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• How to Run Low-Cost Minecraft on a Raspberry Pi for Block Building on the Cheap

  - by Jason Fitzpatrick

  We’ve shown you how to run your own blocktastic personal Minecraft server on a Windows/OSX box, but what if you crave something lighter weight, more energy efficient, and always ready for your friends? Read on as we turn a tiny Raspberry Pi machine into a low-cost Minecraft server you can leave on 24/7 for around a penny a day. Why Do I Want to Do This? There’s two aspects to this tutorial, running your own Minecraft server and specifically running that Minecraft server on a Raspberry Pi. Why would you want to run your own Minecraft server? It’s a really great way to extend and build upon the Minecraft play experience. You can leave the server running when you’re not playing so friends and family can join and continue building your world. You can mess around with game variables and introduce mods in a way that isn’t possible when you’re playing the stand-alone game. It also gives you the kind of control over your multiplayer experience that using public servers doesn’t, without incurring the cost of hosting a private server on a remote host. While running a Minecraft server on its own is appealing enough to a dedicated Minecraft fan, running it on the Raspberry Pi is even more appealing. The tiny little Pi uses so little resources that you can leave your Minecraft server running 24/7 for a couple bucks a year. Aside from the initial cost outlay of the Pi, an SD card, and a little bit of time setting it up, you’ll have an always-on Minecraft server at a monthly cost of around one gumball. What Do I Need? For this tutorial you’ll need a mix of hardware and software tools; aside from the actual Raspberry Pi and SD card, everything is free. 1 Raspberry Pi (preferably a 512MB model) 1 4GB+ SD card This tutorial assumes that you have already familiarized yourself with the Raspberry Pi and have installed a copy of the Debian-derivative Raspbian on the device. If you have not got your Pi up and running yet, don’t worry! Check out our guide, The HTG Guide to Getting Started with Raspberry Pi, to get up to speed. Optimizing Raspbian for the Minecraft Server Unlike other builds we’ve shared where you can layer multiple projects over one another (e.g. the Pi is more than powerful enough to serve as a weather/email indicator and a Google Cloud Print server at the same time) running a Minecraft server is a pretty intense operation for the little Pi and we’d strongly recommend dedicating the entire Pi to the process. Minecraft seems like a simple game, with all its blocky-ness and what not, but it’s actually a pretty complex game beneath the simple skin and required a lot of processing power. As such, we’re going to tweak the configuration file and other settings to optimize Rasbian for the job. The first thing you’ll need to do is dig into the Raspi-Config application to make a few minor changes. If you’re installing Raspbian fresh, wait for the last step (which is the Raspi-Config), if you already installed it, head to the terminal and type in “sudo raspi-config” to launch it again. One of the first and most important things we need to attend to is cranking up the overclock setting. We need all the power we can get to make our Minecraft experience enjoyable. In Raspi-Config, select option number 7 “Overclock”. Be prepared for some stern warnings about overclocking, but rest easy knowing that overclocking is directly supported by the Raspberry Pi foundation and has been included in the configuration options since late 2012. Once you’re in the actual selection screen, select “Turbo 1000MhHz”. Again, you’ll be warned that the degree of overclocking you’ve selected carries risks (specifically, potential corruption of the SD card, but no risk of actual hardware damage). Click OK and wait for the device to reset. Next, make sure you’re set to boot to the command prompt, not the desktop. Select number 3 “Enable Boot to Desktop/Scratch”  and make sure “Console Text console” is selected. Back at the Raspi-Config menu, select number 8 “Advanced Options’. There are two critical changes we need to make in here and one option change. First, the critical changes. Select A3 “Memory Split”: Change the amount of memory available to the GPU to 16MB (down from the default 64MB). Our Minecraft server is going to ruin in a GUI-less environment; there’s no reason to allocate any more than the bare minimum to the GPU. After selecting the GPU memory, you’ll be returned to the main menu. Select “Advanced Options” again and then select A4 “SSH”. Within the sub-menu, enable SSH. There is very little reason to keep this Pi connected to a monitor and keyboard, by enabling SSH we can remotely access the machine from anywhere on the network. Finally (and optionally) return again to the “Advanced Options” menu and select A2 “Hostname”. Here you can change your hostname from “raspberrypi” to a more fitting Minecraft name. We opted for the highly creative hostname “minecraft”, but feel free to spice it up a bit with whatever you feel like: creepertown, minecraft4life, or miner-box are all great minecraft server names. That’s it for the Raspbian configuration tab down to the bottom of the main screen and select “Finish” to reboot. After rebooting you can now SSH into your terminal, or continue working from the keyboard hooked up to your Pi (we strongly recommend switching over to SSH as it allows you to easily cut and paste the commands). If you’ve never used SSH before, check out how to use PuTTY with your Pi here. Installing Java on the Pi The Minecraft server runs on Java, so the first thing we need to do on our freshly configured Pi is install it. Log into your Pi via SSH and then, at the command prompt, enter the following command to make a directory for the installation: sudo mkdir /java/ Now we need to download the newest version of Java. At the time of this publication the newest release is the OCT 2013 update and the link/filename we use will reflect that. Please check for a more current version of the Linux ARMv6/7 Java release on the Java download page and update the link/filename accordingly when following our instructions. At the command prompt, enter the following command: sudo wget --no-check-certificate http://www.java.net/download/jdk8/archive/b111/binaries/jdk-8-ea-b111-linux-arm-vfp-hflt-09_oct_2013.tar.gz Once the download has finished successfully, enter the following command: sudo tar zxvf jdk-8-ea-b111-linux-arm-vfp-hflt-09_oct_2013.tar.gz -C /opt/ Fun fact: the /opt/ directory name scheme is a remnant of early Unix design wherein the /opt/ directory was for “optional” software installed after the main operating system; it was the /Program Files/ of the Unix world. After the file has finished extracting, enter: sudo /opt/jdk1.8.0/bin/java -version This command will return the version number of your new Java installation like so: java version "1.8.0-ea" Java(TM) SE Runtime Environment (build 1.8.0-ea-b111) Java HotSpot(TM) Client VM (build 25.0-b53, mixed mode) If you don’t see the above printout (or a variation thereof if you’re using a newer version of Java), try to extract the archive again. If you do see the readout, enter the following command to tidy up after yourself: sudo rm jdk-8-ea-b111-linux-arm-vfp-hflt-09_oct_2013.tar.gz At this point Java is installed and we’re ready to move onto installing our Minecraft server! Installing and Configuring the Minecraft Server Now that we have a foundation for our Minecraft server, it’s time to install the part that matter. We’ll be using SpigotMC a lightweight and stable Minecraft server build that works wonderfully on the Pi. First, grab a copy of the the code with the following command: sudo wget http://ci.md-5.net/job/Spigot/lastSuccessfulBuild/artifact/Spigot-Server/target/spigot.jar This link should remain stable over time, as it points directly to the most current stable release of Spigot, but if you have any issues you can always reference the SpigotMC download page here. After the download finishes successfully, enter the following command: sudo /opt/jdk1.8.0/bin/java -Xms256M -Xmx496M -jar /home/pi/spigot.jar nogui Note: if you’re running the command on a 256MB Pi change the 256 and 496 in the above command to 128 and 256, respectively. Your server will launch and a flurry of on-screen activity will follow. Be prepared to wait around 3-6 minutes or so for the process of setting up the server and generating the map to finish. Future startups will take much less time, around 20-30 seconds. Note: If at any point during the configuration or play process things get really weird (e.g. your new Minecraft server freaks out and starts spawning you in the Nether and killing you instantly), use the “stop” command at the command prompt to gracefully shutdown the server and let you restart and troubleshoot it. After the process has finished, head over to the computer you normally play Minecraft on, fire it up, and click on Multiplayer. You should see your server: If your world doesn’t popup immediately during the network scan, hit the Add button and manually enter the address of your Pi. Once you connect to the server, you’ll see the status change in the server status window: According to the server, we’re in game. According to the actual Minecraft app, we’re also in game but it’s the middle of the night in survival mode: Boo! Spawning in the dead of night, weaponless and without shelter is no way to start things. No worries though, we need to do some more configuration; no time to sit around and get shot at by skeletons. Besides, if you try and play it without some configuration tweaks first, you’ll likely find it quite unstable. We’re just here to confirm the server is up, running, and accepting incoming connections. Once we’ve confirmed the server is running and connectable (albeit not very playable yet), it’s time to shut down the server. Via the server console, enter the command “stop” to shut everything down. When you’re returned to the command prompt, enter the following command: sudo nano server.properties When the configuration file opens up, make the following changes (or just cut and paste our config file minus the first two lines with the name and date stamp): #Minecraft server properties #Thu Oct 17 22:53:51 UTC 2013 generator-settings= #Default is true, toggle to false allow-nether=false level-name=world enable-query=false allow-flight=false server-port=25565 level-type=DEFAULT enable-rcon=false force-gamemode=false level-seed= server-ip= max-build-height=256 spawn-npcs=true white-list=false spawn-animals=true texture-pack= snooper-enabled=true hardcore=false online-mode=true pvp=true difficulty=1 player-idle-timeout=0 gamemode=0 #Default 20; you only need to lower this if you're running #a public server and worried about loads. max-players=20 spawn-monsters=true #Default is 10, 3-5 ideal for Pi view-distance=5 generate-structures=true spawn-protection=16 motd=A Minecraft Server In the server status window, seen through your SSH connection to the pi, enter the following command to give yourself operator status on your Minecraft server (so that you can use more powerful commands in game, without always returning to the server status window). op [your minecraft nickname] At this point things are looking better but we still have a little tweaking to do before the server is really enjoyable. To that end, let’s install some plugins. The first plugin, and the one you should install above all others, is NoSpawnChunks. To install the plugin, first visit the NoSpawnChunks webpage and grab the download link for the most current version. As of this writing the current release is v0.3. Back at the command prompt (the command prompt of your Pi, not the server console–if your server is still active shut it down) enter the following commands: cd /home/pi/plugins sudo wget http://dev.bukkit.org/media/files/586/974/NoSpawnChunks.jar Next, visit the ClearLag plugin page, and grab the latest link (as of this tutorial, it’s v2.6.0). Enter the following at the command prompt: sudo wget http://dev.bukkit.org/media/files/743/213/Clearlag.jar Because the files aren’t compressed in a .ZIP or similar container, that’s all there is to it: the plugins are parked in the plugin directory. (Remember this for future plugin downloads, the file needs to be whateverplugin.jar, so if it’s compressed you need to uncompress it in the plugin directory.) Resart the server: sudo /opt/jdk1.8.0/bin/java -Xms256M -Xmx496M -jar /home/pi/spigot.jar nogui Be prepared for a slightly longer startup time (closer to the 3-6 minutes and much longer than the 30 seconds you just experienced) as the plugins affect the world map and need a minute to massage everything. After the spawn process finishes, type the following at the server console: plugins This lists all the plugins currently active on the server. You should see something like this: If the plugins aren’t loaded, you may need to stop and restart the server. After confirming your plugins are loaded, go ahead and join the game. You should notice significantly snappier play. In addition, you’ll get occasional messages from the plugins indicating they are active, as seen below: At this point Java is installed, the server is installed, and we’ve tweaked our settings for for the Pi.  It’s time to start building with friends!     

