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• Quartz.Net Windows Service Configure Logging

  - by Tarun Arora

  In this blog post I’ll be covering, Logging for Quartz.Net Windows Service 01 – Why doesn’t Quartz.Net Windows Service log by default 02 – Configuring Quartz.Net windows service for logging to eventlog, file, console, etc 03 – Results: Logging in action If you are new to Quartz.Net I would recommend going through, A brief Introduction to Quartz.net Walkthrough of Installing & Testing Quartz.Net as a Windows Service Writing & Scheduling your First HelloWorld job with Quartz.Net   01 – Why doesn’t Quartz.Net Windows Service log by default If you are trying to figure out why… The Quartz.Net windows service isn’t logging The Quartz.Net windows service isn’t writing anything to the event log The Quartz.Net windows service isn’t writing anything to a file How do I configure Quartz.Net windows service to use log4Net How do I change the level of logging for Quartz.Net Look no further, This blog post should help you answer these questions. Quartz.NET uses the Common.Logging framework for all of its logging needs. If you navigate to the directory where Quartz.Net Windows Service is installed (I have the service installed in C:\Program Files (x86)\Quartz.net, you can find out the location by looking at the properties of the service) and open ‘Quartz.Server.exe.config’ you’ll see that the Quartz.Net is already set up for logging to ConsoleAppender and EventLogAppender, but only ‘ConsoleAppender’ is set up as active. So, unless you have the console associated to the Quartz.Net service you won’t be able to see any logging. <log4net> <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender"> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%d [%t] %-5p %l - %m%n" /> </layout> </appender> <appender name="EventLogAppender" type="log4net.Appender.EventLogAppender"> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%d [%t] %-5p %l - %m%n" /> </layout> </appender> <root> <level value="INFO" /> <appender-ref ref="ConsoleAppender" /> <!-- uncomment to enable event log appending --> <!-- <appender-ref ref="EventLogAppender" /> --> </root> </log4net> Problem: In the configuration above Quartz.Net Windows Service only has ConsoleAppender active. So, no logging will be done to EventLog. More over the RollingFileAppender isn’t setup at all. So, Quartz.Net will not log to an application trace log file. 02 – Configuring Quartz.Net windows service for logging to eventlog, file, console, etc Let’s change this behaviour by changing the config file… In the below config file, I have added the RollingFileAppender. This will configure Quartz.Net service to write to a log file. (<appender name="GeneralLog" type="log4net.Appender.RollingFileAppender">) I have specified the location for the log file (<arg key="configFile" value="Trace/application.log.txt"/>) I have enabled the EventLogAppender and RollingFileAppender to be written to by Quartz. Net windows service Changed the default level of logging from ‘Info’ to ‘All’. This means all activity performed by Quartz.Net Windows service will be logged. You might want to tune this back to ‘Debug’ or ‘Info’ later as logging ‘All’ will produce too much data to the logs. (<level value="ALL"/>) Since I have changed the logging level to ‘All’, I have added applicationSetting to remove logging log4Net internal debugging. (<add key="log4net.Internal.Debug" value="false"/>) <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="quartz" type="System.Configuration.NameValueSectionHandler, System, Version=1.0.5000.0,Culture=neutral, PublicKeyToken=b77a5c561934e089" /> <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" /> <sectionGroup name="common"> <section name="logging" type="Common.Logging.ConfigurationSectionHandler, Common.Logging" /> </sectionGroup> </configSections> <common> <logging> <factoryAdapter type="Common.Logging.Log4Net.Log4NetLoggerFactoryAdapter, Common.Logging.Log4net"> <arg key="configType" value="INLINE" /> <arg key="configFile" value="Trace/application.log.txt"/> <arg key="level" value="ALL" /> </factoryAdapter> </logging> </common> <appSettings> <add key="log4net.Internal.Debug" value="false"/> </appSettings> <log4net> <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender"> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%d [%t] %-5p %l - %m%n" /> </layout> </appender> <appender name="EventLogAppender" type="log4net.Appender.EventLogAppender"> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%d [%t] %-5p %l - %m%n" /> </layout> </appender> <appender name="GeneralLog" type="log4net.Appender.RollingFileAppender"> <file value="Trace/application.log.txt"/> <appendToFile value="true"/> <maximumFileSize value="1024KB"/> <rollingStyle value="Size"/> <layout type="log4net.Layout.PatternLayout"> <conversionPattern value="%d{HH:mm:ss} [%t] %-5p %c - %m%n"/> </layout> </appender> <root> <level value="ALL" /> <appender-ref ref="ConsoleAppender" /> <appender-ref ref="EventLogAppender" /> <appender-ref ref="GeneralLog"/> </root> </log4net> </configuration>   Note – Please ensure you restart the Quartz.Net Windows service for the config changes to be picked up by the service   03 – Results: Logging in action Once you start the Quartz.Net Windows Service up, the logging should be initiated to write all activities in the Console, EventLog and File… See screen shots below… Figure – Quartz.Net Windows Service logging all activity to the event log Figure – Quartz.Net Windows Service logging all activity to the application log file Where is the output from log4Net ConsoleAppender? As a default behaviour, the console isn't available in windows services, web services, windows forms. The output will simply be dismissed. Unless you are running the process interactively. Which you can do by firing up Quartz.Server.exe –i to see the output   This was fourth in the series of posts on enterprise scheduling using Quartz.net, in the next post I’ll be covering troubleshooting why a scheduled task hasn’t fired on Quartz.net windows service. All Quartz.Net specific blog posts can listed here. Thank you for taking the time out and reading this blog post. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Stay tuned!

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• Metro: Understanding Observables

  - by Stephen.Walther

  The goal of this blog entry is to describe how the Observer Pattern is implemented in the WinJS library. You learn how to create observable objects which trigger notifications automatically when their properties are changed. Observables enable you to keep your user interface and your application data in sync. For example, by taking advantage of observables, you can update your user interface automatically whenever the properties of a product change. Observables are the foundation of declarative binding in the WinJS library. The WinJS library is not the first JavaScript library to include support for observables. For example, both the KnockoutJS library and the Microsoft Ajax Library (now part of the Ajax Control Toolkit) support observables. Creating an Observable Imagine that I have created a product object like this: var product = { name: "Milk", description: "Something to drink", price: 12.33 }; Nothing very exciting about this product. It has three properties named name, description, and price. Now, imagine that I want to be notified automatically whenever any of these properties are changed. In that case, I can create an observable product from my product object like this: var observableProduct = WinJS.Binding.as(product); This line of code creates a new JavaScript object named observableProduct from the existing JavaScript object named product. This new object also has a name, description, and price property. However, unlike the properties of the original product object, the properties of the observable product object trigger notifications when the properties are changed. Each of the properties of the new observable product object has been changed into accessor properties which have both a getter and a setter. For example, the observable product price property looks something like this: price: { get: function () { return this.getProperty(“price”); } set: function (value) { this.setProperty(“price”, value); } } When you read the price property then the getProperty() method is called and when you set the price property then the setProperty() method is called. The getProperty() and setProperty() methods are methods of the observable product object. The observable product object supports the following methods and properties: · addProperty(name, value) – Adds a new property to an observable and notifies any listeners. · backingData – An object which represents the value of each property. · bind(name, action) – Enables you to execute a function when a property changes. · getProperty(name) – Returns the value of a property using the string name of the property. · notify(name, newValue, oldValue) – A private method which executes each function in the _listeners array. · removeProperty(name) – Removes a property and notifies any listeners. · setProperty(name, value) – Updates a property and notifies any listeners. · unbind(name, action) – Enables you to stop executing a function in response to a property change. · updateProperty(name, value) – Updates a property and notifies any listeners. So when you create an observable, you get a new object with the same properties as an existing object. However, when you modify the properties of an observable object, then you can notify any listeners of the observable that the value of a particular property has changed automatically. Imagine that you change the value of the price property like this: observableProduct.price = 2.99; In that case, the following sequence of events is triggered: 1. The price setter calls the setProperty(“price”, 2.99) method 2. The setProperty() method updates the value of the backingData.price property and calls the notify() method 3. The notify() method executes each function in the collection of listeners associated with the price property Creating Observable Listeners If you want to be notified when a property of an observable object is changed, then you need to register a listener. You register a listener by using the bind() method like this: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 2.99; } }; app.start(); })(); In the code above, the bind() method is used to associate the price property with a function. When the price property is changed, the function logs the new value of the price property to the Visual Studio JavaScript console. The price property is associated with the function using the following line of code: // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); Coalescing Notifications If you make multiple changes to a property – one change immediately following another – then separate notifications won’t be sent. Instead, any listeners are notified only once. The notifications are coalesced into a single notification. For example, in the following code, the product price property is updated three times. However, only one message is written to the JavaScript console. Only the last value assigned to the price property is written to the JavaScript Console window: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 3.99; observableProduct.price = 2.99; observableProduct.price = 1.99; Only the last value assigned to price, the value 1.99, appears in the console: If there is a time delay between changes to a property then changes result in different notifications. For example, the following code updates the price property every second: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Add 1 to price every second window.setInterval(function () { observableProduct.price += 1; }, 1000); In this case, separate notification messages are logged to the JavaScript Console window: If you need to prevent multiple notifications from being coalesced into one then you can take advantage of promises. I discussed WinJS promises in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-promises.aspx Because the updateProperty() method returns a promise, you can create different notifications for each change in a property by using the following code: // Change the price observableProduct.updateProperty("price", 3.99) .then(function () { observableProduct.updateProperty("price", 2.99) .then(function () { observableProduct.updateProperty("price", 1.99); }); }); In this case, even though the price is immediately changed from 3.99 to 2.99 to 1.99, separate notifications for each new value of the price property are sent. Bypassing Notifications Normally, if a property of an observable object has listeners and you change the property then the listeners are notified. However, there are certain situations in which you might want to bypass notification. In other words, you might need to change a property value silently without triggering any functions registered for notification. If you want to change a property without triggering notifications then you should change the property by using the backingData property. The following code illustrates how you can change the price property silently: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price silently observableProduct.backingData.price = 5.99; console.log(observableProduct.price); // Writes 5.99 The price is changed to the value 5.99 by changing the value of backingData.price. Because the observableProduct.price property is not set directly, any listeners associated with the price property are not notified. When you change the value of a property by using the backingData property, the change in the property happens synchronously. However, when you change the value of an observable property directly, the change is always made asynchronously. Summary The goal of this blog entry was to describe observables. In particular, we discussed how to create observables from existing JavaScript objects and bind functions to observable properties. You also learned how notifications are coalesced (and ways to prevent this coalescing). Finally, we discussed how you can use the backingData property to update an observable property without triggering notifications. In the next blog entry, we’ll see how observables are used with declarative binding to display the values of properties in an HTML document.

