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• Ubuntu server or Debian server (to run C++ apps developed on Ubuntu)

  - by skyeagle

  I have written a number of C++ server side daemons for my website, using my Ubuntu 9.10 dev machine. I am now about to venture out to look for a hosting provider etc. This is my problem: I have read on many posts (admittedly old posts) that Debian server is much more robust than Ubuntu server - is this till the case?. In particular, I am constantly "raising elephants" with my Ubuntu 9.10 - this is "ok" for home use, but for a website server, I would not be so forgiving. Also, there seems to be a new "patch" every few weeks - which I would not like on a server (I want to leave the server well alone, and let it get on with its business of serving pages). So in this instance Debian looks a more attractive proposition. I am worried that the C++ apps I have developed on Ubuntu may not be binary compatable with Debian (or I may need to install additional libraries/packages etc to get things to work), and I have zero experience with Debian. Additionally, I dont want to be grappling with the learning curve associated with a new OS, whilst trying to launch a new web site (I am assuming Debian UI is quite different from Ubuntu). In this case, the maxim "the devil you know is better than the one you dont", seems appropriate - and I find Ubuntu a more attractive proposition (atleast I know my apps will run without any probs etc). Can anyone provide some rational advice (based on actual experience), to help me decide which route to take - given the two (conflicting) trains of thought outlined above?

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• Using PLINQ to calculate and update values within the enclosure does not work

  - by Keith

  I recently needed to do a running total on a report. Where for each group, I order the rows and then calculate the running total based on the previous rows within the group. Aha! I thought, a perfect use case for PLINQ! However, when I wrote up the code, I got some strange behavior. The values I was modifying showed as being modified when stepping through the debugger, but when they were accessed they were always zero. Sample Code: class Item { public int PortfolioID; public int TAAccountID; public DateTime TradeDate; public decimal Shares; public decimal RunningTotal; } List<Item> itemList = new List<Item> { new Item { PortfolioID = 1, TAAccountID = 1, TradeDate = new DateTime(2010, 5, 1), Shares = 5.335m, }, new Item { PortfolioID = 1, TAAccountID = 1, TradeDate = new DateTime(2010, 5, 2), Shares = -2.335m, }, new Item { PortfolioID = 2, TAAccountID = 1, TradeDate = new DateTime(2010, 5, 1), Shares = 7.335m, }, new Item { PortfolioID = 2, TAAccountID = 1, TradeDate = new DateTime(2010, 5, 2), Shares = -3.335m, }, }; var found = (from i in itemList where i.TAAccountID == 1 select new Item { TAAccountID = i.TAAccountID, PortfolioID = i.PortfolioID, Shares = i.Shares, TradeDate = i.TradeDate, RunningTotal = 0 }); found.AsParallel().ForAll(x => { var prevItems = found.Where(i => i.PortfolioID == x.PortfolioID && i.TAAccountID == x.TAAccountID && i.TradeDate <= x.TradeDate); x.RunningTotal = prevItems.Sum(s => s.Shares); }); foreach (Item i in found) { Console.WriteLine("Running total: {0}", i.RunningTotal); } Console.ReadLine(); If I change the select for found to be .ToArray(), then it works fine and I get calculated reuslts. Any ideas what I am doing wrong?

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• Losing URI segments when paginating with CodeIgniter

  - by Danny Herran

  I have a /payments interface where the user should be able to filter via price range, bank, and other stuff. Those filters are standard select boxes. When I submit the filter form, all the post data goes to another method called payments/search. That method performs the validation, saves the post values into a session flashdata and redirects the user back to /payments passing the flashdata name via URL. So my standard pagination links with no filters are exactly like this: payments/index/20/ payments/index/40/ payments/index/60/ And if you submit the filter form, the returning URL is: payments/index/0/b48c7cbd5489129a337b0a24f830fd93 This works just great. If I change the zero for something else, it paginates just fine. The only issue however is that the << 1 2 3 4 page links wont keep the hash after the pagination offset. CodeIgniter is generating the page links ignoring that additional uri segment. My uri_segment config is already set to 3: $config['uri_segment'] = 3; I cannot set the page offset to 4 because that hash may or may not exists. Any ideas of how can I solve this? Is it mandatory for CI to have the offset as the last segment in the uri? Maybe I am trying an incorrect approach, so I am all ears. Thank you folks.

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• Tell me SQL Server Full-Text searcher is crazy, not me.

