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  • Imperative Programming in F#

    This article is taken from the book F# in Action. The authors discuss basics of imperative programming in F# and develop a simple application to show how this type of programming works. They also feature some of the interoperability among languages on .NET platform.

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  • Paradigms fit for UI programming

    - by Inca
    This is a more specific question (or actually two, but they are related) coming from the comments of OOP technology death where someone stated that OOP is not the right paradigm for GUI programming. Reading the comments there and here I still have the feeling there are things to learn: which programming paradigms are considered good fits and why are they better than others (perhaps with examples to illustrate?) I removed the tk-example from the title and question

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  • Choice of Operating System Version for Azure Roles

    - by kaleidoscope
    Customers can now choose when their applications receive new operating system updates and patches by selecting which version of the operating system their applications will run on in Windows Azure.  Right now there is only one available operating system version (released on December 17th, 2009), but new builds with the latest updates and patches will be released regularly.  This new feature allows developers to test their applications when new patches come out before upgrading their production deployments. To select an operating system version for your application, add the new osVersion attribute to your service configuration file.  The full list of available operating system versions is maintained in the Configuring Operating System Versions topic in the Windows Azure MSDN documentation.   Sarang, K

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • Microsoft Sql Server 2008 R2 System Databases

    For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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  • What non-programming books should a programmer read to help develop programming/thinking skills?

    - by FeatureCreep
    There are a lot of questions about what programming books should be on the programmer's bookshelf. How about non-programming related books that can help you become a better programmer or developer? It would also be interesting to know why they would help. My first choice would be Sun Tzu's "Art of War" (however cliché), because it made it obvious that the success of any project depends on the strength of its weakest link (and warfare is a big project).

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  • Programming Languages

    - by Shannon
    I realize this will be a very vague question, but please bear with me. I have a concept for an open-world game, hand to hand combat, with a fairly open storyline, but there is an issue. I'm not sure which programming language to use, as I'm fairly new to programming. I am considering c++, but I would like to hear your opinions on which language you believe would support this type of game most efficiently. Pros and cons would be appreciated.

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  • CMSs & ERPs for hospital management system

    - by Akshey
    Hi, What are the best free CMSs or CMS plugins or ERPs or any other free tools available for developing a hospital management system? I want to develop it for a children's hospital run by my father. The hospital is small with two doctors. Currently, everything is done manually on paper. The main entities who will be using the system are: Receptionist, the two doctors, chemist and the medical laboratorist. They will use it majorly for keeping the records of the patient. The patients would not be interacting with the system directly. The system needs to be user friendly and should be easy to learn. I was thinking to develop such a system using a CMS or an ERP or any other free tool. I have used wordpress/drupal in past but never used an ERP. Can you please guide me to make such a system using free, and preferably open source, tools? Thanks, Akshey

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  • What non-programming books should a programmer read (that helps developing programming skills/thinking)?

    - by FeatureCreep
    There are a lot of questions about what programming books should be on the programmer's bookshelf. How about non-programming related books that can help you become a better programmer or developer? It would also be interesting to know why they would help. My first choice would be Sun Tzu's "Art of War" (however cliché), because it made it obvious that the success of any project depends on the strength of its weakest link (and warfare is a big project).

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  • Where to generate data in an Entity-Component System?

    - by Mark Mandel
    So I'm making a small game where I generate 2D landscape using perlin noise when the game first loads. I've got it working in a OO way, but want to move over to an ES architecure, and I'm just struggling to work out the right place for the code that does the generation to go? In OO world, I have a World object which gets passes a coordinate value that is used as the seed for the perlin noise, and generates all the points for the land mass when the world is created. I'm thinking I need a World component with a coordinate field on it - that's an easy part. From there - is it right for a component to generate data when it's first initialised (or is that too OO?)? Or should a System be doing that instead, when the game first starts? Or... some other solution I'm not aware of? Thanks in advance for any guidance.

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  • Cannot see user desktop (Applications, Places, System...) when I log in

    - by Jesi
    I am very new to Ubuntu. I recently got a new laptop running Windows 7. I am using Virtual Box and just installed the Ubuntu 12.10 ISO as a new Virtual Machine within Virtual Box. Everything seemed to install just fine and I even added the Guest Additions under Devices. The problem is that I cannot see the menus and my login information. The virtual machine says it is running; however, I do not have the Applications, Places, System, etc. tray to select from. Is there something I am supposed to do after logging in to get this? I entered my password and everything seemed fine, I just don't have those drop-down menus available...

