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• Using Git to work with subversion: Ignoring modifications to tracked files

  - by Chris Nicola

  I am currently working with a subversion repository but I am using git to work locally on my machine. It makes work much easier, but it also makes some of the bad behavior going on in the subversion repo quite glaring and that creates problems for me. There is a somewhat complex local build process after pulling down the code and it creates (and unfortunately modifies) a number of files. Obviously these changes are not meant to be committed back to the repository. Unfortunately the build process is actually modifying some tracked files (yes, most likely because someone mistakenly committed these build artifacts at some point to the subversion repository). Since these are modifications adding them to my ignore file does nothing for me. I can avoid checking these changes back it, I simple don't stage or commit them, but having unstaged local changes means I can't rebase without first cleaning them up. What I would like to know is if there any way to ignore future changes to a set of tracked files? Alternatively, is there another way to handle the problem I am having, or will I just have to tell whoever checked in these files to clean them up?

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• Does JAXWS client make difference between an empty collection and a null collection value as returne

  - by snowflake

  Since JAX-WS rely on JAXB, and since I observed the code that unpack the XML bean in JAX-B Reference Implementation, I guess the difference is not made and that a JAXWS client always return an empty collection, even the webservice result was a null element: public T startPacking(BeanT bean, Accessor<BeanT, T> acc) throws AccessorException { T collection = acc.get(bean); if(collection==null) { collection = ClassFactory.create(implClass); if(!acc.isAdapted()) acc.set(bean,collection); } collection.clear(); return collection; } I agree that for best interoperability service contracts should be non ambiguous and avoid such differences, but it seems that the JAX-WS service I'm invoking (hosted on a Jboss server with Jbossws implementation) is returning as expected either null either empty collection (tested with SoapUI). I used for my test code generated by wsimport. Return element is defined as: @XmlElement(name = "return", nillable = true) protected List<String> _return; I even tested to change the Response class getReturn method from : public List<String> getReturn() { if (_return == null) { _return = new ArrayList<String>(); } return this._return; } to public List<String> getReturn() { return this._return; } but without success. Any helpful information/comment regarding this problem is welcome !

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• Does anyone knows any Train-table-api service?

  - by DaNieL

  Hi guys, im wondering if there is any online service who provide API about the train timetables (arrivals, departure, etch..), at least for the european stations. I know www.bahn.de, who provide the accurated timetables for many european countries, but i didin't find any similar to a api service. My goal (well, just a future-project) is to develope an application like gmaps, but instead of giving the car-trip i would like to give the train-trip.. you know, the user set the departure day, time and station, then the first arrival, maybe then add another one, and so on. So, there is something like, that can be queryed by php/python/javascript? Edit: if can help, im wondering to build a service to plan an inter-rail trip! (and any help will be really appreciate) Im stuck. Google's public-service api rely on the information that every local company makes avaiable, much branches are missing (for example, is almost impossible to use it to build an itinerary that touches two or more regions of Europe. As i said before, the only service that i know doing it good is the bahn.de, they really have all the data.. but no api. I tryed to parse theyre result page (in order to use them as API), but seem like the markup is been build exactly to avoid that.. maybe they have business plans behind that or whatever, but i dont think they will ever release some API.. so, my project is going on without this function (p.s: my project is about non-profit cultural organizations, we wont make war to anyone ;P) @El Goorf: if you find a way, and consider the idea of sharing it, count on my hand if need help!

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

  - by jens

  Hello, i would be thankful for your advice. 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 typen? //.. 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 to thest for them?? thanks!!! Jens

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• Javascript scope chain

  - by Geromey

  Hi, I am trying to optimize my program. I think I understand the basics of closure. I am confused about the scope chain though. I know that in general you want a low scope (to access variables quickly). Say I have the following object: var my_object = (function(){ //private variables var a_private = 0; return{ //public //public variables a_public : 1, //public methods some_public : function(){ debugger; alert(this.a_public); alert(a_private); }; }; })(); My understanding is that if I am in the some_public method I can access the private variables faster than the public ones. Is this correct? My confusion comes with the scope level of this. When the code is stopped at debugger, firebug shows the public variable inside the this keyword. The this word is not inside a scope level. How fast is accessing this? Right now I am storing any this.properties as another local variable to avoid accessing it multiple times. Thanks very much!