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• The Sound of Two Toilets Flushing: Constructive Criticism for Virgin Atlantic Complaints Department

  - by Geertjan

  I recently had the experience of flying from London to Johannesburg and back with Virgin Atlantic. The good news was that it was the cheapest flight available and that the take off and landing were absolutely perfect. Hence I really have no reason to complain. Instead, I'd like to offer some constructive criticism which hopefully Richard Branson will find sometime while googling his name. Or maybe someone from the Virgin Atlantic Complaints Department will find it, whatever, just want to put this information out there. Arrangement of restroom facilities. Maybe next time you design an airplane, consider not putting your toilets at a right angle right next to your rows of seats. Being able to reach, without even needing to stretch your arm, from your seat to close, yet again, a toilet door that someone, someone obviously sitting very far from the toilets, carelessly forgot to close is not an indicator of quality interior design. Have you noticed how all other airplanes have their toilets in a cubicle separated from the rows of seats? On those airplanes, people sitting in the seats near the toilets are not constantly being woken up throughout the night whenever someone enters/exits the toilet, whenever the light in the toilet is suddenly switched on, and whenever one of the toilets flushes. Bonus points for Virgin Atlantic passengers in the seats adjoining the toilets is when multiple toilets are flushed simultaneously and multiple passengers enter/exit them at the same time, a bit like an unasked for low budget musical of suddenly illuminated grumpy people in crumpled clothes. What joy that brings at 3 AM is hard to describe. Seats with extra leg room. You know how other airplanes have the seats with the extra leg room? You know what those seats tend to have? Extra leg room. It's really interesting how Virgin Atlantic's seats with extra leg room actually have no extra leg room at all. It should have been a give away, the fact that these special seats are found in the same rows as the standard seats, rather than on the cusp of real glory which is where most airlines put their extra leg room seats, with the only actual difference being that they have a slightly different color. Had you called them "seats with a different color" (i.e., almost not quite green, rather than something vaguely hinting at blue), at least I'd have known what I was getting. Picture the joy at 3 AM, rudely awakened from nightmarish slumber, partly grateful to have been released from a grayish dream of faceless zombies resembling one or two of those in a recent toilet line, by multiple adjoining toilets flushing simultaneously, while you're sitting in a seat with extra leg room that has exactly as much leg room as the seats in neighboring rows. You then have a choice of things to be sincerely annoyed about. Food from the '80's. In the '80's, airplane food came in soggy containers and even breakfast, the most important meal of the day, was a sad heap of vaguely gray colors. The culinary highlight tended to be a squashed tomato, which must have been mashed to a pulp with a brick prior to being regurgitated by a small furry animal, and there was also always a piece of immensely horrid pumpkin, as well as a slice of spongy something you'd never seen before. Sausages and mash at 6 AM on an airplane was always a heavy lump of horribleness. Thankfully, all airlines throughout the world changed from this puke inducing strategy around 1987 sometime. Not Virgin Atlantic, of course. The fatty sausages and mash are still there, bringing you flashbacks to Duran Duran, which is what you were listening to (on your walkman) the last time you saw it in an airplane. Even the golden oldie "squashed tomato attached by slime to three wet peas" is on the menu. How wonderful to have all this in a cramped seat with a long row of early morning bleariness lined up for the toilets, right at your side, bumping into your elbow, groggily, one by one, one after another, more and more, fumble-open-door-silence-flush-fumble-open-door, and on and on, while you tentatively push your fork through a soggy pile of colorless mush, fighting the urge to throw up on the stinky socks of whatever nightmarish zombie is bumping into your elbow at the time. But, then again, the plane landed without a hitch, in fact, extremely smoothly, so I'm certainly not blaming the pilots.

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• await, WhenAll, WaitAll, oh my!!