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  • "Unable to read data from the transport connection: net_io_connectionclosed." - Windows Vista Busine

    - by John DaCosta
    Unable to test sending email from .NET code in Windows Vista Business. I am writing code which I will migrate to an SSIS Package once it its proven. The code is to send an error message via email to a list of recipients. The code is below, however I am getting an exception when I execute the code. I created a simple class to do the mailing... the design could be better, I am testing functionality before implementing more robust functionality, methods, etc. namespace LabDemos { class Program { static void Main(string[] args) { Mailer m = new Mailer(); m.test(); } } } namespace LabDemos { class MyMailer { List<string> _to = new List<string>(); List<string> _cc = new List<string>(); List<string> _bcc = new List<string>(); String _msgFrom = ""; String _msgSubject = ""; String _msgBody = ""; public void test(){ //create the mail message MailMessage mail = new MailMessage(); //set the addresses mail.From = new MailAddress("[email protected]"); //set the content mail.Subject = "This is an email"; mail.Body = "this is a sample body"; mail.IsBodyHtml = false; //send the message SmtpClient smtp = new SmtpClient(); smtp.Host = "emailservername"; smtp.Port = 25; smtp.UseDefaultCredentials = true; smtp.Send(mail); } } Exception Message Inner Exception {"Unable to read data from the transport connection: net_io_connectionclosed."} Stack Trace " at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 offset, Int32 read, Boolean readLine)\r\n at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine)\r\n at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller)\r\n at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)\r\n at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)\r\n at System.Net.Mail.SmtpClient.GetConnection()\r\n at System.Net.Mail.SmtpClient.Send(MailMessage message)" Outer Exception System.Net.Mail.SmtpException was unhandled Message="Failure sending mail." Source="System" StackTrace: at System.Net.Mail.SmtpClient.Send(MailMessage message) at LabDemos.Mailer.test() in C:\Users\username\Documents\Visual Studio 2008\Projects\LabDemos\LabDemos\Mailer.cs:line 40 at LabDemos.Program.Main(String[] args) in C:\Users\username\Documents\Visual Studio 2008\Projects\LabDemos\LabDemos\Program.cs:line 48 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args) at System.Runtime.Hosting.ManifestRunner.Run(Boolean checkAptModel) at System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly() at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData) at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext) at System.Activator.CreateInstance(ActivationContext activationContext) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: System.IO.IOException Message="Unable to read data from the transport connection: net_io_connectionclosed." Source="System" StackTrace: at System.Net.Mail.SmtpReplyReaderFactory.ProcessRead(Byte[] buffer, Int32 offset, Int32 read, Boolean readLine) at System.Net.Mail.SmtpReplyReaderFactory.ReadLines(SmtpReplyReader caller, Boolean oneLine) at System.Net.Mail.SmtpReplyReaderFactory.ReadLine(SmtpReplyReader caller) at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port) at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port) at System.Net.Mail.SmtpClient.GetConnection() at System.Net.Mail.SmtpClient.Send(MailMessage message) InnerException:

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  • Implement a vpn

    - by jackson
    I want to build an application client(client.exe) - server to do the following: when the clients run it they are thrown in a VPN and they can communicate each other within 1 applicataion. For example : clients run client.exe and they can see each other in LAN ONLY in Starcraft. From what i have read the right type of vpn for this situation is Secured Socket Tunneling Protocol: "Secure socket tunneling protocol, also referred to as SSTP, is by definition an application-layer protocol. It is designed to employ a synchronous communication in a back and forth motion between two programs. It allows many application endpoints over one network connection, between peer nodes, thereby enabling efficient usage of the communication resources that are available to that network. " Question: I don't have experience with networking programming so my question for the ones who have, is this the right approach? PS1: i don't want something done like OpenVpn, i do this as learning exercise. PS2: the application is targeting Windows and i plan to use .NET Thanks for reading the whole story, i am waiting for your replies.

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  • Is this too much to ask for a game programming and developing enthusiast? Am I doing this wrong?

