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• Default values - are they good or evil?

  - by Andrew

  The question about default values in general - default return function values, default parameter values, default logic for when something is missing, default logic for handling exceptions, default logic for handling the edge conditions etc. For a long time I considered default values to be a "pure evil" thing, something that "cloaks the catastrophe" and results in a very hard do find bugs. But recently I started to think about default values as some sort of a technical debt ... which is not a straight bad thing but something that could provide some "short term financing" get us to survive the project (how many of us could afford to buy a house without taking out the mortgage?). When I say a "short term" - I don't mean - "do something quickly first and do refactor it out later before it hits the production". No - I am talking about relying on a hardcoded default values in a production software. Granted - it could cause some issues, but what if it only going to cause a single trouble in a whole year. Again - I am talking about the "average" mainstream software here (not a software for a nuclear power station) - the average web site or a UI application for the accounting software, meaning that people lives are not at stake, nor millions of dollars. Again, from my experience, business users would rather live with the software which "works somehow", rather then wait for a perfect one. And the use of default values helps a lot if you develop a software in a RAD style. But again - the longest debug sessions I have spent were because of the bugs introduced by a default value which either stopped being "a default" along the way or because a small subsystem has recently been upgraded and as a result of this upgrade it does not handle the default correctly (e.g. empty list vs null, or null string vs empty string). So my question is - are the default values good or evil. And if they are a technical debt - how do measure up how much you can borrow so you can afford the repayments? Would really appreciate any input. Cheers. EDIT: If I am using the default values as a way to cut the corners during the development - and if the corners cutting results in a bugs and issues - what is the methodology to recover from these issues?

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• Attaching a Command to the WP7 Application Bar.

  - by mbcrump

  One of the biggest problems that I’ve seen with people creating WP7 applications is how do you bind the application bar to a Relay Command. If your using MVVM then this is particular important. Let’s examine the code that one might add to start with.  <phone:PhoneApplicationPage.ApplicationBar> <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True"> <shell:ApplicationBarIconButton x:Name="appbar_button1" IconUri="/icons/appbar.questionmark.rest.png" Text="About"> <i:Interaction.Triggers> <i:EventTrigger EventName="Click"> <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding DisplayAbout, Mode=OneWay}" /> </i:EventTrigger> </i:Interaction.Triggers> </shell:ApplicationBarIconButton> <shell:ApplicationBar.MenuItems> <shell:ApplicationBarMenuItem x:Name="menuItem1" Text="MenuItem 1"></shell:ApplicationBarMenuItem> <shell:ApplicationBarMenuItem x:Name="menuItem2" Text="MenuItem 2"></shell:ApplicationBarMenuItem> </shell:ApplicationBar.MenuItems> </shell:ApplicationBar> </phone:PhoneApplicationPage.ApplicationBar> Everything looks right. But we quickly notice that we have a squiggly line under our Interaction.Triggers. The problem is that the object is not a FrameworkObject. This same code would have worked perfect if this were a normal button. OK. Point has been proved. Let’s make the ApplicationBar support Commands. So, go ahead and create a new project using MVVM Light. If you want to check out the source and work along side this tutorial then click here.  7 Easy Steps to have binding on the Application Bar using MVVM Light (I might add that you don’t have to use MVVM Light to get this functionality, I just prefer it.) 1) Download MVVM Light if you don’t already have it and install the project templates. It is available at http://mvvmlight.codeplex.com/. 2) Click File-New Project and navigate to Silverlight for Windows Phone. Make sure you use the MVVM Light (WP7) Template. 3) Now that we have our project setup and ready to go let’s download a wrapper created by Nicolas Humann here, it is called Phone7.Fx. After you download it then extract it somewhere that you can find it. This wrapper will make our application bar/menu item bindable. 4) Right click References inside your WP7 project and add the .dll file to your project. 5) In your MainPage.xaml you will need to add the proper namespace to it. Don’t forget to build your project afterwards. xmlns:Preview="clr-namespace:Phone7.Fx.Preview;assembly=Phone7.Fx.Preview" 6) Now you can add the BindableAppBar to your MainPage.xaml with a few lines of code.  <Preview:BindableApplicationBar x:Name="AppBar" BarOpacity="1.0" > <Preview:BindableApplicationBarIconButton Command="{Binding DisplayAbout}" IconUri="/icons/appbar.questionmark.rest.png" Text="About" /> <Preview:BindableApplicationBar.MenuItems> <Preview:BindableApplicationBarMenuItem Text="Settings" Command="{Binding InputBox}" /> </Preview:BindableApplicationBar.MenuItems> </Preview:BindableApplicationBar> So your final MainPage.xaml will look similar to this: NOTE: The AppBar will be located inside of the Grid using this wrapper.   <!--LayoutRoot contains the root grid where all other page content is placed--> <Grid x:Name="LayoutRoot" Background="Transparent"> <Grid.RowDefinitions> <RowDefinition Height="Auto" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <!--TitlePanel contains the name of the application and page title--> <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="24,24,0,12"> <TextBlock x:Name="ApplicationTitle" Text="{Binding ApplicationTitle}" Style="{StaticResource PhoneTextNormalStyle}" /> <TextBlock x:Name="PageTitle" Text="{Binding PageName}" Margin="-3,-8,0,0" Style="{StaticResource PhoneTextTitle1Style}" /> </StackPanel> <!--ContentPanel - place additional content here--> <Grid x:Name="ContentGrid" Grid.Row="1"> <TextBlock Text="{Binding Welcome}" Style="{StaticResource PhoneTextNormalStyle}" HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="40" /> </Grid> <Preview:BindableApplicationBar x:Name="AppBar" BarOpacity="1.0" > <Preview:BindableApplicationBarIconButton Command="{Binding DisplayAbout}" IconUri="/icons/appbar.questionmark.rest.png" Text="About" /> <Preview:BindableApplicationBar.MenuItems> <Preview:BindableApplicationBarMenuItem Text="Settings" Command="{Binding InputBox}" /> </Preview:BindableApplicationBar.MenuItems> </Preview:BindableApplicationBar> </Grid> 7) Let’s go ahead and create the RelayCommands and write them up to a MessageBox by editing our MainViewModel.cs file. public class MainViewModel : ViewModelBase { public string ApplicationTitle { get { return "MVVM LIGHT"; } } public string PageName { get { return "My page:"; } } public string Welcome { get { return "Welcome to MVVM Light"; } } public RelayCommand DisplayAbout { get; private set; } public RelayCommand InputBox { get; private set; } /// <summary> /// Initializes a new instance of the MainViewModel class. /// </summary> public MainViewModel() { if (IsInDesignMode) { // Code runs in Blend --> create design time data. } else { DisplayAbout = new RelayCommand(() => { MessageBox.Show("About box called!"); }); InputBox = new RelayCommand(() => { MessageBox.Show("settings button called"); }); } } If you run the project now you should get something similar to this (notice the AppBar at the bottom):  Now if you hit the question mark then you will get the following MessageBox: The MenuItem works as well so for Settings: As you can see, its pretty easy to add a Command to the ApplicationBar/MenuItem. If you want to look through the full source code then click here.   Subscribe to my feed

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• What layer to introduce human readable error messages?

