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  • Good practice to create extension methods that apply to System.Object?

    - by Christian
    Hello, I'm wondering whether I should create extension methods that apply on the object level or whether they should be located at a lower point in the class hierarchy. What I mean is something along the lines of: public static string SafeToString(this Object o) { if (o == null || o is System.DBNull) return ""; else { if (o is string) return (string)o; else return ""; } } public static int SafeToInt(this Object o) { if (o == null || o is System.DBNull) return 0; else { if (o.IsNumeric()) return Convert.ToInt32(o); else return 0; } } //same for double.. etc I wrote those methods since I have to deal a lot with database data (From the OleDbDataReader) that can be null (shouldn't, though) since the underlying database is unfortunately very liberal with columns that may be null. And to make my life a little easier, I came up with those extension methods. What I'd like to know is whether this is good style, acceptable style or bad style. I kinda have my worries about it since it kinda "pollutes" the Object-class. Thank you in advance & Best Regards :) Christian P.S. I didn't tag it as "subjective" intentionally.

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  • Create a Task list, with tasks without executing

    - by Ernesto Araya Eguren
    I have an async method private async Task DoSomething(CancellationToken token) a list of Tasks private List<Task> workers = new List<Task>(); and I have to create N threads that runs that method public void CreateThreads(int n) { tokenSource = new CancellationTokenSource(); token = tokenSource.Token; for (int i = 0; i < n; i++) { workers.Add(DoSomething(token)); } } but the problem is that those have to run at a given time public async Task StartAllWorkers() { if (0 < workers.Count) { try { while (0 < workers.Count) { Task finishedWorker = await Task.WhenAny(workers.ToArray()); workers.Remove(finishedWorker); finishedWorker.Dispose(); } if (workers.Count == 0) { tokenSource = null; } } catch (OperationCanceledException) { throw; } } } but actually they run when i call the CreateThreads Method (before the StartAllWorkers). I searched for keywords and problems like mine but couldn't find anything about stopping the task from running. I've tried a lot of different aproaches but anything that could solve my problem entirely. For example, moving the code from DoSomething into a workers.Add(new Task(async () => { }, token)); would run the StartAllWorkers(), but the threads will never actually start. There is another method for calling the tokenSource.Cancel().

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  • Is there a workaround for Linux mono's refusal to acknowledge that I have resized the columns of my

    - by fantius
    When I resize a column, it does not redraw the data with the updated alignment. I've tried Invalidating, Refreshing, and a few other things. Nothing has worked. Does anyone know a workaround? I have not tried this in mono for Windows. To see what I mean, drop this control on a form, and run it in mono for Linux: using System; using System.Collections.Generic; using System.Text; using System.Windows.Forms; using System.Drawing; class MyListView : ListView { private readonly List<ListViewItem> items_ = new List<ListViewItem>(); public MyListView() { VirtualMode = true; Columns.Add("Col 1"); Columns.Add("Col 2"); Columns.Add("Col 3"); Add(new ListViewItem(new[] { "a", "b", "c" })); Add(new ListViewItem(new[] { "a", "b", "c" })); Add(new ListViewItem(new[] { "a", "b", "c" })); Add(new ListViewItem(new[] { "a", "b", "c" })); Add(new ListViewItem(new[] { "a", "b", "c" })); } protected override void OnRetrieveVirtualItem(RetrieveVirtualItemEventArgs e) { e.Item = items_[e.ItemIndex]; base.OnRetrieveVirtualItem(e); } public void Add(ListViewItem item) { items_.Add(item); VirtualListSize = items_.Count; } protected override void OnDrawColumnHeader(DrawListViewColumnHeaderEventArgs e) { e.DrawText(); base.OnDrawColumnHeader(e); } protected override void OnDrawSubItem(DrawListViewSubItemEventArgs e) { var text = ((ListViewItem.ListViewSubItem)e.SubItem).Text; using (var brush = new SolidBrush(e.SubItem.ForeColor)) { e.Graphics.DrawString(text, Font, brush, e.Bounds); } base.OnDrawSubItem(e); } protected override void OnColumnWidthChanged(ColumnWidthChangedEventArgs e) { base.OnColumnWidthChanged(e); Invalidate(true); // Nope, that didn't work Refresh(); // Nope, that didn't work } }

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  • Using forward declarations for build in datatypes.

