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  • Multi-threading concept and lock in c#

    - by Neeraj
    I read about lock, though not understood nothing at all. My question is why do we use a un-used object and lock that and how this makes something thread-safe or how this helps in multi-threading ? Isn't there other way to make thread-safe code. public class test { private object Lock { get; set; } ... lock (this.Lock) { ... } ... } Sorry is my question is very stupid, but i don't understand, although i've used it many times.

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  • VB6 debugging- doesn't go to error handling code.

    - by Can Ho
    Hi, I'm maintaining a vb6 project(ActiveX DLL). When debugging, the app run into the following function: Public Function HasValue(ByVal vValue) As Boolean On Error GoTo Err If IsMissing(vValue) Then HasValue = False ElseIf IsNull(vValue) Or Len(vValue) = 0 Then HasValue = False ElseIf isEmpty(vValue) Then HasValue = False Else HasValue = True End If Exit Function Err: If IsArray(vValue) Or IsObject(vValue) Then HasValue = True Else HasValue = False End If End Function and it stops at the line ElseIf IsNull(vValue) Or Len(vValue) = 0 Then vValue is a custom object, contains some properties(obviously, not null). Although I didn't put any break point there, the app stopped there and alerted error dialog saying that "Run-time error '438': Object doesn't support this property or method". We had error handling code but the app didn't run to error handling code. It just stopped at the line causing the error and I had to stop the application. Do you have any idea about that? Thank you very much.

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  • Browser not handling exception from AJAX panel, ASP.NET c#

    - by Grant
    Hi, i am having trouble catching errors in an AJAX panel. Even when i throw an exception in the c# code behind the front end completely ignores it. Here is the code i have setup, can anyone see why? I ideally want to show a js alert window on error. Code Behind: protected void btnX_Click(object sender, EventArgs e) { throw new ApplicationException("test"); } protected void ScriptManager_AsyncPostBackError(object sender, AsyncPostBackErrorEventArgs e) { ScriptManager.AsyncPostBackErrorMessage = e.Exception.Message; } Markup: <script type="text/javascript" language="javascript"> Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler); function EndRequestHandler(sender, e) { window.alert(e.get_error().name); } </script> <asp:ScriptManager ID="ScriptManager" runat="server" AllowCustomErrorsRedirect="true" OnAsyncPostBackError="ScriptManager_AsyncPostBackError" />

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  • Login screen using user custom control

    - by Mocco
    Hi, I have followed some advices I got here today and would need a bit more help now: I have an user control with login logic. In mainForm I am using this: private void Form1_Load(object sender, EventArgs e) { LoginScreen login = new MainMenu(); login.Parent = this; login.Dock = DockStyle.Fill; login.Show(); } But I guess it is not modal and thus does not stop the original Form application. Sure I would need the main Form to do not continue until the login form is closed (and login sucessfull). Would using an event correct? Let login object to raise an event that login was successfull and let the MainForm handle it - run the app?

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  • Java template classes using generator or similar?

    - by Hugh Perkins
    Is there some library or generator that I can use to generate multiple templated java classes from a single template? Obviously Java does have a generics implementation itself, but since it uses type-erasure, there are lots of situations where it is less than adequate. For example, if I want to make a self-growing array like this: class EasyArray { T[] backingarray; } (where T is a primitive type), then this isn't possible. This is true for anything which needs an array, for example high-performance templated matrix and vector classes. It should probably be possible to write a code generator which takes a templated class and generates multiple instantiations, for different types, eg for 'double' and 'float' and 'int' and 'String'. Is there something that already exists that does this? Edit: note that using an array of Object is not what I'm looking for, since it's no longer an array of primitives. An array of primitives is very fast, and uses only as much space a sizeof(primitive) * length-of-array. An array of object is an array of pointers/references, that points to Double objects, or similar, which could be scattered all over the place in memory, require garbage collection, allocation, and imply a double-indirection for access. Edit2: good god, voted down for asking for something that probably doesn't currently exist, but is technically possible and feasible? Does that mean that people looking for ways to improve things have already left the java community? Edit3: Here is code to show the difference in performance between primitive and boxed arrays: int N = 10*1000*1000; double[]primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } Object[] objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } tic(); primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } toc(); tic(); objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } toc(); Results: double[] array: 148 ms Double[] array: 4614 ms Not even close!

