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  • Windows Azure Use Case: Hybrid Applications

    - by BuckWoody
    This is one in a series of posts on when and where to use a distributed architecture design in your organization's computing needs. You can find the main post here: http://blogs.msdn.com/b/buckwoody/archive/2011/01/18/windows-azure-and-sql-azure-use-cases.aspx  Description: Organizations see the need for computing infrastructures that they can “rent” or pay for only when they need them. They also understand the benefits of distributed computing, but do not want to create this infrastructure themselves. However, they may have considerations that prevent them from moving all of their current IT investment to a distributed environment: Private data (do not want to send or store sensitive data off-site) High dollar investment in current infrastructure Applications currently running well, but may need additional periodic capacity Current applications not designed in a stateless fashion In these situations, a “hybrid” approach works best. In fact, with Windows Azure, a hybrid approach is an optimal way to implement distributed computing even when the stipulations above do not apply. Keeping a majority of the computing function in an organization local while exploring and expanding that footprint into Windows and SQL Azure is a good migration or expansion strategy. A “hybrid” architecture merely means that part of a computing cycle is shared between two architectures. For instance, some level of computing might be done in a Windows Azure web-based application, while the data is stored locally at the organization. Implementation: There are multiple methods for implementing a hybrid architecture, in a spectrum from very little interaction from the local infrastructure to Windows or SQL Azure. The patterns fall into two broad schemas, and even these can be mixed. 1. Client-Centric Hybrid Patterns In this pattern, programs are coded such that the client system sends queries or compute requests to multiple systems. The “client” in this case might be a web-based codeset actually stored on another system (which acts as a client, the user’s device serving as the presentation layer) or a compiled program. In either case, the code on the client requestor carries the burden of defining the layout of the requests. While this pattern is often the easiest to code, it’s the most brittle. Any change in the architecture must be reflected on each client, but this can be mitigated by using a centralized system as the client such as in the web scenario. 2. System-Centric Hybrid Patterns Another approach is to create a distributed architecture by turning on-site systems into “services” that can be called from Windows Azure using the service Bus or the Access Control Services (ACS) capabilities. Code calls from a series of in-process client application. In this pattern you move the “client” interface into the server application logic. If you do not wish to change the application itself, you can “layer” the results of the code return using a product (such as Microsoft BizTalk) that exposes a Web Services Definition Language (WSDL) endpoint to Windows Azure using the Application Fabric. In effect, this is similar to creating a Service Oriented Architecture (SOA) environment, and has the advantage of de-coupling your computing architecture. If each system offers a “service” of the results of some software processing, the operating system or platform becomes immaterial, assuming it adheres to a service contract. There are important considerations when you federate a system, whether to Windows or SQL Azure or any other distributed architecture. While these considerations are consistent with coding any application for distributed computing, they are especially important for a hybrid application. Connection resiliency - Applications on-premise normally have low-latency and good connection properties, something you’re not always guaranteed in a distributed and hybrid application. Whether a centralized client or a distributed one, the code should be able to handle extended retry logic. Authorization and Access - In a single authorization environment like a Active Directory domain, security is handled at a user-password level. In a distributed computing environment, you have more options. You can mitigate this with  using The Windows Azure Application Fabric feature of ACS to make the Azure application aware of the App Fabric as an ADFS provider. However, a claims-based authentication structure is often a superior choice.  Consistency and Concurrency - When you have a Relational Database Management System (RDBMS), Consistency and Concurrency are part of the design. In a Service Architecture, you need to plan for sequential message handling and lifecycle. Resources: How to Build a Hybrid On-Premise/In Cloud Application: http://blogs.msdn.com/b/ignitionshowcase/archive/2010/11/09/how-to-build-a-hybrid-on-premise-in-cloud-application.aspx  General Architecture guidance: http://blogs.msdn.com/b/buckwoody/archive/2010/12/21/windows-azure-learning-plan-architecture.aspx   

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  • T-SQL Tuesday #006: LOB, row-overflow and locking behavior

    - by Michael Zilberstein
    This post is my contribution to T-SQL Tuesday #006 , hosted this time by Michael Coles . Actually this post was born last Thursday when I attended Kalen Delaney's "Deep dive into SQL Server Internals" seminar in Tel-Aviv. I asked question, Kalen didn't have answer at hand, so during a break I created demo in order to check certain behavior. Demo goes later in this post but first small teaser. I have MyTable table with 10 rows. I take 2 rows that reside on different pages. In first session...(read more)

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  • Troubleshooting High-CPU Utilization for SQL Server

    - by Susantha Bathige
    The objective of this FAQ is to outline the basic steps in troubleshooting high CPU utilization on  a server hosting a SQL Server instance. The first and the most common step if you suspect high CPU utilization (or are alerted for it) is to login to the physical server and check the Windows Task Manager. The Performance tab will show the high utilization as shown below: Next, we need to determine which process is responsible for the high CPU consumption. The Processes tab of the Task Manager will show this information: Note that to see all processes you should select Show processes from all user. In this case, SQL Server (sqlserver.exe) is consuming 99% of the CPU (a normal benchmark for max CPU utilization is about 50-60%). Next we examine the scheduler data. Scheduler is a component of SQLOS which evenly distributes load amongst CPUs. The query below returns the important columns for CPU troubleshooting. Note – if your server is under severe stress and you are unable to login to SSMS, you can use another machine’s SSMS to login to the server through DAC – Dedicated Administrator Connection (see http://msdn.microsoft.com/en-us/library/ms189595.aspx for details on using DAC) SELECT scheduler_id ,cpu_id ,status ,runnable_tasks_count ,active_workers_count ,load_factor ,yield_count FROM sys.dm_os_schedulers WHERE scheduler_id See below for the BOL definitions for the above columns. scheduler_id – ID of the scheduler. All schedulers that are used to run regular queries have ID numbers less than 1048576. Those schedulers that have IDs greater than or equal to 1048576 are used internally by SQL Server, such as the dedicated administrator connection scheduler. cpu_id – ID of the CPU with which this scheduler is associated. status – Indicates the status of the scheduler. runnable_tasks_count – Number of workers, with tasks assigned to them that are waiting to be scheduled on the runnable queue. active_workers_count – Number of workers that are active. An active worker is never preemptive, must have an associated task, and is either running, runnable, or suspended. current_tasks_count - Number of current tasks that are associated with this scheduler. load_factor – Internal value that indicates the perceived load on this scheduler. yield_count – Internal value that is used to indicate progress on this scheduler.                                                                 Now to interpret the above data. There are four schedulers and each assigned to a different CPU. All the CPUs are ready to accept user queries as they all are ONLINE. There are 294 active tasks in the output as per the current_tasks_count column. This count indicates how many activities currently associated with the schedulers. When a  task is complete, this number is decremented. The 294 is quite a high figure and indicates all four schedulers are extremely busy. When a task is enqueued, the load_factor  value is incremented. This value is used to determine whether a new task should be put on this scheduler or another scheduler. The new task will be allocated to less loaded scheduler by SQLOS. The very high value of this column indicates all the schedulers have a high load. There are 268 runnable tasks which mean all these tasks are assigned a worker and waiting to be scheduled on the runnable queue.   The next step is  to identify which queries are demanding a lot of CPU time. The below query is useful for this purpose (note, in its current form,  it only shows the top 10 records). SELECT TOP 10 st.text  ,st.dbid  ,st.objectid  ,qs.total_worker_time  ,qs.last_worker_time  ,qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) st CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp ORDER BY qs.total_worker_time DESC This query as total_worker_time as the measure of CPU load and is in descending order of the  total_worker_time to show the most expensive queries and their plans at the top:      Note the BOL definitions for the important columns: total_worker_time - Total amount of CPU time, in microseconds, that was consumed by executions of this plan since it was compiled. last_worker_time - CPU time, in microseconds, that was consumed the last time the plan was executed.   I re-ran the same query again after few seconds and was returned the below output. After few seconds the SP dbo.TestProc1 is shown in fourth place and once again the last_worker_time is the highest. This means the procedure TestProc1 consumes a CPU time continuously each time it executes.      In this case, the primary cause for high CPU utilization was a stored procedure. You can view the execution plan by clicking on query_plan column to investigate why this is causing a high CPU load. I have used SQL Server 2008 (SP1) to test all the queries used in this article.