    - by bdhar
    I understand that wherever possible we shall use forward declarations instead of includes to speed up the compilation. I have a class Person like this. #pragma once #include <string> class Person { public: Person(std::string name, int age); std::string GetName(void) const; int GetAge(void) const; private: std::string _name; int _age; }; and a class Student like this #pragma once #include <string> class Person; class Student { public: Student(std::string name, int age, int level = 0); Student(const Person& person); std::string GetName(void) const; int GetAge(void) const; int GetLevel(void) const; private: std::string _name; int _age; int _level; }; In Student.h, I have a forward declaration class Person; to use Person in my conversion constructor. Fine. But I have done #include <string> to avoid compilation error while using std::string in the code. How to use forward declaration here to avoid the compilation error? Is it possible? Thanks.

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  • Populating dropdownlist in asp.net mvc doesn't seem to work for me...

    - by Pandiya Chendur
    I use a dropdownlist in one of my create.aspx but it some how doesnt seem to work... public IEnumerable<Materials> FindAllMeasurements() { var mesurements = from mt in db.MeasurementTypes select new Materials() { Id= Convert.ToInt64(mt.Id), Mes_Name= mt.Name }; return mesurements; } and my controller, public ActionResult Create() { var mesurementTypes = consRepository.FindAllMeasurements().AsEnumerable(); ViewData["MeasurementType"] = new SelectList(mesurementTypes, "Id", "Mes_Name"); return View(); } and my create.aspx has this, <p> <label for="MeasurementTypeId">MeasurementType:</label> <%= Html.DropDownList("MeasurementType", ViewData["MeasurementType"])%> <%= Html.ValidationMessage("MeasurementTypeId", "*") %> </p> When i execute this i got these errors, System.Web.Mvc.HtmlHelper<CrMVC.Models.Material>' does not contain a definition for 'DropDownList' and the best extension method overload 'System.Web.Mvc.Html.SelectExtensions.DropDownList(System.Web.Mvc.HtmlHelper, string, System.Collections.Generic.IEnumerable<System.Web.Mvc.SelectListItem>)' has some invalid arguments 2.cannot convert from 'object' to 'System.Collections.Generic.IEnumerable<System.Web.Mvc.SelectListItem>

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  • Why am i getting same values of different JSON date values?

    - by Maxood
    I do not know the reason why am i getting same values of different JSON date values. Here is my code for parsing date values in JSON date format: package com.jsondate.parsing; import java.text.SimpleDateFormat; import java.util.Date; import android.app.Activity; import android.os.Bundle; import android.util.Log; import android.widget.TextView; public class JSONDateParsing extends Activity { /** Called when the activity is first created. */ String myString; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView tv = new TextView(this); //Date d = (new Date(1266029455L)); //Date d = (new Date(1266312467L)); Date d = (new Date(1266036226L)); //String s = d.getDate() + "-" + d.getMonth() + "-" + d.getYear() + d.getHours() + d.getMinutes() + d.getSeconds(); // SimpleDateFormat sdf=new SimpleDateFormat("yyyy MMM dd @ hh:mm aa"); //Toast.makeText(this, d.toString(), Toast.LENGTH_SHORT); Log.e("Value:", d.toString()); myString = d.toString(); String []words = myString.split(" "); for(int i = 0;i < words.length; i++) Log.e("Value:", words[i]); myString = words[2] + "-" + words[1] + "-" + words[5] + " " + words[3]; tv.setText(myString); setContentView(tv); } }

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  • Decoupling the view, presentation and ASP.NET Web Forms