  - by MrLane

  One of the things that I have never been happy with on any project I have worked on over the years and have really not been able to resolve myself is exactly at what tier in an application should human readable error information be retrieved for display to a user. A common approach that has worked well has been to return strongly typed/concrete "result objects" from the methods on the public surface of the business tier/API. A method on the interface may be: public ClearUserAccountsResult ClearUserAccounts(ClearUserAccountsParam param); And the result class implementation: public class ClearUserAccountsResult : IResult { public readonly List<Account> ClearedAccounts{get; set;} public readonly bool Success {get; set;} // Implements IResult public readonly string Message{get; set;} // Implements IResult, human readable // Constructor implemented here to set readonly properties... } This works great when the API needs to be exposed over WCF as the result object can be serialized. Again this is only done on the public surface of the API/business tier. The error message can also be looked up from the database, which means it can be changed and localized. However, it has always been suspect to me, this idea of returning human readable information from the business tier like this, partly because what constitutes the public surface of the API may change over time...and it may be the case that the API will need to be reused by other API components in the future that do not need the human readable string messages (and looking them up from a database would be an expensive waste). I am thinking a better approach is to keep the business objects free from such result objects and keep them simple and then retrieve human readable error strings somewhere closer to the UI layer or only in the UI itself, but I have two problems here: 1) The UI may be a remote client (Winforms/WPF/Silverlight) or an ASP.NET web application hosted on another server. In these cases the UI will have to fetch the error strings from the server. 2) Often there are multiple legitimate modes of failure. If the business tier becomes so vague and generic in the way it returns errors there may not be enough information exposed publicly to tell what the error actually was: i.e: if a method has 3 modes of legitimate failure but returns a boolean to indicate failure, you cannot work out what the appropriate message to display to the user should be. I have thought about using failure enums as a substitute, they can indicate a specific error that can be tested for and coded against. This is sometimes useful within the business tier itself as a way of passing via method returns the specifics of a failure rather than just a boolean, but it is not so good for serialization scenarios. Is there a well worn pattern for this? What do people think? Thanks.

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• Unauthorized response from Server with API upload

  - by Ethan Shafer

  I'm writing a library in C# to help me develop a Windows application. The library uses the Ubuntu One API. I am able to authenticate and can even make requests to get the Quota (access to Account Admin API) and Volumes (so I know I have access to the Files API at least) Here's what I have as my Upload code: public static void UploadFile(string filename, string filepath) { FileStream file = File.OpenRead(filepath); byte[] bytes = new byte[file.Length]; file.Read(bytes, 0, (int)file.Length); RestClient client = UbuntuOneClients.FilesClient(); RestRequest request = UbuntuOneRequests.BaseRequest(Method.PUT); request.Resource = "/content/~/Ubuntu One/" + filename; request.AddHeader("Content-Length", bytes.Length.ToString()); request.AddParameter("body", bytes, ParameterType.RequestBody); client.ExecuteAsync(request, webResponse => UploadComplete(webResponse)); } Every time I send the request I get an "Unauthorized" response from the server. For now the "/content/~/Ubuntu One/" is hardcoded, but I checked and it is the location of my root volume. Is there anything that I'm missing? UbuntuOneClients.FilesClient() starts the url with "https://files.one.ubuntu.com" UbuntuOneRequests.BaseRequest(Method.{}) is the same requests that I use to send my Quota and Volumes requests, basically just provides all of the parameters needed to authenticate. EDIT:: Here's the BaseRequest() method: public static RestRequest BaseRequest(Method method) { RestRequest request = new RestRequest(method); request.OnBeforeDeserialization = resp => { resp.ContentType = "application/json"; }; request.AddParameter("realm", ""); request.AddParameter("oauth_version", "1.0"); request.AddParameter("oauth_nonce", Guid.NewGuid().ToString()); request.AddParameter("oauth_timestamp", DateTime.Now.ToString()); request.AddParameter("oauth_consumer_key", UbuntuOneRefreshInfo.UbuntuOneInfo.ConsumerKey); request.AddParameter("oauth_token", UbuntuOneRefreshInfo.UbuntuOneInfo.Token); request.AddParameter("oauth_signature_method", "PLAINTEXT"); request.AddParameter("oauth_signature", UbuntuOneRefreshInfo.UbuntuOneInfo.Signature); //request.AddParameter("method", method.ToString()); return request; } and the FilesClient() method: public static RestClient FilesClient() { return (new RestClient("https://files.one.ubuntu.com")); }

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• Upstart: How does rc job work / order of (contradicting) "start on ..." and "stop on ..." stanzas

  - by Binarus

  Hi, I just can't understand how Upstart's rc job definition in Natty 11.04 works. To illustrate the problem, here is the definition (empty lines and comments are left out): start on runlevel [0123456] stop on runlevel [!$RUNLEVEL] export RUNLEVEL export PREVLEVEL console output env INIT_VERBOSE task exec /etc/init.d/rc $RUNLEVEL Let's suppose we currently are in runlevel 2 and the rc job is stopped (that is exactly the situation after booting my box and logging in via SSH). Now, let's assume that the system switches to runlevel 3, for example due to a command like "telinit 3" given by root. What will happen to the rc job? Obviously, the rc job will be started since it is currently stopped and the event runlevel 3 is matching the start events. But from now on, things are unclear to me: According to the manual $RUNLEVEL evaluates to the new runlevel when the job is started (that means 3 in our example). Therefore, the next stanza "stop on runlevel [!$RUNLEVEL]" translates to "stop on runlevel [!3]"; that means we have a first stanza which will trigger the job, but the second stanza will never stop the job and seems to be useless. Since I know that the Ubuntu / Upstart people won't do useless things, I must be heavily misunderstanding something. I would be grateful for any explanation. While trying to understand this, an additional question came to my mind. If I had contradicting start and stop triggers, for example start on foo stop on foo what would happen? I swear I never will do that, but I am nevertheless very interested in how Upstart handles that on the theoretical level. Thank you very much! Editing the question as a reaction on geekosaur's first answer: I can see the parallelism, but it is not that easy (at least, not to me). Let's assume the job aurrently is still running, and a new runlevel event comes in (of course, the new runlevel is different from the current one). Then, the following should happen: 1) The job is single instance. That means that "start on ..." won't be triggered since the job is currently running; $RUNLEVEL is not touched. 2) "stop on ..." will be triggered since the new runlevel is different from $RUNLEVEL, so the job will be aborted. 3) Now, the job is stopped and waiting. I can't see how it is restarted with the new runlevel. AFAIK, initctl emits events only once, so "start on ..." won't be triggered and the new runlevel won't be entered. I know that I still misunderstanding something, and I am grateful for explanations. Thank you very much!

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• Play or Lift: which one is more explicit?

  - by Andrea

  I am going to investigate web development with Scala, and the choice is between learning Lift or Play: probably I will not have enough time to try both, at least at first. Now, many comparisons between the two are available on the internet, but I would like to know how do they compare with respect to being explicit and involving less magic. Let me explain what I mean by example. I have used, to various degrees, CakePHP, symfony2, Django and Grails. I feel a very clear distinction between Django and symfony2, which are very explicit about what you are doing, and Grails and CakePHP, which try to do their best to guess what you are trying to achieve and often feel "magical". Let me give some examples comparing Django and Grails. In Django, views are functions that take a request as input and return a response. You can instantiate explicitly an instance of HttpResponse and populate its body with a string, or you can use shortcut functions to leverage the template system. In any case the return value from your view always has the same type. In contrast, the render method from Grails is highly polymorphic. You can throw a context at it and it will try to render a template which is found by convention using that context. Or you can pass it a pair of a template path and a context and that will work too. Or a string. Or XML. Grails tries hard to make sense of whatever you return from your controller. In the Django ORM, each model class has a static attribute representing the manager for that class. That manager exposes a fluent interface to build querysets. In Grails, you can have a similar functionality by composing detached criteria. Still, the most common way to query objects seems to be the use of runtime-generated methods like FindUserByEmailNotNull or FindPostByDateGreaterThan. I will not go further, but my point is that in Django-like frameworks you have control over the whole flow of the request/response process, while in Grails-like ones I feel I only have to feel the blanks and the framework will manage the rest of the flow for me. This is not to criticize Grails or CakePHP; which type you prefer is mainly a matter of preference. In fact, I happen to like some aspects of Grails, but I feel more comfortable with a framework which does less for me. Back to the point of the question: which one among Play and Lift is more explicit about what you do and which one tries to simplify more what you have to do with a layer of "magic"?