  - by Ian Boyd

  i have some customers with a particular address that the user is searching for: 123 generic way There are 5 rows in the database that match: ResidentialAddress1 ============================= 123 GENERIC WAY 123 GENERIC WAY 123 GENERIC WAY 123 GENERIC WAY 123 GENERIC WAY i run a FT query to look for these rows. i'll show you each step as i add more criteria to the search: SELECT ResidentialAddress1 FROM Patrons WHERE CONTAINS(Patrons.ResidentialAddress1, '"123*"') ResidentialAddress1 ========================= 123 MAPLE STREET 12345 TEST 123 MINE STREET 123 GENERIC WAY 123 FAKE STREET ... (30 row(s) affected) Okay, so far so good, now adding the word "generic": SELECT ResidentialAddress1 FROM Patrons WHERE CONTAINS(Patrons.ResidentialAddress1, '"123*"') AND CONTAINS(Patrons.ResidentialAddress1, '"generic*"') ResidentialAddress1 ============================= 123 GENERIC WAY 123 GENERIC WAY 123 GENERIC WAY 123 GENERIC WAY 123 GENERIC WAY (5 row(s) affected) Excellent. And now i'l add the final keyword that the user wants to make sure exists: SELECT ResidentialAddress1 FROM Patrons WHERE CONTAINS(Patrons.ResidentialAddress1, '"123*"') AND CONTAINS(Patrons.ResidentialAddress1, '"generic*"') AND CONTAINS(Patrons.ResidentialAddress1, '"way*"') ResidentialAddress1 ------------------------------ (0 row(s) affected) Huh? No rows? What if i query for just "way*": SELECT ResidentialAddress1 FROM Patrons WHERE CONTAINS(Patrons.ResidentialAddress1, '"way*"') ResidentialAddress1 ------------------------------ (0 row(s) affected) At first i thought that perhaps it's because of the *, and it's requiring that the root way have more characters after it. But that's not true: Searching for "123*" matches "123" Searching for "generic*" matches "generic" Books online says, The asterisk matches zero, one, or more characters What if i remove the * just for s&g: SELECT ResidentialAddress1 FROM Patrons WHERE CONTAINS(Patrons.ResidentialAddress1, '"way"') Server: Msg 7619, Level 16, State 1, Line 1 A clause of the query contained only ignored words. So one might think that you are just not allowed to even search for way, either alone, or as a root. But this isn't true either: SELECT * FROM Patrons WHERE CONTAINS(Patrons.*, '"way*"') AccountNumber FirstName Lastname ------------- --------- -------- 33589 JOHN WAYNE So sum up, the user is searching for rows that contain all the words: 123 generic way Which i, correctly, translate into the WHERE clauses: SELECT * FROM Patrons WHERE CONTAINS(Patrons.*, '"123*"') AND CONTAINS(Patrons.*, '"generic*"') AND CONTAINS(Patrons.*, '"way*"') which returns no rows. Tell me this just isn't going to work, that it's not my fault, and SQL Server is crazy. Note: i've emptied the FT index and rebuilt it.

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• What is the preferred way in C++ for converting a builtin type (int) to bool?

  - by Martin

  When programming with Visual C++, I think every developer is used to see the warning warning C4800: 'BOOL' : forcing value to bool 'true' or 'false' from time to time. The reason obviously is that BOOL is defined as int and directly assigning any of the built-in numerical types to bool is considered a bad idea. So my question is now, given any built-in numerical type (int, short, ...) that is to be interpreted as a boolean value, what is the/your preferred way of actually storing that value into a variable of type bool? Note: While mixing BOOL and bool is probably a bad idea, I think the problem will inevitably pop up whether on Windows or somewhere else, so I think this question is neither Visual-C++ nor Windows specific. Given int nBoolean; I prefer this style: bool b = nBoolean?true:false; The following might be alternatives: bool b = !!nBoolean; bool b = (nBoolean != 0); Is there a generally preferred way? Rationale? I should add: Since I only work with Visual-C++ I cannot really say if this is a VC++ specific question or if the same problem pops up with other compilers. So it would be interesting to specifically hear from g++ or users how they handle the int-bool case. Regarding Standard C++: As David Thornley notes in a comment, the C++ Standard does not require this behavior. In fact it seems to explicitly allow this, so one might consider this a VC++ weirdness. To quote the N3029 draft (which is what I have around atm.): 4.12 Boolean conversions [conv.bool] A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true. (...)

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• Is there a limit for the number of files in a directory on an SD card?