    - by John Leidegren
    I have an ASP.NET Web Forms page which the presenter needs to populate with controls. This interaction is somewhat sensitive to the page-life cycle and I was wondering if there's a trick to it, that I don't know about. I wanna be practical about the whole thing but not compromise testability. Currently I have this: public interface ISomeContract { void InstantiateIn(System.Web.UI.Control container); } This contract has a dependency on System.Web.UI.Control and I need that to be able to do things with the ASP.NET Web Forms programming model. But neither the view nor the presenter may have knowledge about ASP.NET server controls. How do I get around this? How can I work with the ASP.NET Web Forms programming model in my concrete views without taking a System.Web.UI.Control dependency in my contract assemblies? To clarify things a bit, this type of interface is all about UI composition (using MEF). It's known through-out the framework but it's really only called from within the concrete view. The concrete view is still the only thing that knows about ASP.NET Web Forms. However those public methods that say InstantiateIn(System.Web.UI.Control) exists in my contract assemblies and that implies a dependency on ASP.NET Web Forms. I've been thinking about some double dispatch mechanism or even visitor pattern to try and work around this.

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  • Why does GCC need extra declarations in templates when VS does not?

    - by Kyle
    template<typename T> class Base { protected: Base() {} T& get() { return t; } T t; }; template<typename T> class Derived : public Base<T> { public: Base<T>::get; // Line A Base<T>::t; // Line B void foo() { t = 4; get(); } }; int main() { return 0; } If I comment out lines A and B, this code compiles fine under Visual Studio 2008. Yet when I compile under GCC 4.1 with lines A and B commented, I get these errors: In member function ‘void TemplateDerived::foo()’: error: ‘t’ was not declared in this scope error: there are no arguments to ‘get’ that depend on a template parameter, so a declaration of ‘get’ must be available Why would one compiler require lines A and B while the other doesn't? Is there a way to simplify this? In other words, if derived classes use 20 things from the base class, I have to put 20 lines of declarations for every class deriving from Base! Is there a way around this that doesn't require so many declarations?

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  • How to sort HashSet() function data in sequence?

    - by vincent low
    I am new to Java, the function I would like to perform is to load a series of data from a file, into my hashSet() function. the problem is, I able to enter all the data in sequence, but I can't retrieve it out in sequence base on the account name in the file. Can anyone help? below is my code: public Set retrieveHistory(){ Set dataGroup = new HashSet(); try{ File file = new File("C:\\Documents and Settings\\vincent\\My Documents\\NetBeansProjects\\vincenttesting\\src\\vincenttesting\\vincenthistory.txt"); BufferedReader br = new BufferedReader(new FileReader(file)); String data = br.readLine(); while(data != null){ System.out.println("This is all the record:"+data); Customer cust = new Customer(); //break the data based on the , String array[] = data.split(","); cust.setCustomerName(array[0]); cust.setpassword(array[1]); cust.setlocation(array[2]); cust.setday(array[3]); cust.setmonth(array[4]); cust.setyear(array[5]); cust.setAmount(Double.parseDouble(array[6])); cust.settransaction(Double.parseDouble(array[7])); dataGroup.add(cust); //then proced to read next customer. data = br.readLine(); } br.close(); }catch(Exception e){ System.out.println("error" +e); } return dataGroup; } public static void main(String[] args) { FileReadDataModel fr = new FileReadDataModel(); Set customerGroup = fr.retrieveHistory(); System.out.println(e); for(Object obj : customerGroup){ Customer cust = (Customer)obj; System.out.println("Cust name :" +cust.getCustomerName()); System.out.println("Cust amount :" +cust.getAmount()); }

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  • ASP.NET MVC 2 - How do I use DropDownListFor ?

