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  • ubuntu 14.04 freezes randomly

    - by rajesh chowdary
    I have installed Ubuntu 14.04 version along side with windows 7. Ubuntu freezes randomly I am unable to use any keys on keyboard since they are not working even mouse is not working.the only solution to get off from this freeze is restarting my computer.I have ATi/AMD graphic card but I removed it before installing Ubuntu 14.04.I have run memory test no problem with ram.please give some solution to get rid of this abnormal freeze. thanks in advance. system configuration CPU=Intel core 2 duo e7500 2.93ghz motherboard=Intel dg41wv hard disk=Seagate 500gb ram=4gb

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  • Virtualbox windows 7 guest - pressing windows key launches unity menu

    - by Pablo
    Running win7 as guest in full screen mode. When i press windows key or alt+tab the vm looses focus and displays the unity menu or ubuntu's alt+tab. I've set the VBox configuration: File Menu - Input - Auto Capture Keyboard but it looks like some times it captures it and some times it doesn't Do you know how to run win7 in fullscreen and have all windows key or alt+tab strokes captured by the win7vm only?

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  • Dates set according to location not chosen language

    - by aspersieman
    I recently installed Ubuntu 13.10 chose my location as Thailand/Bangkok, keyboard layout and language as South African English. Everything seems to be set up correctly except wherever a date is displayed it is displayed in Thai, instead of English. This is most noticeable in the clock indicator (see images included for what I mean). How can I change my dates to English (South African locale if possible).

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  • Can't use ubuntu 12.04 , after pc crashed while updating

    - by ilias
    few days ago while ubuntu 12.04 was doing a common system uodate , my laptop turned off in the middle of process , due to bad ac power. Since then , i can only login but nothing else. A message about compiz appear , but mouse keyboard , icons , unity are not working. the only thing i was able to do is a boot-repear ,as discribed in ubuntu's site, but neither this helped. Hope you can help me. thanks!

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  • How to restart Gnome Shell after a crash short of killing X?

    - by wintercorn
    How can I restart Gnome Shell after a crash? Alt+F2 and restart won't work as the prompt crashed with the shell. Since windows focus is gone along with the shell as well, I can't type gnome-shell --replace in a terminal, either. The Ctr+Alt+F1 command line can't open the X display. So I'm left with killing X, thus loosing all open applications. Is there a keyboard shortcut for restarting Gnome Shell?

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  • engine for responsive gameplay

    - by zaftcoAgeiha
    Many games have been praised for its responsive gameplay, where each user action input correspond to a quick and precise character movement (eg: super meat boy, shank...) What makes those games responsive? and what prevents other games from achieving the same? How much of it is due to the game framework used to queue mouse/keyboard events and render/update the game and how much is attributed to better coding?

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  • What type of command can I use for shortcut assignment?

    - by navie
    We all know that Ubuntu 12 has a shortcut mapper under "Keyboard" utility. I wonder when it asks for "command" in the new shortcut dialog, what type of command can I use? I used to think that commands in terminal can also be used here, but it seems xdotool is not like that. btw, if xdotool is not the right solution, how to map a key combination to a another key? for e.g.: alt+j to Down arrow key Thank you

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  • xbindkeys slow on Ubuntu 13.10

    - by 3l4ng
    I am using Ubuntu 13.10 64 bit on an Intel 15 with 4GB of RAM. I used xbindkeys for custom keyboard shortcuts in Ubuntu 13.04 because it was easy to configure with the GUI xbindkeys-config. Now I have setup the same on Ubuntu 13.10, and even a simple operation like opening a file using gedit seems to run slow. Reinstalling xbindkeys does not seem to solve the problem. Anyone has any ideas on what could be done, or any alternatives that are easy to configure?

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  • Ubuntu 13.10 problems

    - by user198097
    I have two problems with new Ubuntu 13.10. 1, Black screen problem: - Between GRUB and loading screen adopts black screen for 10 minutes and between the loading screen and the desktop appearance is a black screen for 20-30 seconds. 2, Wake problem: - After the suspension is to move the keyboard does not work or I can not do anything about it, because nothing works. 3, Full screen problem - When I back from full screen, I can't see the Unity, instead I see the window. :/ Please help me.

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  • have to plug/un-plug usb devices on system booting?