  - by cibrax

  If you are dealing with asynchronous work in .NET, you might know that the Task class has become the main driver for wrapping asynchronous calls. Although this class was officially introduced in .NET 4.0, the programming model for consuming tasks was much more simplified in C# 5.0 in .NET 4.5 with the addition of the new async/await keywords. In a nutshell, you can use these keywords to make asynchronous calls as if they were sequential, and avoiding in that way any fork or callback in the code. The compiler takes care of the rest. I was yesterday writing some code for making multiple asynchronous calls to backend services in parallel. The code looked as follow, var allResults = new List<Result>(); foreach(var provider in providers) { var results = await provider.GetResults(); allResults.AddRange(results); } return allResults; You see, I was using the await keyword to make multiple calls in parallel. Something I did not consider was the overhead this code implied after being compiled. I started an interesting discussion with some smart folks in twitter. One of them, Tugberk Ugurlu, had the brilliant idea of actually write some code to make a performance comparison with another approach using Task.WhenAll. There are two additional methods you can use to wait for the results of multiple calls in parallel, WhenAll and WaitAll. WhenAll creates a new task and waits for results in that new task, so it does not block the calling thread. WaitAll, on the other hand, blocks the calling thread. This is the code Tugberk initially wrote, and I modified afterwards to also show the results of WaitAll. class Program { private static Func<Stopwatch, Task>[] funcs = new Func<Stopwatch, Task>[] { async (watch) => { watch.Start(); await Task.Delay(1000); Console.WriteLine("1000 one has been completed."); }, async (watch) => { await Task.Delay(1500); Console.WriteLine("1500 one has been completed."); }, async (watch) => { await Task.Delay(2000); Console.WriteLine("2000 one has been completed."); watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds + "ms has been elapsed."); } }; static void Main(string[] args) { Console.WriteLine("Await in loop work starts..."); DoWorkAsync().ContinueWith(task => { Console.WriteLine("Parallel work starts..."); DoWorkInParallelAsync().ContinueWith(t => { Console.WriteLine("WaitAll work starts..."); WaitForAll(); }); }); Console.ReadLine(); } static async Task DoWorkAsync() { Stopwatch watch = new Stopwatch(); foreach (var func in funcs) { await func(watch); } } static async Task DoWorkInParallelAsync() { Stopwatch watch = new Stopwatch(); await Task.WhenAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } static void WaitForAll() { Stopwatch watch = new Stopwatch(); Task.WaitAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } } After running this code, the results were very concluding. Await in loop work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 4532ms has been elapsed. Parallel work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2007ms has been elapsed. WaitAll work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2009ms has been elapsed. The await keyword in a loop does not really make the calls in parallel.

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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• Clone a VirtualBox Machine

  I just installed VirtualBox, which I want to try out based on recommendations from peers for running a server from within my Windows 7 x64 OS.  Ive never used VirtualBox, so Im certainly no expert at it, but I did want to share my experience with it thus far.  Specifically, my intention is to create a couple of virtual machines.  One I intend to use as a build server, for which a virtual machine makes sense because I can easily move it around as needed if there are hardware issues (its worth noting my need for setting up a build server at the moment is a result of a disk failure on the old build server).  The other VM I want to set up will act as a proxy server for the issue tracking system were using at Code Project, Axosoft OnTime.  They have a Remote Server application for this purpose, and since the OnTime install is 300 miles away from my location, the Remote Server should speed up my use of the OnTime client by limiting the chattiness with the database (at least, thats the hope). So, I need two VMs, and Im lazy.  I dont want to have to install the OS and such twice.  No problem, it should be simple to clone a virtualbox machine, or clone a virtualbox hard drive, right?  Well unfortunately, if you look at the UI for VirtualBox, theres no such command.  Youre left wondering How do I clone a VirtualBox machine? or the slightly related How do I clone a VirtualBox hard drive? If youve used VirtualPC, then you know that its actually pretty easy to copy and move around those VMs.  Not quite so easy with VirtualBox.  Finding the files is easy, theyre located in your user folder within the .VirtualBox folder (possibly within a HardDisks folder).  The disks have a .vdi extension and will be pretty large if youve installed anything.  The one shown here has just Windows Server 2008 R2 installed on it nothing else. If you copy the .vdi file and rename it, you can use the Virtual Media Manager to view it and you can create a new machine and choose the new drive to attach to.  Unfortunately, if you simply make a copy of the drive, this wont work and youll get an error that says something to the effect of: Cannot register the hard disk PATH with UUID {id goes here} because a hard disk PATH2 with UUID {same id goes here} already exists in the media registry (PATH to XML file). There are command line tools you can use to do this in a way that avoids this error.  Specifically, the c:\Program File\Sun\VirtualBox\VBoxManage.exe program is used for all command line access to VirtualBox, and to copy a virtual disk (.vdi file) you would call something like this: VBoxManage clonehd Disk1.vdi Disk1_Copy.vdi However, in my case this didnt work.  I got basically the same error I showed above, along with some debug information for line 628 of VBoxManageDisk.cpp.  As my main task was not to debug the C++ code used to write VirtualBox, I continued looking for a simple way to clone a virtual drive.  I found it in this blog post. The Secret setvdiuuid Command VBoxManage has a whole bunch of commands you can use with it just pass it /? to see the list.  However, it also has a special command called internalcommands that opens up access to even more commands.  The one thats interesting for us here is the setvdiuuid command.  By calling this command and passing in the file path to your vdi file, it will reset the UUID to a new (random, apparently) UUID.  This then allows the virtual media manager to cope with the file, and lets you set up new machines that reference the newly UUIDd virtual drive.  The full command line would be: VBoxManage internalcommands setvdiuuid MyCopy.vdi The following screenshot shows the error when trying clonehd as well as the successful use of setvdiuuid. Summary Now that I can clone machines easily, its a simple matter to set up base builds of any OS I might need, and then fork from there as needed.  Hopefully the GUI for VirtualBox will be improved to include better support for copying machines/disks, as this is Im sure a very common scenario. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• 2D Particle Explosion

  - by TheBroodian

  I'm developing a 2D action game, and in said game I've given my primary character an ability he can use to throw a fireball. I'm trying to design an effect so that when said fireball collides (be it with terrain or with an enemy) that the fireball will explode. For the explosion effect I've created a particle that once placed into game space will follow random, yet autonomic behavior based on random variables. Here is my question: When I generate my explosion (essentially 90 of these particles) I get one of two behaviors, 1) They are all generated with the same random variables, and don't resemble an explosion at all, more like a large mass of clumped sprites that all follow the same randomly generated path. 2) If I assign each particle a unique seed to its random number generator, they are a little bit -more- spread out, yet clumping is still visible (they seem to fork out into 3 different directions) Does anybody have any tips for producing particle-based 2D explosions? I'll include the code for my particle and the event I'm generating them in. Fire particle class: public FireParticle(xTile.Dimensions.Location StartLocation, ContentManager content) { worldLocation = StartLocation; fireParticleAnimation = new FireParticleAnimation(content); random = new Random(); int rightorleft = random.Next(0, 3); int upordown = random.Next(1, 3); int xVelocity = random.Next(0, 101); int yVelocity = random.Next(0, 101); Vector2 tempVector2 = new Vector2(0,0); if (rightorleft == 1) { tempVector2 = new Vector2(xVelocity, tempVector2.Y); } else if (rightorleft == 2) { tempVector2 = new Vector2(-xVelocity, tempVector2.Y); } if (upordown == 1) { tempVector2 = new Vector2(tempVector2.X, -yVelocity); } else if (upordown == 2) { tempVector2 = new Vector2(tempVector2.X, yVelocity); } velocity = tempVector2; scale = random.Next(1, 11); upwardForce = -10; dead = false; } public FireParticle(xTile.Dimensions.Location StartLocation, ContentManager content, int seed) { worldLocation = StartLocation; fireParticleAnimation = new FireParticleAnimation(content); random = new Random(seed); int rightorleft = random.Next(0, 3); int upordown = random.Next(1, 3); int xVelocity = random.Next(0, 101); int yVelocity = random.Next(0, 101); Vector2 tempVector2 = new Vector2(0, 0); if (rightorleft == 1) { tempVector2 = new Vector2(xVelocity, tempVector2.Y); } else if (rightorleft == 2) { tempVector2 = new Vector2(-xVelocity, tempVector2.Y); } if (upordown == 1) { tempVector2 = new Vector2(tempVector2.X, -yVelocity); } else if (upordown == 2) { tempVector2 = new Vector2(tempVector2.X, yVelocity); } velocity = tempVector2; scale = random.Next(1, 11); upwardForce = -10; dead = false; } #endregion #region Update and Draw public void Update(GameTime gameTime) { elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; fireParticleAnimation.Update(gameTime); Vector2 moveAmount = velocity * elapsed; xTile.Dimensions.Location newPosition = new xTile.Dimensions.Location(worldLocation.X + (int)moveAmount.X, worldLocation.Y + (int)moveAmount.Y); worldLocation = newPosition; velocity.Y += upwardForce; if (fireParticleAnimation.finishedPlaying) { dead = true; } } public void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw( fireParticleAnimation.image.Image, new Rectangle((int)drawLocation.X, (int)drawLocation.Y, scale, scale), fireParticleAnimation.image.SizeAndsource, Color.White * fireParticleAnimation.image.Alpha); } Fireball explosion event: public override void Update(GameTime gameTime) { if (enabled) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; foreach (Heart_of_Fire.World_Objects.Particles.FireParticle particle in explosionParticles.ToList()) { particle.Update(gameTime); if (particle.Dead) { explosionParticles.Remove(particle); } } collisionRectangle = new Microsoft.Xna.Framework.Rectangle((int)wrldPstn.X, (int)wrldPstn.Y, 5, 5); explosionCheck = exploded; if (!exploded) { coreGraphic.Update(gameTime); tailGraphic.Update(gameTime); Vector2 moveAmount = velocity * elapsed; moveAmount = horizontalCollision(moveAmount, layer); moveAmount = verticalCollision(moveAmount, layer); Vector2 newPosition = new Vector2(wrldPstn.X + moveAmount.X, wrldPstn.Y + moveAmount.Y); if (hasCollidedHorizontally || hasCollidedVertically) { exploded = true; } wrldPstn = newPosition; worldLocation = new xTile.Dimensions.Location((int)wrldPstn.X, (int)wrldPstn.Y); } if (explosionCheck != exploded) { for (int i = 0; i < 90; i++) { explosionParticles.Add(new World_Objects.Particles.FireParticle( new Location( collisionRectangle.X + random.Next(0, 6), collisionRectangle.Y + random.Next(0, 6)), contentMgr)); } } if (exploded && explosionParticles.Count() == 0) { //enabled = false; } } }