    - by SLC
    I have a simple model / view with things like Username, Password etc. and use helpers fine to hook it up. I now have a field called "NumberOfChildren". I want to store a number in it (int) and I want it render a dropdown box containing "None", "1", "2" etc. My thoughts would be that the model would have a list or a method that returns a list, so I can specify the values such as NumberOfChildren_List that I put the data into, and then DropDownListFor pulls that list and renders it, matching the value to the value of the item in the dropdown. However after spending about 30 minutes on trying to figure out how on earth it works, I gave up and decided to ask here. Any ideas? Edit: Here's some code... <%: Html.DropDownListFor(m => m.NumberOfChildren, new SelectList(Model.NumberOfChildrenListValues))%> and in the model [Required] [DisplayName("How many children do you have?")] public string NumberOfChildren { get; set; } public IEnumerable<string> NumberOfChildrenListValues { get { List<string> list = new List<string>() { "None", "1", "2" }; return list; } set { } } I get an object not set to instance of object error though. Ideas?

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  • cakephp read and display from more than one related table

    - by z22
    I have 2 tables Users and Artists. User: id name password city_id state_id country_id Artist: id user_id description I wish to create add and edit form(single form acts as add and edit). But on click of edit link, I wish to fill in the form fields from user as well as artist table. How do i do that? Below is my controller code: public function artist_register() { $this->country_list(); if ($this->request->is('post')) { $this->request->data['User']['group_id'] = 2; if ($this->{$this->modelClass}->saveAll($this->request->data)) { $this->redirect(array('controller' => 'Users', 'action' => 'login')); } } $this->render('artist_update'); } public function artist_update($id) { $artist = $this->{$this->modelClass}->findByuser_id($id); $artist_id = $artist[$this->modelClass]['id']; if($this->request->is('get')) { $this->request->data = $this->{$this->modelClass}->read(null, $artist_id); $this->request->data = $this->{$this->modelClass}->User->read(null, $id); } else { if($this->{$this->modelClass}->save($this->request->data)) { $this->Session->setFlash('Your Profile has been updated'); $this->redirect(array('action' => 'index')); } } } The code doesnt work. how do i solve it?

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  • Stuck on Object scope in Java

    - by ivor
    Hello, I'm working my way through an exercise to understand Java, and basically I need to merge the functionality of two classes into one app. I'm stuck on one area though - the referencing of objects across classes. What I have done is set up a gui in one class (test1), and this has a textfield in ie. chatLine = new JTextField(); in another class(test2), I was planning on leaving all the functionality in there and referencing the various gui elements set up in test1 - like this test1.chatLine I understand this level of referencing, I tested this by setting up a test method in the test2 class public static void testpass() { test1.testfield.setText("hello"); } I'm trying to understand how to implement the more complex functionality in test2 class though, specifically this existing code; test1.chatLine.addActionListener(new ActionAdapter() { public void actionPerformed(ActionEvent e) { String s = Game.chatLine.getText(); if (!s.equals("")) { appendToChatBox("OUTGOING: " + s + "\n"); Game.chatLine.selectAll(); // Send the string sendString(s); } } }); This is the bit I'm stuck on, if I should be able to do this - as it's failing on the compile, can I add the actionadapter stuff to the gui element thats sat in test1, but do this from test2 - I'm wondering if I'm trying to do something that's not possible. Hope this makes sense, I'm pretty confused over this - I'm trying to understand how the scope and referencing works. Ideally what i'm trying to achieve is one class that has all the main stuff in, the gui etc, then all the related functionality in the other class, and target the first class's gui elements with the results etc. Any thoughts greatly appreciated.

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  • Using Reflection.Emit to emit a "using (x) { ... }" block?