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• Plan Caching and Query Memory Part II (Hash Match) – When not to use stored procedure - Most common performance mistake SQL Server developers make.

  - by sqlworkshops

  SQL Server estimates Memory requirement at compile time, when stored procedure or other plan caching mechanisms like sp_executesql or prepared statement are used, the memory requirement is estimated based on first set of execution parameters. This is a common reason for spill over tempdb and hence poor performance. Common memory allocating queries are that perform Sort and do Hash Match operations like Hash Join or Hash Aggregation or Hash Union. This article covers Hash Match operations with examples. It is recommended to read Plan Caching and Query Memory Part I before this article which covers an introduction and Query memory for Sort. In most cases it is cheaper to pay for the compilation cost of dynamic queries than huge cost for spill over tempdb, unless memory requirement for a query does not change significantly based on predicates.   This article covers underestimation / overestimation of memory for Hash Match operation. Plan Caching and Query Memory Part I covers underestimation / overestimation for Sort. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   To read additional articles I wrote click here.   The best way to learn is to practice. To create the below tables and reproduce the behavior, join the mailing list by using this link: www.sqlworkshops.com/ml and I will send you the table creation script. Most of these concepts are also covered in our webcasts: www.sqlworkshops.com/webcasts  Let’s create a Customer’s State table that has 99% of customers in NY and the rest 1% in WA.Customers table used in Part I of this article is also used here.To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'. --Example provided by www.sqlworkshops.com drop table CustomersState go create table CustomersState (CustomerID int primary key, Address char(200), State char(2)) go insert into CustomersState (CustomerID, Address) select CustomerID, 'Address' from Customers update CustomersState set State = 'NY' where CustomerID % 100 != 1 update CustomersState set State = 'WA' where CustomerID % 100 = 1 go update statistics CustomersState with fullscan go   Let’s create a stored procedure that joins customers with CustomersState table with a predicate on State. --Example provided by www.sqlworkshops.com create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1) end go  Let’s execute the stored procedure first with parameter value ‘WA’ – which will select 1% of data. set statistics time on go --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' goThe stored procedure took 294 ms to complete.  The stored procedure was granted 6704 KB based on 8000 rows being estimated.  The estimated number of rows, 8000 is similar to actual number of rows 8000 and hence the memory estimation should be ok.  There was no Hash Warning in SQL Profiler. To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'.   Now let’s execute the stored procedure with parameter value ‘NY’ – which will select 99% of data. -Example provided by www.sqlworkshops.com exec CustomersByState 'NY' go  The stored procedure took 2922 ms to complete.   The stored procedure was granted 6704 KB based on 8000 rows being estimated.    The estimated number of rows, 8000 is way different from the actual number of rows 792000 because the estimation is based on the first set of parameter value supplied to the stored procedure which is ‘WA’ in our case. This underestimation will lead to spill over tempdb, resulting in poor performance.   There was Hash Warning (Recursion) in SQL Profiler. To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'.   Let’s recompile the stored procedure and then let’s first execute the stored procedure with parameter value ‘NY’.  In a production instance it is not advisable to use sp_recompile instead one should use DBCC FREEPROCCACHE (plan_handle). This is due to locking issues involved with sp_recompile, refer to our webcasts, www.sqlworkshops.com/webcasts for further details.   exec sp_recompile CustomersByState go --Example provided by www.sqlworkshops.com exec CustomersByState 'NY' go  Now the stored procedure took only 1046 ms instead of 2922 ms.   The stored procedure was granted 146752 KB of memory. The estimated number of rows, 792000 is similar to actual number of rows of 792000. Better performance of this stored procedure execution is due to better estimation of memory and avoiding spill over tempdb.   There was no Hash Warning in SQL Profiler.   Now let’s execute the stored procedure with parameter value ‘WA’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go  The stored procedure took 351 ms to complete, higher than the previous execution time of 294 ms.    This stored procedure was granted more memory (146752 KB) than necessary (6704 KB) based on parameter value ‘NY’ for estimation (792000 rows) instead of parameter value ‘WA’ for estimation (8000 rows). This is because the estimation is based on the first set of parameter value supplied to the stored procedure which is ‘NY’ in this case. This overestimation leads to poor performance of this Hash Match operation, it might also affect the performance of other concurrently executing queries requiring memory and hence overestimation is not recommended.     The estimated number of rows, 792000 is much more than the actual number of rows of 8000.  Intermediate Summary: This issue can be avoided by not caching the plan for memory allocating queries. Other possibility is to use recompile hint or optimize for hint to allocate memory for predefined data range.Let’s recreate the stored procedure with recompile hint. --Example provided by www.sqlworkshops.com drop proc CustomersByState go create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1, recompile) end go  Let’s execute the stored procedure initially with parameter value ‘WA’ and then with parameter value ‘NY’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go exec CustomersByState 'NY' go  The stored procedure took 297 ms and 1102 ms in line with previous optimal execution times.   The stored procedure with parameter value ‘WA’ has good estimation like before.   Estimated number of rows of 8000 is similar to actual number of rows of 8000.   The stored procedure with parameter value ‘NY’ also has good estimation and memory grant like before because the stored procedure was recompiled with current set of parameter values.  Estimated number of rows of 792000 is similar to actual number of rows of 792000.    The compilation time and compilation CPU of 1 ms is not expensive in this case compared to the performance benefit.   There was no Hash Warning in SQL Profiler.   Let’s recreate the stored procedure with optimize for hint of ‘NY’. --Example provided by www.sqlworkshops.com drop proc CustomersByState go create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1, optimize for (@State = 'NY')) end go  Let’s execute the stored procedure initially with parameter value ‘WA’ and then with parameter value ‘NY’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go exec CustomersByState 'NY' go  The stored procedure took 353 ms with parameter value ‘WA’, this is much slower than the optimal execution time of 294 ms we observed previously. This is because of overestimation of memory. The stored procedure with parameter value ‘NY’ has optimal execution time like before.   The stored procedure with parameter value ‘WA’ has overestimation of rows because of optimize for hint value of ‘NY’.   Unlike before, more memory was estimated to this stored procedure based on optimize for hint value ‘NY’.    The stored procedure with parameter value ‘NY’ has good estimation because of optimize for hint value of ‘NY’. Estimated number of rows of 792000 is similar to actual number of rows of 792000.   Optimal amount memory was estimated to this stored procedure based on optimize for hint value ‘NY’.   There was no Hash Warning in SQL Profiler.   This article covers underestimation / overestimation of memory for Hash Match operation. Plan Caching and Query Memory Part I covers underestimation / overestimation for Sort. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   Summary: Cached plan might lead to underestimation or overestimation of memory because the memory is estimated based on first set of execution parameters. It is recommended not to cache the plan if the amount of memory required to execute the stored procedure has a wide range of possibilities. One can mitigate this by using recompile hint, but that will lead to compilation overhead. However, in most cases it might be ok to pay for compilation rather than spilling sort over tempdb which could be very expensive compared to compilation cost. The other possibility is to use optimize for hint, but in case one sorts more data than hinted by optimize for hint, this will still lead to spill. On the other side there is also the possibility of overestimation leading to unnecessary memory issues for other concurrently executing queries. In case of Hash Match operations, this overestimation of memory might lead to poor performance. When the values used in optimize for hint are archived from the database, the estimation will be wrong leading to worst performance, so one has to exercise caution before using optimize for hint, recompile hint is better in this case.   I explain these concepts with detailed examples in my webcasts (www.sqlworkshops.com/webcasts), I recommend you to watch them. The best way to learn is to practice. To create the above tables and reproduce the behavior, join the mailing list at www.sqlworkshops.com/ml and I will send you the relevant SQL Scripts.  Register for the upcoming 3 Day Level 400 Microsoft SQL Server 2008 and SQL Server 2005 Performance Monitoring & Tuning Hands-on Workshop in London, United Kingdom during March 15-17, 2011, click here to register / Microsoft UK TechNet.These are hands-on workshops with a maximum of 12 participants and not lectures. For consulting engagements click here.   Disclaimer and copyright information:This article refers to organizations and products that may be the trademarks or registered trademarks of their various owners. Copyright of this article belongs to R Meyyappan / www.sqlworkshops.com. You may freely use the ideas and concepts discussed in this article with acknowledgement (www.sqlworkshops.com), but you may not claim any of it as your own work. This article is for informational purposes only; you use any of the suggestions given here entirely at your own risk.   R Meyyappan [email protected] LinkedIn: http://at.linkedin.com/in/rmeyyappan