    - by user866581
    it's so weired that i have to plug/unplug in my usb devices every time booting ubuntu. it happens for both installing ubuntu and booting ubuntu (10.10 and 11.10) the scenario is like: 1.bios checking - 2.grub start - 3.keyboard & mouse led OFF (black screen with a cursor on top-left) - 4.i plug/unplug in any usb devices - 5.everything is back to normal and ubuntu started it's really frustrating :( please advise the solution.

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  • Should the main game object be static in c++

    - by Som_kun
    I am creating a 2d platformer using SDL and I was thinking that my game object could be static, but I wasn't sure if this was a good idea. The pros (that I can see): Accessing settings options (such as screen size and keyboard bindings) would be easier accessed There should only ever be one main game loop, so this makes sure for me. The cons: From what I've heard, static classes in C++ are a bear to work with I've read that this may cause problems later in development (things don't work right or can't be used properly

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  • Collision detection problem in XNA

    - by Fantasy
    I'm having two problems with my collision detection in XNA. There are two boxes, the red box represents a player and the blue box represents a wall. The first problem is when the player moves to the upper side or bottom side of the wall and collides with it, and then try to go to the left or right, the player will just jump in the opposite direction as seen in the video. However if I go to the right side or the left side of the wall and try to go up or down the player will smoothly go up or down without jumping. The second problem is that when I collide with the box and my key is still pressed down the blue box goes half way through red box and and goes back out and it keeps doing that until I stop pressing the keyboard. its not very clear on the video but the keeps going in and out really fast until I stop pressing the key. Here is a video example:- http://www.youtube.com/watch?v=mKLJsrPviYo and Here is my code Vector2 Position; Rectangle PlayerRectangle, BoxRectangle; float Speed = 0.25f; enum Direction { Up, Right, Down, Left }; Direction direction; protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); KeyboardState keyboardState = Keyboard.GetState(); if (keyboardState.IsKeyDown(Keys.Up)) { Position.Y -= (float)(Speed * gameTime.ElapsedGameTime.TotalMilliseconds); direction = Direction.Up; } if (keyboardState.IsKeyDown(Keys.Down)) { Position.Y += (float)(Speed * gameTime.ElapsedGameTime.TotalMilliseconds); direction = Direction.Down; } if (keyboardState.IsKeyDown(Keys.Right)) { Position.X += (float)(Speed * gameTime.ElapsedGameTime.TotalMilliseconds); direction = Direction.Right; } if (keyboardState.IsKeyDown(Keys.Left)) { Position.X -= (float)(Speed * gameTime.ElapsedGameTime.TotalMilliseconds); direction = Direction.Left; } if (PlayerRectangle.Intersects(BoxRectangle)) { if (direction == Direction.Right) Position.X = BoxRectangle.Left - PlayerRectangle.Width; else if (direction == Direction.Left) Position.X = BoxRectangle.Right; if (direction == Direction.Down) Position.Y = BoxRectangle.Top - PlayerRectangle.Height; else if (direction == Direction.Up) Position.Y = BoxRectangle.Bottom; } PlayerRectangle = new Rectangle((int)Position.X, (int)Position.Y, (int)32, (int)32); base.Update(gameTime); }

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  • Why suspend / hibernate does not work in Ubuntu 10.10? (blank screen problem)

    - by agn0stic
    I've got a problem with Ubuntu 10.10 suspend / hibernation. When I try to do one of these actions, computer prepares but in the end a blank screen comes up with just a single underscore blinking. Computer becomes unresponsive to mouse/keyboard and only pressing power button on chasis restores it. Disks and coolers are working during the suspend / hibernation as if nothing happened. Can anyone give me some advice how to solve it? Thank you.

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  • Unity does not start after installing the fglrx drivers on 12.10 [closed]

    - by f.mcleash
    I installed Ubuntu 12.10 and at first when I go to check the system information I used to have (unknown) on the graphic card section, I used the synaptic manager and downloaded the fglrx, after that I restarted my laptop and now I don't have any menus, all of them are gone. Now I am only using the keyboard shortcuts to use Ubuntu. My graphic card is AMD ATI. What can I do to bring the menus back?

