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• How to have NHibernate persist a String.Empty property value as NULL

  - by Todd

  I have a fairly simple class that I want to save to SQL Server via NHibernate (w/ Fluent mappings). The class is made up mostly of optional string fields. My problem is I default the class fields to string.empty to avoid NullRefExceptions and when NHibernate saves the row to the database each column contains an empty string instead of null. Question: Is there a way for me to get NHibernate to automatically save null when the string property is an empty string? Or do I need to litter my code with if (string.empty) checks?

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• Rails has_one vs belongs_to semantics

  - by Anurag

  I have a model representing a Content item that contains some images. The number of images are fixed as these image references are very specific to the content. For example, the Content model refers to the Image model twice (profile image, and background image). I am trying to avoid a generic has_many, and sticking to multiple has_one's. The current database structure looks like: contents - id:integer - integer:profile_image_id - integer:background_image_id images - integer:id - string:filename - integer:content_id I just can't figure out how to setup the associations correctly here. The Content model could contain two belongs_to references to an Image, but that doesn't seem semantically right cause ideally an image belongs to the content, or in other words, the content has two images. This is the best I could think of (by breaking the semantics): class Content belongs_to :profile_image, :class_name => 'Image', :foreign_key => 'profile_image_id' belongs_to :background_image, :class_name => 'Image', :foreign_key => 'background_image_id' end Am I way off, and there a better way to achieve this association?

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• Mono on OS X Compatible with MSVC 2010 peers?

  - by Chris

  I'm to begin .NET development at work but have the option of using MonoDevelop/Mono on OS X instead of MSVC 2010 on Windows and would prefer it because of my familiarity with OS X. We are likely going to use a number of popular frameworks, such as NHibernate and Castle DI - my question to those of you familiar with .NET development and Mono: will I be at much of a disadvantage? Are there strong incompatibilities or, with some "paper cuts", the two systems are roughly compatible? Again, my colleagues will be using MSVC 2010 and we intend on working on the same codebases together. Thanks for any insight you can give to this .NET newbie. EDIT: I should note I'll primarily be doing development with MVC 2, which I understand does work with Mono, and will have some leeward in choosing frameworks, i.e. I can avoid highly incompatible frameworks.

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• Get previous element in IObservable without re-evaluating the sequence

  - by dcstraw

  In an IObservable sequence (in Reactive Extensions for .NET), I'd like to get the value of the previous and current elements so that I can compare them. I found an example online similar to below which accomplishes the task: sequence.Zip(sequence.Skip(1), (prev, cur) => new { Previous = prev, Current = cur }) It works fine except that it evaluates the sequence twice, which I would like to avoid. You can see that it is being evaluated twice with this code: var debugSequence = sequence.Do(item => Debug.WriteLine("Retrieved an element from sequence")); debugSequence.Zip(debugSequence.Skip(1), (prev, cur) => new { Previous = prev, Current = cur }).Subscribe(); The output shows twice as many of the debug lines as there are elements in the sequence. I understand why this happens, but so far I haven't found an alternative that doesn't evaluate the sequence twice. How can I combine the previous and current with only one sequence evaluation?

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• Syncronizing indices of function pointer table to table contents

  - by Thomas Matthews

  In the embedded system I'm working on, we are using a table of function pointers to support proprietary Dynamic Libraries. We have a header file that uses named constants (#define) for the function pointer indices. These values are used in calculating the location in the table of the function's address. Example: *(export_table.c)* // Assume each function in the table has an associated declaration typedef void (*Function_Ptr)(void); Function_Ptr Export_Function_Table[] = { 0, Print, Read, Write, Process, }; Here is the header file: *export_table.h* #define ID_PRINT_FUNCTION 1 #define ID_READ_FUNCTION 2 #define ID_WRITE_FUNCTION 3 #define ID_PROCESS_FUNCTION 4 I'm looking for a scheme to define the named constants in terms of their location in the array so that when the order of the functions changes, the constants will also change. (Also, I would like the compiler or preprocessor to calculate the indices to avoid human mistakes like typeo's.)