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  • SQL Server Scripts I Use

    - by Bill Graziano
    When I get to a new client I usually find myself using the same set of scripts for maintenance and troubleshooting.  These are all drop in solutions for various maintenance issues. Reindexing.  I use Michelle Ufford’s (SQLFool) re-indexing script.  I like that it has a throttle and only re-indexes when needed.  She also has a variety of other interesting scripts on her blog too. Server Activity.  Adam Machanic is up to version 10 of sp_WhoIsActive.  It’s a great replacement for the sp_who* stored procedures and does so much more.  If a server is acting funny this is one of the first tools I use. Backups.  Tara Kizer has a great little T-SQL script for SQL Server backups.  Wait Stats.  Paul Randal has a great script to display wait stats.  The biggest benefit for me is that his script filters out at least three dozen wait stats that I just don’t care about (for example LAZYWRITER_SLEEP). Update Statistics.  I didn’t find anything I liked so I wrote a simple script to update stats myself.  The big need for me was that it had to run inside a time window and update the oldest statistics first.  Is there a better one? Diagnostic Queries.  Glenn Berry has a huge collection of DMV queries available.  He also just highlighted five of them including two I really like dealing with unused indexes and suggested indexes. Single Use Query Plans.  Kim Tripp has a script that counts the number of single-use query plans.  This should guide you in whether to enable the Optimize for Adhoc Workloads option in SQL Server 2008. Granting Permissions to Developers.  This is one of those scripts I didn’t even know I needed until I needed it.  Kendra Little wrote it to grant a login read-only permission to all the databases.  It also grants view server state and a few other handy permissions.   What else do you use?  What should I add to my list?

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  • Data binding in an ASP.Net application with Entity Framework

    - by nikolaosk
    This is going to be the eighth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here , the third one here , the fourth one here , the fifth one here ,the sixth one here and the seventh one here . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here ...(read more)

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  • Enhanced Dynamic Filtering

    - by Ricardo Peres
    Remember my last post on dynamic filtering? Well, this time I'm extending the code in order to allow two levels of querying: Match type, represented by the following options: public enum MatchType { StartsWith = 0, Contains = 1 } And word match: public enum WordMatch { AnyWord = 0, AllWords = 1, ExactPhrase = 2 } You can combine the two levels in order to achieve the following combinations: MatchType.StartsWith + WordMatch.AnyWord Matches any record that starts with any of the words specified MatchType.StartsWith + WordMatch.AllWords Not available: does not make sense, throws an exception MatchType.StartsWith + WordMatch.ExactPhrase Matches any record that starts with the exact specified phrase MatchType.Contains + WordMatch.AnyWord Matches any record that contains any of the specified words MatchType.Contains + WordMatch.AllWords Matches any record that contains all of the specified words MatchType.Contains + WordMatch.ExactPhrase Matches any record that contains the exact specified phrase Here is the code: public static IList Search(IQueryable query, Type entityType, String dataTextField, String phrase, MatchType matchType, WordMatch wordMatch, Int32 maxCount) { String [] terms = phrase.Split(' ').Distinct().ToArray(); StringBuilder result = new StringBuilder(); PropertyInfo displayProperty = entityType.GetProperty(dataTextField); IList searchList = null; MethodInfo orderByMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "OrderBy").ToArray() [ 0 ].MakeGenericMethod(entityType, displayProperty.PropertyType); MethodInfo takeMethod = typeof(Queryable).GetMethod("Take", BindingFlags.Public | BindingFlags.Static).MakeGenericMethod(entityType); MethodInfo whereMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "Where").ToArray() [ 0 ].MakeGenericMethod(entityType); MethodInfo distinctMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "Distinct" && m.GetParameters().Length == 1).Single().MakeGenericMethod(entityType); MethodInfo toListMethod = typeof(Enumerable).GetMethod("ToList", BindingFlags.Static | BindingFlags.Public).MakeGenericMethod(entityType); MethodInfo matchMethod = typeof(String).GetMethod ( (matchType == MatchType.StartsWith) ? "StartsWith" : "Contains", new Type [] { typeof(String) } ); MemberExpression member = Expression.MakeMemberAccess ( Expression.Parameter(entityType, "n"), displayProperty ); MethodCallExpression call = null; LambdaExpression where = null; LambdaExpression orderBy = Expression.Lambda ( member, member.Expression as ParameterExpression ); switch (matchType) { case MatchType.StartsWith: switch (wordMatch) { case WordMatch.AnyWord: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.Or ( where.Body, exp ), where.Parameters.ToArray() ); } break; case WordMatch.ExactPhrase: call = Expression.Call ( member, matchMethod, Expression.Constant(phrase) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); break; case WordMatch.AllWords: throw (new Exception("The match type StartsWith is not supported with word match AllWords")); } break; case MatchType.Contains: switch (wordMatch) { case WordMatch.AnyWord: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.Or ( where.Body, exp ), where.Parameters.ToArray() ); } break; case WordMatch.ExactPhrase: call = Expression.Call ( member, matchMethod, Expression.Constant(phrase) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); break; case WordMatch.AllWords: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.AndAlso ( where.Body, exp ), where.Parameters.ToArray() ); } break; } break; } query = orderByMethod.Invoke(null, new Object [] { query, orderBy }) as IQueryable; query = whereMethod.Invoke(null, new Object [] { query, where }) as IQueryable; if (maxCount != 0) { query = takeMethod.Invoke(null, new Object [] { query, maxCount }) as IQueryable; } searchList = toListMethod.Invoke(null, new Object [] { query }) as IList; return (searchList); } And this is how you'd use it: IQueryable query = ctx.MyEntities; IList list = Search(query, typeof(MyEntity), "Name", "Ricardo Peres", MatchType.Contains, WordMatch.ExactPhrase, 10 /*0 for all*/); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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  • Watching Green Day and discovering Sitecore, priceless.