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  • sudo refuses my password

    - by fredericf
    I've just installed Ubuntu 12.04 and now that I want to install a program through the terminal with a command starting with sudo, the terminal says Sorry, try again. I just don't get it, this is my user password which I check with through the Software Center. What can be then wrong? (Is it possible that the terminal function differently than the rest of the OS in relation to ASCII keyboard?) Please help.

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  • Assigning shortcuts (accelerators) to Nautilus 3

    - by abruski
    I want to assign some shortcuts to menu actions in Nautilus 3.2.1 running under Ubuntu 11.10. I followed the steps shown here How do you create a "new document" keyboard shortcut? but it did not work for me. Switched to gnome classic so I can get the normal menu, hovered over the desired action pressed the desired keys but nothing happened (restarted nautilus, re-logged and nothing). Any suggestions or ideas on how to assign custom shortcuts to actions in Nautilus 3

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  • Scale effect to preview and switch between windows?

    - by ycelik
    at work ive installed ubuntu 10.10 and love using the Super+a keyboard shortcut to switch between my windows. at home i use kubuntu 12.04 and miss that feature. ive seen a video on youtube and know that it is possible but couldn't figure out how. https://help.ubuntu.com/community/KeyboardShortcuts/ Super + A | Enables the 'scale' effect, it shows all windows from all workspaces. thanks for your time

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  • Merging multiple Google calendar feeds into one JSON object in javascript