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  • to avoid page refresh during button click event in asp.net

    - by ush
    public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) // If page loads for first time { Session["update"] = Server.UrlEncode(System.DateTime.Now.ToString()); // Assign the Session["update"] with unique value //=============== Page load code ========================= //============== End of Page load code =================== } } protected void Button1_Click(object sender, EventArgs e) { if (Session["update"].ToString() == ViewState["update"].ToString()) // If page not Refreshed { //=============== On click event code ========================= Label1.Text = TextBox1.Text; //lblDisplayAddedName.Text = txtName.Text; //=============== End of On click event code ================== // After the event/ method, again update the session Session["update"] = Server.UrlEncode(System.DateTime.Now.ToString()); } else // If Page Refreshed { // Do nothing } } protected override void OnPreRender(EventArgs e) { ViewState["update"] = Session["update"]; } } this is not working for high resolution gradient background

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  • Does this simple cache class need thread synchronization?

    - by DayOne
    Does this simple cache class need thread synchronization ... if I remove the lock _syncLock statement will encounter any problems? I think i can remove the locks as the references should be updated correctly right? ... BUt i'm think whar happens if client code is iterating over the GetMyDataStructure method and it get replaced? Thanks! public sealed class Cache { private readonly object _syncLock = new object(); private IDictionary<int, MyDataStructure> _cache; public Cache() { Refresh(); } public void Refresh() { lock (_syncLock) { _cache = DAL.GetMyDataStructure(); } } public IDictionary<int, MyDataStructure> **GetMyDataStructure**() { lock (_syncLock) { return _cache; } } }

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  • Form graphics not set when form loads

    - by Jimmy
    My form has a group box which contains two overlapping rectangles. The form's other controls are two sets of four numeric up down controls to set the rectangles' colors. (nudF1,2,3 and 4 set the rectangle that's in front, and nudB1,2,3 and 4 set the rectangle that's behind.) Everything works fine, except that the rectangles do not display the colors set in the numeric up downs when the form first loads. The numeric up down controls' ChangeValue events all call the ShowColors() method. The form's Load event calls the csColorsForm_Load() method. Any suggestions? namespace csColors { public partial class csColorsForm : Form { public csColorsForm() { InitializeComponent(); } private void csColorsForm_Load(object sender, EventArgs e) { this.BackColor = System.Drawing.Color.DarkBlue; SetColors(sender, e); } private void SetColors(object sender, EventArgs e) { Control control = (Control)sender; String ctrlName = control.Name; Graphics objGraphics; Rectangle rect1, rect2; int colorBack, colorFore; objGraphics = this.grpColor.CreateGraphics(); // If calling control is not a forecolor control, paint backcolor rectangle if (ctrlName.Substring(0,4)!="nudF") { colorBack = int.Parse(SetColorsB("nudB"), NumberStyles.HexNumber); SolidBrush BrushB = new SolidBrush(Color.FromArgb(colorBack)); rect1 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushB, rect1); } // Always paint forecolor rectangle colorFore = int.Parse(SetColorsB("nudF"), NumberStyles.HexNumber); SolidBrush BrushF = new SolidBrush(Color.FromArgb(colorFore)); rect2 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushF, rect2); objGraphics.Dispose(); } private string SetColorsB(string nam) { string txt=""; for (int n = 1; n <= 4; ++n) { var ud = Controls[nam + n] as NumericUpDown; int hex = (int)ud.Value; txt += hex.ToString("X2"); } return txt; } private void btnClose_Click(object sender, EventArgs e) { this.Close(); } } }

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  • @Secured not working

    - by user3640507
    I am new to spring and trying to implement Role based authorization with the help of @Secured annotation. I have a method which is specifically for ADMIN and I have written @Secured ("ROLE_ADMIN") to secure it. @Secured ("ROLE_ADMIN") public void HelloUser(String name) { System.out.println("Hello ADMIN"); } Now when I call this method by creating a class object it gets called eventhough user dont have ADMIN authority But when I dont create an object and use @autowired annotation instead then it works i.e User is not allowed to access this method. In my security.xml as well as servlet.xml I have added <global-method-security secured-annotations="enabled" /> Can some one please tell me where I am going wrong or is this the natural behaviour in spring ?

