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• Object-oriented GUI development in python

  - by ptabatt

  Hey guys, new programmer here. I have an assignment for class and I'm stuck... What I need to do is a create a GUI that gives someone a basic arithmetic problem in one box, asks the person to answer it, evaluates it, and tells you if you're right or wrong... Basically, what I have is this: [code] class Lesson(Frame): def init (self, parent=None): Frame.init(self, parent) self.pack() Lesson.make_widgets(self) def make_widgets(self): Label(self, text="").pack(side=TOP) ent = Entry(self) self.a = randrange(1,10) self.b = randrange(1,10) self.expr = choice(["+","-"]) ent.insert(END, str(self.a) + str(self.expr) + str(self.a)) [/code] I've broken this down into many little steps and basically, what I'm trying to do right now is insert a default random expression into the first entry widget. When I run this code, I just get a blank Label. Why is that? How can I put a something like "7+7" into the box? If you absolutely need background to the problem, it's question #3 on this link. http://reed.cs.depaul.edu/lperkovic/csc242/homeworks/Homework8.html -Thanks for all help in advance.

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• Problem creating a custom input element using FluentHtml (MVCContrib)

  - by seth

  Hi there, I just recently started dabbling in ASP.NET MVC 1.0 and came across the wonderful MVCContrib. I had originally gone down the path of creating some extended html helpers, but after finding FluentHTML decided to try my hand at creating a custom input element. Basically I am wanting to ultimately create several custom input elements to make it easier for some other devs on the project I'm working on to add their input fields to the page and have all of my preferred markup to render for them. So, in short, I'd like to wrap certain input elements with additional markup.. A TextBox would be wrapped in an <li /> for example. I've created my custom input elements following Tim Scott's answer in another question on here: DRY in the MVC View. So, to further elaborate, I've created my class, "TextBoxListItem": public class TextBoxListItem : TextInput<TextBox> { public TextBoxListItem (string name) : base(HtmlInputType.Text, name) { } public TextBoxListItem (string name, MemberExpression forMember, IEnumerable<IBehaviorMarker> behaviors) : base(HtmlInputType.Text, name, forMember, behaviors) { } public override string ToString() { var liBuilder = new TagBuilder(HtmlTag.ListItem); liBuilder.InnerHtml = ToString(); return liBuilder.ToString(TagRenderMode.SelfClosing); } } I've also added it to my ViewModelContainerExtensions class: public static TextBox TextBoxListItem<T>(this IViewModelContainer<T> view, Expression<Func<T, object>> expression) where T : class { return new TextBoxListItem(expression.GetNameFor(view), expression.GetMemberExpression(), view.Behaviors) .Value(expression.GetValueFrom(view.ViewModel)); } And lastly, I've added it to ViewDataContainerExtensions as well: public static TextBox TextBoxListItem(this IViewDataContainer view, string name) { return new TextBox(name).Value(view.ViewData.Eval(name)); } I'm calling it in my view like so: <%= this.TextBoxListItem("username").Label("Username:") %> Anyway, I'm not getting anything other than the standard FluentHTML TextBox, not wrapped in <li></li> elements. What am I missing here? Thanks very much for any assistance.

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• What is happening in this T-SQL code? (Concatenting the results of a SELECT statement)

  - by Ben McCormack

  I'm just starting to learn T-SQL and could use some help in understanding what's going on in a particular block of code. I modified some code in an answer I received in a previous question, and here is the code in question: DECLARE @column_list AS varchar(max) SELECT @column_list = COALESCE(@column_list, ',') + 'SUM(Case When Sku2=' + CONVERT(varchar, Sku2) + ' Then Quantity Else 0 End) As [' + CONVERT(varchar, Sku2) + ' - ' + Convert(varchar,Description) +'],' FROM OrderDetailDeliveryReview Inner Join InvMast on SKU2 = SKU and LocationTypeID=4 GROUP BY Sku2 , Description ORDER BY Sku2 Set @column_list = Left(@column_list,Len(@column_list)-1) Select @column_list ---------------------------------------- 1 row is returned: ,SUM(Case When Sku2=157 Then Quantity Else 0 End) As [157 -..., SUM(Case ... The T-SQL code does exactly what I want, which is to make a single result based on the results of a query, which will then be used in another query. However, I can't figure out how the SELECT @column_list =... statement is putting multiple values into a single string of characters by being inside a SELECT statement. Without the assignment to @column_list, the SELECT statement would simply return multiple rows. How is it that by having the variable within the SELECT statement that the results get "flattened" down into one value? How should I read this T-SQL to properly understand what's going on?