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• SharePoint 2010 Hosting - ASPHostPortal :: Installing SSRS 2008 R2 on SharePoint 2010

  - by mbridge

  What do you need first? Please download SQL Server® 2008 R2 November CTP Reporting Services Add-in for Microsoft SharePoint® Technologies 2010 and please follow this steps: 1. Install a SharePoint technology instance. (Already did this when installing PowerPivot with SharePoint) 2. Install SQL Server 2008 R2 November CTP Reporting Services and specify that the report server use SharePoint Integrated mode 3. Configure Reporting Services 4. Download the Reporting Services Add-in by clicking the rsSharePoint.msi link later on this page. To start the installation immediately, click Run After installing Reporting services and the add-in your reporting server is ready to be integrated with SharePoint, in SharePoint 2010 we have some new admin screens. To integrate go to central admin, general application settings: When you successfully installed the add-in a reporting services icon will be there. Click Reporting Services Integration: Add the report server web service url (To get the URL, open the Reporting Services Configuration tool, connect to the report server, and click Web Service URL. Click the URL to verify it works. Copy the URL and paste it into Report Server Web Service URL.), select your authentication mode (windows authentication is prefered). Add a username and password of your admin account. Click ok to configure and start the integration. After the installation you can set the reporting services default. What is changed in SP2010 is that there isn’t a report library available. You have to add content types to a default library. So go to a site collection, site actions, View all site content. Create a Asset library: Now we have to make sure we can add reports to the library. To do this we have to add content types: Open the library, click on library tools, library settings, Under Content Types, click Add from existing site content types. In the Select Content Types section, in Select site content types from, click the arrow to select Reporting Services. In the Available Site Content Types list, click Report Builder, Report Data Source and Report and then click Add to move the selected content type to the Content types to add list. Now we are ready to upload reports and execute them from within our webparts: Another interesting post: - Integrating SharePoint 2010 and SQL 2008 R2

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• Anatomy of a .NET Assembly - Custom attribute encoding

  - by Simon Cooper

  In my previous post, I covered how field, method, and other types of signatures are encoded in a .NET assembly. Custom attribute signatures differ quite a bit from these, which consequently affects attribute specifications in C#. Custom attribute specifications In C#, you can apply a custom attribute to a type or type member, specifying a constructor as well as the values of fields or properties on the attribute type: public class ExampleAttribute : Attribute { public ExampleAttribute(int ctorArg1, string ctorArg2) { ... } public Type ExampleType { get; set; } } [Example(5, "6", ExampleType = typeof(string))] public class C { ... } How does this specification actually get encoded and stored in an assembly? Specification blob values Custom attribute specification signatures use the same building blocks as other types of signatures; the ELEMENT_TYPE structure. However, they significantly differ from other types of signatures, in that the actual parameter values need to be stored along with type information. There are two types of specification arguments in a signature blob; fixed args and named args. Fixed args are the arguments to the attribute type constructor, named arguments are specified after the constructor arguments to provide a value to a field or property on the constructed attribute type (PropertyName = propValue) Values in an attribute blob are limited to one of the basic types (one of the number types, character, or boolean), a reference to a type, an enum (which, in .NET, has to use one of the integer types as a base representation), or arrays of any of those. Enums and the basic types are easy to store in a blob - you simply store the binary representation. Strings are stored starting with a compressed integer indicating the length of the string, followed by the UTF8 characters. Array values start with an integer indicating the number of elements in the array, then the item values concatentated together. Rather than using a coded token, Type values are stored using a string representing the type name and fully qualified assembly name (for example, MyNs.MyType, MyAssembly, Version=1.0.0.0, Culture=neutral, PublicKeyToken=0123456789abcdef). If the type is in the current assembly or mscorlib then just the type name can be used. This is probably done to prevent direct references between assemblies solely because of attribute specification arguments; assemblies can be loaded in the reflection-only context and attribute arguments still processed, without loading the entire assembly. Fixed and named arguments Each entry in the CustomAttribute metadata table contains a reference to the object the attribute is applied to, the attribute constructor, and the specification blob. The number and type of arguments to the constructor (the fixed args) can be worked out by the method signature referenced by the attribute constructor, and so the fixed args can simply be concatenated together in the blob without any extra type information. Named args are different. These specify the value to assign to a field or property once the attribute type has been constructed. In the CLR, fields and properties can be overloaded just on their type; different fields and properties can have the same name. Therefore, to uniquely identify a field or property you need: Whether it's a field or property (indicated using byte values 0x53 and 0x54, respectively) The field or property type The field or property name After the fixed arg values is a 2-byte number specifying the number of named args in the blob. Each named argument has the above information concatenated together, mostly using the basic ELEMENT_TYPE values, in the same way as a method or field signature. A Type argument is represented using the byte 0x50, and an enum argument is represented using the byte 0x55 followed by a string specifying the name and assembly of the enum type. The named argument property information is followed by the argument value, using the same encoding as fixed args. Boxed objects This would be all very well, were it not for object and object[]. Arguments and properties of type object allow a value of any allowed argument type to be specified. As a result, more information needs to be specified in the blob to interpret the argument bytes as the correct type. So, the argument value is simple prepended with the type of the value by specifying the ELEMENT_TYPE or name of the enum the value represents. For named arguments, a field or property of type object is represented using the byte 0x51, with the actual type specified in the argument value. Some examples... All property signatures start with the 2-byte value 0x0001. Similar to my previous post in the series, names in capitals correspond to a particular byte value in the ELEMENT_TYPE structure. For strings, I'll simply give the string value, rather than the length and UTF8 encoding in the actual blob. I'll be using the following enum and attribute types to demonstrate specification encodings: class AttrAttribute : Attribute { public AttrAttribute() {} public AttrAttribute(Type[] tArray) {} public AttrAttribute(object o) {} public AttrAttribute(MyEnum e) {} public AttrAttribute(ushort x, int y) {} public AttrAttribute(string str, Type type1, Type type2) {} public int Prop1 { get; set; } public object Prop2 { get; set; } public object[] ObjectArray; } enum MyEnum : int { Val1 = 1, Val2 = 2 } Now, some examples: Here, the the specification binds to the (ushort, int) attribute constructor, with fixed args only. The specification blob starts off with a prolog, followed by the two constructor arguments, then the number of named arguments (zero): [Attr(42, 84)] 0x0001 0x002a 0x00000054 0x0000 An example of string and type encoding: [Attr("MyString", typeof(Array), typeof(System.Windows.Forms.Form))] 0x0001 "MyString" "System.Array" "System.Windows.Forms.Form, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" 0x0000 As you can see, the full assembly specification of a type is only needed if the type isn't in the current assembly or mscorlib. Note, however, that the C# compiler currently chooses to fully-qualify mscorlib types anyway. An object argument (this binds to the object attribute constructor), and two named arguments (a null string is represented by 0xff and the empty string by 0x00) [Attr((ushort)40, Prop1 = 12, Prop2 = "")] 0x0001 U2 0x0028 0x0002 0x54 I4 "Prop1" 0x0000000c 0x54 0x51 "Prop2" STRING 0x00 Right, more complicated now. A type array as a fixed argument: [Attr(new[] { typeof(string), typeof(object) })] 0x0001 0x00000002 // the number of elements "System.String" "System.Object" 0x0000 An enum value, which is simply represented using the underlying value. The CLR works out that it's an enum using information in the attribute constructor signature: [Attr(MyEnum.Val1)] 0x0001 0x00000001 0x0000 And finally, a null array, and an object array as a named argument: [Attr((Type[])null, ObjectArray = new object[] { (byte)2, typeof(decimal), null, MyEnum.Val2 })] 0x0001 0xffffffff 0x0001 0x53 SZARRAY 0x51 "ObjectArray" 0x00000004 U1 0x02 0x50 "System.Decimal" STRING 0xff 0x55 "MyEnum" 0x00000002 As you'll notice, a null object is encoded as a null string value, and a null array is represented using a length of -1 (0xffffffff). How does this affect C#? So, we can now explain why the limits on attribute arguments are so strict in C#. Attribute specification blobs are limited to basic numbers, enums, types, and arrays. As you can see, this is because the raw CLR encoding can only accommodate those types. Special byte patterns have to be used to indicate object, string, Type, or enum values in named arguments; you can't specify an arbitary object type, as there isn't a generalised way of encoding the resulting value in the specification blob. In particular, decimal values can't be encoded, as it isn't a 'built-in' CLR type that has a native representation (you'll notice that decimal constants in C# programs are compiled as several integer arguments to DecimalConstantAttribute). Jagged arrays also aren't natively supported, although you can get around it by using an array as a value to an object argument: [Attr(new object[] { new object[] { new Type[] { typeof(string) } }, 42 })] Finally... Phew! That was a bit longer than I thought it would be. Custom attribute encodings are complicated! Hopefully this series has been an informative look at what exactly goes on inside a .NET assembly. In the next blog posts, I'll be carrying on with the 'Inside Red Gate' series.