    - by Jeramy
    I am trying to bring in the JSON feeds from multiple Google calendars so that I can sort the upcoming events and display the next X number in an "Upcoming Events" list. I have this working with Yahoo! pipes but I want to get away from using a 3rd party to aggregate. I think I am close, but I cannot get the JSON objects created correctly. I am getting the data into the array but not in JSON format, so I can't manipulate it. I have tried var myJsonString = JSON.stringify(JSONData); using https://github.com/douglascrockford/JSON-js but that just threw errors. I suspect because my variable is in the wrong starting format. I have tried just calling the feed like: $.getJSON(url); and creating a function concant1() to do the JSONData=JSONData.concat(data);, but it doesn't fire and I think it would produce the same end result anyway. I have also tried several other methods of getting the end result I want with varying degrees of doom. Here is the closest I have come so far: var JSONData = new Array(); var urllist = ["https://www.google.com/calendar/feeds/dg61asqgqg4pust2l20obgdl64%40group.calendar.google.com/public/full?orderby=starttime&max-results=3&sortorder=ascending&futureevents=true&ctz=America/New_York&singleevents=true&alt=json&callback=concant1","https://www.google.com/calendar/feeds/5oc3kvp7lnu5rd4krg2skcu2ng%40group.calendar.google.com/public/full?orderby=starttime&max-results=3&sortorder=ascending&futureevents=true&ctz=America/New_York&singleevents=true&alt=json&callback=concant1","http://www.google.com/calendar/feeds/rine4umu96kl6t46v4fartnho8%40group.calendar.google.com/public/full?orderby=starttime&max-results=3&sortorder=ascending&futureevents=true&ctz=America/New_York&singleevents=true&alt=json&callback=concant1"]; urllist.forEach(function addFeed(url){ alert("The URL being used: "+ url); if (void 0 != JSONData){JSONData=JSONData.concat($.getJSON(url));} else{JSONData = $.getJSON(url);} alert("The count from concantonated JSONData: "+JSONData.length); }); document.write("The final count from JSONData: "+JSONData.length+"<p>"); console.log(JSONData) UPDATE: Now with full working source!! :) If anyone would like to make suggestions on how to improve the code's efficiency it would be gratefully accepted. I hope others find this useful.: // GCal MFA - Google Calendar Multiple Feed Aggregator // Useage: GCalMFA(CIDs,n); // Where 'CIDs' is a list of comma seperated Google calendar IDs in the format: [email protected], and 'n' is the number of results to display. // While the contained console.log(); outputs are really handy for testing, you will probably waant to remove them for regular usage // Author: Jeramy Kruser - http://jeramy.kruser.me //onerror=function (d, f, g){alert (d+ "\n"+ f+ "\n");} if (!window.console) {console = {log: function() {}};} document.body.className += ' js-enabled'; // Global variables var urllist = []; var maxResults = 3; // The default is 3 results unless a value is sent var JSONData = {}; var eventCount = 0; var errorLog = ""; JSONData = { count: 0, value : { description: "Aggregates multiple Google calendar feeds into a single sorted list", generator: "StackOverflow communal coding - Thanks for the assist Patrick M", website: "http://jeramy.kruser.me", author: "Jeramy & Kasey Kruser", items: [] }}; // For putting dates from feed into a format that can be read by the Date function for calculating event length. function parse (str) { // validate year as 4 digits, month as 01-12, and day as 01-31 str = str.match (/^(\d{4})(0[1-9]|1[0-2])(0[1-9]|[12]\d|3[01])$/); if (str) { // make a date str[0] = new Date ( + str[1], + str[2] - 1, + str[3]); // check if month stayed the same (ie that day number is valid) if (str[0].getMonth () === + str[2] - 1) { return str[0]; } } return undefined; } //For outputting to HTML function output() { var months, day_in_ms, summary, i, item, eventlink, title, calendar, where,dtstart, dtend, endyear, endmonth, endday, startyear, startmonth, startday, endmonthdayyear, eventlinktitle, startmonthday, length, curtextval, k; // Array of month names from numbers for page display. months = {'0':'January', '1':'February', '2':'March', '3':'April', '4':'May', '5':'June', '6':'July', '7':'August', '8':'September', '9':'October', '10':'November', '11':'December'}; // For use in calculating event length. day_in_ms = 24 * 60 * 60 * 1000; // Instantiate HTML Arrays. summary = []; for (i = 0; i < maxResults; i+=1 ) { //console.log("i: "+i+" < "+"maxResults: "+ maxResults); if (!