  - by jamesh

  I have a project written for Android devices. It generates a large number of files, each day. These are all text files and images. The app uses a database to reference these files. The app is supposed to clear up these files after a little use (perhaps after a few days), but this process may or may not be working. This is not the subject of this question. Due to a historic accident, the organization of the files are somewhat naive: everything is in the same directory; a .hidden directory which contains a zero byte .nomedia file to prevent the MediaScanner indexing it. Today, I am seeing an error reported: java.io.IOException: Cannot create: /sdcard/.hidden/file-4200.html at java.io.File.createNewFile(File.java:1263) Regarding the sdcard, I see it has plenty of storage left, but counting $ cd /Volumes/NO_NAME/.hidden $ ls | wc -w 9058 Deleting a number of files seems to have allowed the file creation for today to proceed. Regrettably, I did not try touching a new file to try and reproduce the error on a commandline; I also deleted several hundred files rather than a handful. However, my question is: are there hard limits on filesize or number of files in a directory? am I even on the right track here? Nota Bene: The SD card is as-is - i.e. I haven't formatted it, so I would guess it would be a FAT-* format. The FAT-32 format has hard limits of filesize of 2GB (well above the filesizes I am dealing with) and a limit of number of files in the root directory. I am definitely not writing files in the root directory.

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• CSS Background image in Redmine template arbitrarily not loading

  - by Pekka

  I`m in the process of building a template for Redmine (a project management system based on Ruby on Rails.) Ruby is running on a virtual server from a Bitnami.org installation package. The OS is Windows. The template essentially consists of a styles.css file. In that file, I have the following line: #header { padding: 0px; padding-top: 48px; background-color: #62DFFF; background-image: url(../images/bkg.jpg) background-position: center bottom; background-repeat: repeat-x; height:150px; } It's a header element with a background image. The problem: This background image arbitrarily appears and disappears when reloading. Say you reload ten times in twenty seconds; the image will appear in two instances, and be missing in the 18 others. I would have put this down to server problems, but the weird thing is that when it's missing, the request for the image doesn't appear in Firebug's net tab at all. Even if it were cached, the request should be there. Raw screenshots of the identical page on two reloads: I am 100% sure the CSS file does not change in between. I have examined both instances with Firebug and the CSS is identical. It happens in both Firefox and Chrome so it must be something basic I'm overlooking. What could be causing a browser not to load a resource at all? I have zero idea about Ruby nor Rails - getting Redmine running and customized is all I have ever had to do with this platform - so I don't really know where to look. Apache's, Mongrel's and Redmine's error logs look fine, though.

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• Singleton Pattern combine with a Decorator

  - by Mike

  Attached is a classic Decorator pattern. My question is how would you modify the below code so that you can wrap zero or one of each topping on to the Pizza Right now I can have a Pepporini - Sausage -- Pepporini -- Pizza class driving the total cost up to $10, charging twice for Pepporini. I don't think I want to use the Chain of Responsibility pattern as order does not matter and not all toppings are used? Thank you namespace PizzaDecorator { public interface IPizza { double CalculateCost(); } public class Pizza: IPizza { public Pizza() { } public double CalculateCost() { return 8.00; } } public abstract class Topping : IPizza { protected IPizza _pizzaItem; public Topping(IPizza pizzaItem) { this._pizzaItem = pizzaItem; } public abstract double CalculateCost(); } public class Pepporini : Topping { public Pepporini(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 0.50; } } public class Sausage : Topping { public Sausage(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 1.00; } } public class Onions : Topping { public Onions(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + .25; } } }

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• Explaining the forecasts from an ARIMA model

  - by Samik R.

  I am trying to explain to myself the forecasting result from applying an ARIMA model to a time-series dataset. The data is from the M1-Competition, the series is MNB65. For quick reference, I have a google doc spreadsheet with the data. I am trying to fit the data to an ARIMA(1,0,0) model and get the forecasts. I am using R. Here are some output snippets: > arima(x, order = c(1,0,0)) Series: x ARIMA(1,0,0) with non-zero mean Call: arima(x = x, order = c(1, 0, 0)) Coefficients: ar1 intercept 0.9421 12260.298 s.e. 0.0474 202.717 > predict(arima(x, order = c(1,0,0)), n.ahead=12) $pred Time Series: Start = 53 End = 64 Frequency = 1 [1] 11757.39 11786.50 11813.92 11839.75 11864.09 11887.02 11908.62 11928.97 11948.15 11966.21 11983.23 11999.27 I have a few questions: (1) How do I explain that although the dataset shows a clear downward trend, the forecast from this model trends upward. This also happens for ARIMA(2,0,0), which is the best ARIMA fit for the data using auto.arima (forecast package) and for an ARIMA(1,0,1) model. (2) The intercept value for the ARIMA(1,0,0) model is 12260.298. Shouldn't the intercept satisfy the equation: C = mean * (1 - sum(AR coeffs)), in which case, the value should be 715.52. I must be missing something basic here. (3) This is clearly a series with non-stationary mean. Why is an AR(2) model still selected as the best model by auto.arima? Could there be an intuitive explanation? Thanks.