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• Reduce function calls

  - by Curious2learn

  Hello, I profiled my python program and found that the following function was taking too long to run. Perhaps, I can use a different algorithm and make it run faster. However, I have read that I can also possibly increase the speed by reducing function calls, especially when it gets called repeatedly within a loop. I am a python newbie and would like to learn how to do this and see how much faster it can get. Currently, the function is: def potentialActualBuyers(setOfPeople,theCar,price): count=0 for person in setOfPeople: if person.getUtility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count where setOfPeople is a list of person objects. I tried the following: def potentialActualBuyers(setOfPeople,theCar,price): count=0 Utility=person.getUtility for person in setOfPeople: if Utility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count This, however, gives me an error saying local variable 'person' referenced before assignment Any suggestions, how I can reduce function calls or any other changes that can make the code faster. Again, I am a python newbie and even though I may possibly be able to use a better algorithm, it is still worthwhile learning the answer to the above question. Thanks very much.

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• SQL: select rows with the same order as IN clause

  - by Andrea3000

  I know that this question has been asked several times and I've read all the answer but none of them seem to completely solve my problem. I'm switching from a mySQL database to a MS Access database with MS SQL. In both of the case I use a php script to connect to the database and perform SQL queries. I need to find a suitable replacement for a query I used to perform on mySQL. I want to: perform a first query and order records alphabetically based on one of the columns construct a list of IDs which reflects the previous alphabetical order perform a second query with the IN clause applied with the IDs' list and ordered by this list. In mySQL I used to perform the last query this way: SELECT name FROM users WHERE id IN ($name_ids) ORDER BY FIND_IN_SET(id,'$name_ids') Since FIND_IN_SET is available only in mySQL and CHARINDEX and PATINDEX are not available from my php script, how can I achieve this? I know that I could write something like: SELECT name FROM users WHERE id IN ($name_ids) ORDER BY CASE id WHEN ... THEN 1 WHEN ... THEN 2 WHEN ... THEN 3 WHEN ... THEN 4 END but you have to consider that: IDs' list has variable length and elements because it depends on the first query that list can easily contains thousands of elements Have you got any hint on this? Is there a way to programmatically construct the ORDER BY CASE ... WHEN ... statement? Is there a better approach since my list of IDs can be big?

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• Writing a VM - well formed bytecode?

  - by David Titarenco

  Hi, I'm writing a virtual machine in C just for fun. Lame, I know, but luckily I'm on SO so hopefully no one will make fun :) I wrote a really quick'n'dirty VM that reads lines of (my own) ASM and does stuff. Right now, I only have 3 instructions: add, jmp, end. All is well and it's actually pretty cool being able to feed lines (doing it something like write_line(&prog[1], "jmp", regA, regB, 0); and then running the program: while (machine.code_pointer <= BOUNDS && DONE != true) { run_line(&prog[machine.cp]); } I'm using an opcode lookup table (which may not be efficient but it's elegant) in C and everything seems to be working OK. My question is more of a "best practices" question but I do think there's a correct answer to it. I'm making the VM able to read binary files (storing bytes in unsigned char[]) and execute bytecode. My question is: is it the VM's job to make sure the bytecode is well formed or is it just the compiler's job to make sure the binary file it spits out is well formed? I only ask this because what would happen if someone would edit a binary file and screw stuff up (delete arbitrary parts of it, etc). Clearly, the program would be buggy and probably not functional. Is this even the VM's problem? I'm sure that people much smarter than me have figured out solutions to these problems, I'm just curious what they are!