(JSONData.value.items[i] === undefined)) { item = JSONData.value.items[i]; // Grabbing data for each event in the feed. eventlink = item.link[0]; title = item.title.$t; // Only display the calendar title if there is more than one calendar = ""; if (urllist.length > 1) { calendar = '<br />Calendar: <a href="https://www.google.com/calendar/embed?src=' + item.gd$who[0].email + '&ctz=America/New_York">' + item.author[0].name.$t + '<\/a> (<a href="https://www.google.com/calendar/ical/' + item.gd$who[0].email + '/public/basic.ics">iCal<\/a>)'; } // Grabbing event location, if entered. if ( item.gd$where[0].valueString !== "" ) { where = '<br />' + (item.gd$where[0].valueString); } else { where = (""); } // Grabbing start date and putting in form YYYYmmdd. Subtracting one day from dtend to fix Google's habit of ending an all-day event at midnight on the following day. dtstart = new Date(parse(((item.gd$when[0].startTime).substring(0,10)).replace(/-/g,""))); dtend = new Date(parse(((item.gd$when[0].endTime).substring(0,10)).replace(/-/g,"")) - day_in_ms); // Put dates in pretty form for display. endyear = dtend.getFullYear(); endmonth = months[dtend.getMonth()]; endday = dtend.getDate(); startyear = dtstart.getFullYear(); startmonth = months[dtstart.getMonth()]; startday = dtstart.getDate(); //consolidate some much-used variables for HTML output. endmonthdayyear = endmonth + ' ' + endday + ', ' + endyear; eventlinktitle = '<a href="' + eventlink + '">' + title + '<\/a>'; startmonthday = startmonth + ' ' + startday; // Calculates the number of days between each event's start and end dates. length = ((dtend - dtstart) / day_in_ms); // HTML for each event, depending on which div is available on the page (different HTML applies). Only one div can exist on any one page. if (document.getElementById("homeCalendar") !== null ) { // If the length of the event is greater than 0 days, show start and end dates. if ( length > 0 && startmonth !== endmonth && startday === endday ) { summary[i] = ('<h3>' + eventlink + '">' + startmonthday + ', ' + startyear + ' - ' + endmonthdayyear + '<\/a><\/h3><p>' + title + '<\/p>'); } // If the length of the event is greater than 0 and begins and ends within the same month, shorten the date display. else if ( length > 0 && startmonth === endmonth && startyear === endyear ) { summary[i] = ('<h3><a href="' + eventlink + '">' + startmonthday + '-' + endday + ', ' + endyear + '<\/a><\/h3><p>' + title + '<\/p>'); } // If the length of the event is greater than 0 and begins and ends within different months of the same year, shorten the date display. else if ( length > 0 && startmonth !== endmonth && startyear === endyear ) { summary[i] = ('<h3><a href="' + eventlink + '">' + startmonthday + ' - ' + endmonthdayyear + '<\/a><\/h3><p>' + title + '<\/p>'); } // If the length of the event is less than one day (length < = 0), show only the start date. else { summary[i] = ('<h3><a href="' + eventlink + '">' + startmonthday + ', ' + startyear + '<\/a><\/h3><p>' + title + '<\/p>'); } } else if (document.getElementById("allCalendar") !== null ) { // If the length of the event is greater than 0 days, show start and end dates. if ( length > 0 && startmonth !== endmonth && startday === endday ) { summary[i] = ('<li>' + eventlinktitle + '<br />' + startmonthday + ', ' + startyear + ' - ' + endmonthdayyear + where + calendar + '<br />&#160;<\/li>'); } // If the length of the event is greater than 0 and begins and ends within the same month, shorten the date display. else if ( length > 0 && startmonth === endmonth && startyear === endyear ) { summary[i] = ('<li>' + eventlinktitle + '<br />' + startmonthday + '-' + endday + ', ' + endyear + where + calendar + '<br />&#160;<\/li>'); } // If the length of the event is greater than 0 and begins and ends within different months of the same year, shorten the date display. else if ( length > 0 && startmonth !== endmonth && startyear === endyear ) { summary[i] = ('<li>' + eventlinktitle + '<br />' + startmonthday + ' - ' + endmonthdayyear + where + calendar + '<br />&#160;<\/li>'); } // If the length of the event is less than one day (length < = 0), show only the start date. else { summary[i] = ('<li>' + eventlinktitle + '<br />' + startmonthday + ', ' + startyear + where + calendar + '<br />&#160;<\/li>'); } } } if (summary[i] === undefined) { summary[i] = "";} //console.log(summary[i]); } console.log(JSONData); // Puts the HTML into the div with the appropriate id. Each page can have only one. if (document.getElementById("homeCalendar") !