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• Getter and Setter vs. Builder strategy

  - by Extrakun

  I was reading a JavaWorld's article on Getter and Setter where the basic premise is that getters expose internal content of an object, hence tightening coupling, and go on to provide examples using builder objects. I was rather leery of abolishing getter/setter but on second reading of the article, see to quite like the idea. However, sometimes I just need one cruical element of an entity class, such as the user's id and writing one whole class just to extract that cruical element seems like overkill. It also implies that for different view, a different type of importer/exporter must be implemented (or the whole data of the class to be exported out, thus resulting in waste). Usually I tend towards filtering the result of a getter - for example, if I need to output the price of a product in different currency, I would code it as: return CurrencyOutput::convertTo($product->price(), 'USD'); This is with the understanding that the raw output of a getter is not necessary the final result to be pushed onto a screen or a database. Is getter/setter really as bad as it is protrayed to be? When should one adopt a builder strategy, or a 'get the result and filter it' approach? How do you avoid having a class needing to know about every other objects if you are not using getter/setter?

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• How to log correct context with Threadpool threads using log4net?

  - by myotherme

  I am trying to find a way to log useful context from a bunch of threads. The problem is that a lot of code is dealt with on Events that are arriving via threadpool threads (as far as I can tell) so their names are not in relation to any context. The problem can be demonstrated with the following code: class Program { private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); static void Main(string[] args) { new Thread(TestThis).Start("ThreadA"); new Thread(TestThis).Start("ThreadB"); Console.ReadLine(); } private static void TestThis(object name) { var nameStr = (string)name; Thread.CurrentThread.Name = nameStr; log4net.ThreadContext.Properties["ThreadContext"] = nameStr; log4net.LogicalThreadContext.Properties["LogicalThreadContext"] = nameStr; log.Debug("From Thread itself"); ThreadPool.QueueUserWorkItem(x => log.Debug("From threadpool Thread: " + nameStr)); } } The Conversion pattern is: %date [%thread] %-5level %logger [%property] - %message%newline The output is like so: 2010-05-21 15:08:02,357 [ThreadA] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadA, log4net:HostName=xxx, ThreadContext=ThreadA}] - From Thread itself 2010-05-21 15:08:02,357 [ThreadB] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadB, log4net:HostName=xxx, ThreadContext=ThreadB}] - From Thread itself 2010-05-21 15:08:02,404 [7] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadA 2010-05-21 15:08:02,420 [16] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadB As you can see the last two rows have no Names of useful information to distinguish the 2 threads, other than manually adding the name to the message (which I want to avoid). How can I get the Name/Context into the log for the threadpool threads without adding it to the message at every call?

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• Asynchronous crawling F#

  - by jlezard

  When crawling on webpages I need to be careful as to not make too many requests to the same domain, for example I want to put 1 s between requests. From what I understand it is the time between requests that is important. So to speed things up I want to use async workflows in F#, the idea being make your requests with 1 sec interval but avoid blocking things while waiting for request response. let getHtmlPrimitiveAsyncTimer (uri : System.Uri) (timer:int) = async{ let req = (WebRequest.Create(uri)) :?> HttpWebRequest req.UserAgent<-"Mozilla" try Thread.Sleep(timer) let! resp = (req.AsyncGetResponse()) Console.WriteLine(uri.AbsoluteUri+" got response") use stream = resp.GetResponseStream() use reader = new StreamReader(stream) let html = reader.ReadToEnd() return html with | _ as ex -> return "Bad Link" } Then I do something like: let uri1 = System.Uri "http://rue89.com" let timer = 1000 let jobs = [|for i in 1..10 -> getHtmlPrimitiveAsyncTimer uri1 timer|] jobs |> Array.mapi(fun i job -> Console.WriteLine("Starting job "+string i) Async.StartAsTask(job).Result) Is this alright ? I am very unsure about 2 things: -Does the Thread.Sleep thing work for delaying the request ? -Is using StartTask a problem ? I am a beginner (as you may have noticed) in F# (coding in general actually ), and everything envolving Threads scares me :) Thanks !!