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• Building an MVC application using QuickBooks

  - by dataintegration

  RSSBus ADO.NET Providers can be used from many tools and IDEs. In this article we show how to connect to QuickBooks from an MVC3 project using the RSSBus ADO.NET Provider for QuickBooks. Although this example uses the QuickBooks Data Provider, the same process can be used with any of our ADO.NET Providers. Creating the Model Step 1: Download and install the QuickBooks Data Provider from RSSBus. Step 2: Create a new MVC3 project in Visual Studio. Add a data model to the Models folder using the ADO.NET Entity Data Model wizard. Step 3: Create a new RSSBus QuickBooks Data Source by clicking "New Connection", specify the connection string options, and click Next. Step 4: Select all the tables and views you need, and click Finish to create the data model. Step 5: Right click on the entity diagram and select 'Add Code Generation Item'. Choose the 'ADO.NET DbContext Generator'. Creating the Controller and the Views Step 6: Add a new controller to the Controllers folder. Give it a meaningful name, such as ReceivePaymentsController. Also, make sure the template selected is 'Controller with empty read/write actions'. Before adding new methods to the Controller, create views for your model. We will add the List, Create, and Delete views. Step 7: Right click on the Views folder and go to Add -> View. Here create a new view for each: List, Create, and Delete templates. Make sure to also associate your Model with the new views. Step 10: Now that the views are ready, go back and edit the RecievePayment controller. Update your code to handle the Index, Create, and Delete methods. Sample Project We are including a sample project that shows how to use the QuickBooks Data Provider in an MVC3 application. You may download the C# project here or download the VB.NET project here. You will also need to install the QuickBooks ADO.NET Data Provider to run the demo. You can download a free trial here. To use this demo, you will also need to modify the connection string in the 'web.config'.

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• Microsoft Interview Preparation

  - by Manish

  I have 8 years of java background. Need help in identifying topics I need to prepare for Microsoft interview. I need to know how many rounds Microsoft will have and what all things these rounds consist of. I have identified the following topics. Please let me know if I need to prepare anything else as well. Arrays Linked Lists Recursion Stacks Queue Trees Graph -- What all I should prepare here Dynamic Programming -- again what all I need to prepare Sorting, Searching String Algos

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• Restoring databases to a set drive and directory

  - by okeofs

   Restoring databases to a set drive and directory Introduction Often people say that necessity is the mother of invention. In this case I was faced with the dilemma of having to restore several databases, with multiple ‘ndf’ files, and having to restore them with different physical file names, drives and directories on servers other than the servers from which they originated. As most of us would do, I went to Google to see if I could find some code to achieve this task and found some interesting snippets on Pinal Dave’s website. Naturally, I had to take it further than the code snippet, HOWEVER it was a great place to start. Creating a temp table to hold database file details First off, I created a temp table which would hold the details of the individual data files within the database. Although there are a plethora of fields (within the temp table below), I utilize LogicalName only within this example. The temporary table structure may be seen below:   create table #tmp ( LogicalName nvarchar(128)  ,PhysicalName nvarchar(260)  ,Type char(1)  ,FileGroupName nvarchar(128)  ,Size numeric(20,0)  ,MaxSize numeric(20,0), Fileid tinyint, CreateLSN numeric(25,0), DropLSN numeric(25, 0), UniqueID uniqueidentifier, ReadOnlyLSN numeric(25,0), ReadWriteLSN numeric(25,0), BackupSizeInBytes bigint, SourceBlocSize int, FileGroupId int, LogGroupGUID uniqueidentifier, DifferentialBaseLSN numeric(25,0), DifferentialBaseGUID uniqueidentifier, IsReadOnly bit, IsPresent bit,  TDEThumbPrint varchar(50) )    We now declare and populate a variable(@path), setting the variable to the path to our SOURCE database backup. declare @path varchar(50) set @path = 'P:\DATA\MYDATABASE.bak'   From this point, we insert the file details of our database into the temp table. Note that we do so by utilizing a restore statement HOWEVER doing so in ‘filelistonly’ mode.   insert #tmp EXEC ('restore filelistonly from disk = ''' + @path + '''')   At this point, I depart from what I gleaned from Pinal Dave.   I now instantiate a few more local variables. The use of each variable will be evident within the cursor (which follows):   Declare @RestoreString as Varchar(max) Declare @NRestoreString as NVarchar(max) Declare @LogicalName  as varchar(75) Declare @counter as int Declare @rows as int set @counter = 1 select @rows = COUNT(*) from #tmp  -- Count the number of records in the temp                                    -- table   Declaring and populating the cursor At this point I do realize that many people are cringing about the use of a cursor. Being an Oracle professional as well, I have learnt that there is a time and place for cursors. I would remind the reader that the data that will be read into the cursor is from a local temp table and as such, any locking of the records (within the temp table) is not really an issue.   DECLARE MY_CURSOR Cursor  FOR  Select LogicalName  From #tmp   Parsing the logical names from within the cursor. A small caveat that works in our favour,  is that the first logical name (of our database) is the logical name of the primary data file (.mdf). Other files, except for the very last logical name, belong to secondary data files. The last logical name is that of our database log file.   I now open my cursor and populate the variable @RestoreString Open My_Cursor  set @RestoreString =  'RESTORE DATABASE [MYDATABASE] FROM DISK = N''P:\DATA\ MYDATABASE.bak''' + ' with  '   We now fetch the first record from the temp table.   Fetch NEXT FROM MY_Cursor INTO @LogicalName   While there are STILL records left within the cursor, we dynamically build our restore string. Note that we are using concatenation to create ‘one big restore executable string’.   Note also that the target physical file name is hardwired, as is the target directory.   While (@@FETCH_STATUS <> -1) BEGIN IF (@@FETCH_STATUS <> -2) -- As long as there are no rows missing select @RestoreString = case  when @counter = 1 then -- This is the mdf file    @RestoreString + 'move  N''' + @LogicalName + '''' + ' TO N’’X:\DATA1\'+ @LogicalName + '.mdf' + '''' + ', '   -- OK, if it passes through here we are dealing with an .ndf file -- Note that Counter must be greater than 1 and less than the number of rows.   when @counter > 1 and @counter < @rows then -- These are the ndf file(s)    @RestoreString + 'move  N''' + @LogicalName + '''' + ' TO N’’X:\DATA1\'+ @LogicalName + '.ndf' + '''' + ', '   -- OK, if it passes through here we are dealing with the log file When @LogicalName like '%log%' then    @RestoreString + 'move  N''' + @LogicalName + '''' + ' TO N’’X:\DATA1\'+ @LogicalName + '.ldf' +'''' end --Increment the counter   set @counter = @counter + 1 FETCH NEXT FROM MY_CURSOR INTO @LogicalName END   At this point we have populated the varchar(max) variable @RestoreString with a concatenation of all the necessary file names. What we now need to do is to run the sp_executesql stored procedure, to effect the restore.   First, we must place our ‘concatenated string’ into an nvarchar based variable. Obviously this will only work as long as the length of @RestoreString is less than varchar(max) / 2.   set @NRestoreString = @RestoreString EXEC sp_executesql @NRestoreString   Upon completion of this step, the database should be restored to the server. I now close and deallocate the cursor, and to be clean, I would also drop my temp table.   CLOSE MY_CURSOR DEALLOCATE MY_CURSOR GO   Conclusion Restoration of databases on different servers with different physical names and on different drives are a fact of life. Through the use of a few variables and a simple cursor, we may achieve an efficient and effective way to achieve this task.