== null ) { curtextval = document.getElementById("homeCalendar"); console.log("homeCalendar: "+curtextval); } else if (document.getElementById("oneCalendar") !== null ) { curtextval = document.getElementById("oneCalendar"); console.log("oneCalendar: "+curtextval); } else if (document.getElementById("allCalendar") !== null ) { curtextval = document.getElementById("allCalendar"); console.log("allCalendar: "+curtextval); } if (curtextval.innerHTML.length < 100) { errorLog += '<div id="noEvents">No events found.</div>'; } for (k = 0; k<maxResults; k+=1 ) { curtextval.innerHTML = curtextval.innerHTML + summary[k]; } if (eventCount === 0) { errorLog += '<div id="noEvents">No events found.</div>'; } if (document.getElementById("homeCalendar") === null ) { curtextval.innerHTML = '<ul>' + curtextval.innerHTML + '<\/ul>'; } if (errorLog !== "") { curtextval.innerHTML += errorLog; } } // For taking in each feed, breaking out the events and sorting them into the object by date function sortFeed(event) { var tempEntry, i; tempEntry = event; i = 0; console.log("*** New incoming event object #"+eventCount+" ***"); console.log(event.title.$t); console.log(event); //console.log("i = " + i + " and maxResults " + maxResults); while(i<maxResults) { console.log("i = " + i + " < maxResults " + maxResults); console.log("Sorting event = " + event.title.$t + " by date of " + event.gd$when[0].startTime.substring(0,10).replace(/-/g,"")); if (JSONData.value.items[i]) { console.log("JSONData.value.items[" + i + "] exists and has a startTime of " + JSONData.value.items[i].gd$when[0].startTime.substring(0,10).replace(/-/g,"")); if (event.gd$when[0].startTime.substring(0,10).replace(/-/g,"")<JSONData.value.items[i].gd$when[0].startTime.substring(0,10).replace(/-/g,"")) { console.log("The incoming event value of " + event.gd$when[0].startTime.substring(0,10).replace(/-/g,"") + " is < " + JSONData.value.items[i].gd$when[0].startTime.substring(0,10).replace(/-/g,"")); tempEntry = JSONData.value.items[i]; console.log("Existing JSONData.value.items[" + i + "] value " + JSONData.value.items[i].gd$when[0].startTime.substring(0,10).replace(/-/g,"") + " stored in tempEntry"); JSONData.value.items[i] = event; console.log("Position JSONData.value.items[" + i + "] set to new value: " + event.gd$when[0].startTime.substring(0,10).replace(/-/g,"")); event = tempEntry; console.log("Now sorting event = " + event.title.$t + " by date of " + event.gd$when[0].startTime.substring(0,10).replace(/-/g,"")); } else { console.log("The incoming event value of " + event.gd$when[0].startTime.substring(0,10).replace(/-/g,"") + " is > " + JSONData.value.items[i].gd$when[0].startTime.substring(0,10).replace(/-/g,"") + " moving on..."); } } else { JSONData.value.items[i] = event; console.log("JSONData.value.items[" + i + "] does not exist so it was set to the Incoming value of " + event.gd$when[0].startTime.substring(0,10).replace(/-/g,"")); i = maxResults; } i += 1; } } // For completing the aggregation function complete(result) { var str, j, item; // Track the number of calls completed back, we're not done until all URLs have processed if( complete.count === undefined ){ complete.count = urllist.length; } console.log("complete.count = "+complete.count); console.log(result.feed); if(result.feed.entry){ JSONData.count = maxResults; // Check each incoming item against JSONData.value.items console.log("*** Begin Sorting " + result.feed.entry.length + " Events ***"); //console.log(result.feed.entry); result.feed.entry.forEach( function(event){ eventCount += 1; sortFeed(event); } ); } if( (complete.count-=1)<1 ) { console.log("*** Done Sorting ***"); output(); } } // This is the main function. It takes in the list of Calendar IDs and the number of results to display function GCalMFA(list,results){ var i, calPreProperties, calPostProperties1, calPostProperties2; calPreProperties = "https://www.google.com/calendar/feeds/"; calPostProperties1 = "/public/full?max-results="; calPostProperties2 = "&orderby=starttime&sortorder=ascending&futureevents=true&ctz=America/New_York&singleevents=true&alt=json&callback=?"; if (list) { if (results) { maxResults = results; } urllist = list.split(','); for (i = 0; i < urllist.length; i+=1 ){ if (urllist[i] === 0){ urllist.splice(i,1);} else{ urllist[i] = calPreProperties + urllist[i] + calPostProperties1+maxResults+calPostProperties2;} } console.log("There are " + urllist.length + " URLs"); urllist.forEach(function addFeed(url){ $.getJSON(url, complete); }); } else { errorLog += '<div id="noURLs">No calendars have been selected.</div>'; output(); } }