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• Modify MDT wizard to automate computer naming

  - by Jeramy

  I originally posted this question to StackOverflow, but upon further consideration it might be more appropriate here. Situation: I am imaging new systems using MDT Lite-Touch. I am trying to customize the wizard to automate the naming of new systems so that they include a prefix "AG-", a department code which is selected from a drop-down box in the wizard page (eg. "COMM"), and finally the serial number of the computer being imaged, so that my result in this case would be "AG-COMM-1234567890" Status: I have banged away at this for a while but my Google searches have not turned up answers, my trial-and-error is not producing useful error messages and I think I am missing some fundamentals of how to get variables from the wizard page into the variables used by the lite-touch wizard. Progress: I first created the HTML page which I will include below and added a script to the page to concatenate the pieces into a variable called OSDComputername which, for testing, I could output in a msgbox and get to display correctly. The problem with this is I don't know how to trigger the script then assign it to the OSDComputername variable that is used throughout the rest of the Light-Touch process. I changed the script to a function and added it to DeployWiz_Initization.vbs then used the Initialization field in WDS to call it. I'll include the function below. The problem with this is I would get "Undefined Variable" for OSDComputername and I am not sure it is pulling the data from the HTML correctly. I tried adding the scripting into the customsettings.ini file after the "OSDComputername=" This resulted in the wizard just outputting my code in text as the computer name. I am now trying adding variables to "Properties=" (eg.DepartmentName) in the customsettings.ini, pulling thier value from the HTML Form and setting that value to the variable in my function in DeployWiz_Initization.vbs and calling them after "OSDComputername=" in the fashion "OSDComputername="AG-" & %DepartmentName%" in customsettings.ini I am rebuilding right now and will see how this goes Any help would be appreciated. The HTML page: <HTML> <H1>Configure the computer name.</H1> <span style="width: 95%;"> <p>Please answer the following questions. Your answers will be used to formulate the computer's name and description.</p> <FORM NAME="TestForm"> <p>Departmental Prefix: <!-- <label class=ErrMsg id=DepartmentalPrefix_Err>* Required (MISSING)</label> --> <SELECT NAME="DepartmentalPrefix_Edit" class=WideEdit> <option value="AADC">AADC</option> <option value="AEM">AEM</option> <option value="AIP">AIP</option> <option value="COM">COM</option> <option value="DO">DO</option> <option value="DSOC">DSOC</option> <option value="EDU">EDU</option> <option value="EPE">EPE</option> <option value="ITN">ITN</option> <option value="LA">LA</option> <option value="OAP">OAP</option> <option value="SML">SML</option> </SELECT> </p> <p><span class="Larger">Client's Net<u class=larger>I</u>D:</span> <INPUT NAME="ClientNetID" TYPE="TEXT" ID="ClientNetID" SIZE="15"></p> <p>Building: <!-- <label class=ErrMsg id=Building_Err>* Required (MISSING)</label> --> <SELECT NAME="Building_Edit" class=WideEdit> <option value="Academic Surge Facility A">Academic Surge Facility A</option> <option value="Academic Surge Facility B">Academic Surge Facility B</option> <option value="Caldwell">Caldwell</option> <option value="Kennedy">Kennedy</option> <option value="Roberts">Roberts</option> <option value="Warren">Warren</option> </SELECT> </p> <p> <span class="Larger">Room <u class=larger>N</u>umber:</span> <input type=text id="RoomNumber" name=RoomNumber size=15 /> </p> </FORM> </span> </HTML> The Function: Function SetComputerName OSDComputerName = "AG-" & oEnvironment.Item("DepartmentalPrefix_Edit") ComputerDescription = oEnvironment.Item("DepartmentalPrefix_Edit") & ", " & oEnvironment.Item("ClientNetID") & ", " & oEnvironment.Item("RoomNumber") & " " & oEnvironment.Item("Building_Edit") End Function

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• Cannot log in to the desktop on ubuntu 11.10?

