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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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  • DataGridView cells not editable when using an outside thread call

    - by joslinm
    Hi, I'm not able to edit my datagridview cells when a number of identical calls takes place on another thread. Here's the situation: Dataset table is created in the main window The program receives in files and processes them on a background thread in class TorrentBuilder : BackgroundWorker creating an array objects of another class Torrent My program receives those objects from the BW result and adds them into the dataset The above happens either on my main window thread or in another thread: I have a separate thread watching a folder for files to come in, and when they do come in, they proceed to call TorrentBuilder.RunWorkerAsynch() from that thread, receive the result, and call an outside class that adds the Torrent objects into the table. When the files are received by the latter thread, the datagridview isn't editable. All of the values come up properly into the datagridview, but when I click on a cell to edit it: I can write letters and everything, but when I click out of it, it immediately reverts back to its original value. If I restart the program, I can edit the same cells just fine. If the values are freshly added from the main window thread, I can edit the cells just fine. The outside thread is called from my main window thread, and sits there in the background. I don't believe it to be ReadOnly because I would have gotten an exception. Here's some code: From my main window class: private void dataGridView_DragDrop(object sender, DragEventArgs e) { ArrayList al = new ArrayList(); string[] files = (string[])e.Data.GetData(DataFormats.FileDrop); foreach (string file in files) { string extension = Path.GetExtension(file); if (Path.GetExtension(file).Equals(".zip") || Path.GetExtension(file).Equals(".rar")) { foreach (string unzipped in dh.UnzipFile(file)) al.Add(unzipped); } else if (Path.GetExtension(file).Equals(".torrent")) { al.Add(file); } } dataGridViewProgressBar.Visible = true; tb.RunWorkerCompleted += new RunWorkerCompletedEventHandler(tb_DragDropCompleted); tb.ProgressChanged += new ProgressChangedEventHandler(tb_DragDropProgress); tb.RunWorkerAsync() } void tb_DragDropCompleted(object sender, RunWorkerCompletedEventArgs e) { data.AddTorrents((Torrent[])e.Result); builder.Dispose(); dh.MoveProcessedFiles(data); dataGridViewProgressBar.Visible = false; } From my outside Thread while (autocheck) { if (torrentFiles != null) { builder.RunWorkerAsync(torrentFiles); while (builder.IsBusy) Thread.Sleep(500); } } void builder_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e) { data.AddTorrents((Torrent[])e.Result); builder.Dispose(); dh.MoveProcessedFiles(xml); data.Save(); //Save just does an `AcceptChanges()` and saves to a XML file }

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  • Does declaring many identical anonymous classes waste memory in java?

    - by depsypher
    I recently ran across the following snippet in an existing codebase I'm working on and added the comment you see there. I know this particular piece of code can be rewritten to be cleaner, but I just wonder if my analysis is correct. Will java create a new class declaration and store it in perm gen space for every call of this method, or will it know to reuse an existing declaration? protected List<Object> extractParams(HibernateObjectColumn column, String stringVal) { // FIXME: could be creating a *lot* of anonymous classes which wastes perm-gen space right? return new ArrayList<Object>() { { add(""); } }; }

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  • how to get a constant in java with class

    - by vincent
    basically I need to get a constant for a class however I have no instance of the object but only its class. In PHP I would do constant(XYZ); Is there a similar way of retrieving a constant in JAVA? I need it to facilitate a dynamic getMethod call Class parameterType = Class.forName(class_name); object.setProperty(field name, field value, parameterType); the set property method would then get the correct method and set the specified property, however I cant get a method which has int as parameter type without using Interger.TYPE

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  • How does Git know which Index blob to add to a tree?