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• Is SHA sufficient for checking file duplication? (sha1_file in PHP)

  - by wag2639

  Suppose you wanted to make a file hosting site for people to upload their files and send a link to their friends to retrieve it later and you want to insure files are duplicated where we store them, is PHP's sha1_file good enough for the task? Is there any reason to not use md5_file instead? For the frontend, it'll be obscured using the original file name store in a database but some additional concerns would be if this would reveal anything about the original poster. Does a file inherit any meta information with it like last modified or who posted it or is this stuff based in the file system? Also, is using a salt frivolous since security in regards of rainbow table attack mean nothing to this and the hash could later be used as a checksum? One last thing, scalability? initially, it's only going to be used for small files a couple of megs big but eventually... Edit 1: The point of the hash is primarily to avoid file duplication, not to create obscurity.

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• Check if iOS app is live in app store

  - by MSK

  Is it possible somehow to code like below in iOS app ? if(app is live in app store) { //Do something } else { //Do other thing } I wanted to avoid cases where our QE/Dev team is using app for testing. Is there a way I can detect how app code is signed (Developer/Adhoc/Distribution) to check ? Even if it is possible, it will not eliminate cases when Apple is using our app for testing as part of review. We recorded many downloads of our content by Apple before our app goes live in App store.

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• The underlying connection was closed when using a WSDL web service

  - by joshlrogers

  I am trying to consume this WSDL service: Transit Time Service I successfully connect and get a response the first time but on subsequent calls I receive the exception: The underlying connection was closed: A connection that was expected to be kept alive was closed by the server. I overrode the GetWebRequest in the reference.cs file as such: protected override System.Net.WebRequest GetWebRequest(Uri uri) { HttpWebRequest webRequest = (HttpWebRequest)base.GetWebRequest(uri); webRequest.KeepAlive = false; return webRequest; } This hasn't yielded any improvement. I am at a loss as to what options I have now, does anyone have any other ideas that I could try so that I may avoid this error? Thanks in advance! Josh

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• Why isn't it possible to update an ObservableCollection from a different thread?

  - by MainMa

  In a multi-threaded WPF application, it is not possible to update an ObservableCollection from a thread other than WPF window thread. I know there are workarounds, so my question is not how to avoid the "This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread" exception. My question is, why there is such an exception? Why wasn't it possible to allow collection updates from any thread? Personally, I don't see any reason to block UI update when ObservableCollection is changed from other threads. If two threads (including parallel ones) are accessing the same object, one listening for changes of object properties through events, the other one doing changes, it will always work, at least if locks are used properly. So, what are the reasons?

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• Doing a lot of input validation in VB.NET

  - by Andy

  I have a form set up where users can enter their booking for a room at my college. I want to validate the user input to avoid SQL injection (my program uses a MS Access database) and also stop numbers and synbols in their name, etc. I can do the validation fine, but there is to be a lot of validation and then methods executed only if all validation tests come back as true. I did have something like this: If txtName.Text = "" Then frmBookErr.SetError(txtName, "Name field cannot be left blank.") fail = 1 Else frmBookErr.SetError(txtName, "") fail = 0 End If And then check the fail variable, but it obviously gets overridden later in the form if one of the validation tests come back as true. Can anyone provide some input into this? Thanks.

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• How to put Custom View above built in views in Android?

  - by Lord.F

  Hi All, I am developing a small app for Android. I am creating my own view. I am planning to design the layout to be: <LinearLayout> <MyView> <Button><Button> </LinearLayout> But when I run my program, my custom view will cover the whole screen. Is there anyway to avoid this? I have already tried to add android:layout_width, layout_height to be wrap_content, fill_partent, but no luck.

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• Snapshot on, still deadlocks, ROWLOCK

  - by Patto

  I turned snapshot isolation on in my database using the following code ALTER DATABASE MyDatabase SET ALLOW_SNAPSHOT_ISOLATION ON ALTER DATABASE MyDatabase SET READ_COMMITTED_SNAPSHOT ON and got rid off lots of deadlocks. But my database still produces deadlocks, when I need to run a script every hour to clean up 100,000+ rows. Is there a way I can avoid deadlocks in my cleanup script, do I need to set ROWLOCK specifically in that query? Is there a way to increase the number of row level locks that a database uses? How are locks promoted? From row level to page level to table level? My delete script is rather simple: delete statvalue from statValue, (select dateadd(minute,-60, getdate()) as cutoff_date) cd where temporaryStat = 1 and entrydate < cutoff_date Right now I am looking for quick solution, but a long term solution would be even nicer. Thanks a lot, Patrikc

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• Java Instance of: Supertypes and Subtypes seem to be equal? How to test exactly for Type?