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• Locating SSL certificate, key and CA on server

  - by jovan

  Disclaimer: you don't need to know Node to answer this question but it would help. I have a Node server and I need to make it work with HTTPS. As I researched around the internet, I found that I have to do something like this: var fs = require('fs'); var credentials = { key: fs.readFileSync('path/to/ssl/private-key'), cert: fs.readFileSync('path/to/ssl/cert'), ca: fs.readFileSync('path/to/something/called/CA') }; var app = require('https').createServer(credentials, handler); I have several problems with this. First off, all the examples I found use completely different approaches. Some link to .pem files for both the certificate and key. I don't know what pem files are but I know my certificate is .crt and my key is .key. Some start off at the root folder and some seem to just have these .pem files in the application directory. I don't. Some use the ca thing too and some don't. This CA is supposed to be my domain's CA bundle according to some articles - but none explain where to find this file. In the ssl directory on my server I have one .crt file in the certs directory and one .key file in the keys directory, in addition to an empty csrs directory and an ssl.db file. So, where do I find these 3 files (key, cert, ca) and how do I link to them correctly?

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• How do I serialize an enum value as an int?

  - by Espo

  I want to serialize my enum-value as an int, but i only get the name. Here is my (sample) class and enum: public class Request { public RequestType request; } public enum RequestType { Booking = 1, Confirmation = 2, PreBooking = 4, PreBookingConfirmation = 5, BookingStatus = 6 } And the code (just to be sure i'm not doing it wrong) Request req = new Request(); req.request = RequestType.Confirmation; XmlSerializer xml = new XmlSerializer(req.GetType()); StringWriter writer = new StringWriter(); xml.Serialize(writer, req); textBox1.Text = writer.ToString(); This answer (to another question) seems to indicate that enums should serialize to ints as default, but it doesn't seem to do that. Here is my output: <?xml version="1.0" encoding="utf-16"?> <Request xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <request>Confirmation</request> </Request> I have been able to serialize as the value by putting an "[XmlEnum("X")]" attribute on every value, but this just seems wrong.

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• Assign Multiple Custom User Roles to a Custom Post Type

  - by OUHSD Webmaster

  Okay here's the situation.... I'm working on a my business website. There will be a work/portfolio area. "Work" is a custom post type. "Designer" is a custom user role. "Client" is a custom user role. In creating a new "Work" post I would like to be able to select both a "designer" and "Client" to assign to the piece of work, as I would assign an author to a regular ol' post. I tried the method from this answer but it did not work for me. ) I placed it in my functions.php file. ` add_filter('wp_dropdown_users', 'test'); function test($output) { global $post; //Doing it only for the custom post type if($post->post_type == 'work') { $users = get_users(array('role'=>'designer')); //We're forming a new select with our values, you can add an option //with value 1, and text as 'admin' if you want the admin to be listed as well, //optionally you can use a simple string replace trick to insert your options, //if you don't want to override the defaults $output .= "<select id='post_author_override' name='post_author_override' class=''>"; foreach($users as $user) { $output .= "<option value='".$user->id."'>".$user->user_login."</option>"; } $output .= "</select>"; } return $output; } ` Any help would be extremely appreciated!

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• Selectively allow unsafe html tags in Plone

  - by dhill

  I'm searching for a way to put widgets from several services (PicasaWeb, Yahoo Pipes, Delicious bookmarks, etc.) on the community site I host on Plone (currently 3.2.1). I'm looking for a way to allow a group of users to use dangerous html tags. There are some ways I see, but I don't know how to implement those. One would be changing safe_html for the pages editors own (1). Another would be to allow those tags on some subtree (2). And yet another finding an equivalent of "static text portlet" that would display in the middle panel (3). We could then use some of the composite products (I stumbled upon Collage and CMFContentPanels), to include the unsafe content on other sites. My site has been ridden by advert bots, so I don't want to remove the filtering all together. I don't have an easy (no false positives) way of checking which users are bots, so deploying captcha now wouldn't help either. The question is: How to implement any of those solutions? (I already asked that on plone mailing list without an answer, so I thought I would give it another try here.)

