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• What is an "incompletely constructed object"?

  - by Joonas Pulakka

  Goetz's Java Concurrency in Practice, page 41, mentions how this reference can escape during construction. A "don't do this" example: public class ThisEscape { public ThisEscape(EventSource source) { source.registerListener( new EventListener() { public void onEvent(Event e) { doSomething(e); } }); } } Here this is "escaping" via the fact that doSomething(e) refers to the enclosing ThisEscape instance. The book states: Publishing an object from within its constructor can publish an incompletely constructed object. This is true even if the publication is the last statement in the constructor. If the this reference escapes during construction, the object is considered not properly constructed. I don't quite get this. If the publication is the last statement in the constructor, hasn't all the constructing work been done before that? How come is this not valid by then? Apparently there's some voodoo going on after that, but what?

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• Scheduling Swingworker threads

  - by Simonw

  Hi, I have a 2 processes to perform in my swing application, one to fill a list, and one to do operations on each element on the list. I've just moved the 2 processes into Swingworker threads to stop the GUI locking up while the tasks are performed, and because I will need to do this set of operations to several lists, so concurrency wouldn't be a bad idea in the first place. However, when I just ran fillList.execute();doStuffToList.execute(); the doStuffToList thread to ran on the empty list (duh...). How do I tell the second process to wait until the first one is done? I suppose I could just nest the second process at the end of the first one, but i dunno, it seems like bad practice.

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• ActiveX control loading but not activating correctly (only when using in Reg Free COM)

  - by embnut

  I have an ActiveX control (created using C#) that I am adding to a form in Visual FoxPro using late binding. It works without problems when I register the control. I want to use reg free COM and created necessary manifest files. Now it load and displays in an inactive state until I double click or programatically activate it. I don't think it has anything to do with the reg free com manifest files. However is there something I need to do to set it up before/after making the late binding call AddObject()? this.AddObject('OleControl1', 'oleControl', 'SomeCompany.SomeOleControl') When I check the OleTypeAllowed Property of the OleControl created by AddObject() it is 1 (Embedded OLE object) instead of -2 (ActiveX object). So the OleControl got instantiated to the wrong type. I also tried the following: DEFINE(d) a subclass of OleControl and set the property OleTypeAllowed = -2. Used late binding to load the control. It did not work as required. The OleTypeAllowed came back as 1 Registered the ActiveX control. Added the ActiveX control to the project as a subclass using the visual editor. Unregistered the control. Used late binding to load the control. It did not work as required. The OleTypeAllowed came back as 1. Is it possible to load the OleControl as a ActiveX control? Any input from VB that I can convert to FoxPro would also be appreciated.

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• Parent Control Mouse Enter/Leave Events With Child Controls

  - by Paul Williams

  I have a C# .NET 2.0 WinForms app. My app has a control that is a container for two child controls: a label, and some kind of edit control. You can think of it like this, where the outer box is the parent control: +---------------------------------+ | [Label Control] [Edit Control] | +---------------------------------+ I am trying to do something when the mouse enters or leaves the parent control, but I don't care if the mouse moves into one of its children. I want a single flag to represent "the mouse is somewhere inside the parent or children" and "the mouse has moved outside of the parent control bounds". I've tried handling MouseEnter and MouseLeave on the parent and both child controls, but this means the action begins and ends multiple times as the mouse moves across the control. In other words, I get this: Parent.OnMouseEnter (start doing something) Parent.OnMouseLeave (stop) Child.OnMouseEnter (start doing something) Child.OnMouseLeave (stop) Parent.OnMouseEnter (start doing something) Parent.OnMouseLeave (stop) The intermediate OnMouseLeave events cause some undesired effects as whatever I'm doing gets started and then stopped. I want to avoid that. I don't want to capture the mouse as the parent gets the mouse over, because the child controls need their mouse events, and I want menu and other shortcut keys to work. Is there a way to do this inside the .NET framework? Or do I need to use a Windows mouse hook?