  - by Jichao

  The problem is, I could log in under the terminal, i could ifup eth0, i could do anything I want in the terminal, but if I use ctrl+alt+f7 goto the gnome login screen, after I input the correct password, the system just send me back to same login screen again. I have created a new user, but it didn't work. I have change all the files under ~/ to jichao:jichao(which is my username) with chown -hR jichao:jichao /home/jichao, but it didn't work too. I searched the internet, somebody said I should see the logs under /var/log/gdm, but there is not a /var/log/gdm directory in my box. Here are the tail of files under /var/log/ tail X.org.log [ 3263.348] (II) Loading /usr/lib/xorg/modules/input/evdev_drv.so [ 3263.348] (**) Dell Dell USB Keyboard: always reports core events [ 3263.348] (**) Dell Dell USB Keyboard: Device: "/dev/input/event5" [ 3263.348] (--) Dell Dell USB Keyboard: Found keys [ 3263.348] (II) Dell Dell USB Keyboard: Configuring as keyboard [ 3263.348] (**) Option "config_info" "udev:/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.0/input/input29/event5" [ 3263.348] (II) XINPUT: Adding extended input device "Dell Dell USB Keyboard" (type: KEYBOARD) [ 3263.348] (**) Option "xkb_rules" "evdev" [ 3263.348] (**) Option "xkb_model" "pc105" [ 3263.348] (**) Option "xkb_layout" "us" kern.log Mar 20 09:32:58 jichao-MS-730 kernel: [ 3182.701247] input: Dell Dell USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.0/input/input27 Mar 20 09:32:58 jichao-MS-730 kernel: [ 3182.701392] generic-usb 0003:413C:2003.0018: input,hidraw1: USB HID v1.10 Keyboard [Dell Dell USB Keyboard] on usb-0000:00:1d.0-1.4/input0 Mar 20 09:33:02 jichao-MS-730 kernel: [ 3186.642572] usb 2-1.3: new low speed USB device number 17 using ehci_hcd Mar 20 09:33:02 jichao-MS-730 kernel: [ 3186.741892] input: Microsoft Microsoft 5-Button Mouse with IntelliEye(TM) as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input28 Mar 20 09:33:02 jichao-MS-730 kernel: [ 3186.742080] generic-usb 0003:045E:0047.0019: input,hidraw2: USB HID v1.10 Mouse [Microsoft Microsoft 5-Button Mouse with IntelliEye(TM)] on usb-0000:00:1d.0-1.3/input0 Mar 20 09:33:27 jichao-MS-730 kernel: [ 3212.473901] usb 2-1.3: USB disconnect, device number 17 Mar 20 09:33:28 jichao-MS-730 kernel: [ 3212.702031] usb 2-1.4: USB disconnect, device number 16 Mar 20 09:34:08 jichao-MS-730 kernel: [ 3253.022655] usb 2-1.4: new low speed USB device number 18 using ehci_hcd Mar 20 09:34:08 jichao-MS-730 kernel: [ 3253.124278] input: Dell Dell USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.0/input/input29 Mar 20 09:34:08 jichao-MS-730 kernel: [ 3253.124423] generic-usb 0003:413C:2003.001A: input,hidraw1: USB HID v1.10 Keyboard [Dell Dell USB Keyboard] on usb-0000:00:1d.0-1.4/input0 Mar 20 09:33:02 jichao-MS-730 kernel: [ 3186.741892] input: Microsoft Microsoft 5-Button Mouse with IntelliEye(TM) as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/input/input28 Mar 20 09:33:02 jichao-MS-730 kernel: [ 3186.742080] generic-usb 0003:045E:0047.0019: input,hidraw2: USB HID v1.10 Mouse [Microsoft Microsoft 5-Button Mouse with IntelliEye(TM)] on usb-0000:00:1d.0-1.3/input0 syslog Mar 20 09:33:02 jichao-MS-730 mtp-probe: bus: 2, device: 17 was not an MTP device Mar 20 09:33:27 jichao-MS-730 kernel: [ 3212.473901] usb 2-1.3: USB disconnect, device number 17 Mar 20 09:33:28 jichao-MS-730 kernel: [ 3212.702031] usb 2-1.4: USB disconnect, device number 16 Mar 20 09:34:08 jichao-MS-730 kernel: [ 3253.022655] usb 2-1.4: new low speed USB device number 18 using ehci_hcd Mar 20 09:34:08 jichao-MS-730 mtp-probe: checking bus 2, device 18: "/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4" Mar 20 09:34:08 jichao-MS-730 mtp-probe: bus: 2, device: 18 was not an MTP device Mar 20 09:34:08 jichao-MS-730 kernel: [ 3253.124278] input: Dell Dell USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.0/input/input29 Mar 20 09:34:08 jichao-MS-730 kernel: [ 3253.124423] generic-usb 0003:413C:2003.001A: input,hidraw1: USB HID v1.10 Keyboard [Dell Dell USB Keyboard] on usb-0000:00:1d.0-1.4/input0 auth.log Mar 20 09:18:52 jichao-MS-730 lightdm: pam_ck_connector(lightdm-autologin:session): nox11 mode, ignoring PAM_TTY :0 Mar 20 09:18:53 jichao-MS-730 lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "jichao" Mar 20 09:18:53 jichao-MS-730 dbus[835]: [system] Rejected send message, 2 matched rules; type="method_call", sender=":1.240" (uid=104 pid=6457 comm="/usr/lib/indicator-datetime/indicator-datetime-ser") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination=":1.11" (uid=0 pid=1156 comm="/usr/sbin/console-kit-daemon --no-daemon ") Mar 20 09:19:38 jichao-MS-730 sudo: jichao : TTY=tty6 ; PWD=/home ; USER=root ; COMMAND=/bin/chown -hR jichao:jichao jicha Mar 20 09:19:39 jichao-MS-730 sudo: jichao : TTY=tty6 ; PWD=/home ; USER=root ; COMMAND=/bin/chown -hR jichao:jichao jichao Mar 20 09:20:10 jichao-MS-730 lightdm: pam_unix(lightdm-autologin:session): session closed for user lightdm Mar 20 09:20:11 jichao-MS-730 lightdm: pam_unix(lightdm-autologin:session): session opened for user lightdm by (uid=0) Mar 20 09:20:11 jichao-MS-730 lightdm: pam_ck_connector(lightdm-autologin:session): nox11 mode, ignoring PAM_TTY :0 Mar 20 09:20:12 jichao-MS-730 lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "jichao" Mar 20 09:20:12 jichao-MS-730 dbus[835]: [system] Rejected send message, 2 matched rules; type="method_call", sender=":1.247" (uid=104 pid=6572 comm="/usr/lib/indicator-datetime/indicator-datetime-ser") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination=":1.11" (uid=0 pid=1156 comm="/usr/sbin/console-kit-daemon --no-daemon ") It seems that my .xsession-errors does not grow since yesterday. Here is my .xsession-error: (gnome-settings-daemon:1550): Gdk-WARNING **: The program 'gnome-settings-daemon' received an X Window System error. This probably reflects a bug in the program. The error was 'BadWindow (invalid Window parameter)'. (Details: serial 26702 error_code 3 request_code 2 minor_code 0) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.) (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed (nautilus:3106): GLib-GObject-CRITICAL **: g_value_get_object: assertion `G_VALUE_HOLDS_OBJECT (value)' failed WARN 2012-03-17 19:28:46 glib <unknown>:0 Unable to fetch children: Method "Children" with signature "" on interface "org.ayatana.bamf.view" doesn't exist WARN 2012-03-17 19:28:46 glib <unknown>:0 Unable to fetch children: Method "Children" with signature "" on interface "org.ayatana.bamf.view" doesn't exist (yunio:2430): Gtk-WARNING **: ??????????????:“pixmap”, (yunio:2430): Gtk-WARNING **: ??????????????:“pixmap”, (polkit-gnome-authentication-agent-1:1601): Gtk-WARNING **: ??????????????:“pixmap”, (yunio:2430): Gtk-WARNING **: ??????????????:“pixmap”, (yunio:2430): Gtk-WARNING **: ??????????????:“pixmap”, (polkit-gnome-authentication-agent-1:1601): Gtk-WARNING **: ??????????????:“pixmap”, (polkit-gnome-authentication-agent-1:1601): Gtk-WARNING **: ??????????????:“pixmap”, (polkit-gnome-authentication-agent-1:1601): Gtk-WARNING **: ??????????????:“pixmap”, /usr/share/system-config-printer/applet.py:336: GtkWarning: ??????????????:“pixmap”, self.loop.run () (unity-window-decorator:1652): Gtk-WARNING **: ??????????????:“pixmap”, (unity-window-decorator:1652): Gtk-WARNING **: ??????????????:“pixmap”, (unity-window-decorator:1652): Gtk-WARNING **: ??????????????:“pixmap”, (unity-window-decorator:1652): Gtk-WARNING **: ??????????????:“pixmap”, common-plugin-Message: checking whether we have a device for 4: yes common-plugin-Message: checking whether we have a device for 5: yes common-plugin-Message: checking whether we have a device for 6: yes common-plugin-Message: checking whether we have a device for 7: yes common-plugin-Message: checking whether we have a device for 10: yes common-plugin-Message: checking whether we have a device for 8: yes common-plugin-Message: checking whether we have a device for 9: yes (gnome-settings-daemon:13791): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed [1331983727,000,xklavier.c:xkl_engine_start_listen/] The backend does not require manual layout management - but it is provided by the application ** (gnome-fallback-mount-helper:1584): DEBUG: ConsoleKit session is active 0 (gnome-fallback-mount-helper:1584): Gdk-WARNING **: gnome-fallback-mount-helper: Fatal IO error 11 (???????) on X server :0. (gdu-notification-daemon:1708): Gdk-WARNING **: gdu-notification-daemon: Fatal IO error 11 (???????) on X server :0. unity-window-decorator: Fatal IO error 11 (???????) on X server :0.0. (bluetooth-applet:1583): Gdk-WARNING **: bluetooth-applet: Fatal IO error 11 (???????) on X server :0. (nm-applet:1596): Gdk-WARNING **: nm-applet: Fatal IO error 11 (???????) on X server :0. (nautilus:3106): IBUS-WARNING **: _connection_closed_cb: Underlying GIOStream returned 0 bytes on an async read (update-notifier:1821): Gdk-WARNING **: update-notifier: Fatal IO error 11 (???????) on X server :0. applet.py: Fatal IO error 11 (???????) on X server :0. (nautilus:3106): Gdk-WARNING **: nautilus: Fatal IO error 11 (???????) on X server :0. Could you help me, Thanks.

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• Green (Screen) Computing

  - by onefloridacoder

  I recently was given an assignment to create a UX where a user could use the up and down arrow keys, as well as the tab and enter keys to move through a Silverlight datagrid that is going be used as part of a high throughput data entry UI. And to be honest, I’ve not trapped key codes since I coded JavaScript a few years ago.  Although the frameworks I’m using made it easy, it wasn’t without some trial and error.    The other thing that bothered me was that the customer tossed this into the use case as they were delivering the use case.  Fine.  I’ll take a whack at anything and beat up myself and beg (I’m not beyond begging for help) the community for help to get something done if I have to. It wasn’t as bad as I thought and I thought I would hopefully save someone a few keystrokes if you wanted to build a green screen for your customer.   Here’s the ValueConverter to handle changing the strings to decimals and then back again.  The value is a nullable valuetype so there are few extra steps to take.  Usually the “ConvertBack()” method doesn’t get addressed but in this case we have two-way binding and the converter needs to ensure that if the user doesn’t enter a value it will remain null when the value is reapplied to the model object’s setter.  1: using System; 2: using System.Windows.Data; 3: using System.Globalization; 4:  5: public class NullableDecimalToStringConverter : IValueConverter 6: { 7: public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 8: { 9: if (!(((decimal?)value).HasValue)) 10: { 11: return (decimal?)null; 12: } 13: if (!(value is decimal)) 14: { 15: throw new ArgumentException("The value must be of type decimal"); 16: } 17:  18: NumberFormatInfo nfi = culture.NumberFormat; 19: nfi.NumberDecimalDigits = 4; 20:  21: return ((decimal)value).ToString("N", nfi); 22: } 23:  24: public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) 25: { 26: decimal nullableDecimal; 27: decimal.TryParse(value.ToString(), out nullableDecimal); 28:  29: return nullableDecimal == 0 ? null : nullableDecimal.ToString(); 30: } 31: }            The ConvertBack() method uses TryParse to create a value from the incoming string so if the parse fails, we get a null value back, which is what we would expect.  But while I was testing I realized that if the user types something like “2..4” instead of “2.4”, TryParse will fail and still return a null.  The user is getting “puuu-lenty” of eye-candy to ensure they know how many values are affected in this particular view. Here’s the XAML code.   This is the simple part, we just have a DataGrid with one column here that’s bound to the the appropriate ViewModel property with the Converter referenced as well. 1: <data:DataGridTextColumn 2: Header="On-Hand" 3: Binding="{Binding Quantity, 4: Mode=TwoWay, 5: Converter={StaticResource DecimalToStringConverter}}" 6: IsReadOnly="False" /> Nothing too magical here.  Just some XAML to hook things up.   Here’s the code behind that’s handling the DataGridKeyup event.  These are wired to a local/private method but could be converted to something the ViewModel could use, but I just need to get this working for now. 1: // Wire up happens in the constructor 2: this.PicDataGrid.KeyUp += (s, e) => this.HandleKeyUp(e);   1: // DataGrid.BeginEdit fires when DataGrid.KeyUp fires. 2: private void HandleKeyUp(KeyEventArgs args) 3: { 4: if (args.Key == Key.Down || 5: args.Key == Key.Up || 6: args.Key == Key.Tab || 7: args.Key == Key.Enter ) 8: { 9: this.PicDataGrid.BeginEdit(); 10: } 11: }   And that’s it.  The ValueConverter was the biggest problem starting out because I was using an existing converter that didn’t take nullable value types into account.   Once the converter was passing back the appropriate value (null, “#.####”) the grid cell(s) and the model objects started working as I needed them to. HTH.