    - by Lasse V. Karlsen
    I'm trying to use Reflection.Emit in C# to emit a using (x) { ... } block. At the point I am in code, I need to take the current top of the stack, which is an object that implements IDisposable, store this away in a local variable, implement a using block on that variable, and then inside it add some more code (I can deal with that last part.) Here's a sample C# piece of code I tried to compile and look at in Reflector: public void Test() { TestDisposable disposable = new TestDisposable(); using (disposable) { throw new Exception("Test"); } } This looks like this in Reflector: .method public hidebysig instance void Test() cil managed { .maxstack 2 .locals init ( [0] class LVK.Reflection.Tests.UsingConstructTests/TestDisposable disposable, [1] class LVK.Reflection.Tests.UsingConstructTests/TestDisposable CS$3$0000, [2] bool CS$4$0001) L_0000: nop L_0001: newobj instance void LVK.Reflection.Tests.UsingConstructTests/TestDisposable::.ctor() L_0006: stloc.0 L_0007: ldloc.0 L_0008: stloc.1 L_0009: nop L_000a: ldstr "Test" L_000f: newobj instance void [mscorlib]System.Exception::.ctor(string) L_0014: throw L_0015: ldloc.1 L_0016: ldnull L_0017: ceq L_0019: stloc.2 L_001a: ldloc.2 L_001b: brtrue.s L_0024 L_001d: ldloc.1 L_001e: callvirt instance void [mscorlib]System.IDisposable::Dispose() L_0023: nop L_0024: endfinally .try L_0009 to L_0015 finally handler L_0015 to L_0025 } I have no idea how to deal with that ".try ..." part at the end there when using Reflection.Emit. Can someone point me in the right direction?

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  • how to update div tag in javascript with data from model for onsubmit form asp.net mvc

    - by michael
    In my page i have a form tag which submits to server ,gets data and redirects to same page. problem is the the div tag which has the data from server is not getting updated. how to do that in javascript <% using (Html.BeginForm("Addfile", "uploadfile", FormMethod.Post, new { id = "uploadform", enctype = "multipart/form-data" })) { %> <input type="file" id="addedFile" name="addedFile" /><br /> <input type="submit" id="addfile" value="Addfile" /> <div id="MyGrid"> //data from the model(server side) filelist is not updating</div> what will be the form onsubmit javascript function to update the div tag with the data from the model. and my uploadfile controller get post methods are as [AcceptVerbs(HttpVerbs.Get)] public ActionResult Upload() { return View(); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult AddFile(HttpPostedFileBase addedFile) { static List<string> fileList = new List<string>(); string filename = Path.GetFileName(addedFile.FileName); file.SaveAs(@"D:\Upload\" + filename); fileList.Add(filename); return("Upload",fileList); } thanks, michaela

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  • How to avoid shell execution of a Process?

    - by adeel amin
    When I start a process like process = Runtime.getRuntime().exec("gnome-terminal");, it starts shell execution. I want to stop shell execution and want to redirect I/O from process, can anybody tell how I can do this? My code is: public void start_process() { try { process= Runtime.getRuntime().exec("gnome-terminal"); pw= new PrintWriter(process.getOutputStream(),true); br=new BufferedReader(new InputStreamReader(process.getInputStream())); err=new BufferedReader(new InputStreamReader(process.getErrorStream())); } catch (Exception ioe) { System.out.println("IO Exception-> " + ioe); } } public void execution_command() { if(check==2) { try { boolean flag=thread.isAlive(); if(flag==true) thread.stop(); Thread.sleep(30); thread = new MyReader(br,tbOutput,err,check); thread.start(); }catch(Exception ex){ JOptionPane.showMessageDialog(null, ex.getMessage()+"1"); } } else { try { Thread.sleep(30); thread = new MyReader(br,tbOutput,err,check); thread.start(); check=2; }catch(Exception ex){ JOptionPane.showMessageDialog(null, ex.getMessage()+"1"); } } } private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: command=tfCmd.getText().toString().trim(); pw.println(command); execution_command(); } When I enter some command in textfield and press execute button, nothing is displayed on my output textarea, how I can stop shell execution and redirect input and output?

