source}</source> <target>${maven.compiler.target}</target> <aspectLibraries> <aspectLibrary> <groupId>ProjectA</groupId> <artifactId>ProjectA</artifactId> </aspectLibrary> </aspectLibraries> </configuration> </plugin> Add aspectj dependency After all these steps my problem is, that during compilation I get: [WARNING] advice defined in AspectE has not been applied [Xlint:adviceDidNotMatch] And then when I run my program: Exception in thread "FeatureExcutionThread" java.lang.NoClassDefFoundError: AspectE

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  • JPA - Real primary key generated ID for references

    - by Val
    I have ~10 classes, each of them, have composite key, consist of 2-4 values. 1 of the classes is a main one (let's call it "Center") and related to other as one-to-one or one-to-many. Thinking about correct way of describing this in JPA I think I need to describe all the primary keys using @Embedded / @PrimaryKey annotations. Question #1: My concern is - does it mean that on the database level I will have # of additional columns in each table referring to the "Center" equal to number of column in "Center" PK? If yes, is it possible to avoid it by using some artificial unique key for references? Could you please give an idea how real PK and the artificial one needs to be described in this case? Note: The reason why I would like to keep the real PK and not just use the unique id as PK is - my application have some data loading functionality from external data sources and sometimes they may return records which I already have in local database. If unique ID will be used as PK - for new records I won't be able to do data update, since the unique ID will not be available for just downloaded ones. At the same time it is normal case scenario for application and it just need to update of insert new records depends on if the real composite primary key matches. Question #2: All of the 10 classes have common field "date" which I described in an abstract class which each of them extends. The "date" itself is never a key, but it always a part of composite key for each class. Composite key is different for each class. To be able to use this field as a part of PK should I describe it in each class or is there any way to use it as is? I experimented with @Embedded and @PrimaryKey annotations and always got an error that eclipselink can't find field described in an abstract class. Thank you in advance! PS. I'm using latest version of eclipselink & H2 database.

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  • How to write a JOIN statement to combine data from disparate tables

    - by Amarundo
    I have the following 2 procedures that I use as my source for a report. As of now, I'm presenting 2 different tables in my SQL Server Reporting Services 2008 R2 report, because it doesn't let me put them together as they belong to 2 different data sets. I want to present them in a single table, but I have not been successful trying to use JOIN here. How do I do that? NOTE: cName in IAgentQueueStats corresponds to UserId in AgentActivityLog. /*** Aggregate values for Call Center Agents for calls, talk and hold time ***/ /*** The detail/row values is per 30-minute interval ***/ ALTER PROCEDURE [dbo].[sp_IAgentQueueStats_OnlyCalls_Grouped] @p_StartDate datetime, @p_EndDate datetime, @p_Agents varchar(8000) AS SELECT [cName] ,sum([nAnswered]) SumNAnswered ,sum([nAnsweredAcd]) SumNAnsweredAcd ,sum([tTalkAcd]) SumTTalkAcd ,sum([nHoldAcd]) SumNHoldAcd ,sum([tHoldAcd]) SumTHoldAcd ,sum([tAcw]) SumTAcw FROM [I3_IC].[dbo].[IAgentQueueStats] WHERE dIntervalStart between @p_StartDate and DATEADD(s, 86400-1, @p_EndDate) AND CHARINDEX ( cName ,@p_Agents)> 0 AND cReportGroup <> '*' AND cHKey3 = '*' and cHKey4 ='*' AND nEnteredAcd > 0 AND cReportGroup <> 'CCFax Email' GROUP BY cName And here is the second one: /*** Aggregate values for Call Center Agents for status/activity time ***/ /*** The detail/row values is per start-time/end-time ***/ ALTER PROCEDURE [dbo].[sp_AgentActivity_Grouped] @p_StartDate datetime, @p_EndDate datetime, @p_Agents varchar(8000) AS SELECT [UserId],[StatusCategory],SUM([StateDuration]) [StatusDuration] FROM ( SELECT [UserId] ,[StatusGroup] ,[StatusKey] , CASE [StatusKey] WHEN 'Available' THEN 'Productive' WHEN 'Follow Up' THEN 'Productive' WHEN 'Campaign Call' THEN 'Productive' WHEN 'Awaiting Callback' THEN 'Productive' WHEN 'In a Meeting' THEN 'Not Your Fault' WHEN 'Project Work' THEN 'Not Your Fault' WHEN 'At a Training Session'THEN 'Not Your Fault' WHEN 'System Issues' THEN 'Not Your Fault' WHEN 'Test' THEN 'Not Your Fault' WHEN 'At Lunch' THEN 'Non Productive' WHEN 'Available, Forward' THEN 'Non Productive' WHEN 'Available, Follow-Me' THEN 'Non Productive' WHEN 'At Play' THEN 'Non Productive' WHEN 'AcdAgentNotAnswering' THEN 'Non Productive' WHEN 'Do Not Disturb' THEN 'Non Productive' WHEN 'Available, No ACD' THEN 'Non Productive' WHEN 'Away from desk' THEN 'Non Productive' ELSE [StatusKey] END StatusCategory ,stateduration FROM [I3_IC].[dbo].[AgentActivityLog] WHERE [StatusDateTime] between @p_StartDate and DATEADD(s, 86400-1, @p_EndDate) AND CHARINDEX ( [UserId] ,@p_Agents)> 0 AND [StatusKey] not in ('Gone Home','Out of the Office','On Vacation','Out of Town') ) a GROUP BY [UserId],[StatusCategory] ORDER BY [UserId], [StatusCategory] desc BTW, if I take some time to comment/reply on your posts, it's not lack of interest, but of understanding...