    - by drozzy
    In Pro Git Ch9 the author says: Git normally creates a tree by taking the state of your staging area or index and writing a tree object from it. My question is how does git know which of two consequitive index entries to create the Tree object from? For example: $ echo 'First change' > one.txt $ git add one.txt $ find .git/objects -type f .git/objects/1f/755a7fffe4 //first index entry $ echo 'Second change' > one.txt $ git add one.txt $ find .git/objects -type f .git/objects/2d/234asdf2 //second index entry $ git commit -a -m "Initial commit" $ git cat-file master^{tree} 100644 blob 2d234asdf2 one.txt //How did it know not to take 1f755?? Does it just look at the blob timestamps? Also - what happens to the first blob created - no one is referencing it. Does it just get destroyed or forgotten?

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  • How to call AJAX API function from Windows App?

    - by stiopa
    Some company is providing me with web-based API for using their services. I have no problem calling this API functions from within web brower: <html xmlns="http://www.w3.org/1999/xhtml"> <head> <script type="text/javascript" src="http://someaddress.com?&key=somekey"></script> <script type="text/javascript"> var object = new SomeObject(); object.SomeFunction(); </script> </head> I am interested in return value of SomeFunction(). How would I get this return value from windows application?

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  • Swf files not loaed on IE

    - by Rajeev
    The swf files are not loaded on IE.IS there any settings that needs to be changed on IE <div> <table style="table-layout:fixed;width:100%;"> <tr> <td width="20%"> <object width="100" height="100" id="microphone"> <embed src="/media/players/game.swf" width="250" height="250" type='application/x-shockwave-flash'> </embed> </object> </td> </tr> </table> </div>

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  • page_load another handler?

    - by joe doe
    can someone please explain why this code is not working as expected: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class temp : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Response.Write("foo<br>"); this.Load += new EventHandler(temp_Load); } void temp_Load(object sender, EventArgs e) { Response.Write("bar<br>"); Response.End(); } } trying to add another handler for page Load event so that output would be: foo<br> bar<br>

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  • an error "variable of field declared void"

    - by lego69
    I have this code: header - test.h Inside header I have some class Z and definitions of two functions test and test2 I call function test2 from test void test2(Z z, Z const *za); this is implementation of the function: void test2(Z z, Z const *za){ int i = z; //this row works cout << i << endl; } I call it from test: test2(z1, za1); // za1 is pinter to object and z1 is some object but in my header I receive an 3 errors: Multiple markers at this line - initializer expression list treated as compound expression - `A' was not declared in this scope - variable or field `quiz2' declared void can somebody please explain why? thanks in advance

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  • Socket connection to a telnet-based server hangs on read

    - by mixwhit
    I'm trying to write a simple socket-based client in Python that will connect to a telnet server. I can test the server by telnetting to its port (5007), and entering text. It responds with a NAK (error) or an AK (success), sometimes accompanied by other text. Seems very simple. I wrote a client to connect and communicate with the server, but it hangs on the first attempt to read the response. The connection is successful. Queries like getsockname and getpeername are successful. The send command returns a value that equals the number of characters I'm sending, so it seems to be sending correctly. But in the end, it always hangs when I try to read the response. I've tried using both file-based objects like readline and write (via socket.makefile), as well as using send and recv. With the file object I tried making it with "rw" and reading and writing via that object, and later tried one object for "r" and another for "w" to separate them. None of these worked. I used a packet sniffer to watch what's going on. I'm not versed in all that I'm seeing, but during a telnet session I can see my typed text and the server's text coming back. During my Python socket connection, I can see my text going to the server, but packets back don't seem to have any text in them. Any ideas on what I'm doing wrong, or any strategies to try? Here's the code I'm using (in this case, it's with send and recv): #!/usr/bin/python host = "localhost" port = 5007 msg = "HELLO EMC 1 1" msg2 = "HELLO" import socket import sys try: skt = socket.socket(socket.AF_INET, socket.SOCK_STREAM) except socket.error, e: print("Error creating socket: %s" % e) sys.exit(1) try: skt.connect((host,port)) except socket.gaierror, e: print("Address-related error connecting to server: %s" % e) sys.exit(1) except socket.error, e: print("Error connecting to socket: %s" % e) sys.exit(1) try: print(skt.send(msg)) print("SEND: %s" % msg) except socket.error, e: print("Error sending data: %s" % e) sys.exit(1) while 1: try: buf = skt.recv(1024) print("RECV: %s" % buf) except socket.error, e: print("Error receiving data: %s" % e) sys.exit(1) if not len(buf): break sys.stdout.write(buf)

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  • Why is this NaN to javascript?