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• Best Pattern for AllowUnsafeUpdates

  - by webwires

  So far, in my research I have seen that it is unwise to set AllowUnsafeUpdates on GET request operation to avoid cross site scripting. But, if it is required to allow this, what is the proper way to handle the situation to mitigate any exposure? Here is my best first guess on a reliable pattern if you absolutely need to allow web or site updates on a GET request. Best Practice? protected override void OnLoad(System.EventArgs e) { if(Request.HttpMethod == "POST") { SPUtility.ValidateFormDigest(); // will automatically set AllowSafeUpdates to true } // If not a POST then AllowUnsafeUpdates should be used only // at the point of update and reset immediately after finished // NOTE: Is this true? How is cross-site scripting used on GET // and what mitigates the vulnerability? } // Point of item update SPSecurity.RunWithElevatedPrivledges(delegate() { using(SPSite site = new SPSite(SPContext.Current.Site.Url)) { using (SPWeb web = site.RootWeb) { bool allowUpdates = web.AllowUnsafeUpdates; //store original value web.AllowUnsafeUpdates = true; //... Do something and call Update() ... web.AllowUnsafeUpdates = allowUpdates; //restore original value } } }); Feedback on the best pattern is appreciated.

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• Grails - Recursive computing call "StackOverflowError" and don't update on show

  - by Kedare

  Hello, I have a little problem, I have made a Category domain on Grails, but I want to "cache" the string representation on the database by generating it when the representation field is empty or NULL (to avoid recursive queries at each toString), here is the code : package devkedare class Category { String title; String description; String representation; Date dateCreated; Date lastUpdate; Category parent; static constraints = { title(blank:false, nullable:false, size:2..100); description(blank:true, nullable:false); dateCreated(nullable:true); lastUpdate(nullable:true); autoTimestamp: true; } static hasMany = [childs:Category] @Override String toString() { if((!this.representation) || (this.representation == "")) { this.computeRepresentation(true) } return this.representation; } String computeRepresentation(boolean updateChilds) { if(updateChilds) { for(child in this.childs) { child.representation = child.computeRepresentation(true); } } if(this.parent) { this.representation = "${this.parent.computeRepresentation(false)}/${this.title}"; } else { this.representation = this.title } return this.representation; } void beforeUpdate() { this.computeRepresentation(true); } } There is 2 problems : It don't update the representation when the representation if NULL or empty and toString id called, it only update it on save, how to fix that ? On some category, updating it throw a StackOverflowError, here is an example of my actual category table as CSV : Uploaded the csv file here, pasting csv looks buggy: http://kedare.free.fr/Dist/01.csv Updating the representation works everywhere except on "IT" that throw a StackOverlowError (this is the only category that has many childs). Any idea of how can I fix those 2 problems ? Thank you !

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• Modifying UINavigation Bar Buttons in SubViews

  - by james

  I'm having trouble trying to modify the navigation bar in the subview portion of my application. self.navigationItem.rightBarButtonItem = [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(add_Clicked:)] autorelease]; I have no issues modifying the navigation bar in any of my UIViewControllers classes. The simplified application class outline is as such: AppDelegate - UIViewControllerA (has a left and a right navigationBarButton) - Subview is displayed when a SegmentControl is selected. (Within the subview, I'm trying to modify the right NavigationBarButton that is displayed) [self.view addSubview:newControllerName.view]; Methods I have attempted: Trying to set self.navigationItem.rightBarButtonItem within my subview to a new UIBarButtonItem. Creating a pointer to UIViewControllerA within my AppDelegate. The UIViewControllerA contains a function setNavButton I wrote to set the rightBarButtonItem to a button. Then I am referencing the AppDelegate's reference to UIViewControllerA and attempting to call setNavButton. I included a NSLog call to see if that function is being called and it is executing but the NavigationBar isn't being modified. I'm trying to avoid having to push a UIViewController after the SegmentControl is clicked in UIViewControllerA so that I can simulate the SegmentControl as tabs. I'm not getting any errors during compile or run time. Anyone have any ideas?