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• How does rc job work / order of (contradicting) "start on ..." and "stop on ..." stanzas

  - by Binarus

  Hi, I just can't understand how Upstart's rc job definition in Natty 11.04 works. To illustrate the problem, here is the definition (empty lines and comments are left out): start on runlevel [0123456] stop on runlevel [!$RUNLEVEL] export RUNLEVEL export PREVLEVEL console output env INIT_VERBOSE task exec /etc/init.d/rc $RUNLEVEL Let's suppose we currently are in runlevel 2 and the rc job is stopped (that is exactly the situation after booting my box and logging in via SSH). Now, let's assume that the system switches to runlevel 3, for example due to a command like "telinit 3" given by root. What will happen to the rc job? Obviously, the rc job will be started since it is currently stopped and the event runlevel 3 is matching the start events. But from now on, things are unclear to me: According to the manual $RUNLEVEL evaluates to the new runlevel when the job is started (that means 3 in our example). Therefore, the next stanza "stop on runlevel [!$RUNLEVEL]" translates to "stop on runlevel [!3]"; that means we have a first stanza which will trigger the job, but the second stanza will never stop the job and seems to be useless. Since I know that the Ubuntu / Upstart people won't do useless things, I must be heavily misunderstanding something. I would be grateful for any explanation. While trying to understand this, an additional question came to my mind. If I had contradicting start and stop triggers, for example start on foo stop on foo what would happen? I swear I never will do that, but I am nevertheless very interested in how Upstart handles that on the theoretical level. Thank you very much! Editing the question as a reaction on geekosaur's first answer: I can see the parallelism, but it is not that easy (at least, not to me). Let's assume the job aurrently is still running, and a new runlevel event comes in (of course, the new runlevel is different from the current one). Then, the following should happen: 1) The job is single instance. That means that "start on ..." won't be triggered since the job is currently running; $RUNLEVEL is not touched. 2) "stop on ..." will be triggered since the new runlevel is different from $RUNLEVEL, so the job will be aborted. 3) Now, the job is stopped and waiting. I can't see how it is restarted with the new runlevel. AFAIK, initctl emits events only once, so "start on ..." won't be triggered and the new runlevel won't be entered. I know that I still misunderstanding something, and I am grateful for explanations. Thank you very much!

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• Alternative of SortedDictionary in Silverlight

  - by Rajneesh Verma

  Hi, As we know SortedDictionary is not not present in Silverlightso to find alternative of this i am using Dictionary as System.Collections.Generic . Dictionary (Of TKey, TValue ) . KeyCollection and for sorting i am using LINQ query. see the full code below. Dim sortedLists As New Dictionary(Of String, Object) Dim query = From sortedList In sortedLists Order By sortedList.Key Ascending Select sortedList.Key, sortedList.Value For Each que In query 'get the key value using que.Key 'get the value using...(read more)

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• RPG Monster-Area, Spawn, Loot table Design

  - by daemonfire300

  I currently struggle with creating the database structure for my RPG. I got so far: tables: area (id) monster (id, area.id, monster.id, hp, attack, defense, name) item (id, some other values) loot (id = monster.id, item = item.id, chance) spawn (id = area.id, monster = monster.id, count) It is a browser-based game like e.g. Castle Age. The player can move from area to area. If a player enters an area the system spawns, based on the area.id and using the spawn table data, new monsters into the monster table. If a player kills a monster, the system picks the monster.id looks up the items via the the loot table and adds those items to the player's inventory. First, is this smart? Second, I need some kind of "monster_instance"-table and "area_instance"-table, since each player enters his very own "area" and does damage to his very own "monsters". Another approach would be adding the / a player.id to the monster table, so each monster spawned, has it's own "player", but I still need to assign them to an area, and I think this would overload the monster table if I put in the player.id and the area.id into the monster table. What are your thoughts? Temporary Solution monster (id, attackDamage, defense, hp, exp, etc.) monster_instance (id, player.id, area_instance.id, hp, attackDamage, defense, monster.id, etc.) area (id, name, area.id access, restriction) area_instance (id, area.id, last_visited) spawn (id, area.id, monster.id) loot (id, monster.id, chance, amount, ?area.id?) An example system-flow would be: Player enters area 1: system creates area_instance of type area.id = 1 and sets player.location to area.id = 1 If Player wants to battle monsters in the current area: system fetches all spawn entries matching area.id == player.location and creates a new monster_instance for each spawn by fetching the according monster-base data from table monster. If a monster is fetched more than once it may be cached. If Player actually attacks a monster: system updates the according monster_instance, if monster dies the instance if removed after creating the loot If Player leaves the area: area_instance.last_visited is set to NOW(), if player doesn't return to data area within a certain amount of time area_instance including all its monster_instances are deleted.

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• Do I need to create my own or use a commercial server for the features and matchmaking options I want my game to support?

  - by baptzmoffire

  So I'm developing an indie turn-based game for iOS and, in coding up a Game Center matchmaking class, I'm starting to question whether Game Center is even the best choice for what I want this game to do. I need to figure out whether I need to create my own server, invest in a preexisting client or server service, or if I even need to use a server at all. If I do need to use a ready-made service other than Game Center, which server would accomodate my game's needs best? I have limited resources and funds. Here is the list of features I want my game to support, ideally: Turn-based gameplay (a la "with Friends" and "with Buddies" games) Smart matchmaking (matching users up with other players of comparable skill/achievements) Random matchmaking Facebook matchmaking Specific username matchmaking Contact list matchmaking A way to select what "type" of match you want to challenge an opponent to. (In random, smart, and Facebook matchmaking, there will be different "wagers" the player can make. [e.g. "I wanna play a random opponent for 1000 points. Now, I wanna play my Facebook buddy for 1,000,000 points."] There will be a predetermined range of amounts you can play for. It won't be customizable.) Buddies list capability (Game-buddies, as opposed to contacts and Facebook) A higher concurrent game cap than Game Center offers (which I still can't really find a straight answer on) Scalability (it should support 2 or 20,000,000 players) Objective-C compatibility Flexibility (for all the stuff I haven't thought of yet) Am I dreaming, here? Is there even a service that can handle all of these features? Do I need to invest months in learning a networking language to build my own? If so, how much would I need to spend on hardware? I've been looking around all morning and, so far, the only seemingly viable option is SmartFox. Under "Everything and the kitchen sink" section here, it says they support "virtual world with Zones, Rooms and RoomGroups, create complex game challenges, send invitations, manage buddy lists, create custom permission profiles, oversee the security aspects and tons more." http://www.smartfoxserver.com/overview/platform Is there an option that Im just overlooking? Thanks for any help anyone can provide. Sorry for the long poast. One last question: Does anyone know which server Dice with Buddies uses? I was experimenting with how many concurrent games I could get going and my ADHD kicked in at about 80 games. 80 concurrent games would be great for my game, but again, I need the other features I mentioned too. Thanks again.