    - by I_Question_Things_Deeply
    I have been a computer-fanatic for almost a decade now. I've always loved and wondered how computers work, even from the purest, lowest hardware level to the very smallest pixel on the screen, and all the software around that. That seems to be my problem though ... as I try to write code (I'm pretty fluent at C++) I always sit there enormous amounts of time in front of a text-editor wondering how every line, statement, datum, function, etc. will correspond to every Assembly and machine instruction performed to do absolutely everything necessary for the kernel to allocate memory to run my compiled program, and all of the other hardware being used as well. For example ... I would write cout << "Before memory changed" << endl; and run the debugger to get the Assembly for this, and then try and reverse disassemble the Assembly to machine code based on my ISA, and then research every .dll, library file, linked library, linking process, linker source code of the program, the make file, the kernel I'm using's steps of processing this compilation, the hardware's part aside from the processor (e.g. video card, sound card, chipset, cache latency, byte-sized registers, calling convention use, DDR3 RAM and disk drive, filesystem functioning and so many other things). Am I going about programming wrong? I mean I feel I should know everything that goes on underneath English syntax on a computer program. But the problem is that the more I research every little thing the less I actually accomplish at all. I can never finish anything because of this mentality, yet I feel compelled to know everything... what should I do?

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  • Python: Catching / blocking SIGINT during system call

    - by danben
    I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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  • Catching / blocking SIGINT during system call

    - by danben
    I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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  • How can i uniquely identify users trying to open() a kernel module?

    - by user349072
    Dear Gurus, I'm working on a Kernel module and i'm trying to Uniquely identify each one of the users trying to open() the module ( can be either processes or threads ). what is the best way to identify them? is there an ID i can get from a system call? i wish to get all users in a list that specifies whether they're trying to open the module for read \ write and i need to know which one tried acting... many many thanks. in regards, IK

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  • WCF timedout waiting for System.Diagnostics.Process to finish

    - by Bartek
    Dear All, We have a WCF Service deployed on Windows Server 2003 that handles file transfers. When file is in Unix format, I am converting it to Dos format in the initialization stage using System.Diagnostics.Process (.WaitForExit()). Client calls the service: obj_DataSenderService = New DataSendClient() obj_DataSenderService.InnerChannel.OperationTimeout = New TimeSpan(0, System.Configuration.ConfigurationManager.AppSettings("DatasenderServiceOperationTimeout"), 0) str_DataSenderGUID = obj_DataSenderService.Initialize(xe_InitDetails.GetXMLNode) This works fine, however for large files the conversion takes more than 10 minutes and I am getting exception: A first chance exception of type 'System.ServiceModel.CommunicationException' occurred in mscorlib.dll Additional information: The socket connection was aborted. This could be caused by an error processing your message or a receive timeout being exceeded by the remote host, or an underlying network resource issue. Local socket timeout was '00:59:59.8749992'. I tried configuring both client: <system.serviceModel> <bindings> <netTcpBinding> <binding name="NetTcpBinding_IDataSend" closeTimeout="01:00:00" openTimeout="01:00:00" receiveTimeout="01:00:00" sendTimeout="01:00:00" transactionFlow="false" transferMode="Buffered" transactionProtocol="OleTransactions" hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="524288" maxBufferSize="65536" maxConnections="10" maxReceivedMessageSize="65536"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" /> <security mode="None"> <transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" /> <message clientCredentialType="Windows" /> </security> </binding> </netTcpBinding> </bindings> <client> <endpoint address="net.tcp://localhost:4000/DataSenderEndPoint" binding="netTcpBinding" bindingConfiguration="NetTcpBinding_IDataSend" contract="IDataSend" name="NetTcpBinding_IDataSend"> <identity> <servicePrincipalName value="host/localhost" /> <!--<servicePrincipalName value="host/axopwrapp01.Corp.Acxiom.net" />--> </identity> </endpoint> </client> </system.serviceModel> And service: <system.serviceModel> <bindings> <netTcpBinding> <binding name="NetTcpBinding_IDataSend" closeTimeout="01:00:00" openTimeout="01:00:00" receiveTimeout="01:00:00" sendTimeout="01:00:00" transactionFlow="false" transferMode="Buffered" transactionProtocol="OleTransactions" hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="524288" maxBufferSize="65536" maxConnections="10" maxReceivedMessageSize="65536"> </binding> </netTcpBinding> </bindings> </system.serviceModel> but without luck. In the Service trace viewer I can see: Close process timed out waiting for service dispatch to complete. with stack trace: System.ServiceModel.ServiceChannelManager.CloseInput(TimeSpan timeout) System.ServiceModel.Dispatcher.InstanceContextManager.CloseInput(TimeSpan timeout) System.ServiceModel.ServiceHostBase.OnClose(TimeSpan timeout) System.ServiceModel.Channels.CommunicationObject.Close(TimeSpan timeout) System.ServiceModel.Channels.CommunicationObject.Close() DataSenderService.DataSender.OnStop() System.ServiceProcess.ServiceBase.DeferredStop() System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs) System.Runtime.Remoting.Messaging.StackBuilderSink.PrivateProcessMessage(RuntimeMethodHandle md, Object[] args, Object server, Int32 methodPtr, Boolean fExecuteInContext, Object[]& outArgs) System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(IMessage msg, IMessageSink replySink) System.Runtime.Remoting.Proxies.AgileAsyncWorkerItem.DoAsyncCall() System.Runtime.Remoting.Proxies.AgileAsyncWorkerItem.ThreadPoolCallBack(Object o) System.Threading._ThreadPoolWaitCallback.WaitCallback_Context(Object state) System.Threading.ExecutionContext.runTryCode(Object userData) System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) System.Threading._ThreadPoolWaitCallback.PerformWaitCallbackInternal(_ThreadPoolWaitCallback tpWaitCallBack) System.Threading._ThreadPoolWaitCallback.PerformWaitCallback(Object state) Many thanks Bartek