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  • How to Prevent PostBack Event Handler from Firing

    - by user331744
    I have a custom class (ServerSideValidator.vb) that validates user input on server side (it doesn't use any of the .NET built in validators, therefore Page.Validate() is not an option for me). I am calling the Validate() method on page.IsPostback event and the class performs without any problem My issue is, when validation fails (returns false), I want to stop the postback event handler from firing, but load the page along with all the controls and user-input values in them. If I do, Response.End(), the page comes up blank. I can programmatically instruct the page to go to the previous page (original form before postback), but it loses all user-inputs. I thought of creating a global boolean variable in the page code behind file and check the value before performing any postback method, but this approach takes away from my plan to provide all functionalities inside the class itself. The page object is being referenced to ServerSideValidator. Seems like all the postback related properties/variables I come across inside Page class are 'Readonly' and I can't assign value(s) to control/prevent postback event from firing. Any idiea on how I can accomplish this? Please let me know if you need further details

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  • What about parallelism across network using multiple PCs?

    - by MainMa
    Parallel computing is used more and more, and new framework features and shortcuts make it easier to use (for example Parallel extensions which are directly available in .NET 4). Now what about the parallelism across network? I mean, an abstraction of everything related to communications, creation of processes on remote machines, etc. Something like, in C#: NetworkParallel.ForEach(myEnumerable, () => { // Computing and/or access to web ressource or local network database here }); I understand that it is very different from the multi-core parallelism. The two most obvious differences would probably be: The fact that such parallel task will be limited to computing, without being able for example to use files stored locally (but why not a database?), or even to use local variables, because it would be rather two distinct applications than two threads of the same application, The very specific implementation, requiring not just a separate thread (which is quite easy), but spanning a process on different machines, then communicating with them over local network. Despite those differences, such parallelism is quite possible, even without speaking about distributed architecture. Do you think it will be implemented in a few years? Do you agree that it enables developers to easily develop extremely powerfull stuff with much less pain? Example: Think about a business application which extracts data from the database, transforms it, and displays statistics. Let's say this application takes ten seconds to load data, twenty seconds to transform data and ten seconds to build charts on a single machine in a company, using all the CPU, whereas ten other machines are used at 5% of CPU most of the time. In a such case, every action may be done in parallel, resulting in probably six to ten seconds for overall process instead of forty.