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• Is it safe to lock a static variable in a non-static class?

  - by Dario Solera

  I've got a class that manages a shared resource. Now, since access to the resource depends on many parameters, this class is instantiated and disposed several times during the normal execution of the program. The shared resource does not support concurrency, so some kind of locking is needed. The first thing that came into my mind is having a static instance in the class, and acquire locks on it, like this: // This thing is static! static readonly object MyLock = new object(); // This thing is NOT static! MyResource _resource = ...; public DoSomeWork() { lock(MyLock) { _resource.Access(); } } Does that make sense, or would you use another approach?

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• Can I get the stack traces of all threads in my c# app?

  - by Drew Shafer

  I'm debugging an apparent concurrency issue in a largish app that I hack on at work. The bug in question only manifests on certain lower-performance machines after running for many (12+) hours, and I have never reproduced it in the debugger. Because of this, my debugging tools are basically limited to analyzing log files. C# makes it easy to get the stack trace of the thread throwing the exception, but I'd like to additionally get the stack traces of every other thread currently executing in my AppDomain at the time the exception was thrown. Is this possible?

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• Can Ruby Fibers be Concurrent?

  - by Jesse J

  I'm trying to get some speed up in my program and I've been told that Ruby Fibers are faster than threads and can take advantage of multiple cores. I've looked around, but I just can't find how to actually run different fibers concurrently. With threads you can dO this: threads = [] threads << Thread.new {Do something} threads << Thread.new {Do something} threads.each {|thread| thread.join} I can't see how to do something like this with fibers. All I can find is yield and resume which seems like just a bunch of starting and stopping between the fibers. Is there a way to do true concurrency with fibers?

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• Recommendations for an in memory database vs thread safe data structures

  - by yx

  TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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• ASP.Net Architecture Specific to Shared/Static functions

  - by Maxim Gershkovich

  Hello All, Could someone please advise in the context of a ASP.Net application is a shared/static function common to all users? If for example you have a function Public shared function GetStockByID(StockID as Guid) as Stock Is that function common to all current users of your application? Or is the shared function only specific to the current user and shared in the context of ONLY that current user? So more specifically my question is this, besides database concurrency issues such as table locking do I need to concern myself with threading issues in shared functions in an ASP.Net application? In my head; let’s say my application namespace is MyTestApplicationNamespace. Everytime a new user connects to my site a new instance of the MyTestApplicationNamespace is created and therefore all shared functions are common to that instance and user but NOT common across multiple users. Is this correct?

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• Your thoughts on Best Practices for Scientific Computing?