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• Using Reachability for Internet *or* local WiFi?

  - by randallmeadows

  I've searched SO for the answer to this question, and it's not really addressed, at least not to a point where I can make it work. I was originally only checking for Internet reachability, using: self.wwanReach = [Reachability reachabilityWithHostName:@"www.apple.com"]; [wwanReach startNotifer]; I now need to support a local WiFi connection (in the absence of reaching the Internet in general), and when I found +reachabilityForLocalWiFi, I also noticed there was +reachabilityForInternetConnection. I figured I could use these, instead of hard-coding "www.apple.com" in there, but alas, when I use self.wwanReach = [Reachability reachabilityForInternetConnection]; [wwanReach startNotifer]; self.wifiReach = [Reachability reachabilityForLocalWiFi]; [wifiReach startNotifer]; the reachability callback that I've set up "never" gets called, for values of "never" up to 10, 12, 15 minutes or so (which was as long as my patience lasted. (User's patience will be much less, I'm sure.) Switching back to +reachabilityWithHostName: works within seconds. I also tried each "pair" individually, in case there was an issue with two notifiers in progress simultaneously, but that made no difference. So: what is the appropriate way to determine reachability to either the Internet/WWAN or a local Wifi network (either one, or both)? [This particular use case is an iPhone or iPad connecting to a Mac mini computer-to-computer network; I'm sure other situations apply.]

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• Micro Second resolution timestamps on windows.

  - by Nikhil

  How to get micro second resolution timestamps on windows? I am loking for something better than QueryPerformanceCounter, QueryPerformanceFrequency (these can only give you an elapsed time since boot, and are not necessarily accurate if they are called on different threads - ie QueryPerformanceCounter may return different results on different CPUs. There are also some processors that adjust their frequency for power saving, which apparently isn't always reflected in their QueryPerformanceFrequency result.) There is this, http://msdn.microsoft.com/en-us/magazine/cc163996.aspx but it does not seem to be solid. This looks great but its not available for download any more. http://www.ibm.com/developerworks/library/i-seconds/ This is another resource. http://www.lochan.org/2005/keith-cl/useful/win32time.html But requires a number of steps, running a helper program plus some init stuff also, I am not sure if it works on multiple CPUs Also looked at the Wikipedia link on the subject which is interesting but not that useful. http://en.wikipedia.org/wiki/Time_Stamp_Counter If the answer is just do this with BSD or Linux, its a lot easier thats fine, but I would like to confirm this and get some explanation as to why this is so hard in windows and so easy in linux and bsd. Its the same damm hardware...

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• How to write a flexible modular program with good interaction possibilities between modules?

  - by PeterK

  I went through answers on similar topics here on SO but could't find a satisfying answer. Since i know this is a rather large topic, i will try to be more specific. I want to write a program which processes files. The processing is nontrivial, so the best way is to split different phases into standalone modules which then would be used as necessary (since sometimes i will be only interested in the output of module A, sometimes i would need output of five other modules, etc). The thing is, that i need the modules to cooperate, because the output of one might be the input of another. And i need it to be FAST. Moreover i want to avoid doing certain processing more than once (if module A creates some data which then need to be processed by module B and C, i don't want to run module A twice to create the input for modules B,C ). The information the modules need to share would mostly be blocks of binary data and/or offsets into the processed files. The task of the main program would be quite simple - just parse arguments, run required modules (and perhaps give some output, or should this be the task of the modules?). I don't need the modules to be loaded at runtime. It's perfectly fine to have libs with a .h file and recompile the program every time there is a new module or some module is updated. The idea of modules is here mainly because of code readability, maintaining and to be able to have more people working on different modules without the need to have some predefined interface or whatever (on the other hand, some "guidelines" on how to write the modules would be probably required, i know that). We can assume that the file processing is a read-only operation, the original file is not changed. Could someone point me in a good direction on how to do this in C++ ? Any advice is wellcome (links, tutorials, pdf books...).