  - by jens

  I need to test, if an instance is exactly of a given type. But it seems that instanceof returns true also if the subtype is tested for the supertype (case 3). I never knew this before and I am quite surprised. Am I doing something wrong here? How do I exactly test for a given type? //.. class DataSourceEmailAttachment extends EmailAttachment //... EmailAttachment emailAttachment = new EmailAttachment(); DataSourceEmailAttachment emailAttachmentDS = new DataSourceEmailAttachment(); if (emailAttachment instanceof EmailAttachment){ System.out.println(" 1"); } if (emailAttachment instanceof DataSourceEmailAttachment){ System.out.println(" 2"); } if (emailAttachmentDS instanceof EmailAttachment){ System.out.println(" 3 "); } if (emailAttachmentDS instanceof DataSourceEmailAttachment){ System.out.println(" 4"); } RESULT: 1 3 4 I want to avoid case 3, I only want "exact matches" (case 1 and 4) how do I test for them?

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• JSF navigation on commandbutton

  - by Nitesh Panchal

  Hello, I want to conditionally navigate to some page. If some condition is true i want to navigate to some other page else i want to remain on the same page. I have something like :- <h:commandButton action="#{bean.navigate}"/> in bean.navigate i have something like :- public String navigate(){ if(value <= 0) return "helloWorld"; else return ""; } But if i return "", error is thrown and in h:messages message is appended that page not found etc. How do i avoid this error?

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• Regex to catch all files but those starting with "."

  - by tmslnz

  In a directory with mixed content such as: .afile .anotherfile bfile.file bnotherfile.file .afolder/ .anotherfolder/ bfolder/ bnotherfolder/ How would you catch everything but the files (not dirs) starting with .? I have tried with a negative lookahead ^(?!\.).+? but it doesn't seem to work right. Please note that I would like to avoid doing it by excluding the . by using [a-zA-Z< plus all other possible chars minus the dot >] Any suggestions?

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• How do you compose DataTemplates / link to a child datatemplate in WPF?

  - by Gishu

  Here's the problem. Given a large/intricate datatemplate A, which has 3 sections - General, Properties, Misc. Imagine 3 grids for each. Now I need to reuse the Properties section of the above Datatemplate in another place. Reasons: To avoid redundancy + ensure that further updates to the datatemplate are applied identically to all usages. So I guess what I am asking for is an ability to slot in a link to a child DataTemplate in a parent Datatemplate. What's the best way to go about this ? I found one way to do this.. but I'm not sure if its the right way or the best.. Posting it as an answer below so that it can be rated.

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• deleting a large number of rows from a table

  - by Azeem

  We have a requirement to delete rows in the order of millions from multiple tables as a batch job (note that we are not deleting all the rows, we are deleting based on a timestamp stored in an indexed column). Obviously a normal DELETE takes forever (because of logging, referential constraint checking etc.). I know in the LUW world, we have ALTER TABLE NOT LOGGED INITIALLY but I can't seem to find the an equivalent SQL statement for DB2 v8 z/OS. Any one has any ideas on how to do this really fast? Also, any ideas on how to avoid the referential checks when deleting the rows? Please let me know.

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• "Automatic" class proxy in C++

  - by PierreBdR

  I need to allow the user to change members of two data structures of the same type at the same time. For example: struct Foo { int a, b; } Foo a1 = {1,2}, a2 = {3,4}; dual(a1,a2)->a = 5; // Now a1 = {5,2} and a2 = {5,2} I have a class that works and that change first a1 and then copy a1 into a2. This is fine as long as: the class copied is small the user doesn't mind about everything being copied, not only the part modified. Is there a way to obtain this behavior: dual(a1,a2)->a = 5; // Now a1 = {5,2} and a2 = {5,4} I am opened to alternative syntax, but they should stay simple, and I would like to avoid things like: set_members(a1, a2, &Foo::a, 5); members(a1, a2, &Foo::a) = 5; or anything involving specifying explictely &Foo::

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• jQuery - Animate function

  - by Arun Kumar

  I have a piece of code shown below: $(".tagArea li").mouseover(function(){ $(this).animate({ borderWidth: "2px" }, 1000 ); }); $(".tagArea li").mouseout(function () { $(this).animate({ borderWidth: "1px" }, 1000 ); }); When I try to hover it on a particular list item, it properly animates but doesn't stop doing just once. It keeps doing 2 or 3 times. How to avoid this, I 've tried many a times but no positive result occurs to me. Kindly help.