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• Perl syntax error [closed]

  - by Linny

  I am a beginner taking a Perl programming course. We are trying to write a basic program for counting nucleotides in a DNA string. I'm getting syntax errors on the lines that have a single bracket on lines 28 & 70 and don't know why. It also reads that I have compilation errors. I have no idea where to start figuring that out. # The purpose of this program is to count the number of nucleotides in a strand. Each protein is counted separately # print "/n NOTE: Nucleotide counting /n"; # use strict; # enforce variable declarations use warnings; # enable compiler warnings # Display number of A,a,T,t,G,g,C,c, nucleotides in a word or sequence of letters. # my ($base) = ''; # an extracted letter from a string my ($nuceotide_count) = 0 ; # the current position within the word my ($position) = 0 ; # number of vowels in user-supplied word my ($word) = ''; # word to be processed my ($A_count) = 0 ; # of A nucleotides in the user-supplied sequence my ($a_count) = 0 ; # of A nucleotides in the user-supplied sequence my ($C_count) = 0 ; # of C nucleotides in the user-supplied sequence my ($c_count) = 0 ; # of C nucleotides in the user-supplied sequence my ($G_count) = 0 ; # of G nucleotides in the user-supplied sequence my ($g_count) = 0 ; # of G nucleotides in the user-supplied sequence my ($T_count) = 0 ; # of T nucleotides in the user-supplied sequence my ($t_count) = 0 ; # of T nucleotides in the user-supplied sequence word = (STDIN) for ($position = 0);($position if (($base eq 'a') or ($base eq 'A')) { ++$A_count; } # end if ++$position; if (($base eq 'T') or ($base eq 't')) { ++$T_count; } end if ++$position; if (($base eq 'G') or ($base eq 'g')) { ++$G_count; } # end if ++$position; if (($base eq 'C') or ($base eq 'c')) { ++$C_count; } # end if ++$position; } # end for # Display final results. # print " \n The number of A or a neucleotides is: $A_count"; print " \n The number of T or t neucleotides is: $T_count"; print " \n The number of G or g neucleotides is: $G_count"; print " \n The number of C or c neucleotides is: $C_count"; print " \n\n Program completed successfully. \n" ; exit ;

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• Unit test: How best to provide an XML input?

  - by TheSilverBullet

  I need to write a unit test which validates the serialization of two attributes of an XML(size ~ 30 KB) file. What is the best way to provide an input for this test? Here are the options I have considered: Add the file to the project and use a file reader Pass the contents of the XML as a string Create the XML through a program and pass it Which is my best option and why? If there is another way which you think is better, I would love to hear it.

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• As a tooling/automation developer, can I be making better use of OOP?

  - by Tom Pickles

  My time as a developer (~8 yrs) has been spent creating tooling/automation of one sort or another. The tools I develop usually interface with one or more API's. These API's could be win32, WMI, VMWare, a help-desk application, LDAP, you get the picture. The apps I develop could be just to pull back data and store/report. It could be to provision groups of VM's to create live like mock environments, update a trouble ticket etc. I've been developing in .Net and I'm currently reading into design patterns and trying to think about how I can improve my skills to make better use of and increase my understanding of OOP. For example, I've never used an interface of my own making in anger (which is probably not a good thing), because I honestly cannot identify where using one would benefit later on when modifying my code. My classes are usually very specific and I don't create similar classes with similar properties/methods which could use a common interface (like perhaps a car dealership or shop application might). I generally use an n-tier approach to my apps, having a presentation layer, a business logic/manager layer which interfaces with layer(s) that make calls to the API's I'm working with. My business entities are always just method-less container objects, which I populate with data and pass back and forth between my API interfacing layer using static methods to proxy/validate between the front and the back end. My code by nature of my work, has few common components, at least from what I can see. So I'm struggling to see how I can better make use of OOP design and perhaps reusable patterns. Am I right to be concerned that I could be being smarter about how I work, or is what I'm doing now right for my line of work? Or, am I missing something fundamental in OOP? EDIT: Here is some basic code to show how my mgr and api facing layers work. I use static classes as they do not persist any data, only facilitate moving it between layers. public static class MgrClass { public static bool PowerOnVM(string VMName) { // Perform logic to validate or apply biz logic // call APIClass to do the work return APIClass.PowerOnVM(VMName); } } public static class APIClass { public static bool PowerOnVM(string VMName) { // Calls to 3rd party API to power on a virtual machine // returns true or false if was successful for example } }

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• Grep through subdirectories

  - by Kathryn

  Add a string to a text file from terminal I've been looking at this thread. The solution (number 2, with ls | grep) works perfectly for files called .txt in the current directory. How about if I wanted to search through a directory and the subdirectories therein? For example, I have to search through a directory that has many subdirectories, and they have many subdirectories etc. I'm new to Linux sorry, so I'm not sure if this is the right place

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• How to leverage the internal HTTP endpoint available on Azure web roles?

  - by Alfredo Delsors

  Imagine you have a Web application using an in-memory collection that changes occasionally but is used very often. The collection gets loaded from storage on the Application_Start global.asax event and is updated whenever its content changes. If you want to deploy this application on Azure you need to keep in mind that more than one instance of the application can be running at any time and therefore you need to provide some mechanism to keep all instances informed with the latest changes. Because the communication through internal endpoints between Azure role instances is at no cost, a good solution can be maintaining the information on Azure Storage Tables, reading its contents on the Application_Start event and populating its changes to all other instances using the internal HTTP port available on Azure Web Roles. You need to follow these steps to leverage the internal HTTP endpoint available on Azure web roles to maintain all instances up to date. 1.   Define an internal HTTP endpoint in the Web Role properties, for example InternalHttpEndpoint   2.   Add a new WCF service to the Web Role, for example NotificationService.svc 3.   Disable multiple site bindings in web.config: <serviceHostingEnvironment multipleSiteBindingsEnabled="false"> 4.   Add a method on the new service to receive notifications from other role instances. namespace Service { [ServiceContract] public interface INotificationService { [OperationContract(IsOneWay = true)] void Notify(Information info); } } 5.   Declare a class that inherits from System.ServiceModel.Activation.ServiceHostFactory and override the method CreateServiceHost to host the internal endpoint. public class InternalServiceFactory : ServiceHostFactory { protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses) { var internalEndpointAddress = string.Format( "http://{0}/NotificationService.svc", RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["InternalHttpEndpoint"].IPEndpoint); ServiceHost host = new ServiceHost( typeof(NotificationService), new Uri(internalEndpointAddress)); BasicHttpBinding binding = new BasicHttpBinding(SecurityMode.None); host.AddServiceEndpoint( typeof(INotificationService), binding, internalEndpointAddress); return host; } } Note that you can use SecurityMode.None because the internal endpoint is private to the instances of the service. 6.   Edit the markup of the service right clicking the svc file and selecting "View markup" to add the new factory as the factory to be used to create the service <%@ ServiceHost Language="C#" Debug="true" Factory="Service.InternalServiceFactory" Service="Service.NotificationService" CodeBehind="NotificationService.svc.cs" %> 7.   Now you can notify changes to other instances using this code: var current = RoleEnvironment.CurrentRoleInstance; var endPoints = current.Role.Instances .Where(instance => instance != current) .Select(instance => instance.InstanceEndpoints["InternalHttpEndpoint"]); foreach (var ep in endPoints) { EndpointAddress address = new EndpointAddress( String.Format("http://{0}/NotificationService.svc", ep.IPEndpoint)); BasicHttpBinding binding = new BasicHttpBinding(SecurityMode.None); var factory = new ChannelFactory<INotificationService>(binding); INotificationService instance = factory.CreateChannel(address); instance.Notify(changedinfo); }