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  • C# expression tree for ordinary code

    - by rwallace
    It's possible to create an expression tree, if you declare it as such. But is it possible to get an expression tree for an ordinary chunk of code such as a method or property getter? What I'm trying to do is, let's say for an order processing system, I have a class for order items: class Item : Entity { [Cascade] public Document document { get; set; } public int line { get; set; } public Product product { get; set; } public string description { get; set; } public decimal qty { get; set; } public decimal price { get; set; } public decimal net { get { return qty * price; } } public VatCode vat_code { get; set; } } where the net value equals qty * price, so I'd like to declare it as such, either with a property or method, and then also have the framework introspect that expression so it can generate appropriate SQL for defining a corresponding calculated column in a corresponding database view. The most obvious way to do this would be to get the expression tree for a property getter or a method, but I can't find any indication how to do this, or that it is possible. (I have found a way to get a method body as a byte stream, but that's not what's desired here.) If that isn't possible, I suppose the recommended solution would be to declare something like a static field that is an expression tree, and compile/run it at run time for internal use, and also introspect as normal for SQL generation?

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  • How to programmatically set the text of a cell of database in VB.Net?

    - by manuel
    I have a Microsoft Access database file connected to VB.NET. In the database table, I have a 'No.' and a 'Status' column. Then I have a textbox where I can input an integer. I also have a button, which will change the data cell in 'Status' where 'No.' = txtTitleNo.Text(), when I click it. Let's say I want the 'Status' cell to be changed to "Reserved". What codes should I put in the BtnReserve_Click? Here is the code: Public Class theForm Dim con As New OleDb.OleDbConnection Dim ds As New DataSet Dim daTitles As OleDb.OleDbDataAdapter Private Sub theForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=|DataDirectory|\db1.mdb" con.Open() daTitles = New OleDb.OleDbDataAdapter("SELECT * FROM Titles", con) daTitles.Fill(ds, "Titles") DataGridView1.DataSource = ds.Tables("Titles") DataGridView1.AutoResizeColumns() End Sub Private Sub BtnReserve_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnReserve.Click Dim daReserve As OleDb.OleDbCommand For i As Integer = 1 TReservedo DataGridView1.RowCount() If i = Val(txtTitleNo.Text()) Then daReserve = New OleDb.OleDbCommand("UPDATE Titles SET Status = 'Reserved' WHERE No = '" & i & "'", con) daReserve.ExecuteNonQuery() End If Next Dim cb As New OleDb.OleDbCommandBuilder(daTitles) daTitles.Update(ds, "Titles") End Sub This code still does not change the 'Status'. What should I do?

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  • How to Develop Dynamic Plug-In Based Functionality in C#

    - by Matthew
    Hello: I've been looking around for different methods of providing plug-in support for my application. Ideally, I will be creating a core functionality and based on different customers developing different plug-ins/addons such as importing, exporting data etc... What are the some methods available for making a C# application extensible via a plug-in architecture? Lets make up an example. If we have a program that consists of a main menu ( File, Edit, View, et al. ) along with a TreeView that displays different brands of cars grouped by manufacturer ( Ford, GM, for now). Right clicking on a car displays a context menu with the only option being 'delete car'. How could you develop the application so that plug-ins could be deployed so that you could allow one customer to see a new brand in the TreeView, let's say Honda, and also extent the car context menu so that they may now 'paint a car'? In Eclipse/RCP development this is easily handled by extension points and plug-ins. How does C# handle it? I've been looking into developing my own plug-in architecture and reading up on MEF.

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  • How to check at runtime if a class implements certain interface?