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  • Not found in protocol

    - by Alex
    I've subclassed MKAnnotation so that i can assign objects to annotations and then assign this object to a view controller like so: - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control { PlaceDetailView *detailView = [[PlaceDetailView alloc] initWithStyle:UITableViewStyleGrouped]; detailView.place = [view.annotation place]; [self.navigationController pushViewController:detailView animated:YES]; [detailView release]; } This is working great but i'm having the following issues: If i try and access the place getter method like so view.annotation.place i recieve an error: Accessing unknown place getter method If i acces the place getter method like so [view.annotation place] i receive a warning: place not found in protocol From my understanding this is because the place object is not defined in the MKAnnotation protocol, although i'm aware of this i'm not sure how to tell the complier that place does exist and it's not calling it blind.

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  • How are value types implemented in .NET

    - by Michael
    Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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  • C# Web gridview sortin

    - by tommypiaa
    Any examples how would I enable sorting for the gridview? private void loadlist() { cn.Open(); cmd.CommandText = "select Breed, Name, Image from Animals"; dr = cmd.ExecuteReader(); cn.Close(); } protected void TextBox1_TextChanged(object sender, EventArgs e) { } protected void Button1_Click(object sender, EventArgs e) { AddData(); Addimage(); } protected void AddData() { if (TextBox1.Text != "" & TextBox2.Text != "") { cn.Open(); cmd.CommandText = "insert into Animals (Breed, Name) values ('" + TextBox1.Text + "', '" + TextBox2.Text + "')"; cmd.ExecuteNonQuery(); cmd.Clone(); cn.Close(); loadlist(); } } protected void DisplayData() { cn.Open(); cmd.CommandText = "select Breed, Name from Animals"; dr = cmd.ExecuteReader(); GridView1.DataSource = dr; GridView1.DataBind(); cn.Close(); }

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  • How do I check for Existence of a Record in GAE

    - by VDev
    I am trying to create a simple view in Django & GAE, which will check if the user has a profile entity and prints a different message for each case. I have the program below, but somehow GAE always seem to return a object. My program is below import datetime from django.http import HttpResponse, HttpResponseRedirect from google.appengine.api import users from google.appengine.ext import db from models import Profile import logging #from accounts.views import profile # Create your views here. def login_view(request): user = users.get_current_user() profile = db.GqlQuery("SELECT * FROM Profile WHERE account = :1", users.get_current_user()) logging.info(profile) logging.info(user) if profile: return HttpResponse("Congratulations Your profile is already created.") else: return HttpResponse("Sorry Your profile is NOT created.") My model object is Profile defined as follows: class Profile(db.Model): first_name = db.StringProperty() last_name = db.StringProperty() gender = db.StringProperty(choices=set(["Male", "Female"])) account = db.UserProperty(required = True) friends = db.ListProperty(item_type=users.User) last_login = db.DateTimeProperty(required=True) Thanks for the help.

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  • C# Event routing in code behind

    - by Nate
    I'm building a WPF MVVM-ish application. I want to be able to display an event log containing items in a collection that exists in my viewmodel. I want any of the objects in the model to be able to add data to the event log. Therefore every object needs to be able to pass data back to one central collection for databinding in the view. I could implement an event in every one of my data classes and manually pass the events up the object heirarchy but this seems super clumsy. On the visual tree a Routed Event would take care of this, is there some equivelent in the model scope? Any other ideas?

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  • problem-configure-jboss-to-work-with-jndi(3)

    - by Spiderman
    Sorry for opening new thread every time for the same problem. It's just that I'd like to refine my question during my investigation and it's hard to do it in stackoverflow structure on the same question (maybe on purpose). Anyway, in continuation to this thread http://stackoverflow.com/questions/2843218/problem-configure-jboss-to-work-with-jndi2 I discovered that when running an application that is deployed on my JBoss 4.2.3.GA, when I perform: Context initialContext = new InitialContext(); Object dataSource = initialContext.lookup("java:/DefaultDS"); I get null as a return value even though DefaultDS is the default datasource that comes with Jboss installation. and generally, how come initialContext return null value? if the datasource is not found it should throw NamingException and in other case it should return real object. What can I do with null? isn't it a bad error handling of javax.naming.InitialContext ???

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  • Python: Using `copyreg` to define reducers for types that already have reducers

    - by cool-RR
    (Keep in mind I'm working in Python 3, so a solution needs to work in Python 3.) I would like to use the copyreg module to teach Python how to pickle functions. When I tried to do it, the _Pickler object would still try to pickle functions using the save_global function. (Which doesn't work for unbound methods, and that's the motivation for doing this.) It seems like _Pickler first tries to look in its own dispatch for the type of the object that you want to pickle before looking in copyreg.dispatch_table. I'm not sure if this is intentional. Is there any way for me to tell Python to pickle functions with the reducer that I provide?