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• Who could ask for more with LESS CSS? (Part 3 of 3&ndash;Clrizr)

  - by ToString(theory);

  Welcome back!  In the first two posts in this series, I covered some of the awesome features in CSS precompilers such as SASS and LESS, as well as how to get an initial project setup up and running in ASP.Net MVC 4. In this post, I will cover an actual advanced example of using LESS in a project, and show some of the great productivity features we gain from its usage. Introduction In the first post, I mentioned two subjects that I will be using in this example – constants, and color functions.  I’ve always enjoyed using online color scheme utilities such as Adobe Kuler or Color Scheme Designer to come up with a scheme based off of one primary color.  Using these tools, and requesting a complementary scheme you can get a couple of shades of your primary color, and a couple of shades of a complementary/accent color to display. Because there is no way in regular css to do color operations or store variables, there was no way to accomplish something like defining a primary color, and have a site theme cascade off of that.  However with tools such as LESS, that impossibility becomes a reality!  So, if you haven’t guessed it by now, this post is on the creation of a plugin/module/less file to drop into your project, plugin one color, and have your primary theme cascade from it.  I only went through the trouble of creating a module for getting Complementary colors.  However, it wouldn’t be too much trouble to go through other options such as Triad or Monochromatic to get a module that you could use off of that. Step 1 – Analysis I decided to mimic Adobe Kuler’s Complementary theme algorithm as I liked its simplicity and aesthetics.  Color Scheme Designer is great, but I do believe it can give you too many color options, which can lead to chaos and overload.  The first thing I had to check was if the complementary values for the color schemes were actually hues rotated by 180 degrees at all times – they aren’t.  Apparently Adobe applies some variance to the complementary colors to get colors that are actually more aesthetically appealing to users.  So, I opened up Excel and began to plot complementary hues based on rotation in increments of 10: Long story short, I completed the same calculations for Hue, Saturation, and Lightness.  For Hue, I only had to record the Complementary hue values, however for saturation and lightness, I had to record the values for ALL of the shades.  Since the functions were too complicated to put into LESS since they aren’t constant/linear, but rather interval functions, I instead opted to extrapolate the HSL values using the trendline function for each major interval, onto intervals of spacing 1. For example, using the hue extraction, I got the following values: Interval Function 0-60 60-140 140-270 270-360 Saturation and Lightness were much worse, but in the end, I finally had functions for all of the intervals, and then went the route of just grabbing each shades value in intervals of 1.  Step 2 – Mapping I declared variable names for each of these sections as something that shouldn’t ever conflict with a variable someone would define in their own file.  After I had each of the values, I extracted the values and put them into files of their own for hue variables, saturation variables, and lightness variables…  Example: /*HUE CONVERSIONS*/@clrizr-hue-source-0deg: 133.43;@clrizr-hue-source-1deg: 135.601;@clrizr-hue-source-2deg: 137.772;@clrizr-hue-source-3deg: 139.943;@clrizr-hue-source-4deg: 142.114;.../*SATURATION CONVERSIONS*/@clrizr-saturation-s2SV0px: 0;@clrizr-saturation-s2SV1px: 0;@clrizr-saturation-s2SV2px: 0;@clrizr-saturation-s2SV3px: 0;@clrizr-saturation-s2SV4px: 0;.../*LIGHTNESS CONVERSIONS*/@clrizr-lightness-s2LV0px: 30;@clrizr-lightness-s2LV1px: 31;@clrizr-lightness-s2LV2px: 32;@clrizr-lightness-s2LV3px: 33;@clrizr-lightness-s2LV4px: 34;...   In the end, I have 973 lines of mapping/conversion from source HSL to shade HSL for two extra primary shades, and two complementary shades. The last bit of the work was the file to compose each of the shades from these mappings. Step 3 – Clrizr Mapper The final step was the hardest to overcome as I was still trying to understand LESS to its fullest extent.  Imports As mentioned previously, I had separated the HSL mappings into different files, so the first necessary step is to import those for use into the Clrizr plugin: @import url("hue.less");@import url("saturation.less");@import url("lightness.less"); Extract Component Values For Each Shade Next, I extracted the necessary information for each shade HSL before shade composition: @clrizr-input-saturation: 1px+floor(saturation(@clrizr-input))-1;@clrizr-input-lightness: 1px+floor(lightness(@clrizr-input))-1; @clrizr-complementary-hue: formatstring("clrizr-hue-source-{0}", ceil(hue(@clrizr-input))); @clrizr-primary-2-saturation: formatstring("clrizr-saturation-s2SV{0}",@clrizr-input-saturation);@clrizr-primary-1-saturation: formatstring("clrizr-saturation-s1SV{0}",@clrizr-input-saturation);@clrizr-complementary-1-saturation: formatstring("clrizr-saturation-c1SV{0}",@clrizr-input-saturation); @clrizr-primary-2-lightness: formatstring("clrizr-lightness-s2LV{0}",@clrizr-input-lightness);@clrizr-primary-1-lightness: formatstring("clrizr-lightness-s1LV{0}",@clrizr-input-lightness);@clrizr-complementary-1-lightness: formatstring("clrizr-lightness-c1LV{0}",@clrizr-input-lightness); Here, you can see a couple of odd things…  On the first line, I am using operations to add units to the saturation and lightness.  This is due to some limitations in the operations that would give me saturation or lightness in %, which can’t be in a variable name.  So, I use first add 1px to it, which casts the result of the following functions as px instead of %, and then at the end, I remove that pixel.  You can also see here the formatstring method which is exactly what it sounds like – something like String.Format(string str, params object[] obj). Get Primary & Complementary Shades Now that I have components for each of the different shades, I can now compose them into each of their pieces.  For this, I use the @@ operator which will look for a variable with the name specified in a string, and then call that variable: @clrizr-primary-2: hsl(hue(@clrizr-input), @@clrizr-primary-2-saturation, @@clrizr-primary-2-lightness);@clrizr-primary-1: hsl(hue(@clrizr-input), @@clrizr-primary-1-saturation, @@clrizr-primary-1-lightness);@clrizr-primary: @clrizr-input;@clrizr-complementary-1: hsl(@@clrizr-complementary-hue, @@clrizr-complementary-1-saturation, @@clrizr-complementary-1-lightness);@clrizr-complementary-2: hsl(@@clrizr-complementary-hue, saturation(@clrizr-input), lightness(@clrizr-input)); That’s is it, for the most part.  These variables now hold the theme for the one input color – @clrizr-input.  However, I have one last addition… Perceptive Luminance Well, after I got the colors, I decided I wanted to also get the best font color that would go on top of it.  Black or white depending on light or dark color.  Now I couldn’t just go with checking the lightness, as that is half the story.  You see, the human eye doesn’t see ALL colors equally well but rather has more cells for interpreting green light compared to blue or red.  So, using the ratio, we can calculate the perceptive luminance of each of the shades, and get the font color that best matches it! @clrizr-perceptive-luminance-ps2: round(1 - ( (0.299 * red(@clrizr-primary-2) ) + ( 0.587 * green(@clrizr-primary-2) ) + (0.114 * blue(@clrizr-primary-2)))/255)*255;@clrizr-perceptive-luminance-ps1: round(1 - ( (0.299 * red(@clrizr-primary-1) ) + ( 0.587 * green(@clrizr-primary-1) ) + (0.114 * blue(@clrizr-primary-1)))/255)*255;@clrizr-perceptive-luminance-ps: round(1 - ( (0.299 * red(@clrizr-primary) ) + ( 0.587 * green(@clrizr-primary) ) + (0.114 * blue(@clrizr-primary)))/255)*255;@clrizr-perceptive-luminance-pc1: round(1 - ( (0.299 * red(@clrizr-complementary-1)) + ( 0.587 * green(@clrizr-complementary-1)) + (0.114 * blue(@clrizr-complementary-1)))/255)*255;@clrizr-perceptive-luminance-pc2: round(1 - ( (0.299 * red(@clrizr-complementary-2)) + ( 0.587 * green(@clrizr-complementary-2)) + (0.114 * blue(@clrizr-complementary-2)))/255)*255; @clrizr-col-font-on-primary-2: rgb(@clrizr-perceptive-luminance-ps2, @clrizr-perceptive-luminance-ps2, @clrizr-perceptive-luminance-ps2);@clrizr-col-font-on-primary-1: rgb(@clrizr-perceptive-luminance-ps1, @clrizr-perceptive-luminance-ps1, @clrizr-perceptive-luminance-ps1);@clrizr-col-font-on-primary: rgb(@clrizr-perceptive-luminance-ps, @clrizr-perceptive-luminance-ps, @clrizr-perceptive-luminance-ps);@clrizr-col-font-on-complementary-1: rgb(@clrizr-perceptive-luminance-pc1, @clrizr-perceptive-luminance-pc1, @clrizr-perceptive-luminance-pc1);@clrizr-col-font-on-complementary-2: rgb(@clrizr-perceptive-luminance-pc2, @clrizr-perceptive-luminance-pc2, @clrizr-perceptive-luminance-pc2); Conclusion That’s it!  I have posted a project on clrizr.codePlex.com for this, and included a testing page for you to test out how it works.  Feel free to use it in your own project, and if you have any questions, comments or suggestions, please feel free to leave them here as a comment, or on the contact page!