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• Script to install and compile Python, Django, Virtualenv, Mercurial, Git, LessCSS, etc... on Dreamho

  - by tmslnz

  The Story After cleaning up my Dreamhost shared server's home folder from all the cruft accumulated over time, I decided to start afresh and compile/reinstall Python. All tutorials and snippets I found seemed overly simplistic, assuming (or ignoring) a bunch of dependencies needed by Python to compile all modules correctly. So, starting from http://andrew.io/weblog/2010/02/installing-python-2-6-virtualenv-and-virtualenvwrapper-on-dreamhost/ (so far the best guide I found), I decided to write a set-and-forget Bash script to automate this painful process, including along the way a bunch of other things I am planning to use. The Script I am hosting the script on http://bitbucket.org/tmslnz/python-dreamhost-batch/src/ The TODOs So far it runs fine, and does all it needs to do in about 900 seconds, giving me at the end of the process a fully functional Python / Mercurial / etc... setup without even needing to log out and back in. I though this might be of use for others too, but there are a few things that I think it's missing and I am not quite sure how to go for it, what's the best way to do it, or if this just doesn't make any sense at all. Check for errors and break Check for minor version bumps of the packages and give warnings Check for known dependencies Use arguments to install only some of the packages instead of commenting out lines Organise the code in a manner that's easy to update Optionally make the installers and compiling silent, with error logging to file failproof .bashrc modification to prevent breaking ssh logins and having to log back via FTP to fix it EDIT: The implied question is: can anyone, more bashful than me, offer general advice on the worthiness of the above points or highlight any problems they see with this approach? (see my answer to Ry4an's comment below) The Gist I am no UNIX or Bash or compiler expert, and this has been built iteratively, by trial and error. It is somehow going towards apt-get (well, 1% of it...), but since Dreamhost and others obviously cannot give root access on shared servers, this looks to me like a potentially very useful workaround; particularly so with some community work involved.

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• The perfect web UI framework (with Microsoft stack?) - architecture question?

  - by Igorek

  I'm looking for suggestions for the following issue, and I realize there is really not going to be a perfect answer to my question: I have a UI built in WinForms.NET (v4.0 framework) with WCF back-end and EF4 model objects, that I am looking to port to the web. UI is not huge and is not super complex and is structured well. But it is not a super simple system either. I am looking to pick a technology stack for the web-frontend that will target desktop & partially mobile platforms, provide a good development platform to build on, and facilitate code reuse across UI and back-end tiers... I would rather avoid: custom coding of UI-centric scripts, because they are hard to debug, non-compiled, usually a maintenance nightmare, almost always start to contain business logic, and duplicate some of the logic that back-end tiers have (especially validation) custom-coding for Desktop Web and Mobile Web UI's separately (although I realize that mobile web UI will likely contain fewer of data-entry screens and more reporting screens) non-.NET technology stacks I would love to: target the reporting capabilities of the system toward mobile web browsers not have to write a single line of script (javascript, jquery, etc.) utilize a good collection of controls that produces an elegant UI use .NET for everything The way I see it right now, I need to re-write this app in Silverlight, utilize a 3rd party UI framework like Telerik, and re-do the reports UI again for mobile platforms separately. However, I'm rather concerned about the shelf-life of Silverlight and the needed to deploy a different architecture to deal with mobile platform. Is there an ASP.NET/MVC/Ajax architecture/framework/library that would allow me to get at the power of .NET and without painful (imho) client-side scripting, while providing a decent user experience Thank you

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• Determining when stringByEvaluatingJavaScriptFromString has finished