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• CBO????????

  - by Liu Maclean(???)

  ???Itpub????????CBO??????????, ????????: SQL> create table maclean1 as select * from dba_objects; Table created. SQL> update maclean1 set status='INVALID' where owner='MACLEAN'; 2 rows updated. SQL> commit; Commit complete. SQL> create index ind_maclean1 on maclean1(status); Index created. SQL> exec dbms_stats.gather_table_stats('SYS','MACLEAN1',cascade=>true); PL/SQL procedure successfully completed. SQL> explain plan for select * from maclean1 where status='INVALID'; Explained. SQL> set linesize 140 pagesize 1400 SQL> select * from table(dbms_xplan.display()); PLAN_TABLE_OUTPUT --------------------------------------------------------------------------- Plan hash value: 987568083 ------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 11320 | 1028K| 85 (0)| 00:00:02 | |* 1 | TABLE ACCESS FULL| MACLEAN1 | 11320 | 1028K| 85 (0)| 00:00:02 | ------------------------------------------------------------------------------ Predicate Information (identified by operation id): --------------------------------------------------- 1 - filter("STATUS"='INVALID') 13 rows selected. 10053 trace Access path analysis for MACLEAN1 *************************************** SINGLE TABLE ACCESS PATH   Single Table Cardinality Estimation for MACLEAN1[MACLEAN1]   Column (#10): STATUS(     AvgLen: 7 NDV: 2 Nulls: 0 Density: 0.500000   Table: MACLEAN1  Alias: MACLEAN1     Card: Original: 22639.000000  Rounded: 11320  Computed: 11319.50  Non Adjusted: 11319.50   Access Path: TableScan     Cost:  85.33  Resp: 85.33  Degree: 0       Cost_io: 85.00  Cost_cpu: 11935345       Resp_io: 85.00  Resp_cpu: 11935345   Access Path: index (AllEqRange)     Index: IND_MACLEAN1     resc_io: 185.00  resc_cpu: 8449916     ix_sel: 0.500000  ix_sel_with_filters: 0.500000     Cost: 185.24  Resp: 185.24  Degree: 1   Best:: AccessPath: TableScan          Cost: 85.33  Degree: 1  Resp: 85.33  Card: 11319.50  Bytes: 0 ?????10053????????????,?????Density = 0.5 ?? 1/ NDV ??? ??????????????STATUS='INVALID"???????????, ????????????????? ????”STATUS”=’INVALID’ condition???2?,?status??????,??????dbms_stats?????????????,???CBO????INDEX Range ind_maclean1,???????,??????opitimizer?????? ?????????????????????????,????????,??????????status=’INVALID’???????card??,????????: [oracle@vrh4 ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.2.0 Production on Mon Oct 17 19:15:45 2011 Copyright (c) 1982, 2010, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> select * from v$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production PL/SQL Release 11.2.0.2.0 - Production CORE 11.2.0.2.0 Production TNS for Linux: Version 11.2.0.2.0 - Production NLSRTL Version 11.2.0.2.0 - Production SQL> show parameter optimizer_fea NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ optimizer_features_enable string 11.2.0.2 SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com & www.askmaclean.com SQL> drop table maclean; Table dropped. SQL> create table maclean as select * from dba_objects; Table created. SQL> update maclean set status='INVALID' where owner='MACLEAN'; 2 rows updated. SQL> commit; Commit complete. SQL> create index ind_maclean on maclean(status); Index created. SQL> exec dbms_stats.gather_table_stats('SYS','MACLEAN',cascade=>true, method_opt=>'FOR ALL COLUMNS SIZE 2'); PL/SQL procedure successfully completed. ???????2?bucket????, ??????????????? ???Quest???Guy Harrison???????FREQUENCY????????,??????: rem rem Generate a histogram of data distribution in a column as recorded rem in dba_tab_histograms rem rem Guy Harrison Jan 2010 : www.guyharrison.net rem rem hexstr function is from From http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:707586567563 set pagesize 10000 set lines 120 set verify off col char_value format a10 heading "Endpoint|value" col bucket_count format 99,999,999 heading "bucket|count" col pct format 999.99 heading "Pct" col pct_of_max format a62 heading "Pct of|Max value" rem col endpoint_value format 9999999999999 heading "endpoint|value" CREATE OR REPLACE FUNCTION hexstr (p_number IN NUMBER) RETURN VARCHAR2 AS l_str LONG := TO_CHAR (p_number, 'fm' || RPAD ('x', 50, 'x')); l_return VARCHAR2 (4000); BEGIN WHILE (l_str IS NOT NULL) LOOP l_return := l_return || CHR (TO_NUMBER (SUBSTR (l_str, 1, 2), 'xx')); l_str := SUBSTR (l_str, 3); END LOOP; RETURN (SUBSTR (l_return, 1, 6)); END; / WITH hist_data AS ( SELECT endpoint_value,endpoint_actual_value, NVL(LAG (endpoint_value) OVER (ORDER BY endpoint_value),' ') prev_value, endpoint_number, endpoint_number, endpoint_number - NVL (LAG (endpoint_number) OVER (ORDER BY endpoint_value), 0) bucket_count FROM dba_tab_histograms JOIN dba_tab_col_statistics USING (owner, table_name,column_name) WHERE owner = '&owner' AND table_name = '&table' AND column_name = '&column' AND histogram='FREQUENCY') SELECT nvl(endpoint_actual_value,endpoint_value) endpoint_value , bucket_count, ROUND(bucket_count*100/SUM(bucket_count) OVER(),2) PCT, RPAD(' ',ROUND(bucket_count*50/MAX(bucket_count) OVER()),'*') pct_of_max FROM hist_data; WITH hist_data AS ( SELECT endpoint_value,endpoint_actual_value, NVL(LAG (endpoint_value) OVER (ORDER BY endpoint_value),' ') prev_value, endpoint_number, endpoint_number, endpoint_number - NVL (LAG (endpoint_number) OVER (ORDER BY endpoint_value), 0) bucket_count FROM dba_tab_histograms JOIN dba_tab_col_statistics USING (owner, table_name,column_name) WHERE owner = '&owner' AND table_name = '&table' AND column_name = '&column' AND histogram='FREQUENCY') SELECT hexstr(endpoint_value) char_value, bucket_count, ROUND(bucket_count*100/SUM(bucket_count) OVER(),2) PCT, RPAD(' ',ROUND(bucket_count*50/MAX(bucket_count) OVER()),'*') pct_of_max FROM hist_data ORDER BY endpoint_value; ?????,??????????FREQUENCY?????: ??dbms_stats ?????STATUS=’INVALID’ bucket count=9 percent = 0.04 ,??????10053 trace????????: SQL> explain plan for select * from maclean where status='INVALID'; Explained. SQL>  select * from table(dbms_xplan.display()); PLAN_TABLE_OUTPUT ------------------------------------- Plan hash value: 3087014066 ------------------------------------------------------------------------------------------- | Id  | Operation                   | Name        | Rows  | Bytes | Cost (%CPU)| Time     | ------------------------------------------------------------------------------------------- |   0 | SELECT STATEMENT            |             |     9 |   837 |     2   (0)| 00:00:01 | |   1 |  TABLE ACCESS BY INDEX ROWID| MACLEAN     |     9 |   837 |     2   (0)| 00:00:01 | |*  2 |   INDEX RANGE SCAN          | IND_MACLEAN |     9 |       |     1   (0)| 00:00:01 | ------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): ---------------------------------------------------    2 - access("STATUS"='INVALID') ??????????????CBO???????STATUS=’INVALID’?cardnality?? , ??????????? ,??index range scan??Full table scan? ????????????????10053 trace: SQL> alter system flush shared_pool; System altered. SQL> oradebug setmypid; Statement processed. SQL> oradebug event 10053 trace name context forever ,level 1; Statement processed. SQL> explain plan for select * from maclean where status='INVALID'; Explained. SINGLE TABLE ACCESS PATH Single Table Cardinality Estimation for MACLEAN[MACLEAN] Column (#10): NewDensity:0.000199, OldDensity:0.000022 BktCnt:22640, PopBktCnt:22640, PopValCnt:2, NDV:2 ???NewDensity= bucket_count / SUM(bucket_count) /2 Column (#10): STATUS( AvgLen: 7 NDV: 2 Nulls: 0 Density: 0.000199 Histogram: Freq #Bkts: 2 UncompBkts: 22640 EndPtVals: 2 Table: MACLEAN Alias: MACLEAN Card: Original: 22640.000000 Rounded: 9 Computed: 9.00 Non Adjusted: 9.00 Access Path: TableScan Cost: 85.30 Resp: 85.30 Degree: 0 Cost_io: 85.00 Cost_cpu: 10804625 Resp_io: 85.00 Resp_cpu: 10804625 Access Path: index (AllEqRange) Index: IND_MACLEAN resc_io: 2.00 resc_cpu: 20763 ix_sel: 0.000398 ix_sel_with_filters: 0.000398 Cost: 2.00 Resp: 2.00 Degree: 1 Best:: AccessPath: IndexRange Index: IND_MACLEAN Cost: 2.00 Degree: 1 Resp: 2.00 Card: 9.00 Bytes: 0 ???????????2 bucket?????CBO????????????,???????????????????,???dbms_stats.DEFAULT_METHOD_OPT????????????????????? ???dbms_stats?????????????????????col_usage$??????predicate???????,??col_usage$??<????????SMON??(?):??col_usage$????>? ??????????dbms_stats????????,col_usage$????????????predicate???,??dbms_stats??????????????????, ?: SQL> drop table maclean; Table dropped. SQL> create table maclean as select * from dba_objects; Table created. SQL> update maclean set status='INVALID' where owner='MACLEAN'; 2 rows updated. SQL> commit; Commit complete. SQL> create index ind_maclean on maclean(status); Index created. ??dbms_stats??method_opt??maclean? SQL> exec dbms_stats.gather_table_stats('SYS','MACLEAN'); PL/SQL procedure successfully completed. @histogram.sql Enter value for owner: SYS old  12:    WHERE owner = '&owner' new  12:    WHERE owner = 'SYS' Enter value for table: MACLEAN old  13:      AND table_name = '&table' new  13:      AND table_name = 'MACLEAN' Enter value for column: STATUS old  14:      AND column_name = '&column' new  14:      AND column_name = 'STATUS' no rows selected ????col_usage$?????,????????status????? declare begin for i in 1..500 loop execute immediate ' alter system flush shared_pool'; DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO; execute immediate 'select count(*) from maclean where status=''INVALID'' ' ; end loop; end; / PL/SQL procedure successfully completed. SQL> select obj# from obj$ where name='MACLEAN';       OBJ# ----------      97215 SQL> select * from  col_usage$ where  OBJ#=97215;       OBJ#    INTCOL# EQUALITY_PREDS EQUIJOIN_PREDS NONEQUIJOIN_PREDS RANGE_PREDS LIKE_PREDS NULL_PREDS TIMESTAMP ---------- ---------- -------------- -------------- ----------------- ----------- ---------- ---------- ---------      97215          1              1              0                 0           0          0          0 17-OCT-11      97215         10            499              0                 0           0          0          0 17-OCT-11 SQL> exec dbms_stats.gather_table_stats('SYS','MACLEAN'); PL/SQL procedure successfully completed. @histogram.sql Enter value for owner: SYS Enter value for table: MACLEAN Enter value for column: STATUS Endpoint        bucket         Pct of value            count     Pct Max value ---------- ----------- ------- -------------------------------------------------------------- INVALI               2     .04 VALIC3           5,453   99.96  *************************************************