    - by jonel
    I’m feeling inspired and I’d like to share a technique we’ve implemented in Sitecore to address a URL mapping from our legacy site that we wanted to carry over to the new beautiful Littelfuse.com. The challenge is to carry over all of our series URLs that have been published in our datasheets, we currently have a lot of series and having to create a manual mapping for those could be really tedious. It has the format of http://www.littelfuse.com/series/series-name.html, for instance, http://www.littelfuse.com/series/flnr.html. It would have been easier if we have our information architecture defined like this but that would have been too easy. I took a solution that is 2-fold. First, I need to create a URL rewrite rule using the IIS URL Rewrite Module 2.0. Secondly, we need to implement a handler that will take care of the actual lookup of the actual series. It will be amazing after we’ve gone over the details. Let’s start with the URL rewrite. Create a new blank rule, you can name it with anything you wish. The key part here to talk about is the Pattern and the Action groups. The Pattern is nothing but regex. Basically, I’m telling it to match the regex I have defined. In the Action group, I am telling it what to do, in this case, rewrite to the redirect.aspx webform. In this implementation, I will be using Rewrite instead of redirect so the URL sticks in the browser. If you opt to use Redirect, then the URL bar will display the new URL our webform will redirect to. Let me explain one small thing, the (\w+) in my Pattern group’s regex, will actually translate to {R:1} in my Action’s group. This is where the magic begins. Now let’s see what our Redirect.aspx contains. Remember our {R:1} above which becomes the query string variable s? This are basic .Net code. The only thing that you will probably ask is the LFSearch class. It’s our own implementation of addressing finding items by using a field search, we supply the fieldname, the value of the field, the template name of the item we are after, and the value of true or false if we want to do an exact search, or not. If eureka, then redirect to that item’s Path (Url). If not, tell the user tough luck, here’s the 404 page as a consolation. Amazing, ain’t it?

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  • July, the 31 Days of SQL Server DMO’s – Day 24 (sys.dm_db_index_operational_stats)

    - by Tamarick Hill
    The sys.dm_db_index_operational_stats Dynamic Management Function returns information about the IO, locking, and access methods for the indexes that you currently have on your SQL Server Instance. This function takes four input parameters which are (1) database_id, (2) object_id, (3) index_id, and (4) partition_number. Let’s have a look at the results from this function against our AdventureWorks2012 database. This function returns a ton of columns, so not only will I not attempt to describe each of the columns, I wont even attempt to display all of them here. My query below will give you a subset of the columns returned from this function. SELECT database_id, object_id, index_id, partition_number, leaf_insert_count, leaf_delete_count, leaf_update_count, leaf_ghost_count, nonleaf_insert_count, nonleaf_delete_count, nonleaf_update_count, range_scan_count, forwarded_fetch_count, row_lock_count, row_lock_wait_count, page_lock_count, page_lock_wait_count, Index_lock_promotion_attempt_count, index_lock_promotion_count, page_compression_attempt_count, page_compression_success_count FROM sys.dm_db_index_operational_stats(db_id('AdventureWorks2012'), NULL, NULL, NULL) The first four columns in the result set represent the values that we passed in as our input parameters. If you use NULL’s as I did, then you will see results for every index on your system. I specified a database_id so my result set only shows those records pertaining to my AdventureWorks2012 database. The next columns in the result set provide you with information on how may inserts, deletes, or updates that have taken place on your leaf and nonleaf index levels. The nonleaf levels would refer to the intermediate and root index levels. In the middle of these you see a leaf_ghost_count column, which represents the number of records that have been logically deleted and marked as “ghosted”  and are waiting on the background ghost cleanup process to physically remove them. The range_scan_count column represents the number of range or table scans that have been performed against an index. The forwarded_fetch_count column represents the number of rows that were returned from a forwarding row pointer. The row_lock_count and row_lock_wait_count represent the number of row locks that have been requested for an index and the number of times SQL has had to wait on a row lock respectively. The page_lock_count and page_lock_wait_count represent the number of page locks that have been requested for an index and the number of times SQL has had to wait on a page lock respectively. The index_lock_promotion_attempt_count represents the number of times the database engine has attempted to promote a lock to the index level. The index_lock_promotion_count column displays how many times that index lock promotion was successful. Lastly the page_compression_attempt_count and page_compression_success_count represents how many times a page was attempted to be compressed and how many times the attempt was successful. As you can see there is a ton of information returned from this DMV. The DMV we reviewed on yesterday (sys.dm_db_index_usage_stats) provided you with good information on when and how indexes have been used, but this DMF takes an even deeper dive into these statistics. If you are interested in performing a very detailed analysis on the operational stats of your indexes, this is not only a good place to start, but more than likely the best place. For more information on this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms174281.aspx Follow me on Twitter @PrimeTimeDBA

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  • July, the 31 Days of SQL Server DMO’s – Day 30 (sys.dm_server_registry)

    - by Tamarick Hill
    The sys.dm_server_registry DMV is used to provide SQL Server configuration and installation information that is currently stored in your Windows Registry. It is a very simple DMV that returns only three columns. The first column returned is the registry_key. The second column returned is the value_name which is the name of the actual registry key value. The third and final column returned is the value_data which is the value of the registry key data. Lets have a look at the information this DMV returns as well as some key values from the Windows Registy. SELECT * FROM sys.dm_server_registry View using RegEdit to view the registy: This DMV provides you with a quick and easy way to view SQL Server Instance registry values. For more information about this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/hh204561.aspx Follow me on Twitter @PrimeTimeDBA