  - by alku83

  I have a UIWebView which loads up an HTML page. This page has two buttons on it, say Exit and Submit. I don't want users to be able to click the Exit button, so once the page has finished loading (ie. webViewDidFinishLoad is called), I use stringByEvaluatingJavaScriptFromString to remove one of these buttons, by manipulating the HTML. I also disable user interaction on the UIWebView on webViewDidStartLoad, and enable it again on webViewDidFinishLoad. The problem I am finding is that stringByEvaluatingJavaScriptFromString takes a second or two to complete, and it seems to be done in it's own thread. So what is happening is that webViewDidFinishLoad is called, user interaction is enabled on the UIWebView, and if the user is quick, they can click the Exit button before stringByEvaluatingJavaScriptFromString has finished. As stringByEvaluatingJavaScriptFromString seems to be on it's own thread with no way to know when it's finished (it doesnt call webViewDidFinishLoad), the only way to completely prevent users from tapping the Exit button that I can see is to only enable user interaction on the UIWebView after some delay, which is unreliable (how can I really know how long to delay for?). Am I correct in that stringByEvaluatingJavaScriptFromString is done on it's on thread, and I have no way of being able to tell when it's finished? Any other suggestions for how to get around this problem? EDIT: In short, what I want to know is if it is possible to disable a UIWebView while stringByEvaluatingJavaScriptFromString is executing, and re-enable the UIWebView when the javascript is finished. EDIT 2: There's an article here which seems to imply you can somehow poll the JS engine to see when it's finished, but I can't find any other references saying the same thing: http://drnicwilliams.com/2008/11/10/to-webkit-or-not-to-webkit-within-your-iphone-app/ EDIT 3 Based on the answer from Brad Smith, it seems that I actually need to know when the UIWebView has finished loading itself after the javascript has executed. It's looking more and more like I just need to put a delay of sorts in there.

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• Get the last checked checkboxes...

  - by Sara

  Hi everyone, I'm not sure how to accomplish this issue which has been confusing me for a few days. I have a form that updates a user record in MySQL when a checkbox is checked. Now, this is how my form does this: if (isset($_POST['Update'])) { $paymentr = $_POST['paymentr']; //put checkboxes array into variable $paymentr2 = implode(', ', $paymentr); //implode array for mysql $query = "UPDATE transactions SET paymentreceived=NULL"; $result = mysql_query($query); $query = "UPDATE transactions SET paymentdate='0000-00-00'"; $result = mysql_query($query); $query = "UPDATE transactions SET paymentreceived='Yes' WHERE id IN ($paymentr2)"; $result = mysql_query($query); $query = "UPDATE transactions SET paymentdate=NOW() WHERE id IN ($paymentr2)"; $result = mysql_query($query); foreach ($paymentr as $v) { //should collect last updated records and put them into variable for emailing. $query = "SELECT id, refid, affid FROM transactions WHERE id = '$v'"; $result = mysql_query($query) or die("Query Failed: ".mysql_errno()." - ".mysql_error()."<BR>\n$query<BR>\n"); $trans = mysql_fetch_array($result, MYSQL_ASSOC); $transactions .= '<br>User ID:'.$trans['id'].' -- '.$trans['refid'].' -- '.$trans['affid'].'<br>'; } } Unfortunately, it then updates ALL the user records with the latest date which is not what I want it to do. The alternative I thought of was, via Javascript, giving the checkbox a value that would be dynamically updated when the user selected it. Then, only THOSE checkboxes would be put into the array. Is this possible? Is there a better solution? I'm not even sure I could wrap my brain around how to do that WITH Javascript. Does the answer perhaps lie in how my mysql code is written? Thanks - I sincerely appreciate it!!!

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• WPF ContextMenu bind some property to another property of the same control

  - by bebicasoft

  I have a ContextMenu and a ColumnHeaderStyle defined in Window.Resource section witch i use-it to a DataGrid ColumnHeader. My code is something like this: <ContextMenu x:Key="cm_columnHeaderMenu"/> <Style x:Key="DefaultColumnHeaderStyle" TargetType="{x:Type DataGridColumnHeader}"> <Setter Property="ContextMenu" Value="{StaticResource cm_columnHeaderMenu}" /> </Style> <DataGrid Grid.Column="2" Grid.Row="1" x:Name="dgridFiles" IsReadOnly="True" ColumnHeaderStyle="{StaticResource DefaultColumnHeaderStyle}"> I want to know if I can (and if the answer it true, then HOW I could do it) bind the ContextMenu Visibility property to same control ContextMenu Items.Count>0 property. Initially based on some other treeView control selections made there shoud be no items in the context menu, but i wish to add dinamically items in ContextMenu based on selection in treeView. This part is done, the context has those items. On some selections there are no-items, but still on the grid it appears an empty ContextMenu. So I believe the easiest part it would be to bind the Visibility to Items.Count property of the same control. Sorry if my english is not good enought, I'll try to explain better if i didnt make clear 1st time.