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  • How do i change this method to get strings instead of ints

    - by David
    here is the original code: public static int getInt () { Scanner in = new Scanner (System.in) ; if (in.hasNextInt()) { int a = in.nextInt() ; return a ; } else { System.out.println ("try again:") ; return getInt () ; } } This checks and sees if the input it receives is an int. If it is then it returns the int, if not it tells you to try again and re-runs. This is what i tried to do to change it: public static String getIns () { Scanner in = new Scanner (System.in) ; if (in.hasNextString()) { String a = in.nextString() ; return a ; } else { System.out.println ("try again:") ; return getIns () ; } } This doesn't work though. I looked through the documentation for the scanner class and i think the problem is that there is no such method as in.hasNextString or in.nextString What methods from the scanner class can i use to do what i intend these to do?

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  • Delete ONE SPECIFIC table of a database - leave the rest intact

    - by Jayomat
    Hi, I have a database where I store two different kinds of data. One table is for favorite routes, the other stores the retrieved routes from a server. I can retrieve the routes etc just fine. But after retrieving the first Route, pressing back or HOME, and then retrieving another route, the routes table is filled with all the old routes plus the new ones. So my question: how do I delete ONLY the routes table and not the whole database because I don't want to delete the added favorites....?! I found the following function in the android docs: public int delete (String table, String whereClause, String[] whereArgs) and I tried to implement it, but I must pass a SQLiteDataBase as an argument. But how? I implemented: public void deleteTableRoutes(SQLiteDataBase db){ db.delete("routes", null, null); } But I want to call this function from a different class where I have no reference to the database.. so what do I have to pass as an argument? Or how do I get a reference to my database? I build my database upon the code example of the NotePadExample from the dev docs. How to solve this problem? thanks

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  • How to fix IllegalStateException error when trying to update a listview?

    - by Michael Vetrano
    Hi guys, I am trying to get this code to run, but I get an IllegalStateException when I run this code saying that the content of the listview wasn't notified, yet I have a notification upon updating the data. This is a custom listview adapter. Here is the relevant part of my code: class LoadingThread extends Thread { public void run() { int itemsOriginallyLoaded = 0; synchronized( items ) { itemsOriginallyLoaded = items.size(); } for( int i = itemsOriginallyLoaded ; i < itemsToLoad ; ++i ) { Log.d( LOG_TAG, "Loading item #"+i ); //String item = "FAIL"; //try { String item = "FAIL"; try { item = stockGrabber.getStockString(dataSource.get(i)); } catch (ApiException e) { Log.e(LOG_TAG, "Problem making API request", e); } catch (ParseException e) { Log.e(LOG_TAG, "Problem parsing API request", e); } //} catch (ApiException e) { // Log.e(TAG, "Problem making API request", e); //} catch (ParseException e) { // Log.e(TAG, "Problem parsing API request", e); //} synchronized( items ) { items.add( item ); } itemsLoaded = i+1; uiHandler.post( updateTask ); Log.d( LOG_TAG, "Published item #"+i ); } if( itemsLoaded >= ( dataSource.size() - 1 ) ) allItemsLoaded = true; synchronized( loading ) { loading = Boolean.FALSE; } } } class UIUpdateTask implements Runnable { public void run() { Log.d( LOG_TAG, "Publishing progress" ); notifyDataSetChanged(); } }

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  • Downloading a file from a PHP page in C#

    - by FoxyShadoww
    Okay, we have a PHP script that creates an download link from a file and we want to download that file via C#. This works fine with progress etc but when the PHP page gives an error the program downloads the error page and saves it as the requested file. Here is the code we have atm: PHP Code: <?php $path = 'upload/test.rar'; if (file_exists($path)) { $mm_type="application/octet-stream"; header("Pragma: public"); header("Expires: 0"); header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); header("Cache-Control: public"); header("Content-Description: File Transfer"); header("Content-Type: " . $mm_type); header("Content-Length: " .(string)(filesize($path)) ); header('Content-Disposition: attachment; filename="'.basename($path).'"'); header("Content-Transfer-Encoding: binary\n"); readfile($path); exit(); } else { print 'Sorry, we could not find requested download file.'; } ?> C# Code: private void btnDownload_Click(object sender, EventArgs e) { string url = "http://***.com/download.php"; WebClient client = new WebClient(); client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted); client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged); client.DownloadFileAsync(new Uri(url), @"c:\temp\test.rar"); } private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e) { progressBar.Value = e.ProgressPercentage; } void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e) { MessageBox.Show(print); }