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• Simple in-place discrete fourier transform ( DFT )

  - by Adam

  I'm writing a very simple in-place DFT. I am using the formula shown here: http://en.wikipedia.org/wiki/Discrete_Fourier_transform#Definition along with Euler's formula to avoid having to use a complex number class just for this. So far I have this: private void fft(double[] data) { double[] real = new double[256]; double[] imag = new double[256]; double pi_div_128 = -1 * Math.PI / 128; for (int k = 0; k < 256; k++) { for (int n = 0; n < 256; n++) { real[k] += data[k] * Math.Cos(pi_div_128 * k * n); imag[k] += data[k] * Math.Sin(pi_div_128 * k * n); } data[k] = Math.Sqrt(real[k] * real[k] + imag[k] * imag[k]); } } But the Math.Cos and Math.Sin terms eventually go both positive and negative, so as I'm adding those terms multiplied with data[k], they cancel out and I just get some obscenely small value. I see how it is happening, but I can't make sense of how my code is perhaps mis-representing the mathematics. Any help is appreciated. FYI, I do have to write my own, I realize I can get off-the shelf FFT's.

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• How to restrict access to a class's data based on state?

  - by Marcus Swope

  In an ETL application I am working on, we have three basic processes: Validate and parse an XML file of customer information from a third party Match values received in the file to values in our system Load customer data in our system The issue here is that we may need to display the customer information from any or all of the above states to an internal user and there is data in our customer class that will never be populated before the values have been matched in our system (step 2). For this reason, I would like to have the values not even be available to be accessed when the customer is in this state, and I would like to have to avoid some repeated logic everywhere like: if (customer.IsMatched) DisplayTextOnWeb(customer.SomeMatchedValue); My first thought for this was to add a couple interfaces on top of Customer that would only expose the properties and behaviors of the current state, and then only deal with those interfaces. The problem with this approach is that there seems to be no good way to move from an ICustomerWithNoMatchedValues to an ICustomerWithMatchedValues without doing direct casts, etc... (or at least I can't find one). I can't be the first to have come across this, how do you normally approach this? As a last caveat, I would like for this solution to play nice with FluentNHibernate :) Thanks in advance...

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• jQuery capture all changes to named inpt on a form

  - by Brian M. Hunt

  I'm trying to determine when any of a set of named input/select/radio/checked/hidden fields in a form change. In particular, I'd like to capture when any changes are made to fields matching jQuery's selector $("form :input"), and where that input is has a name attribute. However, the form isn't static i.e. some of the fields are dynamically added later. My initial thought is to keep track of when new named elements matching :input are added, and then add an event handler, like this: function on_change() { alert("The form element with name " + $(this).attr("name") + " has changed"); } function reg_new_e_handler(input_element) { input_element.change(on_change); } However, I'm quite hopeful I can avoid this with some jQuery magic. In particular, is there a way to register an event handler in jQuery that would handle input elements that match the following: $("form :input").filter( function () { $(this).attr("name") } ).change(on_change); However, have this event set update whenever new input elements are added. I've thought that it may be possible to capture keyup event on the form node with $("form").keyup(on_change), but I'm not so sure how one could capture change events. I'd also like this to capture keyup events. Thank you for reading. Brian