  - by John Smith

  A recent paper by Wilson et al (2014) pointed out 24 Best Practices for scientific programming. It's worth to have a look. I would like to hear opinions about these points from experienced programmers in scientific data analysis. Do you think these advices are helpful and practical? Or are they good only in an ideal world? Wilson G, Aruliah DA, Brown CT, Chue Hong NP, Davis M, Guy RT, Haddock SHD, Huff KD, Mitchell IM, Plumbley MD, Waugh B, White EP, Wilson P (2014) Best Practices for Scientific Computing. PLoS Biol 12:e1001745. http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001745 Box 1. Summary of Best Practices Write programs for people, not computers. (a) A program should not require its readers to hold more than a handful of facts in memory at once. (b) Make names consistent, distinctive, and meaningful. (c) Make code style and formatting consistent. Let the computer do the work. (a) Make the computer repeat tasks. (b) Save recent commands in a file for re-use. (c) Use a build tool to automate workflows. Make incremental changes. (a) Work in small steps with frequent feedback and course correction. (b) Use a version control system. (c) Put everything that has been created manually in version control. Don’t repeat yourself (or others). (a) Every piece of data must have a single authoritative representation in the system. (b) Modularize code rather than copying and pasting. (c) Re-use code instead of rewriting it. Plan for mistakes. (a) Add assertions to programs to check their operation. (b) Use an off-the-shelf unit testing library. (c) Turn bugs into test cases. (d) Use a symbolic debugger. Optimize software only after it works correctly. (a) Use a profiler to identify bottlenecks. (b) Write code in the highest-level language possible. Document design and purpose, not mechanics. (a) Document interfaces and reasons, not implementations. (b) Refactor code in preference to explaining how it works. (c) Embed the documentation for a piece of software in that software. Collaborate. (a) Use pre-merge code reviews. (b) Use pair programming when bringing someone new up to speed and when tackling particularly tricky problems. (c) Use an issue tracking tool. I'm relatively new to serious programming for scientific data analysis. When I tried to write code for pilot analyses of some of my data last year, I encountered tremendous amount of bugs both in my code and data. Bugs and errors had been around me all the time, but this time it was somewhat overwhelming. I managed to crunch the numbers at last, but I thought I couldn't put up with this mess any longer. Some actions must be taken. Without a sophisticated guide like the article above, I started to adopt "defensive style" of programming since then. A book titled "The Art of Readable Code" helped me a lot. I deployed meticulous input validations or assertions for every function, renamed a lot of variables and functions for better readability, and extracted many subroutines as reusable functions. Recently, I introduced Git and SourceTree for version control. At the moment, because my co-workers are much more reluctant about these issues, the collaboration practices (8a,b,c) have not been introduced. Actually, as the authors admitted, because all of these practices take some amount of time and effort to introduce, it may be generally hard to persuade your reluctant collaborators to comply them. I think I'm asking your opinions because I still suffer from many bugs despite all my effort on many of these practices. Bug fix may be, or should be, faster than before, but I couldn't really measure the improvement. Moreover, much of my time has been invested on defence, meaning that I haven't actually done much data analysis (offence) these days. Where is the point I should stop at in terms of productivity? I've already deployed: 1a,b,c, 2a, 3a,b,c, 4b,c, 5a,d, 6a,b, 7a,7b I'm about to have a go at: 5b,c Not yet: 2b,c, 4a, 7c, 8a,b,c (I could not really see the advantage of using GNU make (2c) for my purpose. Could anyone tell me how it helps my work with MATLAB?)

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• EF4 Code First Control Unicode and Decimal Precision, Scale with Attributes