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  • Passing Derived Class Instances as void* to Generic Callbacks in C++

    - by Matthew Iselin
    This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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  • Class initialization and synchronized class method

    - by nybon
    Hi there, In my application, there is a class like below: public class Client { public synchronized static print() { System.out.println("hello"); } static { doSomething(); // which will take some time to complete } } This class will be used in a multi thread environment, many threads may call the Client.print() method simultaneously. I wonder if there is any chance that thread-1 triggers the class initialization, and before the class initialization complete, thread-2 enters into print method and print out the "hello" string? I see this behavior in a production system (64 bit JVM + Windows 2008R2), however, I cannot reproduce this behavior with a simple program in any environments. In Java language spec, section 12.4.1 (http://java.sun.com/docs/books/jls/second_edition/html/execution.doc.html), it says: A class or interface type T will be initialized immediately before the first occurrence of any one of the following: T is a class and an instance of T is created. T is a class and a static method declared by T is invoked. A static field declared by T is assigned. A static field declared by T is used and the reference to the field is not a compile-time constant (§15.28). References to compile-time constants must be resolved at compile time to a copy of the compile-time constant value, so uses of such a field never cause initialization. According to this paragraph, the class initialization will take place before the invocation of the static method, however, it is not clear if the class initialization need to be completed before the invocation of the static method. JVM should mandate the completion of class initialization before entering its static method according to my intuition, and some of my experiment supports my guess. However, I did see the opposite behavior in another environment. Can someone shed me some light on this? Any help is appreciated, thanks.

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  • Flex fixed and variable height - can it be set in markup?

    - by Prutswonder
    I've got the following Flex application markup: <app:MyApplicationClass xmlns:app="*" width="100%" height="100%" layout="vertical" horizontalScrollPolicy="off" verticalScrollPolicy="off"> <mx:VBox id="idPageContainer" width="100%" height="100%" verticalGap="0" horizontalScrollPolicy="off" verticalScrollPolicy="off"> <mx:HBox id="idTopContainer" width="100%" height="28" horizontalGap="2"> (top menu stuff goes here) </mx:HBox> <mx:HBox id="idBottomContainer" width="100%" height="100%" verticalScrollPolicy="off" clipContent="false"> (page stuff goes here) </mx:HBox> </mx:VBox> </app:MyApplicationClass> When I run it, it displays top panel with a fixed height, and a bottom panel with variable height. I expect the bottom panel's height to contain the remaining height, but it somehow overflows off-page. The only way I found to fix this height issue (so far) is to programmatically set the height to be fixed instead of variable: <mx:HBox id="idBottomContainer" width="100%" height="700" verticalScrollPolicy="off" clipContent="false"> (page stuff goes here) </mx:HBox> And code-behind: package { import mx.containers.HBox; import mx.core.Application; import mx.events.ResizeEvent; // (...) public class MyApplicationClass extends Application { public var idBottomContainer:HBox; // (...) private function ON_CreationComplete (event:FlexEvent) : void { // (...) addEventListener(ResizeEvent.RESIZE, ON_Resize); } private function ON_Resize (event:Event) : void { idBottomContainer.height = this.height - idTopContainer.height; } } } But this solution is too "dirty" and I'm looking for a more elegant way. Does anyone know an alternative?