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  • Entity Framework and Plain Old CLR Objects in an ASP.Net application

    - by nikolaosk
    This is going to be the sixth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here , the fourth one here and the fifth one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In this post I will be looking...(read more)

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  • Using TPL and PLINQ to raise performance of feed aggregator

    - by DigiMortal
    In this posting I will show you how to use Task Parallel Library (TPL) and PLINQ features to boost performance of simple RSS-feed aggregator. I will use here only very basic .NET classes that almost every developer starts from when learning parallel programming. Of course, we will also measure how every optimization affects performance of feed aggregator. Feed aggregator Our feed aggregator works as follows: Load list of blogs Download RSS-feed Parse feed XML Add new posts to database Our feed aggregator is run by task scheduler after every 15 minutes by example. We will start our journey with serial implementation of feed aggregator. Second step is to use task parallelism and parallelize feeds downloading and parsing. And our last step is to use data parallelism to parallelize database operations. We will use Stopwatch class to measure how much time it takes for aggregator to download and insert all posts from all registered blogs. After every run we empty posts table in database. Serial aggregation Before doing parallel stuff let’s take a look at serial implementation of feed aggregator. All tasks happen one after other. internal class FeedClient {     private readonly INewsService _newsService;     private const int FeedItemContentMaxLength = 255;       public FeedClient()     {          ObjectFactory.Initialize(container =>          {              container.PullConfigurationFromAppConfig = true;          });           _newsService = ObjectFactory.GetInstance<INewsService>();     }       public void Execute()     {         var blogs = _newsService.ListPublishedBlogs();           for (var index = 0; index <blogs.Count; index++)         {              ImportFeed(blogs[index]);         }     }       private void ImportFeed(BlogDto blog)     {         if(blog == null)             return;         if (string.IsNullOrEmpty(blog.RssUrl))             return;           var uri = new Uri(blog.RssUrl);         SyndicationContentFormat feedFormat;           feedFormat = SyndicationDiscoveryUtility.SyndicationContentFormatGet(uri);           if (feedFormat == SyndicationContentFormat.Rss)             ImportRssFeed(blog);         if (feedFormat == SyndicationContentFormat.Atom)             ImportAtomFeed(blog);                 }       private void ImportRssFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = RssFeed.Create(uri);           foreach (var item in feed.Channel.Items)         {             SaveRssFeedItem(item, blog.Id, blog.CreatedById);         }     }       private void ImportAtomFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = AtomFeed.Create(uri);           foreach (var item in feed.Entries)         {             SaveAtomFeedEntry(item, blog.Id, blog.CreatedById);         }     } } Serial implementation of feed aggregator downloads and inserts all posts with 25.46 seconds. Task parallelism Task parallelism means that separate tasks are run in parallel. You can find out more about task parallelism from MSDN page Task Parallelism (Task Parallel Library) and Wikipedia page Task parallelism. Although finding parts of code that can run safely in parallel without synchronization issues is not easy task we are lucky this time. Feeds import and parsing is perfect candidate for parallel tasks. We can safely parallelize feeds import because importing tasks doesn’t share any resources and therefore they don’t also need any synchronization. After getting the list of blogs we iterate through the collection and start new TPL task for each blog feed aggregation. internal class FeedClient {     private readonly INewsService _newsService;     private const int FeedItemContentMaxLength = 255;       public FeedClient()     {          ObjectFactory.Initialize(container =>          {              container.PullConfigurationFromAppConfig = true;          });           _newsService = ObjectFactory.GetInstance<INewsService>();     }       public void Execute()     {         var blogs = _newsService.ListPublishedBlogs();                var tasks = new Task[blogs.Count];           for (var index = 0; index <blogs.Count; index++)         {             tasks[index] = new Task(ImportFeed, blogs[index]);             tasks[index].Start();         }           Task.WaitAll(tasks);     }       private void ImportFeed(object blogObject)     {         if(blogObject == null)             return;         var blog = (BlogDto)blogObject;         if (string.IsNullOrEmpty(blog.RssUrl))             return;           var uri = new Uri(blog.RssUrl);         SyndicationContentFormat feedFormat;           feedFormat = SyndicationDiscoveryUtility.SyndicationContentFormatGet(uri);           if (feedFormat == SyndicationContentFormat.Rss)             ImportRssFeed(blog);         if (feedFormat == SyndicationContentFormat.Atom)             ImportAtomFeed(blog);                }       private void ImportRssFeed(BlogDto blog)     {          var uri = new Uri(blog.RssUrl);          var feed = RssFeed.Create(uri);           foreach (var item in feed.Channel.Items)          {              SaveRssFeedItem(item, blog.Id, blog.CreatedById);          }     }     private void ImportAtomFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = AtomFeed.Create(uri);           foreach (var item in feed.Entries)         {             SaveAtomFeedEntry(item, blog.Id, blog.CreatedById);         }     } } You should notice first signs of the power of TPL. We made only minor changes to our code to parallelize blog feeds aggregating. On my machine this modification gives some performance boost – time is now 17.57 seconds. Data parallelism There is one more way how to parallelize activities. Previous section introduced task or operation based parallelism, this section introduces data based parallelism. By MSDN page Data Parallelism (Task Parallel Library) data parallelism refers to scenario in which the same operation is performed concurrently on elements in a source collection or array. In our code we have independent collections we can process in parallel – imported feed entries. As checking for feed entry existence and inserting it if it is missing from database doesn’t affect other entries the imported feed entries collection is ideal candidate for parallelization. internal class FeedClient {     private readonly INewsService _newsService;     private const int FeedItemContentMaxLength = 255;       public FeedClient()     {          ObjectFactory.Initialize(container =>          {              container.PullConfigurationFromAppConfig = true;          });           _newsService = ObjectFactory.GetInstance<INewsService>();     }       public void Execute()     {         var blogs = _newsService.ListPublishedBlogs();                var tasks = new Task[blogs.Count];           for (var index = 0; index <blogs.Count; index++)         {             tasks[index] = new Task(ImportFeed, blogs[index]);             tasks[index].Start();         }           Task.WaitAll(tasks);     }       private void ImportFeed(object blogObject)     {         if(blogObject == null)             return;         var blog = (BlogDto)blogObject;         if (string.IsNullOrEmpty(blog.RssUrl))             return;           var uri = new Uri(blog.RssUrl);         SyndicationContentFormat feedFormat;           feedFormat = SyndicationDiscoveryUtility.SyndicationContentFormatGet(uri);           if (feedFormat == SyndicationContentFormat.Rss)             ImportRssFeed(blog);         if (feedFormat == SyndicationContentFormat.Atom)             ImportAtomFeed(blog);                }       private void ImportRssFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = RssFeed.Create(uri);           feed.Channel.Items.AsParallel().ForAll(a =>         {             SaveRssFeedItem(a, blog.Id, blog.CreatedById);         });      }        private void ImportAtomFeed(BlogDto blog)      {         var uri = new Uri(blog.RssUrl);         var feed = AtomFeed.Create(uri);           feed.Entries.AsParallel().ForAll(a =>         {              SaveAtomFeedEntry(a, blog.Id, blog.CreatedById);         });      } } We did small change again and as the result we parallelized checking and saving of feed items. This change was data centric as we applied same operation to all elements in collection. On my machine I got better performance again. Time is now 11.22 seconds. Results Let’s visualize our measurement results (numbers are given in seconds). As we can see then with task parallelism feed aggregation takes about 25% less time than in original case. When adding data parallelism to task parallelism our aggregation takes about 2.3 times less time than in original case. More about TPL and PLINQ Adding parallelism to your application can be very challenging task. You have to carefully find out parts of your code where you can safely go to parallel processing and even then you have to measure the effects of parallel processing to find out if parallel code performs better. If you are not careful then troubles you will face later are worse than ones you have seen before (imagine error that occurs by average only once per 10000 code runs). Parallel programming is something that is hard to ignore. Effective programs are able to use multiple cores of processors. Using TPL you can also set degree of parallelism so your application doesn’t use all computing cores and leaves one or more of them free for host system and other processes. And there are many more things in TPL that make it easier for you to start and go on with parallel programming. In next major version all .NET languages will have built-in support for parallel programming. There will be also new language constructs that support parallel programming. Currently you can download Visual Studio Async to get some idea about what is coming. Conclusion Parallel programming is very challenging but good tools offered by Visual Studio and .NET Framework make it way easier for us. In this posting we started with feed aggregator that imports feed items on serial mode. With two steps we parallelized feed importing and entries inserting gaining 2.3 times raise in performance. Although this number is specific to my test environment it shows clearly that parallel programming may raise the performance of your application significantly.