  - by Dane Morgridge

  There are several attributes available when using code first with the Entity Framework 4 CTP5 Code First option.  When working with strings you can use [MaxLength(length)] to control the length and [Required] will work on all properties.  But there are a few things missing. By default all string will be created using unicode so you will get nvarchar instead of varchar.  You can change this using the fluent API or you can create an attribute to make the change.  If you have a lot of properties, the attribute will be much easier and require less code. You will need to add two classes to your project to create the attribute itself: 1: public class UnicodeAttribute : Attribute 2: { 3: bool _isUnicode; 4:  5: public UnicodeAttribute(bool isUnicode) 6: { 7: _isUnicode = isUnicode; 8: } 9:  10: public bool IsUnicode { get { return _isUnicode; } } 11: } 12:  13: public class UnicodeAttributeConvention : AttributeConfigurationConvention<PropertyInfo, StringPropertyConfiguration, UnicodeAttribute> 14: { 15: public override void Apply(PropertyInfo memberInfo, StringPropertyConfiguration configuration, UnicodeAttribute attribute) 16: { 17: configuration.IsUnicode = attribute.IsUnicode; 18: } 19: } The UnicodeAttribue class gives you a [Unicode] attribute that you can use on your properties and the UnicodeAttributeConvention will tell EF how to handle the attribute. You will need to add a line to the OnModelCreating method inside your context for EF to recognize the attribute: 1: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) 2: { 3: modelBuilder.Conventions.Add(new UnicodeAttributeConvention()); 4: base.OnModelCreating(modelBuilder); 5: } Once you have this done, you can use the attribute in your classes to make sure that you get database types of varchar instead of nvarchar: 1: [Unicode(false)] 2: public string Name { get; set; }   Another option that is missing is the ability to set the precision and scale on a decimal.  By default decimals get created as (18,0).  If you need decimals to be something like (9,2) then you can once again use the fluent API or create a custom attribute.  As with the unicode attribute, you will need to add two classes to your project: 1: public class DecimalPrecisionAttribute : Attribute 2: { 3: int _precision; 4: private int _scale; 5:  6: public DecimalPrecisionAttribute(int precision, int scale) 7: { 8: _precision = precision; 9: _scale = scale; 10: } 11:  12: public int Precision { get { return _precision; } } 13: public int Scale { get { return _scale; } } 14: } 15:  16: public class DecimalPrecisionAttributeConvention : AttributeConfigurationConvention<PropertyInfo, DecimalPropertyConfiguration, DecimalPrecisionAttribute> 17: { 18: public override void Apply(PropertyInfo memberInfo, DecimalPropertyConfiguration configuration, DecimalPrecisionAttribute attribute) 19: { 20: configuration.Precision = Convert.ToByte(attribute.Precision); 21: configuration.Scale = Convert.ToByte(attribute.Scale); 22:  23: } 24: } Add your line to the OnModelCreating: 1: protected override void OnModelCreating(System.Data.Entity.ModelConfiguration.ModelBuilder modelBuilder) 2: { 3: modelBuilder.Conventions.Add(new UnicodeAttributeConvention()); 4: modelBuilder.Conventions.Add(new DecimalPrecisionAttributeConvention()); 5: base.OnModelCreating(modelBuilder); 6: } Now you can use the following on your properties: 1: [DecimalPrecision(9,2)] 2: public decimal Cost { get; set; } Both these options use the same concepts so if there are other attributes that you want to use, you can create them quite simply.  The key to it all is the PropertyConfiguration classes.   If there is a class for the datatype, then you should be able to write an attribute to set almost everything you need.  You could also create a single attribute to encapsulate all of the possible string combinations instead of having multiple attributes on each property. All in all, I am loving code first and having attributes to control database generation instead of using the fluent API is huge and saves me a great deal of time.

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• WPF add c# code to customcontrol

  - by 0xDEAD BEEF

  I want to create simple custom control (derived from control and with look defined in generics.xaml). I need to change size of elements defined in generic.xaml, when control is resized! It would be great to write some of that generic.xaml part in C#. Is that possible? Or is there a way to create MVVM like custom control? What i am willing to create is simple blinking led control (on,blinking, off).

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• Dual Control / Four Eyes Principle

  - by Ralf

  I have the requirement to implement some kind of Dual Control or Four-Eyes-Principle, meaning that every change of an object done by user A has to be checked by user B. A trivial example would be a publishing system where an author writes an article and another has to proofread it before it is published. I am a little bit surprised that you find nearly nothing about it on the net. No patterns, no libraries (besides cibet), no workflow solutions etc. Is this requirement really so uncommon? Or am I searching for the wrong terms? I am not looking for a specific solution. More for a pattern or best practice approach.

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• T-4 Templates for ASP.NET Web Form Databound Control Friendly Logical Layers

  - by Mohammad Ashraful Alam

  I just released an open source project at codeplex, which includes a set of T-4 templates that will enable you to build ASP.NET Web Form Data Bound controls friendly testable logical layer based on Entity Framework 4.0 with just few clicks! In this open source project you will get Entity Framework 4.0 based T-4 templates for following types of logical layers: Data Access Layer: Entity Framework 4.0 provides excellent ORM data access layer. It also includes support for T-4 templates, as built-in code generation strategy in Visual Studio 2010, where we can customize default structure of data access layer based on Entity Framework. default structure of data access layer has been enhanced to get support for mock testing in Entity Framework 4.0 object model. Business Logic Layer: ASP.NET web form based data bound control friendly business logic layer, which will enable you few clicks to build data bound web applications on top of ASP.NET Web Form and Entity Framework 4.0 quickly with great support of mock testing. Download it to make your web development productive. Enjoy!