    - by mare
    Let's say I have some content classes like Page, TabGroup, Tab, etc. Certain of those will be implementing my IWidgetContainer interface - it means they will geet an additional field named ContainedItems from the interface and some methods for manipulating this field. Now I need to reflect the fact that some class implements this interface by rendering out some special custom controls in my ASP.NET MVC Views (like jQuery Add/Remove/Move/Reorder buttons). For instance, TabGroup will implement IWidgetContainer because it will contain tabs but a tab will not implement it because it won't have the ability to contain anything. So I have to somehow check in my view, when I render my content objects (The problem is, I use my base class as strong type in my view not concrete classes), whether it implements IWidgetContainer. How is that possible or have I completely missed something? To rephrase the question, how do you reflect some special properties of a class (like interface implementation) in the UI in general (not necessarily ASP.NET MVC)? Here's my code so far: [DataContract] public class ContentClass { [DataMember] public string Slug; [DataMember] public string Title; [DataMember] protected ContentType Type; } [DataContract] public class Group : ContentClass, IWidgetContainer { public Group() { Type = ContentType.TabGroup; } public ContentList ContainedItems { get; set; } public void AddContent(ContentListItem toAdd) { throw new NotImplementedException(); } public void RemoveContent(ContentListItem toRemove) { throw new NotImplementedException(); } } [DataContract] public class GroupElement : ContentClass { public GroupElement() { Type = ContentType.Tab; } } Interface: interface IWidgetContainer { [DataMember] ContentList ContainedItems { get; set; } void AddContent(ContentListItem toAdd); void RemoveContent(ContentListItem toRemove); }

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  • How to duplicate all data in a table except for a single column that should be changed.

    - by twiga
    I have a question regarding a unified insert query against tables with different data structures (Oracle). Let me elaborate with an example: tb_customers ( id NUMBER(3), name VARCHAR2(40), archive_id NUMBER(3) ) tb_suppliers ( id NUMBER(3), name VARCHAR2(40), contact VARCHAR2(40), xxx, xxx, archive_id NUMBER(3) ) The only column that is present in all tables is [archive_id]. The plan is to create a new archive of the dataset by copying (duplicating) all records to a different database partition and incrementing the archive_id for those records accordingly. [archive_id] is always part of the primary key. My problem is with select statements to do the actual duplication of the data. Because the columns are variable, I am struggling to come up with a unified select statement that will copy the data and update the archive_id. One solution (that works), is to iterate over all the tables in a stored procedure and do a: CREATE TABLE temp as (SELECT * from ORIGINAL_TABLE); UPDATE temp SET archive_id=something; INSERT INTO temp (select * from temp); DROP TABLE temp; I do not like this solution very much as the DDL commands muck up all restore points. Does anyone else have any solution?

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  • Importing external .jar file to Android project

    - by robintw
    I've read various answers to similar questions on StackOverflow, so I apologise if I'm repeating another question, but I can't seem to get this to work. I have a standard java project in which I've written code to parse some BBC Radio XML data from the internet. The project is called BBCSchedules and the class I'm interested in is called BBCChannel. I'm now trying to use the BBCChannel class in an android application. How should I go about doing this? I've tried various things, following various bits of advice on the internet, and the place I've got to at the moment is compiling my BBCSchedules project to a .jar file, and importing that to the Android project using the Build Path/Library/Add External Jar option. However, Eclispe still doesn't recognise the BBCChannel class, and won't let me run the application because of this. I guess I've done something silly wrong, but what is it? Cheers, Robin UPDATE: I've tried the steps listed in http://stackoverflow.com/questions/1334802/how-can-i-use-external-jars-in-an-android-project and various other StackOverflow questions I can find that seem to be related to this, but absolutely nothing seems to work. Any other ideas? UPDATE: The discussions I've had with the author of the first answer below suggest that it is something to do with how I am using Eclipse to attach the .jar file. The project he sent me with the .jar file already attached didn't work. Any other ideas anyone?

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