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• How do I manage dependencies for automated builds on my build server?

  - by Tom Pickles

  I'm trying to implement continuous integration into our day to day workings. In our team, we're moving from just building our code in Visual Studio on our workstations and deploying, to using MSBuild.exe and automating on our build server (which is Jenkins) without the use of Visual Studio. We have external dependencies to references such as Automap in our projects. Because the automap (for example) dll isn't on the build server, the msbuild execution fails, for obvious reasons. There are other dll's which I need to be part of the build, I'm just using automap as an example. So what's the best way to get any dependencies onto the build server as part of the automated build? I've seen references to using a 'lib' folder, but I don't really understand where I should be putting it (in my project, filesystem, SVN ...?), and how the build server will get to it. I've also read that NuGet can do something with dependencies, but my build server isn't connected to the internet, and I don't understand how I can get my build to pull a NuGet package I may have created, and how it works together. Edit: I'm using subversion and we cannot use TeamCity as we would have to buy it and there's zero chance of funding.

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• Flag bit computation and detection

  - by Majid

  Hi all, In some code I'm working on I should take care of ten independent parameters which can take one of two values (0 or 1). This creates 2^10 distinct conditions. Some of the conditions never occur and can be left out, but those which do occur are still A LOT and making a switch to handle all cases is insane. I want to use 10 if statements instead of a huge switch. For this I know I should use flag bits, or rather flag bytes as the language is javascript and its easier to work with a 10 byte string with to represent a 10-bit binary. Now, my problem is, I don't know how to implement this. I have seen this used in APIs where multiple-selectable options are exposed with numbers 1, 2, 4, 8, ... , n^(n-1) which are decimal equivalents of 1, 10, 100, 1000, etc. in binary. So if we make call like bar = foo(7), bar will be an object with whatever options the three rightmost flags enable. I can convert the decimal number into binary and in each if statement check to see if the corresponding digit is set or not. But I wonder, is there a way to determine the n-th digit of a decimal number is zero or one in binary form, without actually doing the conversion?

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• Calculating distance from latitude, longitude and height using a geocentric co-ordinate system

  - by Sarge

  I've implemented this method in Javascript and I'm roughly 2.5% out and I'd like to understand why. My input data is an array of points represented as latitude, longitude and the height above the WGS84 ellipsoid. These points are taken from data collected from a wrist-mounted GPS device during a marathon race. My algorithm was to convert each point to cartesian geocentric co-ordinates and then compute the Euclidean distance (c.f Pythagoras). Cartesian geocentric is also known as Earth Centred Earth Fixed. i.e. it's an X, Y, Z co-ordinate system which rotates with the earth. My test data was the data from a marathon and so the distance should be very close to 42.26km. However, the distance comes to about 43.4km. I've tried various approaches and nothing changes the result by more than a metre. e.g. I replaced the height data with data from the NASA SRTM mission, I've set the height to zero, etc. Using Google, I found two points in the literature where lat, lon, height had been transformed and my transformation algorithm is matching. What could explain this? Am I expecting too much from Javascript's double representation? (The X, Y, Z numbers are very big but the differences between two points is very small). My alternative is to move to computing the geodesic across the WGS84 ellipsoid using Vincenty's algorithm (or similar) and then calculating the Euclidean distance with the two heights but this seems inaccurate. Thanks in advance for your help!

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• How to create a "Shell IDList Array" to support drag-and-drop of virtual files from C# to Windows Ex

  - by JustABill

  I started trying to implement drag-and-drop of virtual files (from a C# 4/WPF app) with this codeplex tutorial. After spending some time trying to figure out a DV_E_FORMATETC error, I figured out I need to support the "Shell IDList Array" data format. But there seems to be next to zero documentation on what this format actually does. After some searching, I found this page on advanced data transfer which said that a Shell IDList Array was a pointer to a CIDA structure. This CIDA structure then contains the number of PIDLs, and a list of offsets to them. So what the hell is a PIDL? After some more searching, this page sort of implies it's a pointer to an ITEMIDLIST, which itself contains a single member that is a list of SHITEMIDs. My next idea was to try dragging a file from another application with virtual files. I just got a MemoryStream back for this format. At least I know what class to provide for the thing, but that doesn't help at all for explaining what to put in it. So now that that's explained, I still have no idea how to create one of these things so that it's valid. There's two real questions here: What is a valid "abID" member for a SHITEMID? These virtual files only exist with my program; will the thing they are dragged to pass the "abID" back later when it executes GetData? Do they have to be system-unique? Why are there two levels of lists; a list of PIDLs and each PIDL has a list of SHITEMIDs? I'm assuming one of them is one for each file, but what's the other one for? Multiple IDs for the same file? Any help or even links that explain what I should be doing would be greatly appreciated.