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• "Enumeration yielded no results" When using Query Syntax in C#

  - by Shantanu Gupta

  I have created this query to fetch some result from database. Here is my table structure. What exaclty is happening. DtMapGuestDepartment as Table 1 DtDepartment as Table 2 Are being used var dept_list= from map in DtMapGuestDepartment.AsEnumerable() where map.Field<Nullable<long>>("GUEST_ID") == DRowGuestPI.Field<Nullable<long>>("PK_GUEST_ID") join dept in DtDepartment.AsEnumerable() on map.Field<Nullable<long>>("DEPARTMENT_ID") equals dept.Field<Nullable<long>>("DEPARTMENT_ID") select dept.Field<string>("DEPARTMENT_ID"); I am performing this query on DataTables and expect it to return me a datatable. Here I want to select distinct department from Table 1 as well which will be my next quest. Please answer to that also if possible.

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• Is there any gmap's api function to concatenate address string from AddressDetails structure?

  - by Vadim

  Hello! I’am using Google Map’s GClientGeocoder for reversing map coordinates into string address. Exactly as shown in google’s example here http://code.google.com/apis/ajax/playground/?exp=maps#geocoding_reverse But, I would like to extract LocalityName (place.AddressDetails.Country.AdministrativeArea.Locality.LocalityName) from place.address. The straight way will be join all AddressDetails elements, excluding LocalityName. However order of the structure elements in final string representation is depends from geographical location. For example: Order for Australia city: ThoroughfareName + “, ” + LocalityName + “ ” + AdministrativeAreaName + “ ” + PostalCodeNumber + “, ” + CountryName Order for Russian city: CountryName + “, ” + PostalCodeNumber + “, ” + LocalityName + “, ” +ThoroughfareName Moreover PostalCodeNumber was not supplied in AddressDetails for the last example. Please, help!