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• Discover the Value of Specialization for your Business - Free, Live and Online!

  - by julien.haye

  Pre-qualified leads. New customers. Greater revenues. A higher market profile. And increased profitability. Specialization with Oracle can deliver all of this and more! Join us online at 14:00 CET on Monday January 24th 2011 for: a clear definition of the value of specialization with Oracle; full details on how and why Oracle proactively helps its specialized partners attract and engage with their ideal customers; all you need to know about OPN Specialized tools and resources; sessions tailored to specific regions, business models and Oracle solution areas; first-hand testimony from your peers about how specialization is helping them succeed. The event will also feature a networking lounge, interactive information booths staffed by Oracle experts, and live Q&A sessions! Click here now to register for this essential online event!

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• I want to master ASP.NET - What concepts should I focus on/What concepts do you most value?

  - by Josh

  I start a job this summer doing work in ASP.NET 4 (C#). I plan on working with some legacy code as well as MVC. I want to get a running start. I have good understanding of HTML/CSS/Javascript, and pretty good understanding of C# itself, Design principles, Design Patterns, and understand masterpages, basic MVC2, and code behinds for web forms. In your opinion what aspects of ASP.NET are the most important to master for web applications? What do you value most in your usage of ASP.NET? Do you have a recommendation for understanding the internals of ASP.NET itself?

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• Javascript Date Range Validation

  Here is a Javascript function that will tell you if 2 dates make a valid date range. function isValidDateRange( objstartMonth,objstartDay, objstartYear, objendMonth,objendDay, objendYear) { var startDate = new Date(objstartYear.options[objstartYear.selectedIndex].value, objstartMonth.options[objstartMonth.selectedIndex].value, objstartDay.options[objstartDay.selectedIndex].value); var endDate = new Date(objendYear.options[objendYear.selectedIndex].value, objendMonth.options[objendMonth.selectedIndex].value, objendDay.options[objendDay.selectedIndex].value); if (startDate >= endDate){ alert("Invaild Date Range"); return false; } else{ return true; } }

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• C#/.NET Little Wonders: Interlocked CompareExchange()

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Two posts ago, I discussed the Interlocked Add(), Increment(), and Decrement() methods (here) for adding and subtracting values in a thread-safe, lightweight manner.  Then, last post I talked about the Interlocked Read() and Exchange() methods (here) for safely and efficiently reading and setting 32 or 64 bit values (or references).  This week, we’ll round out the discussion by talking about the Interlocked CompareExchange() method and how it can be put to use to exchange a value if the current value is what you expected it to be. Dirty reads can lead to bad results Many of the uses of Interlocked that we’ve explored so far have centered around either reading, setting, or adding values.  But what happens if you want to do something more complex such as setting a value based on the previous value in some manner? Perhaps you were creating an application that reads a current balance, applies a deposit, and then saves the new modified balance, where of course you’d want that to happen atomically.  If you read the balance, then go to save the new balance and between that time the previous balance has already changed, you’ll have an issue!  Think about it, if we read the current balance as $400, and we are applying a new deposit of $50.75, but meanwhile someone else deposits $200 and sets the total to $600, but then we write a total of $450.75 we’ve lost $200! Now, certainly for int and long values we can use Interlocked.Add() to handles these cases, and it works well for that.  But what if we want to work with doubles, for example?  Let’s say we wanted to add the numbers from 0 to 99,999 in parallel.  We could do this by spawning several parallel tasks to continuously add to a total: 1: double total = 0; 2:  3: Parallel.For(0, 10000, next => 4: { 5: total += next; 6: }); Were this run on one thread using a standard for loop, we’d expect an answer of 4,999,950,000 (the sum of all numbers from 0 to 99,999).  But when we run this in parallel as written above, we’ll likely get something far off.  The result of one of my runs, for example, was 1,281,880,740.  That is way off!  If this were banking software we’d be in big trouble with our clients.  So what happened?  The += operator is not atomic, it will read in the current value, add the result, then store it back into the total.  At any point in all of this another thread could read a “dirty” current total and accidentally “skip” our add.   So, to clean this up, we could use a lock to guarantee concurrency: 1: double total = 0.0; 2: object locker = new object(); 3:  4: Parallel.For(0, count, next => 5: { 6: lock (locker) 7: { 8: total += next; 9: } 10: }); Which will give us the correct result of 4,999,950,000.  One thing to note is that locking can be heavy, especially if the operation being locked over is trivial, or the life of the lock is a high percentage of the work being performed concurrently.  In the case above, the lock consumes pretty much all of the time of each parallel task – and the task being locked on is relatively trivial. Now, let me put in a disclaimer here before we go further: For most uses, lock is more than sufficient for your needs, and is often the simplest solution!    So, if lock is sufficient for most needs, why would we ever consider another solution?  The problem with locking is that it can suspend execution of your thread while it waits for the signal that the lock is free.  Moreover, if the operation being locked over is trivial, the lock can add a very high level of overhead.  This is why things like Interlocked.Increment() perform so well, instead of locking just to perform an increment, we perform the increment with an atomic, lockless method. As with all things performance related, it’s important to profile before jumping to the conclusion that you should optimize everything in your path.  If your profiling shows that locking is causing a high level of waiting in your application, then it’s time to consider lighter alternatives such as Interlocked. CompareExchange() – Exchange existing value if equal some value So let’s look at how we could use CompareExchange() to solve our problem above.  The general syntax of CompareExchange() is: T CompareExchange<T>(ref T location, T newValue, T expectedValue) If the value in location == expectedValue, then newValue is exchanged.  Either way, the value in location (before exchange) is returned. Actually, CompareExchange() is not one method, but a family of overloaded methods that can take int, long, float, double, pointers, or references.  It cannot take other value types (that is, can’t CompareExchange() two DateTime instances directly).  Also keep in mind that the version that takes any reference type (the generic overload) only checks for reference equality, it does not call any overridden Equals(). So how does this help us?  Well, we can grab the current total, and exchange the new value if total hasn’t changed.  This would look like this: 1: // grab the snapshot 2: double current = total; 3:  4: // if the total hasn’t changed since I grabbed the snapshot, then 5: // set it to the new total 6: Interlocked.CompareExchange(ref total, current + next, current); So what the code above says is: if the amount in total (1st arg) is the same as the amount in current (3rd arg), then set total to current + next (2nd arg).  This check and exchange pair is atomic (and thus thread-safe). This works if total is the same as our snapshot in current, but the problem, is what happens if they aren’t the same?  Well, we know that in either case we will get the previous value of total (before the exchange), back as a result.  Thus, we can test this against our snapshot to see if it was the value we expected: 1: // if the value returned is != current, then our snapshot must be out of date 2: // which means we didn't (and shouldn't) apply current + next 3: if (Interlocked.CompareExchange(ref total, current + next, current) != current) 4: { 5: // ooops, total was not equal to our snapshot in current, what should we do??? 6: } So what do we do if we fail?  That’s up to you and the problem you are trying to solve.  It’s possible you would decide to abort the whole transaction, or perhaps do a lightweight spin and try again.  Let’s try that: 1: double current = total; 2:  3: // make first attempt... 4: if (Interlocked.CompareExchange(ref total, current + i, current) != current) 5: { 6: // if we fail, go into a spin wait, spin, and try again until succeed 7: var spinner = new SpinWait(); 8:  9: do 10: { 11: spinner.SpinOnce(); 12: current = total; 13: } 14: while (Interlocked.CompareExchange(ref total, current + i, current) != current); 15: } 16:  This is not trivial code, but it illustrates a possible use of CompareExchange().  What we are doing is first checking to see if we succeed on the first try, and if so great!  If not, we create a SpinWait and then repeat the process of SpinOnce(), grab a fresh snapshot, and repeat until CompareExchnage() succeeds.  You may wonder why not a simple do-while here, and the reason it’s more efficient to only create the SpinWait until we absolutely know we need one, for optimal efficiency. Though not as simple (or maintainable) as a simple lock, this will perform better in many situations.  Comparing an unlocked (and wrong) version, a version using lock, and the Interlocked of the code, we get the following average times for multiple iterations of adding the sum of 100,000 numbers: 1: Unlocked money average time: 2.1 ms 2: Locked money average time: 5.1 ms 3: Interlocked money average time: 3 ms So the Interlocked.CompareExchange(), while heavier to code, came in lighter than the lock, offering a good compromise of safety and performance when we need to reduce contention. CompareExchange() - it’s not just for adding stuff… So that was one simple use of CompareExchange() in the context of adding double values -- which meant we couldn’t have used the simpler Interlocked.Add() -- but it has other uses as well. If you think about it, this really works anytime you want to create something new based on a current value without using a full lock.  For example, you could use it to create a simple lazy instantiation implementation.  In this case, we want to set the lazy instance only if the previous value was null: 1: public static class Lazy<T> where T : class, new() 2: { 3: private static T _instance; 4:  5: public static T Instance 6: { 7: get 8: { 9: // if current is null, we need to create new instance 10: if (_instance == null) 11: { 12: // attempt create, it will only set if previous was null 13: Interlocked.CompareExchange(ref _instance, new T(), (T)null); 14: } 15:  16: return _instance; 17: } 18: } 19: } So, if _instance == null, this will create a new T() and attempt to exchange it with _instance.  If _instance is not null, then it does nothing and we discard the new T() we created. This is a way to create lazy instances of a type where we are more concerned about locking overhead than creating an accidental duplicate which is not used.  In fact, the BCL implementation of Lazy<T> offers a similar thread-safety choice for Publication thread safety, where it will not guarantee only one instance was created, but it will guarantee that all readers get the same instance.  Another possible use would be in concurrent collections.  Let’s say, for example, that you are creating your own brand new super stack that uses a linked list paradigm and is “lock free”.  We could use Interlocked.CompareExchange() to be able to do a lockless Push() which could be more efficient in multi-threaded applications where several threads are pushing and popping on the stack concurrently. Yes, there are already concurrent collections in the BCL (in .NET 4.0 as part of the TPL), but it’s a fun exercise!  So let’s assume we have a node like this: 1: public sealed class Node<T> 2: { 3: // the data for this node 4: public T Data { get; set; } 5:  6: // the link to the next instance 7: internal Node<T> Next { get; set; } 8: } Then, perhaps, our stack’s Push() operation might look something like: 1: public sealed class SuperStack<T> 2: { 3: private volatile T _head; 4:  5: public void Push(T value) 6: { 7: var newNode = new Node<int> { Data = value, Next = _head }; 8:  9: if (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next) 10: { 11: var spinner = new SpinWait(); 12:  13: do 14: { 15: spinner.SpinOnce(); 16: newNode.Next = _head; 17: } 18: while (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next); 19: } 20: } 21:  22: // ... 23: } Notice a similar paradigm here as with adding our doubles before.  What we are doing is creating the new Node with the data to push, and with a Next value being the original node referenced by _head.  This will create our stack behavior (LIFO – Last In, First Out).  Now, we have to set _head to now refer to the newNode, but we must first make sure it hasn’t changed! So we check to see if _head has the same value we saved in our snapshot as newNode.Next, and if so, we set _head to newNode.  This is all done atomically, and the result is _head’s original value, as long as the original value was what we assumed it was with newNode.Next, then we are good and we set it without a lock!  If not, we SpinWait and try again. Once again, this is much lighter than locking in highly parallelized code with lots of contention.  If I compare the method above with a similar class using lock, I get the following results for pushing 100,000 items: 1: Locked SuperStack average time: 6 ms 2: Interlocked SuperStack average time: 4.5 ms So, once again, we can get more efficient than a lock, though there is the cost of added code complexity.  Fortunately for you, most of the concurrent collection you’d ever need are already created for you in the System.Collections.Concurrent (here) namespace – for more information, see my Little Wonders – The Concurent Collections Part 1 (here), Part 2 (here), and Part 3 (here). Summary We’ve seen before how the Interlocked class can be used to safely and efficiently add, increment, decrement, read, and exchange values in a multi-threaded environment.  In addition to these, Interlocked CompareExchange() can be used to perform more complex logic without the need of a lock when lock contention is a concern. The added efficiency, though, comes at the cost of more complex code.  As such, the standard lock is often sufficient for most thread-safety needs.  But if profiling indicates you spend a lot of time waiting for locks, or if you just need a lock for something simple such as an increment, decrement, read, exchange, etc., then consider using the Interlocked class’s methods to reduce wait. Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked,CompareExchange,threading,concurrency