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• Check mail attachment

  - by comii

  Hi! I am using vb.net to display email from outlook express! Everything work fine but when some message has attachment, i can not display message that email has attachment! This is my code: Private Sub LoginButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LoginButton.Click Dim oItem Dim i As Integer Dim Message As MAPI.Message Dim items As String() = New String(6) {} ' Items are the sender name,subject and date and read/unread value Dim PrSenderEmail, PrBodyEmail Session = CreateObject("MAPI.Session") ' we use a session object of MAPI Component Session.Logon(ProfileName:=Me.UserId.Text, ProfilePassword:=Me.Password.Text) Session.MAPIOBJECT = Session.MAPIOBJECT ' Folder = CObj(Session.Inbox) ' choose the folder Application = CreateObject("Outlook.Application") Namespace1 = Application.GetNamespace("MAPI") Namespace1.Logon() ' for getting the sender name and avoid security validation of Outlook/Exchange server 2003 ' we are using the "Redemption" component sItem = CreateObject("Redemption.SafeMailItem") Cursor.Current = Cursors.WaitCursor ' show we're busy doing the sort ListInbox.BeginUpdate() ' Notify that update begins ListInbox.Items.Clear() i = 0 ' first email message is 0 For Each Message In Folder.Messages Try i = i + 1 ' increment to the next email message 'get e-mail from the Inbox, can be any other item oItem = Application.Session.GetDefaultFolder(6).Items(i) ' GetDefaultFolder(6) refers to Inbox sItem.Item = oItem 'sItem is an object of Redemption COM and is used to get the senders name items(0) = sItem.SenderName() Catch items(0) = "error" End Try Dim objApp As Outlook.Application = New Outlook.Application 'Get Mapi NameSpace Dim objNS As Outlook.NameSpace = objApp.GetNamespace("MAPI") Dim oMsg As Outlook.MailItem Dim pp As String Dim b As Integer Dim objAttachment As Outlook.Attachment pp = Message.StoreID items(1) = Message.Subject items(2) = Message.TimeReceived items(4) = Message.Subject items(5) = Message.Size Dim objInbox As Outlook.MAPIFolder = objNS.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox) Dim objItems As Outlook.Items = objInbox.Items items(5) = Message.Size.ToString / 1000 & "kb" If Message.Unread = True Then items(3) = "unread" Else items(3) = "read" End If ListInbox.Items.Add(New ListViewItem(items)) Next ListInbox.EndUpdate() ' Notify that update ends Cursor.Current = Cursors.Default End If End Sub How I can display message that email has attachment?

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• Get directory path by fd

  - by tylerl

  I've run into the need to be able refer to a directory by path given its file descriptor in Linux. The path doesn't have to be canonical, it just has to be functional so that I can pass it to other functions. So, taking the same parameters as passed to a function like fstatat(), I need to be able to call a function like getxattr() which doesn't have a f-XYZ-at() variant. So far I've come up with these solutions; though none are particularly elegant. The simplest solution is to avoid the problem by calling openat() and then using a function like fgetxattr(). This works, but not in every situation. So another method is needed to fill the gaps. The next solution involves looking up the information in proc: if (!access("/proc/self/fd",X_OK)) { sprintf(path,"/proc/self/fd/%i/",fd); } This, of course, totally breaks on systems without proc, including some chroot environments. The last option, a more portable but potentially-race-condition-prone solution, looks like this: DIR* save = opendir("."); fchdir(fd); getcwd(path,PATH_MAX); fchdir(dirfd(save)); closedir(save); The obvious problem here is that in a multithreaded app, changing the working directory around could have side effects. However, the fact that it works is compelling: if I can get the path of a directory by calling fchdir() followed by getcwd(), why shouldn't I be able to just get the information directly: fgetcwd() or something. Clearly the kernel is tracking the necessary information. So how do I get to it?

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• Building an extension framework for a Rails app

  - by obvio171

  I'm starting research on what I'd need in order to build a user-level plugin system (like Wordpress plugins) for a Rails app, so I'd appreciate some general pointers/advice. By user-level plugin I mean a package a user can extract into a folder and have it show up on an admin interface, allowing them to add some extra configuration and then activate it. What is the best way to go about doing this? Is there any other opensource project that does this already? What does Rails itself already offer for programmer-level plugins that could be leveraged? Any Rails plugins that could help me with this? A plugin would have to be able to: run its own migrations (with this? it's undocumented) have access to my models (plugins already do) have entry points for adding content to views (can be done with content_for and yield) replace entire views or partials (how?) provide its own admin and user-facing views (how?) create its own routes (or maybe just announce its presence and let me create the routes for it, to avoid plugins stepping on each other's toes) Anything else I'm missing? Also, is there a way to limit which tables/actions the plugin has access to concerning migrations and models, and also limit their access to routes (maybe letting them include, but not remove routes)? P.S.: I'll try to keep this updated, compiling stuff I figure out and relevant answers so as to have a sort of guide for others.