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  • Lazy Loading,Eager Loading,Explicit Loading in Entity Framework 4

    - by nikolaosk
    This is going to be the ninth post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here , the third one here , the fourth one here , the fifth one here ,the sixth one here ,the seventh one here and the eighth one here . I have a post regarding ASP.Net and EntityDataSource . You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a...(read more)

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  • Making a Statement: How to retrieve the T-SQL statement that caused an event

    - by extended_events
    If you’ve done any troubleshooting of T-SQL, you know that sooner or later, probably sooner, you’re going to want to take a look at the actual statements you’re dealing with. In extended events we offer an action (See the BOL topic that covers Extended Events Objects for a description of actions) named sql_text that seems like it is just the ticket. Well…not always – sounds like a good reason for a blog post. When is a statement not THE statement? The sql_text action returns the same information that is returned from DBCC INPUTBUFFER, which may or may not be what you want. For example, if you execute a stored procedure, the sql_text action will return something along the lines of “EXEC sp_notwhatiwanted” assuming that is the statement you sent from the client. Often times folks would like something more specific, like the actual statements that are being run from within the stored procedure or batch. Enter the stack Extended events offers another action, this one with the descriptive name of tsql_stack, that includes the sql_handle and offset information about the statements being run when an event occurs. With the sql_handle and offset values you can retrieve the specific statement you seek using the DMV dm_exec_sql_statement. The BOL topic for dm_exec_sql_statement provides an example for how to extract this information, so I’ll cover the gymnastics required to get the sql_handle and offset values out of the tsql_stack data collected by the action. I’m the first to admit that this isn’t pretty, but this is what we have in SQL Server 2008 and 2008 R2. We will be making it easier to get statement level information in the next major release of SQL Server. The sample code For this example I have a stored procedure that includes multiple statements and I have a need to differentiate between those two statements in my tracing. I’m going to track two events: module_end tracks the completion of the stored procedure execution and sp_statement_completed tracks the execution of each statement within a stored procedure. I’m adding the tsql_stack events (since that’s the topic of this post) and the sql_text action for comparison sake. (If you have questions about creating event sessions, check out Pedro’s post Introduction to Extended Events.) USE AdventureWorks2008GO -- Test SPCREATE PROCEDURE sp_multiple_statementsASSELECT 'This is the first statement'SELECT 'this is the second statement'GO -- Create a session to look at the spCREATE EVENT SESSION track_sprocs ON SERVERADD EVENT sqlserver.module_end (ACTION (sqlserver.tsql_stack, sqlserver.sql_text)),ADD EVENT sqlserver.sp_statement_completed (ACTION (sqlserver.tsql_stack, sqlserver.sql_text))ADD TARGET package0.ring_bufferWITH (MAX_DISPATCH_LATENCY = 1 SECONDS)GO -- Start the sessionALTER EVENT SESSION track_sprocs ON SERVERSTATE = STARTGO -- Run the test procedureEXEC sp_multiple_statementsGO -- Stop collection of events but maintain ring bufferALTER EVENT SESSION track_sprocs ON SERVERDROP EVENT sqlserver.module_end,DROP EVENT sqlserver.sp_statement_completedGO Aside: Altering the session to drop the events is a neat little trick that allows me to stop collection of events while keeping in-memory targets such as the ring buffer available for use. If you stop the session the in-memory target data is lost. Now that we’ve collected some events related to running the stored procedure, we need to do some processing of the data. I’m going to do this in multiple steps using temporary tables so you can see what’s going on; kind of like having to “show your work” on a math test. The first step is to just cast the target data into XML so I can work with it. After that you can pull out the interesting columns, for our purposes I’m going to limit the output to just the event name, object name, stack and sql text. You can see that I’ve don a second CAST, this time of the tsql_stack column, so that I can further process this data. -- Store the XML data to a temp tableSELECT CAST( t.target_data AS XML) xml_dataINTO #xml_event_dataFROM sys.dm_xe_sessions s INNER JOIN sys.dm_xe_session_targets t    ON s.address = t.event_session_addressWHERE s.name = 'track_sprocs' SELECT * FROM #xml_event_data -- Parse the column data out of the XML blockSELECT    event_xml.value('(./@name)', 'varchar(100)') as [event_name],    event_xml.value('(./data[@name="object_name"]/value)[1]', 'varchar(255)') as [object_name],    CAST(event_xml.value('(./action[@name="tsql_stack"]/value)[1]','varchar(MAX)') as XML) as [stack_xml],    event_xml.value('(./action[@name="sql_text"]/value)[1]', 'varchar(max)') as [sql_text]INTO #event_dataFROM #xml_event_data    CROSS APPLY xml_data.nodes('//event') n (event_xml) SELECT * FROM #event_data event_name object_name stack_xml sql_text sp_statement_completed NULL <frame level="1" handle="0x03000500D0057C1403B79600669D00000100000000000000" line="4" offsetStart="94" offsetEnd="172" /><frame level="2" handle="0x01000500CF3F0331B05EC084000000000000000000000000" line="1" offsetStart="0" offsetEnd="-1" /> EXEC sp_multiple_statements sp_statement_completed NULL <frame level="1" handle="0x03000500D0057C1403B79600669D00000100000000000000" line="6" offsetStart="174" offsetEnd="-1" /><frame