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• What's the problem with Scala's XML literals?

  - by Oak

  In this post, Martin (the language's head honcho) writes: [XML literals] Seemed a great idea at the time, now it sticks out like a sore thumb. I believe with the new string interpolation scheme we will be able to put all of XML processing in the libraries, which should be a big win. Being interested in language design myself, I'm wondering: Why does he write that it was a mistake to incorporate XML literals into the language? What is the controversy regarding this feature?

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• Passing a parameter so that it cannot be changed – C#

  - by nmarun

  I read this requirement of not allowing a user to change the value of a property passed as a parameter to a method. In C++, as far as I could recall (it’s been over 10 yrs, so I had to refresh memory), you can pass ‘const’ to a function parameter and this ensures that the parameter cannot be changed inside the scope of the function. There’s no such direct way of doing this in C#, but that does not mean it cannot be done!! Ok, so this ‘not-so-direct’ technique depends on the type of the parameter – a simple property or a collection. Parameter as a simple property: This is quite easy (and you might have guessed it already). Bulent Ozkir clearly explains how this can be done here. Parameter as a collection property: Obviously the above does not work if the parameter is a collection of some type. Let’s dig-in. Suppose I need to create a collection of type KeyTitle as defined below. 1: public class KeyTitle 2: { 3: public int Key { get; set; } 4: public string Title { get; set; } 5: } My class is declared as below: 1: public class Class1 2: { 3: public Class1() 4: { 5: MyKeyTitleList = new List<KeyTitle>(); 6: } 7: 8: public List<KeyTitle> MyKeyTitleList { get; set; } 9: public ReadOnlyCollection<KeyTitle> ReadonlyKeyTitleCollection 10: { 11: // .AsReadOnly creates a ReadOnlyCollection<> type 12: get { return MyKeyTitleList.AsReadOnly(); } 13: } 14: } See the .AsReadOnly() method used in the second property? As MSDN says it: “Returns a read-only IList<T> wrapper for the current collection.” Knowing this, I can implement my code as: 1: public static void Main() 2: { 3: Class1 class1 = new Class1(); 4: class1.MyKeyTitleList.Add(new KeyTitle { Key = 1, Title = "abc" }); 5: class1.MyKeyTitleList.Add(new KeyTitle { Key = 2, Title = "def" }); 6: class1.MyKeyTitleList.Add(new KeyTitle { Key = 3, Title = "ghi" }); 7: class1.MyKeyTitleList.Add(new KeyTitle { Key = 4, Title = "jkl" }); 8:  9: TryToModifyCollection(class1.MyKeyTitleList.AsReadOnly()); 10:  11: Console.ReadLine(); 12: } 13:  14: private static void TryToModifyCollection(ReadOnlyCollection<KeyTitle> readOnlyCollection) 15: { 16: // can only read 17: for (int i = 0; i < readOnlyCollection.Count; i++) 18: { 19: Console.WriteLine("{0} - {1}", readOnlyCollection[i].Key, readOnlyCollection[i].Title); 20: } 21: // Add() - not allowed 22: // even the indexer does not have a setter 23: } The output is as expected: The below image shows two things. In the first line, I’ve tried to access an element in my read-only collection through an indexer. It shows that the ReadOnlyCollection<> does not have a setter on the indexer. The second line tells that there’s no ‘Add()’ method for this type of collection. The capture below shows there’s no ‘Remove()’ method either, there-by eliminating all ways of modifying a collection. Mission accomplished… right? Now, even if you have a collection of different type, all you need to do is to somehow cast (used loosely) it to a List<> and then do a .AsReadOnly() to get a ReadOnlyCollection of your custom collection type. As an example, if you have an IDictionary<int, string>, you can create a List<T> of this type with a wrapper class (KeyTitle in our case). 1: public IDictionary<int, string> MyDictionary { get; set; } 2:  3: public ReadOnlyCollection<KeyTitle> ReadonlyDictionary 4: { 5: get 6: { 7: return (from item in MyDictionary 8: select new KeyTitle 9: { 10: Key = item.Key, 11: Title = item.Value, 12: }).ToList().AsReadOnly(); 13: } 14: } Cool huh? Just one thing you need to know about the .AsReadOnly() method is that the only way to modify your ReadOnlyCollection<> is to modify the original collection. So doing: 1: public static void Main() 2: { 3: Class1 class1 = new Class1(); 4: class1.MyKeyTitleList.Add(new KeyTitle { Key = 1, Title = "abc" }); 5: class1.MyKeyTitleList.Add(new KeyTitle { Key = 2, Title = "def" }); 6: class1.MyKeyTitleList.Add(new KeyTitle { Key = 3, Title = "ghi" }); 7: class1.MyKeyTitleList.Add(new KeyTitle { Key = 4, Title = "jkl" }); 8: TryToModifyCollection(class1.MyKeyTitleList.AsReadOnly()); 9:  10: Console.WriteLine(); 11:  12: class1.MyKeyTitleList.Add(new KeyTitle { Key = 5, Title = "mno" }); 13: class1.MyKeyTitleList[2] = new KeyTitle{Key = 3, Title = "GHI"}; 14: TryToModifyCollection(class1.MyKeyTitleList.AsReadOnly()); 15:  16: Console.ReadLine(); 17: } Gives me the output of: See that the second element’s Title is changed to upper-case and the fifth element also gets displayed even though we’re still looping through the same ReadOnlyCollection<KeyTitle>. Verdict: Now you know of a way to implement ‘Method(const param1)’ in your code!