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  • C# 4.0: Dynamic Programming

    - by Paulo Morgado
    The major feature of C# 4.0 is dynamic programming. Not just dynamic typing, but dynamic in broader sense, which means talking to anything that is not statically typed to be a .NET object. Dynamic Language Runtime The Dynamic Language Runtime (DLR) is piece of technology that unifies dynamic programming on the .NET platform, the same way the Common Language Runtime (CLR) has been a common platform for statically typed languages. The CLR always had dynamic capabilities. You could always use reflection, but its main goal was never to be a dynamic programming environment and there were some features missing. The DLR is built on top of the CLR and adds those missing features to the .NET platform. The Dynamic Language Runtime is the core infrastructure that consists of: Expression Trees The same expression trees used in LINQ, now improved to support statements. Dynamic Dispatch Dispatches invocations to the appropriate binder. Call Site Caching For improved efficiency. Dynamic languages and languages with dynamic capabilities are built on top of the DLR. IronPython and IronRuby were already built on top of the DLR, and now, the support for using the DLR is being added to C# and Visual Basic. Other languages built on top of the CLR are expected to also use the DLR in the future. Underneath the DLR there are binders that talk to a variety of different technologies: .NET Binder Allows to talk to .NET objects. JavaScript Binder Allows to talk to JavaScript in SilverLight. IronPython Binder Allows to talk to IronPython. IronRuby Binder Allows to talk to IronRuby. COM Binder Allows to talk to COM. Whit all these binders it is possible to have a single programming experience to talk to all these environments that are not statically typed .NET objects. The dynamic Static Type Let’s take this traditional statically typed code: Calculator calculator = GetCalculator(); int sum = calculator.Sum(10, 20); Because the variable that receives the return value of the GetCalulator method is statically typed to be of type Calculator and, because the Calculator type has an Add method that receives two integers and returns an integer, it is possible to call that Sum method and assign its return value to a variable statically typed as integer. Now lets suppose the calculator was not a statically typed .NET class, but, instead, a COM object or some .NET code we don’t know he type of. All of the sudden it gets very painful to call the Add method: object calculator = GetCalculator(); Type calculatorType = calculator.GetType(); object res = calculatorType.InvokeMember("Add", BindingFlags.InvokeMethod, null, calculator, new object[] { 10, 20 }); int sum = Convert.ToInt32(res); And what if the calculator was a JavaScript object? ScriptObject calculator = GetCalculator(); object res = calculator.Invoke("Add", 10, 20); int sum = Convert.ToInt32(res); For each dynamic domain we have a different programming experience and that makes it very hard to unify the code. With C# 4.0 it becomes possible to write code this way: dynamic calculator = GetCalculator(); int sum = calculator.Add(10, 20); You simply declare a variable who’s static type is dynamic. dynamic is a pseudo-keyword (like var) that indicates to the compiler that operations on the calculator object will be done dynamically. The way you should look at dynamic is that it’s just like object (System.Object) with dynamic semantics associated. Anything can be assigned to a dynamic. dynamic x = 1; dynamic y = "Hello"; dynamic z = new List<int> { 1, 2, 3 }; At run-time, all object will have a type. In the above example x is of type System.Int32. When one or more operands in an operation are typed dynamic, member selection is deferred to run-time instead of compile-time. Then the run-time type is substituted in all variables and normal overload resolution is done, just like it would happen at compile-time. The result of any dynamic operation is always dynamic and, when a dynamic object is assigned to something else, a dynamic conversion will occur. Code Resolution Method double x = 1.75; double y = Math.Abs(x); compile-time double Abs(double x) dynamic x = 1.75; dynamic y = Math.Abs(x); run-time double Abs(double x) dynamic x = 2; dynamic y = Math.Abs(x); run-time int Abs(int x) The above code will always be strongly typed. The difference is that, in the first case the method resolution is done at compile-time, and the others it’s done ate run-time. IDynamicMetaObjectObject The DLR is pre-wired to know .NET objects, COM objects and so forth but any dynamic language can implement their own objects or you can implement your own objects in C# through the implementation of the IDynamicMetaObjectProvider interface. When an object implements IDynamicMetaObjectProvider, it can participate in the resolution of how method calls and property access is done. The .NET Framework already provides two implementations of IDynamicMetaObjectProvider: DynamicObject : IDynamicMetaObjectProvider The DynamicObject class enables you to define which operations can be performed on dynamic objects and how to perform those operations. For example, you can define what happens when you try to get or set an object property, call a method, or perform standard mathematical operations such as addition and multiplication. ExpandoObject : IDynamicMetaObjectProvider The ExpandoObject class enables you to add and delete members of its instances at run time and also to set and get values of these members. This class supports dynamic binding, which enables you to use standard syntax like sampleObject.sampleMember, instead of more complex syntax like sampleObject.GetAttribute("sampleMember").