level="2" handle="0x01000500CF3F0331B05EC084000000000000000000000000" line="1" offsetStart="0" offsetEnd="-1" /> EXEC sp_multiple_statements module_end sp_multiple_statements <frame level="1" handle="0x03000500D0057C1403B79600669D00000100000000000000" line="0" offsetStart="0" offsetEnd="0" /><frame level="2" handle="0x01000500CF3F0331B05EC084000000000000000000000000" line="1" offsetStart="0" offsetEnd="-1" /> EXEC sp_multiple_statements After parsing the columns it’s easier to see what is recorded. You can see that I got back two sp_statement_completed events, which makes sense given the test procedure I’m running, and I got back a single module_end for the entire statement. As described, the sql_text isn’t telling me what I really want to know for the first two events so a little extra effort is required. -- Parse the tsql stack information into columnsSELECT    event_name,    object_name,    frame_xml.value('(./@level)', 'int') as [frame_level],    frame_xml.value('(./@handle)', 'varchar(MAX)') as [sql_handle],    frame_xml.value('(./@offsetStart)', 'int') as [offset_start],    frame_xml.value('(./@offsetEnd)', 'int') as [offset_end]INTO #stack_data    FROM #event_data        CROSS APPLY    stack_xml.nodes('//frame') n (frame_xml)    SELECT * from #stack_data event_name object_name frame_level sql_handle offset_start offset_end sp_statement_completed NULL 1 0x03000500D0057C1403B79600669D00000100000000000000 94 172 sp_statement_completed NULL 2 0x01000500CF3F0331B05EC084000000000000000000000000 0 -1 sp_statement_completed NULL 1 0x03000500D0057C1403B79600669D00000100000000000000 174 -1 sp_statement_completed NULL 2 0x01000500CF3F0331B05EC084000000000000000000000000 0 -1 module_end sp_multiple_statements 1 0x03000500D0057C1403B79600669D00000100000000000000 0 0 module_end sp_multiple_statements 2 0x01000500CF3F0331B05EC084000000000000000000000000 0 -1 Parsing out the stack information doubles the fun and I get two rows for each event. If you examine the stack from the previous table, you can see that each stack has two frames and my query is parsing each event into frames, so this is expected. There is nothing magic about the two frames, that’s just how many I get for this example, it could be fewer or more depending on your statements. The key point here is that I now have a sql_handle and the offset values for those handles, so I can use dm_exec_sql_statement to get the actual statement. Just a reminder, this DMV can only return what is in the cache – if you have old data it’s possible your statements have been ejected from the cache. “Old” is a relative term when talking about caches and can be impacted by server load and how often your statement is actually used. As with most things in life, your mileage may vary. SELECT    qs.*,     SUBSTRING(st.text, (qs.offset_start/2)+1,         ((CASE qs.offset_end          WHEN -1 THEN DATALENGTH(st.text)         ELSE qs.offset_end         END - qs.offset_start)/2) + 1) AS statement_textFROM #stack_data AS qsCROSS APPLY sys.dm_exec_sql_text(CONVERT(varbinary(max),sql_handle,1)) AS st event_name object_name frame_level sql_handle offset_start offset_end statement_text sp_statement_completed NULL 1 0x03000500D0057C1403B79600669D00000100000000000000 94 172 SELECT 'This is the first statement' sp_statement_completed NULL 1 0x03000500D0057C1403B79600669D00000100000000000000 174 -1 SELECT 'this is the second statement' module_end sp_multiple_statements 1 0x03000500D0057C1403B79600669D00000100000000000000 0 0 C Now that looks more like what we were after, the statement_text field is showing the actual statement being run when the sp_statement_completed event occurs. You’ll notice that it’s back down to one row per event, what happened to frame 2? The short answer is, “I don’t know.” In SQL Server 2008 nothing is returned from dm_exec_sql_statement for the second frame and I believe this to be a bug; this behavior has changed in the next major release and I see the actual statement run from the client in frame 2. (In other words I see the same statement that is returned by the sql_text action  or DBCC INPUTBUFFER) There is also something odd going on with frame 1 returned from the module_end event; you can see that the offset values are both 0 and only the first letter of the statement is returned. It seems like the offset_end should actually be –1 in this case and I’m not sure why it’s not returning this correctly. This behavior is being investigated and will hopefully be corrected in the next major version. You can workaround this final oddity by ignoring the offsets and just returning the entire cached statement. SELECT    event_name,    sql_handle,    ts.textFROM #stack_data    CROSS APPLY sys.dm_exec_sql_text(CONVERT(varbinary(max),sql_handle,1)) as ts event_name sql_handle text sp_statement_completed 0x0300070025999F11776BAF006F9D00000100000000000000 CREATE PROCEDURE sp_multiple_statements AS SELECT 'This is the first statement' SELECT 'this is the second statement' sp_statement_completed 0x0300070025999F11776BAF006F9D00000100000000000000 CREATE PROCEDURE sp_multiple_statements AS SELECT 'This is the first statement' SELECT 'this is the second statement' module_end 0x0300070025999F11776BAF006F9D00000100000000000000 CREATE PROCEDURE sp_multiple_statements AS SELECT 'This is the first statement' SELECT 'this is the second statement' Obviously this gives more than you want for the sp_statement_completed events, but it’s the right information for module_end. I leave it to you to determine when this information is needed and use the workaround when appropriate. Aside: You might think it’s odd that I’m showing apparent bugs with my samples, but you’re going to see this behavior if you use this method, so you need to know about it.I’m all about transparency. Happy Eventing- Mike Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Creating Property Set Expression Trees In A Developer Friendly Way