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• Non-blocking TCP connection issues.

  - by Poni

  Hi! I think I'm in a problem. I have two TCP apps connected to each other which use winsock I/O completion ports to send/receive data (non-blocking sockets). Everything works just fine until there's a data transfer burst. The sender starts sending incorrect/malformed data. I allocate the buffers I'm sending on the stack, and if I understand correctly, that's a wrong to do, because these buffers should remain as I sent them until I get the "write complete" notification from IOCP. Take this for example: void some_function() { char cBuff[1024]; // filling cBuff with some data WSASend(...); // sending cBuff, non-blocking mode // filling cBuff with other data WSASend(...); // again, sending cBuff // ..... and so forth! } If I understand correctly, each of these WSASend() calls should have its own unique buffer, and that buffer can be reused only when the send completes. Correct? Now, what strategies can I implement in order to maintain a big sack of such buffers, how should I handle them etc'? And, if I am to use buffers that means I should copy the data to be sent from the source buffer to the temporary one, thus, I'd set SO_SNDBUF on each socket to zero, so the system will not re-copy what I already copied. Are you with me? Please let me know if I wasn't clear.

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• Trouble with Unions in C program.

  - by Jordan S

  I am working on a C program that uses a Union. The union definition is in FILE_A header file and looks like this... // FILE_A.h**************************************************** xdata union { long position; char bytes[4]; }CurrentPosition; If I set the value of CurrentPosition.position in FILE_A.c and then call a function in FILE_B.c that uses the union, the data in the union is back to Zero. This is demonstrated below. // FILE_A.c**************************************************** int main.c(void) { CurrentPosition.position = 12345; SomeFunctionInFileB(); } // FILE_B.c**************************************************** void SomeFunctionInFileB(void) { // After the following lines execute I see all zeros in the flash memory. WriteByteToFlash(CurrentPosition.bytes[0]; WriteByteToFlash(CurrentPosition.bytes[1]; WriteByteToFlash(CurrentPosition.bytes[2]; WriteByteToFlash(CurrentPosition.bytes[3]; } Now, If I pass a long to SomeFunctionInFileB(long temp) and then store it into CurrentPosition.bytes within that function, and finally call WriteBytesToFlash(CurrentPosition.bytes[n]... it works just fine. It appears as though the CurrentPosition Union is not global. So I tried changing the union definition in the header file to include the extern keyword like this... extern xdata union { long position; char bytes[4]; }CurrentPosition; and then putting this in the source (.c) file... xdata union { long position; char bytes[4]; }CurrentPosition; but this causes a compile error that says: C:\SiLabs\Optec Programs\AgosRot\MotionControl.c:76: error 91: extern definition for 'CurrentPosition' mismatches with declaration. C:\SiLabs\Optec Programs\AgosRot\/MotionControl.h:48: error 177: previously defined here So what am I doing wrong? How do I make the union global?

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• How can I force a ListView with a custom panel to re-measure when the ListView width goes below the

  - by Scott Whitlock

  Sorry for the long winded question (I'm including background here). If you just want the question, go to the end. I have a ListView with a custom Panel implementation that I'm using to implement something similar to a WrapPanel, but not quite. I'm overriding the MeasureOverride and ArrangeOverride methods in the custom panel. If I do the naive implementation of a WrapPanel in the MeasureOverride method it doesn't work when the ListView is resized. Let's say the custom panel does a measure and the constraint is a width of 100 and let's say I have 3 items that are 40 wide each. The naive approach is to return a size of 80,80 but when I resize the window that the ListView is in, down to say 75, it just turns on the horizontal scrollbar and never calls measure or arrange again (it does keep measuring and arranging if the width is greater than 80). To get around this, I hard coded the measurement to only have a width of the widest item. Then in the arrange, it gives me more space than I asked for and I use as much horizontal space as I can before wrapping. If I resize the window smaller than the smallest item in the ListView, then it turns on the scrollbar, which is great. Unfortunately this is causing a big problem when I have one of these ListViews with a custom panel nested inside of another one. The outside one works ok, but I can't get the inside one to "take as much as it needs". It always sizes to the smallest item, and the only way around it is to set the MinWidth to be something greater than zero. Anyway, stepping back for a second, I think the real way to fix this is to go back to the Naive implementation of the WrapPanel but force it to re-measure when the ListView width goes below the Size I previously returned as a measurement. That should solve my problem with the nested one. So, that's my question: I have a ListView with a custom panel If I return a measurement width on the panel and the ListView is resized to less than that width, it stops calling MeasureOverride How can I get it to continue calling MeasureOverride?