    - by MJB
    I have this object printed with console.log Array[1] 0: Object address: "blablabalbala" datatype: "Location" icon: "cafetaria" id: "/mensa/wo_mensa1_turm.std.php" kind: "Mensa" lat: 50.777016 lon: 6.080348 sortkey: "zeltmensa, forum cafete" stationId: "/mensa/wo_mensa1_turm.std.php" title: "Zeltmensa, Forum Cafete" type: "Mensa" But console.log("nav to: "+data[0].lat+" "+data[0].lon); gives me undefined undefined, and at another point NaN NaN.. I don't understand this. It also doesn't let me use any other attributes like data[0].addresse, which returns undefined aswell. Thanks for help.

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  • How can I call a COM component using JavaScript in Mozilla?

    - by kumar
    I am calling a COM component in IE. Here is the code <object align="left" classid="CLSID:22D6F312-B0F6-11D0-94AB-0080C74C7E95" id="Winvideo-Silverlight2RTW-Hypervideo-Part1-WMVa.wmv"> <param name="FileName" value="Winvideo-Silverlight2RTW-Hypervideo-Part1-WMVa.wmv"> <param name="AutoRewind" value="true"> <param name="AutoStart" value="false"> <param name="ClickToPlay" value="true"> <param name="Mute" value="false"> <param name="ShowControls" value="true"> <param name="ShowDisplay" value="true"> <param name="ShowTracker" value="true"> <param name="PlayCount" value="1"> </object> It is working fine in IE, but not in Mozilla Firefox.

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  • C++ : Swapping template class elements of different types?

    - by metamemetics
    template< class T1, class T2 > class Pair { T1 first; T2 second; }; I'm being asked to write a swap() method so that the first element becomes the second and the second the first. I have: Pair<T2,T1> swap() { return Pair<T2,T1>(second, first); } But this returns a new object rather than swapping, where I think it needs to be a void method that changes its own data members. Is this possible to do since T1 and T2 are potentially different class types? In other words I can't simply set temp=first, first=second, second=temp because it would try to convert them to different types. I'm not sure why you would potentially want to have a template object that changes order of its types as it seems that would cause confusion but that appears to be what I'm being asked to do.

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  • ideas for simple objects for day to day web-dev use?

    - by Joel
    Dang-I know this is a subjective question so will probably get booted off/locked, but I'll try anyway, because I don't know where else to ask (feel free to point me to a better place to ask this!) I'm just wrapping my head around oop with PHP, but I'm still not using frameworks or anything. I'd like to create several small simple objects that I could use in my own websites to better get a feel for them. Can anyone recommend a list or a resource that could point me to say 10 day-to-day objects that people would use in basic websites? The reason I'm asking is because I'm confusing myself a bit. For example, I was thinking of a "database connection" object, but then I'm just thinking that is just a function, and not really an "object"?? So the question is: What are some examples of objects used in basic PHP websites (not including "shopping cart" type websites) Thanks!

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  • Will lock() statement block all threads in the proccess/appdomain?

    - by MikeJ
    Maybe the question sounds silly, but I don't understand 'something about threads and locking and I would like to get a confirmation (here's why I ask). So, if I have 10 servers and 10 request in the same time come to each server, that's 100 request across the farm. Without locking, thats 100 request to the database. If I do something like this: private static readonly object myLockHolder = new object(); if (Cache[key] == null) { lock(myLockHolder) { if (Cache[key] == null) { Cache[key] = LengthyDatabaseCall(); } } } How many database requests will I do? 10? 100? Or as much as I have threads?