    - by Paulo Morgado
    In a previous post I showed how to create expression trees to set properties on an object. The way I did it was not very developer friendly. It involved explicitly creating the necessary expressions because the compiler won’t generate expression trees with property or field set expressions. Recently someone contacted me the help develop some kind of command pattern framework that used developer friendly lambdas to generate property set expression trees. Simply putting, given this entity class: public class Person { public string Name { get; set; } } The person in question wanted to write code like this: var et = Set((Person p) => p.Name = "me"); Where et is the expression tree that represents the property assignment. So, if we can’t do this, let’s try the next best thing that is splitting retrieving the property information from the retrieving the value to assign o the property: var et = Set((Person p) => p.Name, () => "me"); And this is something that the compiler can handle. The implementation of Set receives an expression to retrieve the property information from and another expression the retrieve the value to assign to the property: public static Expression<Action<TEntity>> Set<TEntity, TValue>( Expression<Func<TEntity, TValue>> propertyGetExpression, Expression<Func<TValue>> valueExpression) The implementation of this method gets the property information form the body of the property get expression (propertyGetExpression) and the value expression (valueExpression) to build an assign expression and builds a lambda expression using the same parameter of the property get expression as its parameter: public static Expression<Action<TEntity>> Set<TEntity, TValue>( Expression<Func<TEntity, TValue>> propertyGetExpression, Expression<Func<TValue>> valueExpression) { var entityParameterExpression = (ParameterExpression)(((MemberExpression)(propertyGetExpression.Body)).Expression); return Expression.Lambda<Action<TEntity>>( Expression.Assign(propertyGetExpression.Body, valueExpression.Body), entityParameterExpression); } And now we can use the expression to translate to another context or just compile and use it: var et = Set((Person p) => p.Name, () => name); Console.WriteLine(person.Name); // Prints: p => (p.Name = “me”) var d = et.Compile(); d(person); Console.WriteLine(person.Name); // Prints: me It can even support closures: var et = Set((Person p) => p.Name, () => name); Console.WriteLine(person.Name); // Prints: p => (p.Name = value(<>c__DisplayClass0).name) var d = et.Compile(); name = "me"; d(person); Console.WriteLine(person.Name); // Prints: me name = "you"; d(person); Console.WriteLine(person.Name); // Prints: you Not so useful in the intended scenario (but still possible) is building an expression tree that receives the value to assign to the property as a parameter: public static Expression<Action<TEntity, TValue>> Set<TEntity, TValue>(Expression<Func<TEntity, TValue>> propertyGetExpression) { var entityParameterExpression = (ParameterExpression)(((MemberExpression)(propertyGetExpression.Body)).Expression); var valueParameterExpression = Expression.Parameter(typeof(TValue)); return Expression.Lambda<Action<TEntity, TValue>>( Expression.Assign(propertyGetExpression.Body, valueParameterExpression), entityParameterExpression, valueParameterExpression); } This new expression can be used like this: var et = Set((Person p) => p.Name); Console.WriteLine(person.Name); // Prints: (p, Param_0) => (p.Name = Param_0) var d = et.Compile(); d(person, "me"); Console.WriteLine(person.Name); // Prints: me d(person, "you"); Console.WriteLine(person.Name); // Prints: you The only caveat is that we need to be able to write code to read the property in order to write to it.

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  • SQL Social

    - by SteveP
    Wanted to thanks Simon for putting together a great event last night.  It was a real pleasure to be in the company of some of the greats(Itzik, Greg, Davide, Bill and not forgetting Mr Sabin) in the SQL server space.  The venue was superb and the knowledge of the panel covered pretty much every corner of the SQL Server platform.  I'm very much looking forward to seeing how the social evenings progress.  It's going to be hard to follow this one. 

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  • MCM Lab exam this week

    - by Rob Farley
    In two days I’ll’ve finished the MCM Lab exam, 88-971. If you do an internet search for 88-971, it’ll tell you the answer is –883. Obviously. It’ll also give you a link to the actual exam page, which is useful too, once you’ve finished being distracted by the calculator instead of going to the thing you’re actually looking for. (Do people actually search the internet for the results of mathematical questions? Really?) The list of Skills Measured for this exam is quite short, but can essentially be broken down into one word “Anything”. The Preparation Materials section is even better. Classroom Training – none available. Microsoft E-Learning – none available. Microsoft Press Books – none available. Practice Tests – none available. But there are links to Readiness Videos and a page which has no resources listed, but tells you a list of people who have already qualified. Three in Australia who have MCM SQL Server 2008 so far. The list doesn’t include some of the latest batch, such as Jason Strate or Tom LaRock. I’ve used SQL Server for almost 15 years. During that time I’ve been awarded SQL Server MVP seven times, but the MVP award doesn’t actually mean all that much when considering this particular certification. I know lots of MVPs who have tried this particular exam and failed – including Jason and Tom. Right now, I have no idea whether I’ll pass or not. People tell me I’ll pass no problem, but I honestly have no idea. There’s something about that “Anything” aspect that worries me. I keep looking at the list of things in the Readiness Videos, and think to myself “I’m comfortable with Resource Governor (or whatever) – that should be fine.” Except that then I feel like I maybe don’t know all the different things that can go wrong with Resource Governor (or whatever), and I wonder what kind of situations I’ll be faced with. And then I find myself looking through the stuff that’s explained in the videos, and wondering what kinds of things I should know that I don’t, and then I get amazingly bored and frustrated (after all, I tell people that these exams aren’t supposed to be studied for – you’ve been studying for the last 15 years, right?), and I figure “What’s the worst that can happen? A fail?” I’m told that the exam provides a list of scenarios (maybe 14 of them?) and you have 5.5 hours to complete them. When I say “complete”, I mean complete – you don’t get to leave them unfinished, that’ll get you ‘nil points’ for that scenario. Apparently no-one gets to complete all of them. Now, I’m a consultant. I get called on to fix the problems that people have on their SQL boxes. Sometimes this involves fixing corruption. Sometimes it’s figuring out some performance problem. Sometimes it’s as straight forward as getting past a full transaction log; sometimes it’s as tricky as recovering a database that has lost its metadata, without backups. Most situations aren’t a problem, but I also have the confidence of being able to do internet searches to verify my maths (in case I forget it’s –883). In the exam, I’ll have maybe twenty minutes per scenario (but if I need longer, I’ll have to take longer – no point in stopping half way if it takes more than twenty minutes, unless I don’t see an end coming up), so I’ll have time constraints too. And of course, I won’t have any of my usual tools. I can’t take scripts in, I can’t take staff members. Hopefully I can use the coffee machine that will be in the room. I figure it’s going to feel like one of those days when I’ve gone into a client site, and found that the problems are way worse than I expected, and that the site is down, with people standing over me needing me to get things right first time... ...so it should be fine, I’ve done that before. :) If I do fail, it won’t make me any less of a consultant. It won’t make me any less able to help all of my clients (including you if you get in touch – hehe), it’ll just mean that the particular problem might’ve taken me more than the twenty minutes that the exam gave me. @rob_farley PS: Apparently the done thing is to NOT advertise that you’re sitting the exam at a particular time, only that you’re expecting to take it at some point in the future. I think it’s akin to the idea of not telling people you’re pregnant for the first few months – it’s just in case the worst happens. Personally, I’m happy to tell you all that I’m going to take this exam the day after tomorrow (which is the 19th in the US, the 20th here). If I end up failing, you can all commiserate and tell me that I’m not actually as unqualified as I feel.