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  • afterTransactionCompletion not working

    - by Attilah
    I created an hibernate interceptor : public class MyInterceptor extends EmptyInterceptor { private boolean isCanal=false; public boolean onSave(Object entity, Serializable arg1, Object[] arg2, String[] arg3, Type[] arg4) throws CallbackException { for(int i=0;i<100;i++){ System.out.println("Inside MyInterceptor(onSave) : "+entity.toString()); } if(entity instanceof Canal){ isCanal=true; } return false; } public void afterTransactionCompletion(Transaction tx){ if(tx.wasCommitted()&&(isCanal)){ for(int i=0;i<100;i++){ System.out.println("Inside MyInterceptor(afterTransactionCompletion) : Canal was saved to DB."); } } } but the method afterTransactionCompletion doesn't get executed after a transaction is commited. I've tried all the ways I know of but I can't make it work. What's more surprising is that the onSave method works fine. Help ! Could this be due to this bug ? : http://opensource.atlassian.com/projects/hibernate/browse/HHH-1956 How can I circumvent this bug if it's the cause ?

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  • Is there an difference between transient properties defined in the data model, or in the custom subc

    - by mystify
    I was reading that setting the value of a transient property always results in marking the managed object as "dirty". However, what I don't get is this: If I make a subclass of NSManagedObject and use some extra properties which I don't need to be persistet, how does Core Data know about them and how can it mark the object as dirty when I access these? Again, they're not defined in the data model, so Core Data has no really good hint that they are there. Or does Core Data use some kind of introspection to analyze my custom class and figure out what properties I have in there?

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  • Is it possible to start an activity from a regular java class?

    - by Yotam
    In my ActionBarSherlock I have the same menu items for all activities, so it seems unwise to define onClick handlers in each activity - they all do the same. Instead I created a class called MyClickListener that implements com.actionbarsherlock.view.MenuItem.OnMenuItemClickListener, and in there I have a simple switch block that starts the appropriate activity. Problem is that Intent constructor's first argument is of type Context, and even when I pass this to MyClickListener's constructor, I can't start any activity. The same goes for every method that has a Context object as a parameter. Is there a way to work around it? What is a context object? Thanks

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  • ActionScript display zero value

    - by bwong
    It seems the number Datatype handles zeros and nulls the same. I need to display a zero value on the screen, but AS displays nothing. When it's saved, the value is saved as a zero, and therefore shows up zero on the screen. Is there a way to display the zero value using a new object? public class myObject{ private var numVar:Number } My AS file: var temp:MyObject temp.numVar = 0; When I debug, temp.numVar contains a value of 0, but does not show anything on the UI. If this object is then saved to the DB, and then displayed to the UI, it shows a 0. My question is - how do I get temp.numVar to display 0 before persistenting it to the DB?

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  • Confusion using MYSQLI

    - by user1020069
    I just started using mysqli API for PHP. Apparently, every time an object of the class MYSQLI is instantiated, it can setup a connection to the database as it connects to the server unlike mysql_connect, which connects to the server first and then you are required to specify the database to query. Now this is a good problem if the db exists, in my case, the db does not exist on the first ever connection to the server/execution of the problem, hence I must connect without specifying the database, which is fine, since the msyqli constructor does not make this database mandatory. My challenge is essentially, how do I check if the database exists before attempting the first connection. The only way to really do this would be to establish a conection to the server and then use the result of the following query to gauge if the database exists: SELECT COUNT(*) AS `exists` FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMATA.SCHEMA_NAME="dbname" ; If this returns true, then the database exists, but now the challenge is how do I get the mysqli object to query this database rather than having to prefix the name of the database in the query. Thanks much

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  • C# Asynchronous Sockets questions.

    - by ccppjava
    Based on my reading and testing, with asynchronous sockets, the socket itself can be passed using state object (IAsyncResult result), also if store the socket as a private field, it would be captured by the callback methods. I am wondering how the IAysnResult is kepted between the BeginXXX and ReceiveXXX? It looks to me that after the BeginXXX call and the method ends, the state object would be disposed by GC if there is no reference to it. In the case of private field, how the private field is shared between threads? (As far as I know, a callback is executed using a thread from the default thread pool, which would be considered as a new thread.) Many thanks, hope the questions themselves are clear.

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  • Lifetime of implicitly casted temporaries

    - by Answeror
    I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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