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• Return from parent sub in Perl

  - by JS Bangs

  I want to write a subroutine which causes the caller to return under certain conditions. This is meant to be used as a shortcut for validating input to a function. What I have so far is: sub needs($$) { my ($condition, $message) = @_; if (not $condition) { print "$message\n"; # would like to return from the *parent* here } return $condition; } sub run_find { my $arg = shift @_; needs $arg, "arg required" or return; needs exists $lang{$arg}, "No such language: $arg" or return; # etc. } The advantage of returning from the caller in needs would then be to avoid having to write the repetitive or return inside run_find and similar functions.

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• Hashing a python function to regenerate output when the function is modified

  - by Seth Johnson

  I have a python function that has a deterministic result. It takes a long time to run and generates a large output: def time_consuming_function(): # lots_of_computing_time to come up with the_result return the_result I modify time_consuming_function from time to time, but I would like to avoid having it run again while it's unchanged. [time_consuming_function only depends on functions that are immutable for the purposes considered here; i.e. it might have functions from Python libraries but not from other pieces of my code that I'd change.] The solution that suggests itself to me is to cache the output and also cache some "hash" of the function. If the hash changes, the function will have been modified, and we have to re-generate the output. Is this possible or ridiculous? Updated: based on the answers, it looks like what I want to do is to "memoize" time_consuming_function, except instead of (or in addition to) arguments passed into an invariant function, I want to account for a function that itself will change.

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• Is it possible to use RedirectToAction() inside a custom AuthorizeAttribute class?

  - by Lance McNearney

  Using ASP.Net MVC 2, is there any way to use the RedirectToAction() method of the Controller class inside a class that is based on the AuthorizeAttribute class? public class CustomAttribute : AuthorizeAttribute { protected override bool AuthorizeCore(HttpContextBase context) { // Custom authentication goes here return false; } public override void OnAuthorization(AuthorizationContext context) { base.OnAuthorization(context); // This would be my ideal result context.Result = RedirectToAction("Action", "Controller"); } } I'm looking for a way to re-direct the user to a specific controller / action when they fail the authentication instead of returning them to the login page. Is it possible to have the re-direct URL generated for that controller / action and then use RedirectResult()? I'm trying to avoid the temptation to just hard-code the URL.

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• Selecting one object from a one-to-many relationship in Hibernate

  - by Nick Thomson

  I have two tables: Job job_id, <other data> Job_Link job_link_id, job_id, start_timestamp, end_timestamp, <other data> There may be multiple records in Job_Link specifying the same job_id with the start_timestamp and end_timestamps to indicate when those records are considered "current", it is guaranteed that start_timestamp and end_timestamp will not overlap. We have entities for both the Job and Job_Link tables and defining a one-to-many relationship to load all the job_links wouldn't be a problem. However we'd like to avoid that and have a single job_link item in the Job entity that will contain only the "current" Job_Link object. Is there any way to achive that?

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• Response.Redirect exception

  - by Tedd Hansen

  Executing the line: Response.Redirect("Whateva.aspx", true); Results in: A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code The exception is because of the "true" part, telling it to end the current request immediately. Is this how it should be? If we consider: Exceptions are generally considered heavy, and many times the reason for ending the request early is to avoid processing the rest of the page. Exceptions show up in performance monitoring, so monitoring the solution will show a false number of exceptions. Is there an alternative way to achieve the same?

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• Appending target="_blank" to links in an iframe without using <body onload>

  - by CincauHangus

  I'm trying to change the links in an iframe to load in a new window instead of the iframe itself. Currently I use this code in head: $(document).ready(function() { var oIFrame = document.getElementById("iframeID"); var oDoc = (oIFrame.contentWindow || oIFrame.contentDocument); if(oDoc.document) oDoc = oDoc.document; var links = oDoc.getElementsByTagName("a"); for(var i=0; i<links.length; i++) { links[i].target="_blank"; } }); However, the code above is triggered before the iframe is fully loaded with its contents. I know this code would work if it's triggered in the body onload attribute, but I'd like to avoid that method and implement it in a function or a file instead.

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