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• Fluent NHibernate: mapping complex many-to-many (with additional columns) and setting fetch

  - by HackedByChinese

  I need a Fluent NHibernate mapping that will fulfill the following (if nothing else, I'll also take the appropriate NHibernate XML mapping and reverse engineer it). DETAILS I have a many-to-many relationship between two entities: Parent and Child. That is accomplished by an additional table to store the identities of the Parent and Child. However, I also need to define two additional columns on that mapping that provide more information about the relationship. This is roughly how I've defined my types, at least the relevant parts (where Entity is some base type that provides an Id property and checks for equivalence based on that Id): public class Parent : Entity { public virtual IList<ParentChildRelationship> Children { get; protected set; } public virtual void AddChildRelationship(Child child, int customerId) { var relationship = new ParentChildRelationship { CustomerId = customerId, Parent = this, Child = child }; if (Children == null) Children = new List<ParentChildRelationship>(); if (Children.Contains(relationship)) return; relationship.Sequence = Children.Count; Children.Add(relationship); } } public class Child : Entity { // child doesn't care about its relationships } public class ParentChildRelationship { public int CustomerId { get; set; } public Parent Parent { get; set; } public Child Child { get; set; } public int Sequence { get; set; } public override bool Equals(object obj) { if (ReferenceEquals(null, obj)) return false; if (ReferenceEquals(this, obj)) return true; var other = obj as ParentChildRelationship; if (return other == null) return false; return (CustomerId == other.CustomerId && Parent == other.Parent && Child == other.Child); } public override int GetHashCode() { unchecked { int result = CustomerId; result = Parent == null ? 0 : (result*397) ^ Parent.GetHashCode(); result = Child == null ? 0 : (result*397) ^ Child.GetHashCode(); return result; } } } The tables in the database look approximately like (assume primary/foreign keys and forgive syntax): create table Parent ( id int identity(1,1) not null ) create table Child ( id int identity(1,1) not null ) create table ParentChildRelationship ( customerId int not null, parent_id int not null, child_id int not null, sequence int not null ) I'm OK with Parent.Children being a lazy loaded property. However, the ParentChildRelationship should eager load ParentChildRelationship.Child. Furthermore, I want to use a Join when I eager load. The SQL, when accessing Parent.Children, NHibernate should generate an equivalent query to: SELECT * FROM ParentChildRelationship rel LEFT OUTER JOIN Child ch ON rel.child_id = ch.id WHERE parent_id = ? OK, so to do that I have mappings that look like this: ParentMap : ClassMap<Parent> { public ParentMap() { Table("Parent"); Id(c => c.Id).GeneratedBy.Identity(); HasMany(c => c.Children).KeyColumn("parent_id"); } } ChildMap : ClassMap<Child> { public ChildMap() { Table("Child"); Id(c => c.Id).GeneratedBy.Identity(); } } ParentChildRelationshipMap : ClassMap<ParentChildRelationship> { public ParentChildRelationshipMap() { Table("ParentChildRelationship"); CompositeId() .KeyProperty(c => c.CustomerId, "customerId") .KeyReference(c => c.Parent, "parent_id") .KeyReference(c => c.Child, "child_id"); Map(c => c.Sequence).Not.Nullable(); } } So, in my test if i try to get myParentRepo.Get(1).Children, it does in fact get me all the relationships and, as I access them from the relationship, the Child objects (for example, I can grab them all by doing parent.Children.Select(r => r.Child).ToList()). However, the SQL that NHibernate is generating is inefficient. When I access parent.Children, NHIbernate does a SELECT * FROM ParentChildRelationship WHERE parent_id = 1 and then a SELECT * FROM Child WHERE id = ? for each child in each relationship. I understand why NHibernate is doing this, but I can't figure out how to set up the mapping to make NHibernate query the way I mentioned above.

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• Django/Mod_WSGI error: UnboundLocalError: local variable 'resolver' referenced before assignment

  - by ycseattle

  Hello, I've setup the Django with mod_wsgi and run into this error. I thought maybe the sys.path was not setup correctly but I tried everything I could think of with no luck. Any suggestions? The following is the apache2 log for the error: mod_wsgi (pid=2579): Exception occurred processing WSGI script '/home/myapp/myapp.wsgi'. Traceback (most recent call last): File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/wsgi.py", line 241, in __call__ response = self.get_response(request) File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/base.py", line 142, in get_response return self.handle_uncaught_exception(request, resolver, exc_info) UnboundLocalError: local variable 'resolver' referenced before assignment The following is the content in the myapp.wsgi: import os import sys # put the Django project on sys.path sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "../"))) os.environ["DJANGO_SETTINGS_MODULE"] = "photopier.settings" #os.environ["PYTHONPATH"]="/home" from django.core.handlers.wsgi import WSGIHandler application = WSGIHandler()

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• How can I eager-load a child collection mapped to a non-primary key in NHibernate 2.1.2?

  - by David Rubin

  Hi, I have two objects with a many-to-many relationship between them, as follows: public class LeftHandSide { public LeftHandSide() { Name = String.Empty; Rights = new HashSet<RightHandSide>(); } public int Id { get; set; } public string Name { get; set; } public ICollection<RightHandSide> Rights { get; set; } } public class RightHandSide { public RightHandSide() { OtherProp = String.Empty; Lefts = new HashSet<LeftHandSide>(); } public int Id { get; set; } public string OtherProp { get; set; } public ICollection<LeftHandSide> Lefts { get; set; } } and I'm using a legacy database, so my mappings look like: Notice that LeftHandSide and RightHandSide are associated by a different column than RightHandSide's primary key. <class name="LeftHandSide" table="[dbo].[lefts]" lazy="false"> <id name="Id" column="ID" unsaved-value="0"> <generator class="identity" /> </id> <property name="Name" not-null="true" /> <set name="Rights" table="[dbo].[lefts2rights]"> <key column="leftId" /> <!-- THIS IS THE IMPORTANT BIT: I MUST USE PROPERTY-REF --> <many-to-many class="RightHandSide" column="rightProp" property-ref="OtherProp" /> </set> </class> <class name="RightHandSide" table="[dbo].[rights]" lazy="false"> <id name="Id" column="id" unsaved-value="0"> <generator class="identity" /> </id> <property name="OtherProp" column="otherProp" /> <set name="Lefts" table="[dbo].[lefts2rights]"> <!-- THIS IS THE IMPORTANT BIT: I MUST USE PROPERTY-REF --> <key column="rightProp" property-ref="OtherProp" /> <many-to-many class="LeftHandSide" column="leftId" /> </set> </class> The problem comes when I go to do a query: LeftHandSide lhs = _session.CreateCriteria<LeftHandSide>() .Add(Expression.IdEq(13)) .UniqueResult<LeftHandSide>(); works just fine. But LeftHandSide lhs = _session.CreateCriteria<LeftHandSide>() .Add(Expression.IdEq(13)) .SetFetchMode("Rights", FetchMode.Join) .UniqueResult<LeftHandSide>(); throws an exception (see below). Interestingly, RightHandSide rhs = _session.CreateCriteria<RightHandSide>() .Add(Expression.IdEq(127)) .SetFetchMode("Lefts", FetchMode.Join) .UniqueResult<RightHandSide>(); seems to be perfectly fine as well. NHibernate.Exceptions.GenericADOException Message: Error performing LoadByUniqueKey[SQL: SQL not available] Source: NHibernate StackTrace: c:\opt\nhibernate\2.1.2\source\src\NHibernate\Type\EntityType.cs(563,0): at NHibernate.Type.EntityType.LoadByUniqueKey(String entityName, String uniqueKeyPropertyName, Object key, ISessionImplementor session) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Type\EntityType.cs(428,0): at NHibernate.Type.EntityType.ResolveIdentifier(Object value, ISessionImplementor session, Object owner) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Type\EntityType.cs(300,0): at NHibernate.Type.EntityType.NullSafeGet(IDataReader rs, String[] names, ISessionImplementor session, Object owner) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Persister\Collection\AbstractCollectionPersister.cs(695,0): at NHibernate.Persister.Collection.AbstractCollectionPersister.ReadElement(IDataReader rs, Object owner, String[] aliases, ISessionImplementor session) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Collection\Generic\PersistentGenericSet.cs(54,0): at NHibernate.Collection.Generic.PersistentGenericSet`1.ReadFrom(IDataReader rs, ICollectionPersister role, ICollectionAliases descriptor, Object owner) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(706,0): at NHibernate.Loader.Loader.ReadCollectionElement(Object optionalOwner, Object optionalKey, ICollectionPersister persister, ICollectionAliases descriptor, IDataReader rs, ISessionImplementor session) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(385,0): at NHibernate.Loader.Loader.ReadCollectionElements(Object[] row, IDataReader resultSet, ISessionImplementor session) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(326,0): at NHibernate.Loader.Loader.GetRowFromResultSet(IDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode[] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[] keys, Boolean returnProxies) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(453,0): at NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(236,0): at NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(1649,0): at NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(1568,0): at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Loader.cs(1562,0): at NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces, IType[] resultTypes) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Loader\Criteria\CriteriaLoader.cs(73,0): at NHibernate.Loader.Criteria.CriteriaLoader.List(ISessionImplementor session) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Impl\SessionImpl.cs(1936,0): at NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Impl\CriteriaImpl.cs(246,0): at NHibernate.Impl.CriteriaImpl.List(IList results) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Impl\CriteriaImpl.cs(237,0): at NHibernate.Impl.CriteriaImpl.List() c:\opt\nhibernate\2.1.2\source\src\NHibernate\Impl\CriteriaImpl.cs(398,0): at NHibernate.Impl.CriteriaImpl.UniqueResult() c:\opt\nhibernate\2.1.2\source\src\NHibernate\Impl\CriteriaImpl.cs(263,0): at NHibernate.Impl.CriteriaImpl.UniqueResult[T]() D:\proj\CMS3\branches\nh_auth\DomainModel2Tests\Authorization\TempTests.cs(46,0): at CMS.DomainModel.Authorization.TempTests.Test1() Inner Exception System.Collections.Generic.KeyNotFoundException Message: The given key was not present in the dictionary. Source: mscorlib StackTrace: at System.ThrowHelper.ThrowKeyNotFoundException() at System.Collections.Generic.Dictionary`2.get_Item(TKey key) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs(2047,0): at NHibernate.Persister.Entity.AbstractEntityPersister.GetAppropriateUniqueKeyLoader(String propertyName, IDictionary`2 enabledFilters) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs(2037,0): at NHibernate.Persister.Entity.AbstractEntityPersister.LoadByUniqueKey(String propertyName, Object uniqueKey, ISessionImplementor session) c:\opt\nhibernate\2.1.2\source\src\NHibernate\Type\EntityType.cs(552,0): at NHibernate.Type.EntityType.LoadByUniqueKey(String entityName, String uniqueKeyPropertyName, Object key, ISessionImplementor session) I'm using NHibernate 2.1.2 and I've been debugging into the NHibernate source, but I'm coming up empty. Any suggestions? Thanks so much!