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• How to add complex data type from Groovy script to the response in SoapUI

  - by SeeU

  My question is about putting data elements (from groovy script) in the response in SoapUI. I've an array of data that I would like to put in my response (in different tags/elements) I'm aware of putting a simple element like this: The element "MyName" in the Xml response: <ns:MyName>${MyName}</ns:MyName> Is mapped from the Groovy script by context.setProperty("MyName" , "My name" ) Now the problem: my Xml response looks like this: <soapenv:Body> <ns:GetDataSummaryResponse> <!--Optional:--> <ns:GetDataSummaryResult> <ns:DataSummary> <!--Zero or more repetitions:--> <ns:DataSummaryResponseDetail> <ns:Name>?</ns:Name> <!--Optional:--> <ns:DataProgress> <!--Optional:--> <From>?</From> <!--Optional:--> <Procent>?</Procent> <!--Optional:--> <To>?</To> <!--Optional:--> In Groovy I've built data array which is filled with data for example like this: context:[DataSummary:[DataSummaryResponseDetail:[Name:My name, DataProgress:[From:some text, Procent:some value, To:some text]]] In the response I'm able to see the whole value of ${DataSummary} but how do I get the element "Procent" I maybe am wrong about how to build my context data, but feel free to adjust! BR/SeeU

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• Silverlight 4 ComboBox - Binding to Nullable data (tried TargetNullValue but not working as expected)

  - by Laurence

  (Please note - I am a Silverlight beginner and am looking for the simplest solution here, e.g. that doesn't involve writing/installing a replacement for the ComboBox control!) This is an issue with a Silverlight 4 application that uses the View Model (MVVM) approach. I have a simple form for editing a "Product" object. Product has a CategoryID property which is nullable (int?). A ComboBox is used to view and set the CategoryID - this is bound to an ObservableCollection of Categories. Product also has number of non-nullable properties bound to TextBoxes. I want the user to see "N/A" in the ComboBox for a product with no category, and to be use this "N/A" option to set CategoryID to null. So, I manually added a Category object with CategoryID=0 and CategoryName="N/A" to the collection; then I set TargetNullValue=0 in the SelectedValue Binding of the ComboBox. My thinking was - when the ComboBox SelectedValue was bound to a null CategoryID it would substitute zero, and therefore select the "N/A" option. When editing a Product with a non-null CategoryID, everything works. However when a null CategoryID is found, two problems occur: No option is selected in the ComboBox (its blank) The ComboBox binding seems broken from this point onwards - any Product I subsequently edit (incl. ones with a non-null CategoryID) have nothing selected in the ComboBox (its still populated with all categories - just no selected item). I've seen reports of problem #2 (here, here) but I was under the impression that #1 should have worked. What am I missing to get the "N/A" option to be selected? XAML for ComboBox: <ComboBox x:Name="cboCategory" ItemsSource="{Binding colCategories, Mode=OneWay}" SelectedValuePath="CategoryID" DisplayMemberPath="CategoryName" SelectedValue="{Binding CurrentProduct.CategoryID, Mode=TwoWay, TargetNullValue=0}" Height="24" Width="344"></ComboBox>

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• What most efficient method to find a that triangle which contains the given point?

  - by Christo

  Given the triangle with vertices (a,b,c): c / \ / \ / \ a - - - b Which is then subdivided into four triangles by halving each of the edges: c / \ / \ ca / \ bc /\ - - - /\ / \ / \ / \ / \ a- - - - ab - - - -b Wich results in four triangles (a, ab, ca), (b, bc, ab), (c, ca, bc), (ab, bc, ca). Now given a point p. How do I determine in which triangle p lies, given that p is within the outer triangle (a, b, c)? Currently I intend to use ab as the origin. Check whether it is to the left of right of the line "ca - ab" using the perp of "ca - ab" and checking the sign against the dot product of "ab - a" and the perp vector and the vector "p - ab". If it is the same or the dot product is zero then it must be in (a, ab, ca)... Continue with this procedure with the other outer triangles (b, ba, ab) & (c, ca, ba). In the end if it didn't match with these it must be contained within the inner triangle (ab, bc, ca). Is there a better way to do it?

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• How do I ensure that a regex does not match an empty string?