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  • Reinventing the Paged IEnumerable, Weigert Style!

    - by adweigert
    I am pretty sure someone else has done this, I've seen variations as PagedList<T>, but this is my style of a paged IEnumerable collection. I just store a reference to the collection and generate the paged data when the enumerator is needed, so you could technically add to a list that I'm referencing and the properties and results would be adjusted accordingly. I don't mind reinventing the wheel when I can add some of my own personal flare ... // Extension method for easy use public static PagedEnumerable AsPaged(this IEnumerable collection, int currentPage = 1, int pageSize = 0) { Contract.Requires(collection != null); Contract.Assume(currentPage >= 1); Contract.Assume(pageSize >= 0); return new PagedEnumerable(collection, currentPage, pageSize); } public class PagedEnumerable : IEnumerable { public PagedEnumerable(IEnumerable collection, int currentPage = 1, int pageSize = 0) { Contract.Requires(collection != null); Contract.Assume(currentPage >= 1); Contract.Assume(pageSize >= 0); this.collection = collection; this.PageSize = pageSize; this.CurrentPage = currentPage; } IEnumerable collection; int currentPage; public int CurrentPage { get { if (this.currentPage > this.TotalPages) { return this.TotalPages; } return this.currentPage; } set { if (value < 1) { this.currentPage = 1; } else if (value > this.TotalPages) { this.currentPage = this.TotalPages; } else { this.currentPage = value; } } } int pageSize; public int PageSize { get { if (this.pageSize == 0) { return this.collection.Count(); } return this.pageSize; } set { this.pageSize = (value < 0) ? 0 : value; } } public int TotalPages { get { return (int)Math.Ceiling(this.collection.Count() / (double)this.PageSize); } } public IEnumerator GetEnumerator() { var pageSize = this.PageSize; var currentPage = this.CurrentPage; var startCount = (currentPage - 1) * pageSize; return this.collection.Skip(startCount).Take(pageSize).GetEnumerator(); } IEnumerator IEnumerable.GetEnumerator() { return this.GetEnumerator(); } }

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  • The WaitForAll Roadshow

    - by adweigert
    OK, so I took for granted some imaginative uses of WaitForAll but lacking that, here is how I am using. First, I have a nice little class called Parallel that allows me to spin together a list of tasks (actions) and then use WaitForAll, so here it is, WaitForAll's 15 minutes of fame ... First Parallel that allows me to spin together several Action delegates to execute, well in parallel.   public static class Parallel { public static ParallelQuery Task(Action action) { return new Action[] { action }.AsParallel(); } public static ParallelQuery> Task(Action action) { return new Action[] { action }.AsParallel(); } public static ParallelQuery Task(this ParallelQuery actions, Action action) { var list = new List(actions); list.Add(action); return list.AsParallel(); } public static ParallelQuery> Task(this ParallelQuery> actions, Action action) { var list = new List>(actions); list.Add(action); return list.AsParallel(); } }   Next, this is an example usage from an app I'm working on that just is rendering some basic computer information via WMI and performance counters. The WMI calls can be expensive given the distance and link speed of some of the computers it will be trying to communicate with. This is the actual MVC action from my controller to return the data for an individual computer.  public PartialViewResult Detail(string computerName) { var computer = this.Computers.Get(computerName); var perf = Factory.GetInstance(); var detail = new ComputerDetailViewModel() { Computer = computer }; try { var work = Parallel .Task(delegate { // Win32_ComputerSystem var key = computer.Name + "_Win32_ComputerSystem"; var system = this.Cache.Get(key); if (system == null) { using (var impersonation = computer.ImpersonateElevatedIdentity()) { system = computer.GetWmiContext().GetInstances().Single(); } this.Cache.Set(key, system); } detail.TotalMemory = system.TotalPhysicalMemory; detail.Manufacturer = system.Manufacturer; detail.Model = system.Model; detail.NumberOfProcessors = system.NumberOfProcessors; }) .Task(delegate { // Win32_OperatingSystem var key = computer.Name + "_Win32_OperatingSystem"; var os = this.Cache.Get(key); if (os == null) { using (var impersonation = computer.ImpersonateElevatedIdentity()) { os = computer.GetWmiContext().GetInstances().Single(); } this.Cache.Set(key, os); } detail.OperatingSystem = os.Caption; detail.OSVersion = os.Version; }) // Performance Counters .Task(delegate { using (var impersonation = computer.ImpersonateElevatedIdentity()) { detail.AvailableBytes = perf.GetSample(computer, "Memory", "Available Bytes"); } }) .Task(delegate { using (var impersonation = computer.ImpersonateElevatedIdentity()) { detail.TotalProcessorUtilization = perf.GetValue(computer, "Processor", "% Processor Time", "_Total"); } }).WithExecutionMode(ParallelExecutionMode.ForceParallelism); if (!work.WaitForAll(TimeSpan.FromSeconds(15), task => task())) { return PartialView("Timeout"); } } catch (Exception ex) { this.LogException(ex); return PartialView("Error.ascx"); } return PartialView(detail); }

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