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• NetBeans IDE 7.3 Knows Null

  - by Geertjan

  What's the difference between these two methods, "test1" and "test2"? public int test1(String str) {     return str.length(); } public int test2(String str) {     if (str == null) {         System.err.println("Passed null!.");         //forgotten return;     }     return str.length(); } The difference, or at least, the difference that is relevant for this blog entry, is that whoever wrote "test2" apparently thinks that the variable "str" may be null, though did not provide a null check. In NetBeans IDE 7.3, you see this hint for "test2", but no hint for "test1", since in that case we don't know anything about the developer's intention for the variable and providing a hint in that case would flood the source code with too many false positives:  Annotations are supported in understanding how a piece of code is intended to be used. If method return types use @Nullable, @NullAllowed, @CheckForNull, the value is considered to be "strongly possible to be null", as well as if the variable is tested to be null, as shown above. When using @NotNull, @NonNull, @Nonnull, the value is considered to be non-null. (The exact FQNs of the annotations are ignored, only simple names are checked.) Here are examples showing where the hints are displayed for the non-null hints (the "strongly possible to be null" hints are not shown below, though you can see one of them in the screenshot above), together with a comment showing what is shown when you hover over the hint: There isn't a "one size fits all" refactoring for these various instances relating to null checks, hence you can't do an automated refactoring across your code base via tools in NetBeans IDE, as shown yesterday for class member reordering across code bases. However, you can, instead, go to Source | Inspect and then do a scan throughout a scope (e.g., current file/package/project or combinations of these or all open projects) for class elements that the IDE identifies as potentially having a problem in this area: Thanks to Jan Lahoda, who reports that this currently also works in NetBeans IDE 7.3 dev builds for fields but that may need to be disabled since right now too many false positives are returned, for help with the info above and any misunderstandings are my own fault!

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• Techniques to re-factor garbage and maintain sanity?

  - by Incognito

  So I'm sitting down to a nice bowl of c# spaghetti, and need to add something or remove something... but I have challenges everywhere from functions passing arguments that doesn't make sense, someone who doesn't understand data structures abusing strings, redundant variables, some comments are red-hearings, internationalization is on a per-every-output-level, SQL doesn't use any kind of DBAL, database connections are left open everywhere... Are there any tools or techniques I can use to at least keep track of the "functional integrity" of the code (meaning my "improvements" don't break it), or a resource online with common "bad patterns" that explains a good way to transition code? I'm basically looking for a guidebook on how to spin straw into gold. Here's some samples from the same 500 line function: protected void DoSave(bool cIsPostBack) { //ALWAYS a cPostBack cIsPostBack = true; SetPostBack("1"); string inCreate ="~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~"; parseValues = new string []{"","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""}; if (!cIsPostBack) { //....... //.... //.... if (!cIsPostBack) { } else { } //.... //.... strHPhone = StringFormat(s1.Trim()); s1 = parseValues[18].Replace(encStr," "); strWPhone = StringFormat(s1.Trim()); s1 = parseValues[11].Replace(encStr," "); strWExt = StringFormat(s1.Trim()); s1 = parseValues[21].Replace(encStr," "); strMPhone = StringFormat(s1.Trim()); s1 = parseValues[19].Replace(encStr," "); //(hundreds of lines of this) //.... //.... SQL = "...... lots of SQL .... "; SqlCommand curCommand; curCommand = new SqlCommand(); curCommand.Connection = conn1; curCommand.CommandText = SQL; try { curCommand.ExecuteNonQuery(); } catch {} //.... } I've never had to refactor something like this before, and I want to know if there's something like a guidebook or knowledgebase on how to do this sort of thing, finding common bad patterns and offering the best solutions to repair them. I don't want to just nuke it from orbit,

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• Improving the performance of JDeveloper11g (part 2) and JVMs in general

  - by asantaga

  Just received an email from one of our JVM developers who read my blog entry on Performance tuning JDeveloper11g and he's confirmed that all of the above parameters are totally supported :-) He's also provided a description of the parameters so we can learn what magic is actually being applied. - -XX:+AggressiveOpts -- this enables the latest and greatest JVM optimizations. It will likely help most Java applications. It's fully supported. The downside of it is that because it has the latest and greatest optimizations, there is some small probability that it may not offer as good of an experience. As those features enabled with this command line option have "matured", they are made the default in a future JDK release. So, you can think of this command line option as the place where the newest optimizations get introduced. Some time later they are moved out from under AggressiveOpts to become default behavior. -XX:+OptimizeStringConcat -- only works with the -server JVM. It may be enabled by the default in a future JDK 7 update release. This option delays the construction of a StringBuilder/StringBuffer and attempts to avoid re-sizing the underlying char[] by attempting to detect the size of the char[] to allocate based on what's being appended to the StringBuilder/StringBuffer. -XX:+UseStringCache -- I would not suggest using this unless you knew that JDeveloper allocated the same string over and over again. And, the string that's allocated over and over again is one of the first 100,000 allocated strings. In short, I'd recommend against using it. And, in fact, in Java 7 (currently) does not include this feature. -XX:+UseCompressedOops -- applicable to 64-bit JVMs. And, if you're using a 64-bit JVM, I'd suggest you use it. It's auto enabled in JDK 7 64-bit JVMs and later JDK 6 64-bit JVMs enable it by default too. -XX:+UseGCOverheadLimit -- by default this option is already enabled. One other command line option to consider is -XX:+TieredCompilation for a JDK 6 Update 25 or later, or JDK 7. This gives you the startup of a -client JVM and the peak performance of a -server JVM. Awesome-ness!  Finally, Charlies also pointed out to me a "new" book he's just published where he goes into the details of JVM tuning, a must for all Fusion Middleware tuning exercises..  (click the book)  Thanks Charlie!

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• Fixing a NoClassDefFoundError

  - by Chris Okyen

  I have some code: package ftc; import java.util.Scanner; public class Fer_To_Cel { public static void main(String[] argv) { // Scanner object to get the temp in degrees Farenheit Scanner keyboard = new Scanner(System.in); boolean isInt = true; // temporarily put as true in case the user enters a valid int the first time int degreesF = 0; // initialy set to 0 do { try { // Input the temperature text. System.out.print("\nPlease enter a temperature (integer number, no fractional part) in degrees Farenheit: "); degreesF = Integer.parseInt(keyboard.next()); // Get user input and Assign the far. temperature variable, which is casted from String to int. } // Let the user know in a user friendly notice that the value entered wasnt an int ( give int value range ) , and then give error log catch(java.lang.Exception e) { System.out.println("Sorry but you entered a non-int value ( needs to be between ( including ) -2,147,483,648 and 2,147,483,647 ).. \n"); e.printStackTrace(); isInt = false; } } while(!isInt); System.out.println(""); // print a new line. final int degreesC = (5*(degreesF-32)/9); // convert the degrees from F to C and store the resulting expression in degreesC // Print out a newline, then print what X degrees F is in Celcius. System.out.println("\n" + degreesF + " degrees Farenheit is " + degreesC + " degrees Celcius"); } } And The following error: C:\Program Files\Java\jdk1.7.0_06\bin>java Fer_To_Cel Exception in thread "main" java.lang.NoClassDefFoundError: Fer_To_Cel (wrong name: ftc/Fer_To_Cel) at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:791) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14 at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:423) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:356) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:480) The code compiled without compile errors, but presented errors during execution. Which leads me to two questions. I know Errors can be termed Compiler, Runtime and Logic Errors, but the NoClassDefFoundError inherits java.lang.LinkageError. Does that make it a Linker error, being niether of the three types of errors I listed, If I am right this is the answer. For someone else who obtains the singular .java file and compiles it, would this be the only way to solve this problem? Or can I (should I ) do/have done something to fix this problem? Basically, based on a basis of programming, is this a fault of me as the writer? Could this be done once on, my half and be distributed and not needed be done again?

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