  - by Dancrumb

  I'm using the Jison parser generator for Javascript and am having problems with my language specification. The program I'm writing will be a calculator that can handle feet, inches and sixteenths. In order to do this, I have the following specification: %% ([0-9]+\s*"'")?\s*([0-9]+\s*"\"")?\s*([0-9]+\s*"s")? {return 'FIS';} [0-9]+("."[0-9]+)?\b {return 'NUMBER';} \s+ {/* skip whitespace */} "*" {return '*';} "/" {return '/';} "-" {return '-';} "+" {return '+';} "(" {return '(';} ")" {return ')';} <<EOF>> {return 'EOF';} Most of these lines come from a basic calculator specification. I simply added the first line. The regex correctly matches feet, inch, sixteenths, such as 6'4" (six feet, 4 inches) or 4"5s (4 inches, 5 sixteenths) with any kind of whitespace between the numbers and indicators. The problem is that the regex also matches a null string. As a result, the lexical analysis always records a FIS at the start of the line and then the parsing fails. Here is my question: is there a way to modify this regex to guarantee that it will only match a non-zero length string?

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• Module not found

  - by TMP

  Hi There! I've been working on this one quite a bit and haven't gotten any closer to a solution. I juut dug up my old copy of the WindowsHookLib again - It's available with source at http://www.codeproject.com/KB/DLL/WindowsHookLib.aspx. This library allows Global Windows Mouse/Keyboard/Clipboard Hooks, which is very useful. I'm trying to use the Mouse Hook in here to Capture Mouse-Motion (I could use a Timer that always polls Cursor.Position, but I plan on using more features of WindowsHookLib later). Code as follows: MouseHook mh = new MouseHook(); mh.InstallHook(); mh.MouseMove += new EventHandler<WindowsHookLib.MouseEventArgs>(mh_MouseMove); But on the call to InstallHook(), I get an Exception: "The specified Module could not be found". Strange. Searching, I found that someone thought this occurs because a DLL is not in a place included in the Windows PATH variable, and because placing it in system32 didn't help I went the whole hog and translated the thing to C# for inclusion directly in my project (I was curious how it works). However the error was obstinately persistent, so I dug a bit on this, and found the Code in the Library that is responsible: In InstallHook(), we have IntPtr hinstDLL = Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]); this._hMouseHook = UnsafeNativeMethods.SetWindowsHookEx(14, this._mouseProc, hinstDLL, 0); if (this._hMouseHook == IntPtr.Zero) { throw new MouseHookException(new Win32Exception(Marshal.GetLastWin32Error()).Message); } And this (after modification and recompile) tells me that what I'm really getting is a Windows error "ERROR_MOD_NOT_FOUND"! Now, Here I'm stumped. Didn't I just compile the Hook Library directly into my project? (UnsafeMethods.SetWindowsHookEx is just a DllImported Method from user32) Any Answers, or Prods in the right direction, or any hints, pointers or similar are very much appreciated!

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• Executing logic before save or validation with EF Code-First Models

  - by Ryan Norbauer

  I'm still getting accustomed to EF Code First, having spent years working with the Ruby ORM, ActiveRecord. ActiveRecord used to have all sorts of callbacks like before_validation and before_save, where it was possible to modify the object before it would be sent off to the data layer. I am wondering if there is an equivalent technique in EF Code First object modeling. I know how to set object members at the time of instantiation, of course, (to set default values and so forth) but sometimes you need to intervene at different moments in the object lifecycle. To use a slightly contrived example, say I have a join table linking Authors and Plays, represented with a corresponding Authoring object: public class Authoring { public int ID { get; set; } [Required] public int Position { get; set; } [Required] public virtual Play Play { get; set; } [Required] public virtual Author Author { get; set; } } where Position represents a zero-indexed ordering of the Authors associated to a given Play. (You might have a single "South Pacific" Play with two authors: a "Rodgers" author with a Position 0 and a "Hammerstein" author with a Position 1.) Let's say I wanted to create a method that, before saving away an Authoring record, it checked to see if there were any existing authors for the Play to which it was associated. If no, it set the Position to 0. If yes, it would find set the Position of the highest value associated with that Play and increment by one. Where would I implement such logic within an EF code first model layer? And, in other cases, what if I wanted to massage data in code before it is checked for validation errors? Basically, I'm looking for an equivalent to the Rails lifecycle hooks mentioned above, or some way to fake it at least. :)

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• Varchar columns: Nullable or not.