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  • Can certain system-hungry modules be disabled in Ubuntu?

    - by Ole Thomsen Buus
    Hi, Let me add some context: I am currently using Ubuntu 9.10 64-bit (Desktop) on a relatively powerful stationary PC (Intel Core i7 920, 12GB ram). My purpose is highspeed imaging with a pointgrey Grashopper machine-vision camera (for research, PhD project). This camera is capable of 200 fps at full VGA (640x480) resolution. The camera is connected using Firewire (1394b) and the drivers and software from Pointgrey works great. I have developed a console C++ application that can grap a certain number of frames to preallocated memory and after this also save the grapped frames to harddrive. Currently it works fine but sometimes I am observing a few framedrops (1-3). When this happens I reset the experiment and repeat the recording and usually i am lucky the second time with no framedrops (the camera-driver has a internal framecounter that I am using). Question: I usually go to tty1 and use "sudo service gdm stop" to disable the graphical frontend. It seems to release some memory though that is not my main concern. My concern is CPU resources. Are there other system hungry modules that can be disabled temporarily such that the CPU gets less busy on Ubuntu 9.10? At some point in the future I will update to 10.10. Should I perhaps option for the server edition instead? Thanks.

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  • How to manipulate *huge* amounts of data

    - by Alejandro
    Hi there! I'm having the following problem. I need to store huge amounts of information (~32 GB) and be able to manipulate it as fast as possible. I'm wondering what's the best way to do it (combinations of programming language + OS + whatever you think its important). The structure of the information I'm using is a 4D array (NxNxNxN) of double-precission floats (8 bytes). Right now my solution is to slice the 4D array into 2D arrays and store them in separate files in the HDD of my computer. This is really slow and the manipulation of the data is unbearable, so this is no solution at all! I'm thinking on moving into a Supercomputing facility in my country and store all the information in the RAM, but I'm not sure how to implement an application to take advantage of it (I'm not a professional programmer, so any book/reference will help me a lot). An alternative solution I'm thinking on is to buy a dedicated server with lots of RAM, but I don't know for sure if that will solve the problem. So right now my ignorance doesn't let me choose the best way to proceed. What would you do if you were in this situation? I'm open to any idea. Thanks in advance!

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  • Why does System.Web.Hosting.ApplicationHost.CreateApplicationHost throw System.IO.FileNotFoundExcept

    - by Scott Langham
    I saw something about needing to have the assembly available for the type of the first argument passed to the function. I think it is, I can't figure out what am I missing. This code is in a service. I was running the service under the 'NETWORK SERVICES' user account, when I changed the account to that of the session I was logged on with it worked ok. But, what's the difference, and how can I get it to work for the NETWORK SERVICES user.