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• Two related cells: give a value in one, calculate the other, and vice versa?

  - by Virtlink

  How can I have a cell that uses the literal value written into it, or calculates its value when no literal value was given? For example: I have two columns: column B with a price including VAT, and column C with a price without VAT. If I put a price with VAT in B2, then I want cell C2 to calculate the price without VAT based on B2. But if I put a price without VAT in C2, then I want cell B2 to calculate the price with VAT from C2. I want to give this spreadsheet to my mother, who barely understands Excel. She just has to enter the values that she knows, and the worksheet should derive the other values from that.

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• Query something and return the reason if nothing has been found

  - by Daniel Hilgarth

  Assume I have a Query - as in CQS that is supposed to return a single value. Let's assume that the case that no value is found is not exceptional, so no exception will be thrown in this case. Instead, null is returned. However, if no value has been found, I need to act according to the reason why no value has been found. Assuming that the Query knows the reason, how would I communicate it to the caller of the Query? A simple solution would be not return the value directly but a container object that contains the value and the reason: public class QueryResult { public TValue Value { get; private set; } public TReason ReasonForNoValue { get; private set; } } But that feels clumsy, because if a value is found, ReasonForNoValue makes no sense and if no value has been found, Value makes no sense. What other options do I have to communicate the reason? What do you think of one event per reason? For reference: This is going to be implemented in C#.

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• What is the value of the Cloudera Hadoop Certification for people new to the IT industry?

  - by Saumitra

  I am a software developer with 8 months of experience in the IT industry, currently working on the development of tools for BIG DATA analytics. I have learned Hadoop basics on my own and I am pretty comfortable with writing MapReduce Jobs, PIG, HIVE, Flume and other related projects. I am thinking of taking the exam for the Cloudera Hadoop Certification. Will this certification add value, considering that I have less than 1 year of experience? Many of the jobs I've seen relating to Hadoop require at least 3 years of experience. Should I invest more time in learning Hadoop and improving my skills to take this certification?

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• "Ubuntu One" Value could not be retrieved. (ValueError: cannot convert float NaN to integer)

  - by SimoneRaso

  When I try to start Ubuntu one (after the registration) I receive the this error. Plus it keeps saying "loading.." I am using Ubuntu 11.10 freshly installed. I've try to reinstall ubuntuone after remove them from "ubuntu software center" and remove all the entri ubuntuone* from synaptic. Only the last slice of the ubuntu one control panel seems responding and display "Value could not be retrieved. (ValueError: cannot convert float NaN to integer)". After I reinstall completely ubuntu and when I retry, receive the same. tank's

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• Callbacks: when to return value, and when to modify parameter?

  - by MarkN

  When writing a callback, when is best to have the callback return a value, and when is it best to have the callback modify a parameter? Is there a difference? For example, if we wanted to grab a list of dependencies, when would you do this: function GetDependencies(){ return [{"Dep1" : 1.1}, {"Dept2": 1.2}, {"Dep3" : 1.3}]; } And when would you do this? function RegisterDependencies(register){ register.add("Dep1", 1.1); register.add("Dep2", 1.2); register.add("Dep3", 1.3); }

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• Which is the appropriate content-type meta tag value?

  - by Argoron

  I have a question about the meta tag content-type. When starting to build my site (HTML+PHP+JS), I copied a lot of the meta tags over from elsewhere, and I have, amongst others, the following: <meta http-equiv="content-type" content="application/xhtml+xml; charset=iso-8859-1" /> Now, I've seen that tag is being used a lot with the value "text/html". I've been searching the web but could not find a comprehensive explanation regarding what the difference between both is. The "text/html" intuitively sounds more straightforward to me. Should I change my tag to that, or might the "application/xhtml+xml" be an equivalent solution ? Alternatively, can anyone point me to a resource where the different values for these tags are listed and explained in a clear manner? Thanks in advance

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• Which is the appropriate content-type meta tag value ?