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  • How to instantiate a Singleton multiple times?

    - by Sebi
    I need a singleton in my code. I implemented it in Java and it works well. The reason I did it, is to ensure that in a mulitple environment, there is only one instance of this class. But now I want to test my Singleton object locally with a Unit test. For this reason I need to simulate another instance of this Singleton (the object that would be from another device). So is there a possiblity to instantiate a Singleton a second time for testing purpose or do I have to mock it? I'm not sure, but I think it could be possible by using a different class loader?

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  • PHP class referencing confusion across multiple files

    - by DssTrainer
    I have an index.php file that has 3 includes <?php require_once('mod.php'); $mod = new Mod(); require_once('start.php'); require_once('tools.php'); ....some code.... ?> I need to be able to reference the $mod object inside the start.php and tools.php. How do I pass that object to be referenced by those 2 other require files? Basically the mod.php is a class that has an array list generated in its __construct(). I want to use that array list data inside the startup.php and tools.php file but not sure how to pass in the existing one without calling "new" inside both of those files separately which doesn't do what I need since it resets everything. Thanks!

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  • How do I create a create and execute an SQL command using OleDB directly?

    - by Pagis
    I want to use the OleDB interfaces directly to open a connection to a DB, create a command and executing it (for example using the ICommandText interface). The main thing I can't find is how to create the connection and the command object and how to connect the object that implements the ICommandText to the connection. In ADO I would just use the ActiveConnection property but I want to do this directly on the OleDB interfaces. Also, if anyone can recommend a tutorial to OleDB, ether online or a book, free or not that would be great (but a tutorial and not just a reference / API) I'm using C++ but any native code would be fine.

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  • In Java, how do I set a return type if an exception occurs?

    - by beagleguy
    hey all, I'm new to Java and was wondering if I define a method to return a database object like import java.sql.*; public class DbConn { public Connection getConn() { Connection conn; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); if(System.getenv("MY_ENVIRONMENT") == "development") { String hostname = "localhost"; String username = "root"; String password = "root"; } conn = DriverManager.getConnection("jdbc:mysql:///mydb", username, password); return conn; } catch(Exception e) { throw new Exception(e.getMessage()); } } } if the connection fails when I try to create it what should I return? eclipse is telling me I have to return a Connection object but if it fails I'm not sure what to do. thanks!

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  • Questions Regarding Handling of Received SMS

    - by Edwin
    Hi, i have managed to successfully write a little test app that can receive and send SMS, but got a couple of questions. (That's 'cos part of the code i copied from elsewhere and i would like to understand better). In my AndroidManifest as well as the sub-class of BroadcastReceiver, there is reference to the string literal "android.provider.Telephony.SMS_RECEIVED". However, i couldn't find any reference in the API that mentions this. Could someone point me to some reference that lists/explains these? As part of getting the message from the Intent, i did this: Object[] pdus = (Object[]) intent.getExtras().get("pdus"); Again this question is related to the use of hardcoded string literal. Where is the string "pdus" listed and described? Thanks in advance!

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  • pass value to servlet from a hidden input type

    - by kawtousse
    I am trying to pass the parameter called value in the hidden input type to my servlet. It is like that: retour.append("<input type=\"hidden\" id=\"id_" + nomTab + "_" + compteur + "\" value=\"" + object.getIdDailyTimeSheet() + "\"/>"); retour.append("<button id=edit name=edit type=submit onClick= editarow()>"); retour.append("<img src=edit.gif />"); retour.append("</button>"); retour.append("</td>"); But the method get parameter recommend a name to be able to get the value here. So how can I deal with it? Here I want to pass to the servlet the value of object.getIdDailyTimeSheet().

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