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  • Roadblocks in creating a custom operating system

    - by Dinah
    It seems to me that the most common overly ambitious project that programmers (esp. Comp. Sci. grads) try to tackle is building your own operating system. (Trying to create your own programming language + compiler is probably even more common but not nearly as ambitious.) For those (like myself) foolish enough to try: aside from the sheer size, what are the biggest *gotcha*s or unexpected roadblocks you've encountered in trying to create your own OS from the ground up? Edit: A great OS question: http://stackoverflow.com/questions/43180/how-to-get-started-in-operating-system-development/

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  • Where did System.Design go?

    - by Nilbert
    I am making a C# project in which I am using ScintillaNet, and it says: The referenced assembly "ScintillaNet" could not be resolved because it has a dependency on "System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" which is not in the currently targeted framework ".NETFramework,Version=v4.0,Profile=Client". Please remove references to assemblies not in the targeted framework or consider retargeting your project. I tried adding a reference to System.Design, but it doesn't exist in my list. Do I need to download it somewhere? I have MS Visual Studio 10.

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  • ASP.NET FormView: "Object of type 'System.Int32' cannot be converted to type 'System.String"

    - by Vinzcent
    Hey I have a problem with my FromView. I would like to show some data from a Database Table in my FormView. But some data is from the tupe Int32, while this data should be in a TextBox, a string. How do you convert these Int32's. FormView and my ObjectDataSource <asp:FormView ID="fvDetailOrder" runat="server"> <ItemTemplate> Aantal:<br /> <asp:Label CssClass="txtBox" ID="Label15" runat="server" Text='<%# Eval("COUNT") %>' /><br /> Prijs:<br /> <asp:Label CssClass="txtBox" ID="Label16" runat="server" Text='<%# Eval("PRICE") %>' /><br /> Korting:<br /> <asp:Label CssClass="txtBox" ID="Label17" runat="server" Text='' /><br /> Totaal:<br /> <asp:Label CssClass="txtBox" ID="Label18" runat="server" Text='<%# Eval("AMOUNT") %>' /><br /> Betaald:<br /> <asp:Label CssClass="txtBox" ID="Label19" runat="server" Text='<%# Eval("PAID") %>' /><br /> Datum betaling:<br /> <asp:Label CssClass="txtBox" ID="Label20" runat="server" Text='<%# Eval("PDATE") %>' /><br /> </ItemTemplate> </asp:FormView> <asp:ObjectDataSource ID="objdsOrderID" runat="server" OnSelecting="objdsOrderID_Selecting" SelectMethod="getOrdersByID" TypeName="DAL.OrdersDAL"> <SelectParameters> <asp:Parameter Name="id" Type="Int32" /> </SelectParameters> </asp:ObjectDataSource> My Code behind protected void gvOrdersAdmin_SelectedIndexChanged(object sender, EventArgs e) { fvDetailOrder.DataSource = objdsOrderID; fvDetailOrder.DataBind(); // <-- HERE I GET THE ERROR } protected void objdsOrderID_Selecting(object sender, ObjectDataSourceSelectingEventArgs e) { e.InputParameters["id"] = gvOrdersAdmin.DataKeys[gvOrdersAdmin.SelectedRow.RowIndex].Values[0]; ; } My Data Acces Layer public static DataTable getOrdersByID(string id) { string sql = "SELECT 'AUTHOR' = tblAuthors.FIRSTNAME + ' ' + tblAuthors.LASTNAME, tblBooks.*, tblGenres.*, tblLanguages.*, tblOrders.* FROM tblAuthors INNER JOIN tblBooks ON tblAuthors.AUTHOR_ID = tblBooks.AUTHOR_ID INNER JOIN tblGenres ON tblBooks.GENRE_ID = tblGenres.GENRE_ID INNER JOIN tblLanguages ON tblBooks.LANG_ID = tblLanguages.LANG_ID INNER JOIN tblOrders ON tblBooks.BOOK_ID = tblOrders.BOOK_ID" + " WHERE tblOrders.ID = @id;"; SqlDataAdapter da = new SqlDataAdapter(sql, GetConnectionString()); da.SelectCommand.Parameters["id"].Value = id; DataSet ds = new DataSet(); da.Fill(ds, "Orders"); return ds.Tables["Orders"]; } Thanks a lot, Vincent

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