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• Location, Orientation, and Writing a Custom Control with Mono for Android, .NET, and C#

  - by Wallym

  Like real estate, mobile is about location, location, location. That means that direction is an important item. And just as important is how this information is presented to the user. In Nov. 2011, we talked about building a user interface in Mono For Android. In this article, I'll expand a little bit on that by creating a compass that displays north. We'll use Android's built-in sensor support to determine the orientation of the device, then use a custom control to display North. The output will look like

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• Oracle Database 11g Helps Control Exponential Data Growth

  - by [email protected]

  The 2010 ESG annual customer survey is now available. As part of it, ESG interviewed 300 customers about their IT priorities and, unsurprisingly, "Manage Data Growth" is top of the list. Perhaps less self-evident is the proposed solution to target this prime concern: "Often overlooked because it is a database platform, Oracle Database 11g offers additional capabilities such as automatic storage management (ASM), advanced data compression, and data protection that make managing data growth much easier for organizations of any size." The paper goes on to discuss these capabilities and highlights their potential benefits. Oracle Database 11g Helps Control Exponential Database Growth - a worthwhile read for anyone having to deal with rapidly increasing amounts of data. Download your free copy here.

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• Hack Your Lights for Remote Control

  - by Jason Fitzpatrick

  This clever hack combines a modified wall switch with unused buttons on a universal remote to create one-touch wireless control of the lighting in a media room. Andrew, the tinker behind this home theater hack, writes: I really liked the idea of controlling my “Home Theater” lights with a remote (TV or other), this would save me the exhausting task of heaving myself off the couch to turn the lights on or off. I found one of my remotes has a spare power button, its one of those stupid “universal” remotes that comes with DVD players or TVs but only work if you have all the same brand equipment, I don’t so this made a good option for a light switch. Hit up the link below to check out more photos of his project and download the source code. Why Does 64-Bit Windows Need a Separate “Program Files (x86)” Folder? Why Your Android Phone Isn’t Getting Operating System Updates and What You Can Do About It How To Delete, Move, or Rename Locked Files in Windows

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• How to control CPU frequency

  - by Tim

  I am using CPU Frequency Scaling Monitor 2.30.0 on the panel to show and control CPU frequency. My CPU frequency by default will change according to load. But I want to make CPU work at the lowest level and so I choose 800 MHz in CPU Frequency Scaling Monitor. After a few seconds, however, it automatically changes back to Powersave or Performance mode which has automatic adjustment to CPU frequency. I was wondering how to actually make CPU work at the lowest level? Thanks!

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• Cannot control the fan on a Sony Vaio laptop

  - by Xobb

  I've got Sony Vaio laptop and my fan is on all the time, though the temperature on the video-adapter is always over 60°?. As I've googled, vaiofand does not support VPC-EA series. Is there anything I can do with that or I need another laptop? I'm using the following graphics card: 01:00.0 VGA compatible controller: ATI Technologies Inc Manhattan [Mobility Radeon HD 5000 Series] though the problem is not with the graphics card. I've mentioned its temperature as the highest (64°C now btw). Seems like the notebook is always overheated and I cannot control the fan speed to make it cooler. And yes, I'm using the proprietary driver ATI/AMD FGLRX graphics driver. I'm using Kubuntu 11.04.