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• php scandir --> search for files/directories

  - by Peter

  Hi! I searched before I ask, without lucky.. I looking for a simple script for myself, which I can search for files/folders. Found this code snippet in the php manual (I think I need this), but it is not work for me. "Was looking for a simple way to search for a file/directory using a mask. Here is such a function. By default, this function will keep in memory the scandir() result, to avoid scaning multiple time for the same directory." <?php function sdir( $path='.', $mask='*', $nocache=0 ){ static $dir = array(); // cache result in memory if ( !isset($dir[$path]) || $nocache) { $dir[$path] = scandir($path); } foreach ($dir[$path] as $i=>$entry) { if ($entry!='.' && $entry!='..' && fnmatch($mask, $entry) ) { $sdir[] = $entry; } } return ($sdir); } ?> Thank you for any help, Peter

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• Calling MethodBase's Invoke on a constructor (reflection)

  - by Alix

  Hi everyone. First of all, sorry if this has been asked before. I've done a pretty comprehensive search and found nothing quite like it, but I may have missed something. And now to the question: I'm trying to invoke a constructor through reflection, with no luck. Basically, I have an object that I want to clone, so I look up the copy constructor for its type and then want to invoke it. Here's what I have: public Object clone(Object toClone) { MethodBase copyConstructor = type.GetConstructor( new Type[] { toClone.GetType() }); return method.Invoke(toClone, new object[] { toClone }); //<-- doesn't work } I call the above method like so: List list = new List(new int[] { 0, 1, 2 }); List clone = (List) clone(list); Now, notice the invoke method I'm using is MethodBase's invoke. ConstructorInfo provides an invoke method that does work if invoked like this: return ((ConstructorInfo) method).Invoke(new object[] { toClone }); However, I want to use MethodBase's method, because in reality instead of looking up the copy constructor every time I will store it in a dictionary, and the dictionary contains both methods and constructors, so it's a Dictionary<MethodBase>, not Dictionary<ConstructorInfo>. I could of course cast to ConstructorInfo as I do above, but I'd rather avoid the casting and use the MethodBase method directly. I just can't figure out the right parameters. Any help? Thanks so much.

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• Binding UpdateSourceTrigger=Explicit, updates source at program startup

  - by GTD

  I have following code: <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300"> <Grid> <TextBox Text="{Binding Path=Name, Mode=OneWayToSource, UpdateSourceTrigger=Explicit, FallbackValue=default text}" KeyUp="TextBox_KeyUp" x:Name="textBox1"/> </Grid> public partial class Window1 : Window { public Window1() { InitializeComponent(); } private void TextBox_KeyUp(object sender, KeyEventArgs e) { if (e.Key == Key.Enter) { BindingExpression exp = this.textBox1.GetBindingExpression(TextBox.TextProperty); exp.UpdateSource(); } } } public class ViewModel { public string Name { set { Debug.WriteLine("setting name: " + value); } } } public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { base.OnStartup(e); Window1 window = new Window1(); window.DataContext = new ViewModel(); window.Show(); } } I want to update source only when "Enter" key is pressed in textbox. This works fine. However binding updates source at program startup. How can I avoid this? Am I missing something?

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• what webserver / mod / technique should I use to serve everything from memory?

  - by reinier

  I've lots of lookuptables from which I'll generate my webresponse. I think IIS with Asp.net enables me to keep static lookuptables in memory which I can use to serve up my responses very fast. Are there however also non .net solutions which can do the same? I've looked at fastcgi, but I think this starts X processes, of which anyone can handle Y requests. But the processes are by definition shielded from eachother. I could configure fastcgi to use just 1 process, but does this have scalability implications? anything using PHP or any other interpreted language won't fly because it is also cgi or fastcgi bound right? I understand memcache could be an option, though this would require another (local) socket connection which I'd rather avoid since everything in memory would be much faster. The solution can work under WIndows or Unix... it doesn't matter too much. The only thing which matters is that there will be a lot of requests (100/sec now and growing to 500/sec in a year), and I want to reduce the amount of webservers needed to process it. The current solution is done using PHP and memcache (and the occasional hit to the SQL server backend). Although it is fast (for php anyway), Apache has real problems when the 50/sec is passed. I've put a bounty on this question since I've not seen enough responses to make a wise choice. At the moment I'm considering either Asp.net or fastcgi with C(++).