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• Using ADO.NET Entities LINQ Provider to model complex SQL Queries?

  - by Ivan Zlatanov

  What I find really powerful in ADO.NET Entities or LINQ to SQL, is the ability to model complex queries. I really don't need the mappings that Entities or LINQ to SQL are doing for me - I just need the ability to model complex expressions that can be translated into T-SQL. My question is - am I abusing too much? Can I use the Entity Framework for modeling queries and just that? Should I? I know I can write my own custom LINQ to SQL provider, but that is just not possible to handle in the time spans I have. What is the best approach to model complex T-SQL queries? How do you handle conditional group byes, orders, joins, unions etc in the OOP world? Using StringBuilders for this kind of job feels too ugly and harder to maintain given the possibilities we have with Expression Trees. When I use StringBuilder to model a complex SQL Query I feel kind of guilty! I feel the same way as when I have to hard code any number into my code that is different than 0 or 1. Feeling that makes you ask yourself if there is a better and cleaner way of doing it... I must mention that I am using C# 4.0, but I am not specifically looking for an answer in this language, but rather in the domain of CLR 4.

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• Difference in BackgroundWorker thread access in VS2010 / .NET 4.0?

  - by Jonners

  Here's an interesting one - in VS2005 / VS2008 running against .NET 2.0 / .NET 3.0 / .NET 3.5, a BackgroundWorker thread may not directly update controls on a WinForms form that initiated that thread - you'll get a System.InvalidOperationException out of the BackgroundWorker stating "Cross-thread operation not valid: Control 'thecontrol' accessed from a thread other than the thread it was created on". I remember hitting this back in 2004 or so when I first started writing .NET WinForms apps with background threads. There are several ways around the problem - this is not a question asking for that answer. I've been told recently that this kind of operation is now allowed when written in VS2010 / .NET 4.0. This seems unlikely to me, since this kind of object access restriction has always been a fairly fundamental part of thread-safe programming. Allowing a BackgroundWorker thread direct access to objects owned not by itself but by its parent UI form seems contrary to that principle. A trawl through the .NET 4.0 docs hasn't revealed any obvious changes that could account for this behaviour. I don't have VS2010 / .NET 4.0 to test this out - does anyone who has access to that toolset know for sure whether the model has changed to allow that kind of thread interaction? I'd like to either take advantage of it in future, or deploy the cluestick. ;)

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• Unsort: remembering a permutation and undoing it.

  - by dreeves

  Suppose I have a function f that takes a vector v and returns a new vector with the elements transformed in some way. It does that by calling function g that assumes the vector is sorted. So I want f to be defined like so: f[v_] := Module[{s, r}, s = Sort[v]; (* remember the permutation applied in order to sort v *) r = g[s]; Unsort[r] (* apply the inverse of that permutation *) ] What's the best way to do the "Unsort"? Or could we get really fancy and have this somehow work: answer = Unsort[g[Sort[v]]]; ADDED: Let's make this concrete with a toy example. Suppose we want a function f that takes a vector and transforms it by adding to each element the next smallest element, if any. That's easy to write if we assume the vector is sorted, so let's write a helper function g that makes that assumption: g[v_] := v + Prepend[Most@v, 0] Now for the function we really want, f, that works whether or not v is sorted: f[v_] := (* remember the order; sort it; call g on it; put it back in the original order; return it *)

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• Bookmarkable URLs after Ajax for Wicket