  - by NYSystemsAnalyst

  The database development standards in our organization state the varchar fields should not allow null values. They should have a default value of an empty string (""). I know this makes querying and concatenation easier, but today, one of my coworkers questioned me about why that standard only existed for varchar types an not other datatypes (int, datetime, etc). I would like to know if others consider this to be a valid, defensible standard, or if varchar should be treated the same as fields of other data types? I believe this standard is valid for the following reason: I believe that an empty string and null values, though technically different, are conceptually the same. An empty, zero length string is a string that does not exist. It has no value. However, a numeric value of 0 is not the same as NULL. For example, if a field called OutstandingBalance has a value of 0, it means there are $0.00 remaining. However, if the same field is NULL, that means the value is unknown. On the other hand, a field called CustomerName with a value of "" is basically the same as a value of NULL because both represent the non-existence of the name. I read somewhere that an analogy for an empty string vs. NULL is that of a blank CD vs. no CD. However, I believe this to be a false analogy because a blank CD still phyically exists and still has physical data space that does not have any meaningful data written to it. Basically, I believe a blank CD is the equivalent of a string of blank spaces (" "), not an empty string. Therefore, I believe a string of blank spaces to be an actual value separate from NULL, but an empty string to be the absense of value conceptually equivalent to NULL. Please let me know if my beliefs regarding variable length strings are valid, or please enlighten me if they are not. I have read several blogs / arguments regarding this subject, but still do not see a true conceptual difference between NULLs and empty strings.

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• Exception while hosting a WCF Service in a DependencyInjection Module ?

  - by Maciek

  Hello, I've written a small just-for-fun console project using Ninject, I'm pasting some of the code below just so that you get the idea : Program.cs using System; using Ninject; using Ninjectionn.Modules; // My namespace for my modules namespace Ninjections { class Program { static void Main(string[] args) { IKernel kernel = new StandardKernel(); kernel.Load<ServicesHostModule>(); Console.ReadKey(); } } } ServicesHostModule.cs using System; using System.ServiceModel; using Ninject; using Ninject.Modules; namespace Ninjections.Modules { public class ServicesHostModule : INinjectModule { #region INinjectModule Members public string Name { get { return "ServicesHost"; }} public void OnLoad(IKernel kernel) { if(m_host != null) m_host.Close(); else m_host = new ServiceHost(typeof(WCFTestService)); m_host.Open(); // (!) EXCEPTION HERE } public void OnUnLoad(IKernel kernel) { m_host.Close(); } #endregion } } ITestWCFService.cs using System.ServiceModel; namespace Ninjections.Modules { [ServiceContract] public interface ITestWCFService { [OperationContract] string GetString1(); [OperationContract] string GetString2(); } } An auto-generated App.config is in the ServicesHostModule project. I've "added" an existing item (the app config) as link in the main project. Q: at the m_host.Open(); line, an InvalidOperationException occurs. The message says : "Service "Ninjections.Modules.TestWCFService" has zero application endopints. What's wrong?

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• Box2dx: Cancel force on a body?

  - by Rosarch

  I'm doing pathfinding where I use force to push body to waypoints. However, once they get close enough to the waypoint, I want to cancel out the force. How can I do this? Do I need to maintain separately all the forces I've applied to the body in question? I'm using Box2dx (C#/XNA). Here is my attempt, but it doesn't work at all: internal PathProgressionStatus MoveAlongPath(PositionUpdater posUpdater) { Vector2 nextGoal = posUpdater.Goals.Peek(); Vector2 currPos = posUpdater.Model.Body.Position; float distanceToNextGoal = Vector2.Distance(currPos, nextGoal); bool isAtGoal = distanceToNextGoal < PROXIMITY_THRESHOLD; Vector2 forceToApply = new Vector2(); double angleToGoal = Math.Atan2(nextGoal.Y - currPos.Y, nextGoal.X - currPos.X); forceToApply.X = (float)Math.Cos(angleToGoal) * posUpdater.Speed; forceToApply.Y = (float)Math.Sin(angleToGoal) * posUpdater.Speed; float rotation = (float)(angleToGoal + Math.PI / 2); posUpdater.Model.Body.Rotation = rotation; if (!isAtGoal) { posUpdater.Model.Body.ApplyForce(forceToApply, posUpdater.Model.Body.Position); posUpdater.forcedTowardsGoal = true; } if (isAtGoal) { // how can the body be stopped? posUpdater.forcedTowardsGoal = false; //posUpdater.Model.Body.SetLinearVelocity(new Vector2(0, 0)); //posUpdater.Model.Body.ApplyForce(-forceToApply, posUpdater.Model.Body.GetPosition()); posUpdater.Goals.Dequeue(); if (posUpdater.Goals.Count == 0) { return PathProgressionStatus.COMPLETE; } } UPDATE If I do keep track of how much force I've applied, it fails to account for other forces that may act on it. I could use reflection and set _force to zero directly, but that feels dirty.

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