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• SQL Subquery in LINQ for Entity Framework 4.0

  - by Jorin

  I'm new to LINQ and EF, but I've been able to stumble through for the majority of the queries I have, but this one has me completely confused. No matter what I try, it comes up in SQL Profiler as a big mess :-). I have two tables: Users and UsersProjects. The goal of this query is to list all the users who are working on projects with the specified user. Here is the query as I have it written in SQL. It's a subquery, but I don't know of a way to simplify it further, but I'm open to suggestions there as well. SELECT DISTINCT Users.FirstName, Users.LastName FROM Users INNER JOIN UsersProjects ON Users.ID=UsersProjects.UserID WHERE UsersProjects.ProjectID IN (SELECT ProjectID FROM UsersProjects WHERE UserID=@UserID) Anybody able to help?? It seems like a fairly simple subquery in SQL, but in LINQ, I'm baffled. Thanks, Jorin

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• pre-commit hook in svn: could not be translated from the native locale to UTF-8

  - by Alexandre Moraes

  Hi everybody, I have a problem with my pre-commit hook. This hook test if a file is locked when the user commits. When a bad condition happens, it should output that the another user is locking this file or if nobody is locking, it should show "you are not locking this file message (file´s name)". The error happens when the file´s name has some latin character like "ç" and tortoise show me this in the output. Commit failed (details follow): Commit blocked by pre-commit hook (exit code 1) with output: [Erro output could not be translated from the native locale to UTF-8.] Do you know how can I solve this? Thanks, Alexandre My shell script is here: #!/bin/sh REPOS="$1" TXN="$2" export LANG="en_US.UTF-8" /app/svn/hooks/ensure-has-need-lock.pl "$REPOS" "$TXN" if [ $? -ne 0 ]; then exit 1; fi exit 0 And my perl is here: !/usr/bin/env perl #Turn on warnings the best way depending on the Perl version. BEGIN { if ( $] >= 5.006_000) { require warnings; import warnings; } else { $^W = 1; } } use strict; use Carp; &usage unless @ARGV == 2; my $repos = shift; my $txn = shift; my $svnlook = "/usr/local/bin/svnlook"; my $user; my $ok = 1; foreach my $program ($svnlook) { if (-e $program) { unless (-x $program) { warn "$0: required program $program' is not executable, ", "edit $0.\n"; $ok = 0; } } else { warn "$0: required program $program' does not exist, edit $0.\n"; $ok = 0; } } exit 1 unless $ok; unless (-e $repos){ &usage("$0: repository directory $repos' does not exist."); } unless (-d $repos){ &usage("$0: repository directory $repos' is not a directory."); } foreach my $user_tmp (&read_from_process($svnlook, 'author', $repos, '-t', $txn)) { $user = $user_tmp; } my @errors; foreach my $transaction (&read_from_process($svnlook, 'changed', $repos, '-t', $txn)){ if ($transaction =~ /^U. (.*[^\/])$/){ my $file = $1; my $err = 0; foreach my $locks (&read_from_process($svnlook, 'lock', $repos, $file)){ $err = 1; if($locks=~ /Owner: (.*)/){ if($1 != $user){ push @errors, "$file : You are not locking this file!"; } } } if($err==0){ push @errors, "$file : You are not locking this file!"; } } elsif($transaction =~ /^D. (.*[^\/])$/){ my $file = $1; my $tchan = &read_from_process($svnlook, 'lock', $repos, $file); foreach my $locks (&read_from_process($svnlook, 'lock', $repos, $file)){ push @errors, "$1 : cannot delete locked Files"; } } elsif($transaction =~ /^A. (.*[^\/])$/){ my $needs_lock; my $path = $1; foreach my $prop (&read_from_process($svnlook, 'proplist', $repos, '-t', $txn, '--verbose', $path)){ if ($prop =~ /^\s*svn:needs-lock : (\S+)/){ $needs_lock = $1; } } if (not $needs_lock){ push @errors, "$path : svn:needs-lock is not set. Pleas ask TCC for support."; } } } if (@errors) { warn "$0:\n\n", join("\n", @errors), "\n\n"; exit 1; } else { exit 0; } sub usage { warn "@_\n" if @_; die "usage: $0 REPOS TXN-NAME\n"; } sub safe_read_from_pipe { unless (@_) { croak "$0: safe_read_from_pipe passed no arguments.\n"; } print "Running @_\n"; my $pid = open(SAFE_READ, '-|'); unless (defined $pid) { die "$0: cannot fork: $!\n"; } unless ($pid) { open(STDERR, ">&STDOUT") or die "$0: cannot dup STDOUT: $!\n"; exec(@_) or die "$0: cannot exec @_': $!\n"; } my @output; while (<SAFE_READ>) { chomp; push(@output, $_); } close(SAFE_READ); my $result = $?; my $exit = $result >> 8; my $signal = $result & 127; my $cd = $result & 128 ? "with core dump" : ""; if ($signal or $cd) { warn "$0: pipe from @_' failed $cd: exit=$exit signal=$signal\n"; } if (wantarray) { return ($result, @output); } else { return $result; } } sub read_from_process { unless (@_) { croak "$0: read_from_process passed no arguments.\n"; } my ($status, @output) = &safe_read_from_pipe(@_); if ($status) { if (@output) { die "$0: @_' failed with this output:\n", join("\n", @output), "\n"; } else { die "$0: @_' failed with no output.\n"; } } else { return @output; } }

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• ASP.NET MVC:Why does the CheckBoxFor render an additional input tag and how can I get the value usin

  - by Nikron

  Hi, In my ASP.NET MVC app I am rendering out a checkbox using the following code: <%= Html.CheckBoxFor(i=>i.ReceiveRSVPNotifications) %> Now I see that this renders both the checkbox input tag and a hidden input tag. The problem that I am having is when I try retrieve the value from the checkbox using the FormCollection: FormValues["ReceiveRSVPNotifications"] I get the value "true,false". When looking at the rendered out HTML I can see the following: <input id="ReceiveRSVPNotifications" name="ReceiveRSVPNotifications" value="true" type="checkbox"> <input name="ReceiveRSVPNotifications" value="false" type="hidden"> So the FormValues collection seems to join these two values since they have the same name. Any Ideas?