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• Remote Control Holder Mod Stores Tablet Close At Hand

  - by Jason Fitzpatrick

  If you spend most of your iPad time lounging on your couch or in bed, this simple IKEA hack will keep your favorite tablet stowed right at your finger tips. IKEA’s inexpensive remote control holder, the $4.99 Flort, is easy to hack from a remote holster into an tablet holder. You simply flip it around, sew up the edge of the back flap, and holster your tablet in it–your tablet fits all the way inside, in the above image the iPad is tucked in semi-precariously to demonstrate it sliding inside. Hit up the link below for step-by-step pictures. Smartest Way to Store Your iPad for $4.99 [IKEAHackers] HTG Explains: When Do You Need to Update Your Drivers? How to Make the Kindle Fire Silk Browser *Actually* Fast! Amazon’s New Kindle Fire Tablet: the How-To Geek Review

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• How to create dynamically LinkButton with Literal Control in ASP.NET

  - by SAMIR BHOGAYTA

  Step 1 : First take following control into the .aspx page. asp:UpdatePanel id="up1" runat="server" contenttemplate asp:Literal ID="lt1" Text="" runat="server" asp:PlaceHolder ID="ph1" runat="server" /asp:PlaceHolder /contenttemplate /asp:UpdatePanel Step 2 : string query = query for fill the dataset; DataSet ds = new DataSet(); ds = pass the query to retrive data; int i = 0; LinkButton lt = new LinkButton(); for (i = 0; i { lt = new LinkButton(); lt.ID = "link" + i.ToString(); lt.Text = ds.Tables[0].Rows[i].ItemArray[1].ToString(); ph1.Controls.Add(lt); ph1.Controls.Add(new LiteralControl(" ")); }

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• complex access control system

  - by Atul Gupta

  I want to build a complex access control system just like Facebook. How should I design my database so that: A user may select which streams to see (via liking a page) and may further select to see all or only important streams. Also he get to see posts of a friend, but if a friend changes visibility he may or may not see it. A user may be an owner or member of a group and accordingly he have access. So for a user there is so many access related information and also for each data point. I use Perl/MySQL/Apache. Any help will be appreciated.

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• AI control for a ship with physics model

  - by Petteri Hietavirta

  I am looking for ideas how to implement following in 2D space. Unfortunately I don't know much about AI/path finding/autonomous control yet. Let's say this ship can move freely but it has mass and momentum. Also, external forces might affect it (explosions etc). The player can set a target for the ship at any time and it should reach that spot and stop. Without physics this would be simple, just point to the direction and go. But how to deal with existing momentum and then stopping on the spot? I don't want to modify ship's placement directly. edit: Just to make clear, the physics related math of the ship itself is not the problem.

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• Generate ASP.NET + AJAX with Ajax Control Toolkit

  Code OnTime LLC announces immediate availability of the free code generator project Web Site Builder for our free ASP.NET code generator. The new code generation project delivers premium functionality at no charge in the hands of ASP.NET developers.   The ASP.NET web applications generated with Web Site Builder are using Microsoft ASP.NET Ajax Extensions and Ajax Control Toolkit. Now you can create stunning applications straight from your database with adaptive filtering, fast sorting...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Cloud Control 12c: Verteilen von beliebiger Software mit Deployment Prozeduren

  - by Ralf Durben (DBA Community)

  Mit dem Lifecycle Management Pack von Oracle Enterprise Manager Cloud Control 12c können Sie Software aus der grafischen Konsole heraus auf Zielsysteme verteilen und installieren, also provisionieren. Dieses funktioniert für viele Oracle Produkte in einer vorgefertigen Form unter Verwendung von Deployment Prozeduren, die als eine Art Spezialformat für Provisionierungsskripte angesehen werden können. Dabei können die vorgefertigten Deployment Prozeduren direkt oder für die eigenen Bedürfnisse modifiziert verwendet werden. Sie können diese Technik jedoch auch für die Provisionierung beliebiger Software nutzen, indem Sie eigene Deployment Prozeduren erstellen. Als einfaches Beispiel einer solchen Provisionierung soll in diesem Tipp das Verteilen einer ZIP-Datei mit anschliessendem Auspacken betrachtet werden. Bewusst wird in diesem Tipp versucht, das Beispiel einfach zu halten, um einen leichten Einstieg zu ermöglichen. Dieser Tipp zeigt Ihnen, wie Sie eine ZIP-Datei mit einer selbstgeschriebenen Deployment Prozedur provisionieren können.

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