  - by Argoron

  I have a question about the meta tag content-type. When starting to build my site (HTML+PHP+JS), I copied a lot of the meta tags over from elsewhere, and I have, amongst others, the following: <meta http-equiv="content-type" content="application/xhtml+xml; charset=iso-8859-1" /> Now, I've seen that tag is being used a lot with the value "text/html". I've been searching the web but could not find a comprehensive explanation regarding what the difference between both is. The "text/html" intuitively sounds more straightforward to me. Should I change my tag to that, or might the "application/xhtml+xml" be an equivalent solution ? Alternatively, can anyone point me to a resource where the different values for these tags are listed and explained in a clear manner? Thanks in advance

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• Excel 2010: dynamic update of drop down list based upon datasource validation worksheet changes

  - by hornetbzz

  I have one worksheet for setting up the data sources of multiple data validation lists. in other words, I'm using this worksheet to provide drop down lists to multiple other worksheets. I need to dynamically update all worksheets upon any of a single or several changes on the data source worksheet. I may understand this should come with event macro over the entire workbook. My question is how to achieve this keeping the "OFFSET" formula across the whole workbook ? Thx To support my question, I put the piece of code that I'm trying to get it working : Provided the following informations : I'm using such a formula for a pseudo dynamic update of the drop down lists, for example : =OFFSET(MyDataSourceSheet!$O$2;0;0;COUNTA(MyDataSourceSheet!O:O)-1) I looked into the pearson book event chapter but I'm too noob for this. I understand this macro and implemented it successfully as a test with the drop down list on the same worksheet as the data source. My point is that I don't know how to deploy this over a complete workbook. Macro related to the datasource worksheet : Option Explicit Private Sub Worksheet_Change(ByVal Target As Range) ' Macro to update all worksheets with drop down list referenced upon ' this data source worksheet, base on ref names Dim cell As Range Dim isect As Range Dim vOldValue As Variant, vNewValue As Variant Dim dvLists(1 To 6) As String 'data validation area Dim OneValidationListName As Variant dvLists(1) = "mylist1" dvLists(2) = "mylist2" dvLists(3) = "mylist3" dvLists(4) = "mylist4" dvLists(5) = "mylist5" dvLists(6) = "mylist6" On Error GoTo errorHandler For Each OneValidationListName In dvLists 'Set isect = Application.Intersect(Target, ThisWorkbook.Names("STEP").RefersToRange) Set isect = Application.Intersect(Target, ThisWorkbook.Names(OneValidationListName).RefersToRange) ' If a change occured in the source data sheet If Not isect Is Nothing Then ' Prevent infinite loops Application.EnableEvents = False ' Get previous value of this cell With Target vNewValue = .Value Application.Undo vOldValue = .Value .Value = vNewValue End With ' LOCAL dropdown lists : For every cell with validation For Each cell In Me.UsedRange.SpecialCells(xlCellTypeAllValidation) With cell ' If it has list validation AND the validation formula matches AND the value is the old value If .Validation.Type = 3 And .Validation.Formula1 = "=" & OneValidationListName And .Value = vOldValue Then ' Debug ' MsgBox "Address: " & Target.Address ' Change the cell value cell.Value = vNewValue End If End With Next cell ' Call to other worksheets update macros Call Sheets(5).UpdateDropDownList(vOldValue, vNewValue) ' GoTo NowGetOut Application.EnableEvents = True End If Next OneValidationListName NowGetOut: Application.EnableEvents = True Exit Sub errorHandler: MsgBox "Err " & Err.Number & " : " & Err.Description Resume NowGetOut End Sub Macro UpdateDropDownList related to the destination worksheet : Sub UpdateDropDownList(Optional vOldValue As Variant, Optional vNewValue As Variant) ' Debug MsgBox "Received info for update : " & vNewValue ' For every cell with validation For Each cell In Me.UsedRange.SpecialCells(xlCellTypeAllValidation) With cell ' If it has list validation AND the validation formula matches AND the value is the old value ' If .Validation.Type = 3 And .Value = vOldValue Then If .Validation.Type = 3 And .Value = vOldValue Then ' Change the cell value cell.Value = vNewValue End If End With Next cell End Sub

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• Naming interfaces for persistent values

  - by orip

  I have 2 distinct types of persistent values that I'm having trouble naming well. They're defined with the following Java-esque structure, borrowing Guava's Optional for the example and using generic names to avoid anchoring: interface Foo<T> { T get(); void set(T value); } interface Bar<T> { Optional<T> get(); void set(T value); } With Foo, if the value hasn't been set explicitly then there's some default value available or pre-set. With Bar, if the value hasn't been set explicitly then there's a distinct "no value" state. I'm trying to optimize the names for their call sites. For example, someone using Foo may not care whether there's a default value involved, only that they're guaranteed to always have a value. How would you go about naming these interfaces?

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• forwarding my domain to ning site, vs paying for mapping. SEO value? [closed]

  - by myf

  Possible Duplicate: Could I buy a domain name to increase traffic to my site like this? hello, and thanks for your time to answer. really appreciate that! my domain url is keyword stuffed (homes for sale and the city name). does it make a difference if I foward that to my ning site, which is www.homesforsale(in city name).ning.com or is it just the same for SEO / pagerank value as paying ning for the proper url mapping. thanks so much!

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• Is there anyway that I can set the 'real' memory usage value while running my java code?

  - by vira

  I'm running a code on a server to generate a 10,000x10,000 matrix and save each value into a table (MySQL). I was informed by the administrator that I can use up to 32g of the physical memory of our server but have no idea how to do it. I googling around and so far only found information about setting the virtual memory using -Xmx. I tried it anyway and using top command I got this: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3981 gv 35 15 32.4g 304m 10m S 1 0.5 9:54.84 java So, it shows that the -Xmx set the VIRT and not the RES value. Is there anyway that I can set the RES value into 32g?

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• Using label tags in a validation summary error list?

  - by patridge

  I was thinking about making use of <label> tags in my validation error summary on a failed form submit and I can't figure out if it is going to get me in trouble down the line. Can anyone think of a good reason to avoid this approach? Usability, functionality, design, or other issues are all helpful. I really like the idea of clicking a line item in the error list and being jumped to the offending input element, especially in a mobile HTML scenario where vertical orientation is more common and scrolling is a pain. So far the only problem I can find is that labels don't navigate for radio buttons or checkboxes without individual IDs (Clicking a label for a single ID-tagged radio/checkbox element alters its selection). It doesn't make it any worse than no label, though. Here is a stripped down HTML test sample of this idea (CSS omitted for simplicity). <div class="validation-errors"> <p>There was a problem saving your form.</p> <ul> <li><label for="select1">Select 1 is invalid.</label></li> <li><label for="text1">Text 1 is invalid.</label></li> <li><label for="textarea1">TextArea 1 is invalid.</label></li> <li><label for="radio1">Radio 1 is invalid.</label></li> <li><label for="checkbox1">Checkbox 1 is invalid.</label></li> </ul> </div> <form action="/somewhere"> <fieldset><legend>Some Form</legend> <ol> <li><label for="select1">select1</label> <select id="select1" name="select1"> <option value="value1">Value 1</option> <option value="value2">Value 2</option> <option selected="selected" value="value3">Value 3</option> </select></li> <li><label for="text1">text1</label> <input id="text1" name="text1" type="text" value="sometext" /></li> <li><label for="textarea1">textarea1</label> <textarea id="textarea1" name="textarea1" rows="5" cols="25">sometext</textarea></li> <li><ul> <li><label><input type="radio" name="radio1" value="value1" />Value 1</label></li> <li><label><input type="radio" name="radio1" value="value2" checked="checked" />Value 2</label></li> <li><label><input type="radio" name="radio1" value="value3" />Value 3</label></li> </ul></li> <li><ul> <li><label><input type="checkbox" name="checkbox1" value="value1" checked="checked" />Value 1</label></li> <li><label><input type="checkbox" name="checkbox1" value="value2" />Value 2</label></li> <li><label><input type="checkbox" name="checkbox1" value="value3" checked="checked" />Value 3</label></li> </ul></li> <li><input type="submit" value="Save &amp; Continue" /></li> </ol> </fieldset> </form> The only thing I have added to make the click-capable behavior more obvious is to add a CSS rule for the labels. .validation-errors label { text-decoration: underline; cursor: pointer; }

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• How to create a generic method in C# that's all applicable to many types - ints, strings, doubles et

  - by satyajit

  Let's I have a method to remove duplicates in an integer Array public int[] RemoveDuplicates(int[] elems) { HashSet<int> uniques = new HashSet<int>(); foreach (int item in elems) uniques.Add(item); elems = new int[uniques.Count]; int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } How can I make this generic such that now it accepts a string array and remove duplicates in it? How about a double array? I know I am probably mixing things here in between primitive and value types. For your reference the following code won't compile public List<T> RemoveDuplicates(List<T> elems) { HashSet<T> uniques = new HashSet<T>(); foreach (var item in elems) uniques.Add(item); elems = new List<T>(); int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } The reason is that all generic types should be closed at run time. Thanks for you comments

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