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• Best "For Pay" wpf controls

  - by Vaccano

  If this question has been asked then I applogize and I will join in voting to close it (or just delete it), but I could not find it being asked before. We are potentially embarking on making many of our apps using WPF. Most of our apps are normal business apps that will not need too much eye candy. Tasteful ui is nice, but I don't see us doing lost of custom animations and such. So, my question is what 3rd party control sets are the best ones to purchase to save you time in development of apps like this? (These should work with both Visual Studio 2008 and 2010.)

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• iPhone SSL Website Certificate Warning

  - by Sonny

  I have a few sites that have SSL Certificates installed. When an SSL request is made with my employer's iPhone, this error message is displayed: Accept Website Certificate The certificate for this website is invalid. Tap Accept to connect to this website anyway. I've pulled up the same pages in other browsers, including Safari, and they do not show any issues with the certs. These two URLs exhibit the problem: https://www.powerlunchbunch.com/index.php?template=join&nav=20 https://www.councilonagingmartin.org/index.php?template=donate&nav=257 Additional Information: Both SSL certs are issued by Network Solutions

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• SQL Server add primary key

  - by Paul

  I have a table that needs to be given a new primary key, as my predecesor used a varchar(8) row as the primary key, and we are having problems with it now. I know how to add the primary key, but am not sure of the correct way to add this new primary key to other tables that have the foreign key. Here is what I have: users table: old_user_id varchar(8) ... ... new_user_id int(11) orders table: order_id int(11) ... ... old_user_fk varchar(8) new_user_fk int(11) I need to get the same results whether I join the tables on users.old_user_id=orders.old_user_fk or users.new_user_id=orders.new_user_fk. Any help is appreciated.

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• ruby super keyword

  - by ash34

  Hi, From what I understand, 'super' keyword invokes a method with the same name as the current method in the superclass of the current class. Below in the autoload method, there is a call to 'super'. I would like to know in which superclass I would find a method with the same name or what does the call to 'super' do module ActiveSupport module Autoload ... def autoload(const_name, path = @@at_path) full = [self.name, @@under_path, const_name.to_s, path].compact.join("::") location = path || Inflector.underscore(full) if @@eager_autoload @@autoloads[const_name] = location end super const_name, location end .... end end module ActiveRecord extend ActiveSupport::Autoload ... autoload :TestCase autoload :TestFixtures, 'active_record/fixtures' end This code is from the rails master branch. Thanks much.

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• c++0x, std::thread error (thread not member of std)

  - by luis

  Hello I compiled & installed gcc4.4 using macports. When I try to compile using - g++ -g -Wall -ansi -pthread -std=c++0x main.cpp...: #include ... std::thread t(handle); t.join(); .... The compiler returns: cserver.cpp: In member function 'int CServer::run()': cserver.cpp:48: error: 'thread' is not a member of 'std' cserver.cpp:48: error: expected ';' before 't' cserver.cpp:49: error: 't' was not declared in this scope But std::cout <<... compiles fine.. Can anyone help me? Thanks! Luis

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• C# SQL Statement transformed TO LINQ how can i translate this statement to a working linq

  - by BlackTea

  I am having trouble with this I have 3 Data tables i use over and over again which are cached I would like to write a LINQ statement which would do the following is this possible? T-SQL VERSION: SELECT P.[CID],P.[AID] ,B.[AID], B.[Data], B.[Status], B.[Language] FROM MY_TABLE_1 P JOIN ( SELECT A.[AID], A.[Data], A.[Status], A.[Language] FROM MY_TABLE_2 A UNION ALL SELECT B.[AID], B.[Data], B.[Status], B.[Language] FROM MY_TABLE_3 B ) B on P.[AID] = B.[AID] WHERE B.[Language] = 'EN' OR B.[Language] = 'ANY' AND B.STATUS = 1 AND B.[Language] = 'EN' OR B.[Language] = 'ANY' AND B.STATUS = 1 Then i would like it to create a result set of the following Results: |CID|AID|DATA|STATUS|LANGUAGE

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• Complex query in nHibernate using DetachedCriteria

  - by paszczi

  Hello! I'm currently trying to move from hand-crafted hql to queries constructed via DetachedCriteria. I have and HQL: from GenericObject genericObject left join fetch genericObject.Positions positions where (positions.Key.TrackedSourceID, positions.Key.PositionTimestamp) in (select gp.Key.TrackedSourceID, max(gp.Key.PositionTimestamp) from GenericPosition gp group by gp.Key.TrackedSourceID) Now using DetachedCriteria: var subquery = DetachedCriteria .For (typeof (GenericPosition), "gp") .SetProjection (Projections.ProjectionList () .Add (Projections.Property ("gp.Key.TrackedSourceID")) .Add (Projections.Max ("gp.Key.PositionTimestamp")) .Add (Projections.GroupProperty ("gp.Key.TrackedSourceID")) ); var criteriaQuery = DetachedCriteria .For (typeof (GenericObject), "genericObject") .CreateAlias ("genericObject.Positions", "positions") .SetFetchMode ("genericObject.Positions", FetchMode.Eager) .Add (Subqueries.In (??, subquery)) I don't know what to type instead of ?? to create expression like (positions.Key.TrackedSourceID, positions.Key.PositionTimestamp)

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• Linq filtering an IQueryable<T> (System.Data.Linq.DataQuery) object by a List<T> (System.Collection.

  - by Klaptrap

  My IQueryable line is: // find all timesheets for this period - from db so System.Data.Linq.DataQuery var timesheets = _timesheetRepository.FindByPeriod(dte1, dte2); My List line is: // get my team from AD - from active directory so System.Collection.Generic.List var adUsers = _adUserRepository.GetMyTeam(User.Identity.Name); I wish to only show timesheets for those users in the timesheet collection that are present in the user collection. If I use a standard c# expression such as: var teamsheets = from t in timesheets join user in adUsers on t.User1.username equals user.fullname select t; I get the error "An IQueryable that returns a self-referencing Constant expression is not supported" Any recommendations?

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• Translate query to NHibernate

  - by Rob Walker

  I am trying to learn NHibernate, and am having difficulty translating a SQL query into one using the criteria API. The data model has tables: Part (Id, Name, ...), Order (Id, PartId, Qty), Shipment (Id, PartId, Qty) For all the parts I want to find the total quantity ordered and the total quantity shipped. In SQL I have: select shipment.part_id, sum(shipment.quantity), sum(order.quantity) from shipment cross join order on order.part_id = shipment.part_id group by shipment.part_id Alternatively: select id, (select sum(quantity) from shipment where part_id = part.id), (select sum(quantity) from order where part_id = part.id) from part But the latter query takes over twice as long to execute. Any suggestions on how to create these queries in (fluent) NHibernate? I have all the tables mapped and loading/saving/etc the entities works fine.

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• How to pass Multivalued parameters through URL in SSRS 2005

  - by Kali Charan Tripathi

  Hi All, I have main matrix report and I want to navigate my sub report from main report by Jump To URL:(Using below JavaScript function) method. ="javascript:void(window.open('http://localhost/ReportServer/Pages/ReportViewer.aspx?%2fKonsolidata_Data_Exporting_Project%2fEXPORT_REPORT_TEST&rs:Command=Render&RP_cntry="+Fields!STD_CTRY_NM.Value+"&RP_cll_typ_l1="+Join(Parameters!RP_cll_typ_l1.Value,",")+"'))" It is ok for the Single valued but giving exception for the multivalued Like An error has occurred during report processing. (rsProcessingAborted) Cannot read the next data row for the data set DS_GRID_DATA. (rsErrorReadingNextDataRow) Conversion failed when converting the nvarchar value '1,2,3,4' to data type int. Basically I have defined Parameters!RP_cll_typ_l1 as multivalued into my subreport as per ssrs multivalued parameter passing method. The value is going on sub report as '1,2,3,4' (not understandable by data set) It should be like as '1’,’2’,’3’,’4' or 1,2,3,4 How can I resolve this please help if any have solution? Thanks Kali Charan Tripathi(India) [email protected] [email protected]

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