  - by Wolfgang

  There is this well-known problem that browsers don't put Ajax request in the request history and cause problems for bookmarkability, forward/back button, and refresh. Also, there is a common solution to that problem that appends the hash symbol # and some additional parameters to the URL by using Javascript window.location.hash = .... In this question a basic solution to this problem is proposed, for example. = My question is if such a solution has been integrated in Wicket, so that existing Wicket facilities are used and no custom Javascript had to be added. If not, I'd be interested in how this could be done. Such a solution had to answer the question what should be put after the hash. I like the idea that the bookmarkable URL that (in the non-Ajax case) were in front of the hash could be put behind it. For example, when you are on http://host/catalog and reach a page http://host/product/xyz the Ajax-triggered URL would be http://host/catalog#/product/xyz. Then it would be easy to write an onload handler that checks for the # and does a redirect to the URL after the hash.

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• MVC3 custom validation attribute for an "at least one is required" situation

  - by Pricey

  Hi I have found this answer already: MVC3 Validation - Require One From Group Which is fairly specific to the checking of group names and uses reflection. My example is probably a bit simpler and I was just wondering if there was a simpler way to do it. I have the below: public class TimeInMinutesViewModel { private const short MINUTES_OR_SECONDS_MULTIPLIER = 60; //public string Label { get; set; } [Range(0,24, ErrorMessage = "Hours should be from 0 to 24")] public short Hours { get; set; } [Range(0,59, ErrorMessage = "Minutes should be from 0 to 59")] public short Minutes { get; set; } /// <summary> /// /// </summary> /// <returns></returns> public short TimeInMinutes() { // total minutes should not be negative if (Hours <= 0 && Minutes <= 0) { return 0; } // multiplier operater treats the right hand side as an int not a short int // so I am casting the result to a short even though both properties are already short int return (short)((Hours * MINUTES_OR_SECONDS_MULTIPLIER) + (Minutes * MINUTES_OR_SECONDS_MULTIPLIER)); } } I want to add a validation attribute either to the Hours & Minutes properties or the class itself.. and the idea is to just make sure at least 1 of these properties (Hours OR minutes) has a value, server and client side validation using a custom validation attribute. Does anyone have an example of this please? Thanks

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• Checking instance of non-class constrained type parameter for null in generic method

  - by casperOne

  I currently have a generic method where I want to do some validation on the parameters before working on them. Specifically, if the instance of the type parameter T is a reference type, I want to check to see if it's null and throw an ArgumentNullException if it's null. Something along the lines of: // This can be a method on a generic class, it does not matter. public void DoSomething<T>(T instance) { if (instance == null) throw new ArgumentNullException("instance"); Note, I do not wish to constrain my type parameter using the class constraint. I thought I could use Marc Gravell's answer on "How do I compare a generic type to its default value?", and use the EqualityComparer<T> class like so: static void DoSomething<T>(T instance) { if (EqualityComparer<T>.Default.Equals(instance, null)) throw new ArgumentNullException("instance"); But it gives a very ambiguous error on the call to Equals: Member 'object.Equals(object, object)' cannot be accessed with an instance reference; qualify it with a type name instead How can I check an instance of T against null when T is not constrained on being a value or reference type?

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• Modifying CSS class property values on the fly with JavaScript / jQuery

  - by JPN

  all. I've run into a unique situation that I have so far been unable to find a solution for: dynamically assigning a value to a CSS style. I know how to use jQuery to assign width, height, etc. to an element, but what I'm trying to do is actually change the value defined in the stylesheet so that the dynamically-created value can be assigned to multiple elements. What I'm building is a slideshow of images that occupy the full viewport, recalculating the image's width, height, and left properties on resize so that the image is always centered, favors width over height, except when the viewport is taller than it is wide (resizing does not reload the page, just fires a function to resize the image). I have successfully been able to get it to work on one image, and now I'm trying to determine the best way to assign those property values to all images in the slideshow without having to specify those three things individually for every image. Can the values of properties in a class be modified on the fly? I'm sure the answer is out there, I'm probably just not using the correct terminology in my searches. Hope I did a good job of describing the problem. TIA.

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