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  • Problem with relative file path

    - by Richard Knop
    So here is my program, which works ok: import java.io.FileReader; import java.io.BufferedReader; import java.io.IOException; import java.util.Scanner; import java.util.Locale; public class ScanSum { public static void main(String[] args) throws IOException { Scanner s = null; double sum = 0; try { s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); s.useLocale(Locale.US); while (s.hasNext()) { if (s.hasNextDouble()) { sum += s.nextDouble(); } else { s.next(); } } } finally { s.close(); } System.out.println(sum); } } As you can see, I am using absolute path to the file I am reading from: s = new Scanner(new BufferedReader(new FileReader("D:/java-projects/HelloWorld/bin/usnumbers.txt"))); The problem arises when I try to use the relative path: s = new Scanner(new BufferedReader(new FileReader("usnumbers.txt"))); I get an error: Exception in thread "main" java.lang.NullPointerException at ScanSum.main(ScanSum.java:24) The file usnumbers.txt is in the same directory as the ScanSum.class file: D:/java-projects/HelloWorld/bin/ScanSum.class D:/java-projects/HelloWorld/bin/usnumbers.txt How could I solve this?

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  • Convert SQL to LINQ in MVC3 with Ninject

    - by Jeff
    I'm using MVC3 and still learning LINQ. I'm having some trouble trying to convert a query to LINQ to Entities. I want to return an employee object. SELECT E.EmployeeID, E.FirstName, E.LastName, MAX(EO.EmployeeOperationDate) AS "Last Operation" FROM Employees E INNER JOIN EmployeeStatus ES ON E.EmployeeID = ES.EmployeeID INNER JOIN EmployeeOperations EO ON ES.EmployeeStatusID = EO.EmployeeStatusID INNER JOIN Teams T ON T.TeamID = ES.TeamID WHERE T.TeamName = 'MyTeam' GROUP BY E.EmployeeID, E.FirstName, E.LastName ORDER BY E.FirstName, E.LastName What I have is a few tables, but I need to get only the newest status based on the EmployeeOpertionDate. This seems to work fine in SQL. I'm also using Ninject and set my query to return Ienumerable. I played around with the group by option but it then returns IGroupable. Any guidance on converting and returning the property object type would be appreciated. Edit: I started writing this out in LINQ but I'm not sure how to properly return the correct type or cast this. public IQueryable<Employee> GetEmployeesByTeam(int teamID) { var q = from E in context.Employees join ES in context.EmployeeStatuses on E.EmployeeID equals ES.EmployeeID join EO in context.EmployeeOperations on ES.EmployeeStatusID equals EO.EmployeeStatusID join T in context.Teams on ES.TeamID equals T.TeamID where T.TeamName == "MyTeam" group E by E.EmployeeID into G select G; return q; } Edit2: This seems to work for me public IQueryable<Employee> GetEmployeesByTeam(int teamID) { var q = from E in context.Employees join ES in context.EmployeeStatuses on E.EmployeeID equals ES.EmployeeID join EO in context.EmployeeOperations.OrderByDescending(eo => eo.EmployeeOperationDate) on ES.EmployeeStatusID equals EO.EmployeeStatusID join T in context.Teams on ES.TeamID equals T.TeamID where T.TeamID == teamID group E by E.EmployeeID into G select G.FirstOrDefault(); return q; }

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  • non static method cannot be referenced from a static context.

    - by David
    First some code: import java.util.*; ... class TicTacToe { ... public static void main (String[]arg) { Random Random = new Random() ; toerunner () ; // this leads to a path of methods that eventualy gets us to the rest of the code } ... public void CompTurn (int type, boolean debug) { ... boolean done = true ; int a = 0 ; while (!done) { a = Random.nextInt(10) ; if (debug) { int i = 0 ; while (i<20) { System.out.print (a+", ") ; i++; }} if (possibles[a]==1) done = true ; } this.board[a] = 2 ; } ... } //to close the class Here is the error message: TicTacToe.java:85: non-static method nextInt(int) cannot be referenced from a static context a = Random.nextInt(10) ; ^ What exactly went wrong? What does that error message "non static method cannot be referenced from a static context" mean?

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