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• Multithreading and Interrupts

  - by Nicholas Flynt

  I'm doing some work on the input buffers for my kernel, and I had some questions. On Dual Core machines, I know that more than one "process" can be running simultaneously. What I don't know is how the OS and the individual programs work to protect collisions in data. There are two things I'd like to know on this topic: (1) Where do interrupts occur? Are they guaranteed to occur on one core and not the other, and could this be used to make sure that real-time operations on one core were not interrupted by, say, file IO which could be handled on the other core? (I'd logically assume that the interrupts would happen on the 1st core, but is that always true, and how would you tell? Or perhaps does each core have its own settings for interrupts? Wouldn't that lead to a scenario where each core could react simultaneously to the same interrupt, possibly in different ways?) (2) How does the dual core processor handle opcode memory collision? If one core is reading an address in memory at exactly the same time that another core is writing to that same address in memory, what happens? Is an exception thrown, or is a value read? (I'd assume the write would work either way.) If a value is read, is it guaranteed to be either the old or new value at the time of the collision? I understand that programs should ideally be written to avoid these kinds of complications, but the OS certainly can't expect that, and will need to be able to handle such events without choking on itself.

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• Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

  - by lazyconfabulator

  I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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• Delphi, PGDac vs Zeos, Fetch, Lookup?

  - by durumdara

  Hi! I used Zeos to test to know: is ZTable uses fetch technics, or not? May in the future we migrate our lesser system to PGSQL, and this used now "Table" components (as BDE, but it have an SQL-like server). These tables use real cursors, a "Window" with N record, so lookup is very fast, because the Locate/Lookup is started on server, and only these N records are refreshed, no matter, how many records in the lookup table. PGSQL uses fetch technics as I know, and I tested it with a table (id int, name varchar(100)), and 1 million records. (I also trying this with mysql). The adapter is Zeos. ID, sec to find, allocated memory in bytes on client. MySQL 500000 2,761 113 196 344 1000000 3,214 225 471 232 313800 0,437 225 471 232 328066 0,468 225 471 232 276374 0,390 225 471 232 905984 1,264 225 471 232 260253 0,359 225 471 232 PGSQL 500000 3,042 113 188 184 1000000 3,744 225 463 064 313800 0,436 225 463 064 328066 0,452 225 463 064 276374 0,375 225 463 064 905984 1,295 225 463 064 260253 0,359 225 463 064 142023 0,203 225 463 064 As you see the records are fetched locally, this cause the 225 MB usage, and searches are slow a little, based where is the record we must find. I want to ask more things: a.) Is PGDAC have some technics to we can use the lookups without pay the fetch with memory and secs? b.) Or is PG ODBC driver can help in this problem with ADO? (As I know ADO can use server side cursors)? c.) Have anybody some experience with lookup tables, and performance? Is this critical question or it is not? (With client memory usage too). d.) If no chance to avoid fetch hell with lookups, what we can do? Server Side Joins, and unique code for Lookup field changing without real Lookup? Thanks for your help: dd

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• EF + UnitOfWork + SharePoint RunWithElevatedPrivileges

  - by Lorenzo

  In our SharePoint application we have used the UnitOfWork + Repository patterns together with Entity Framework. To avoid the usage of the passthrough authentication we have developed a piece of code that impersonate a single user before creating the ObjectContext instance in a similar way that is described in "Impersonating user with Entity Framework" on this site. The only difference between our code and the referred question is that, to do the impersonation, we are using RunWithElevatedPrivileges to impersonate the Application Pool identity as in the following sample. SPSecurity.RunWithElevatedPrivileges(delegate() { using (SPSite site = new SPSite(url)) { _context = new MyDataContext(ConfigSingleton.GetInstance().ConnectionString); } }); We have done this way because we expected that creating the ObjectContext after impersonation and, due to the fact that Repositories are receiving the impersonated ObjectContext would solve our requirement. Unfortunately it's not so easy. In fact we experienced that, even if the ObjectContext is created before and under impersonation circumstances, the real connection is made just before executing the query, and so does not use impersonation, which break our requirement. I have checked the ObjectContext class to see if there was any event through which we can inject the impersonation but unfortunately found nothing. Any help?

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