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  • A free standing ASP.NET Pager Web Control

    - by Rick Strahl
    Paging in ASP.NET has been relatively easy with stock controls supporting basic paging functionality. However, recently I built an MVC application and one of the things I ran into was that I HAD TO build manual paging support into a few of my pages. Dealing with list controls and rendering markup is easy enough, but doing paging is a little more involved. I ended up with a small but flexible component that can be dropped anywhere. As it turns out the task of creating a semi-generic Pager control for MVC was fairly easily. Now I’m back to working in Web Forms and thought to myself that the way I created the pager in MVC actually would also work in ASP.NET – in fact quite a bit easier since the whole thing can be conveniently wrapped up into an easily reusable control. A standalone pager would provider easier reuse in various pages and a more consistent pager display regardless of what kind of 'control’ the pager is associated with. Why a Pager Control? At first blush it might sound silly to create a new pager control – after all Web Forms has pretty decent paging support, doesn’t it? Well, sort of. Yes the GridView control has automatic paging built in and the ListView control has the related DataPager control. The built in ASP.NET paging has several issues though: Postback and JavaScript requirements If you look at paging links in ASP.NET they are always postback links with javascript:__doPostback() calls that go back to the server. While that works fine and actually has some benefit like the fact that paging saves changes to the page and post them back, it’s not very SEO friendly. Basically if you use javascript based navigation nosearch engine will follow the paging links which effectively cuts off list content on the first page. The DataPager control does support GET based links via the QueryStringParameter property, but the control is effectively tied to the ListView control (which is the only control that implements IPageableItemContainer). DataSource Controls required for Efficient Data Paging Retrieval The only way you can get paging to work efficiently where only the few records you display on the page are queried for and retrieved from the database you have to use a DataSource control - only the Linq and Entity DataSource controls  support this natively. While you can retrieve this data yourself manually, there’s no way to just assign the page number and render the pager based on this custom subset. Other than that default paging requires a full resultset for ASP.NET to filter the data and display only a subset which can be very resource intensive and wasteful if you’re dealing with largish resultsets (although I’m a firm believer in returning actually usable sets :-}). If you use your own business layer that doesn’t fit an ObjectDataSource you’re SOL. That’s a real shame too because with LINQ based querying it’s real easy to retrieve a subset of data that is just the data you want to display but the native Pager functionality doesn’t support just setting properties to display just the subset AFAIK. DataPager is not Free Standing The DataPager control is the closest thing to a decent Pager implementation that ASP.NET has, but alas it’s not a free standing component – it works off a related control and the only one that it effectively supports from the stock ASP.NET controls is the ListView control. This means you can’t use the same data pager formatting for a grid and a list view or vice versa and you’re always tied to the control. Paging Events In order to handle paging you have to deal with paging events. The events fire at specific time instances in the page pipeline and because of this you often have to handle data binding in a way to work around the paging events or else end up double binding your data sources based on paging. Yuk. Styling The GridView pager is a royal pain to beat into submission for styled rendering. The DataPager control has many more options and template layout and it renders somewhat cleaner, but it too is not exactly easy to get a decent display for. Not a Generic Solution The problem with the ASP.NET controls too is that it’s not generic. GridView, DataGrid use their own internal paging, ListView can use a DataPager and if you want to manually create data layout – well you’re on your own. IOW, depending on what you use you likely have very different looking Paging experiences. So, I figured I’ve struggled with this once too many and finally sat down and built a Pager control. The Pager Control My goal was to create a totally free standing control that has no dependencies on other controls and certainly no requirements for using DataSource controls. The idea is that you should be able to use this pager control without any sort of data requirements at all – you should just be able to set properties and be able to display a pager. The Pager control I ended up with has the following features: Completely free standing Pager control – no control or data dependencies Complete manual control – Pager can render without any data dependency Easy to use: Only need to set PageSize, ActivePage and TotalItems Supports optional filtering of IQueryable for efficient queries and Pager rendering Supports optional full set filtering of IEnumerable<T> and DataTable Page links are plain HTTP GET href Links Control automatically picks up Page links on the URL and assigns them (automatic page detection no page index changing events to hookup) Full CSS Styling support On the downside there’s no templating support for the control so the layout of the pager is relatively fixed. All elements however are stylable and there are options to control the text, and layout options such as whether to display first and last pages and the previous/next buttons and so on. To give you an idea what the pager looks like, here are two differently styled examples (all via CSS):   The markup for these two pagers looks like this: <ww:Pager runat="server" id="ItemPager" PageSize="5" PageLinkCssClass="gridpagerbutton" SelectedPageCssClass="gridpagerbutton-selected" PagesTextCssClass="gridpagertext" CssClass="gridpager" RenderContainerDiv="true" ContainerDivCssClass="gridpagercontainer" MaxPagesToDisplay="6" PagesText="Item Pages:" NextText="next" PreviousText="previous" /> <ww:Pager runat="server" id="ItemPager2" PageSize="5" RenderContainerDiv="true" MaxPagesToDisplay="6" /> The latter example uses default style settings so it there’s not much to set. The first example on the other hand explicitly assigns custom styles and overrides a few of the formatting options. Styling The styling is based on a number of CSS classes of which the the main pager, pagerbutton and pagerbutton-selected classes are the important ones. Other styles like pagerbutton-next/prev/first/last are based on the pagerbutton style. The default styling shown for the red outlined pager looks like this: .pagercontainer { margin: 20px 0; background: whitesmoke; padding: 5px; } .pager { float: right; font-size: 10pt; text-align: left; } .pagerbutton,.pagerbutton-selected,.pagertext { display: block; float: left; text-align: center; border: solid 2px maroon; min-width: 18px; margin-left: 3px; text-decoration: none; padding: 4px; } .pagerbutton-selected { font-size: 130%; font-weight: bold; color: maroon; border-width: 0px; background: khaki; } .pagerbutton-first { margin-right: 12px; } .pagerbutton-last,.pagerbutton-prev { margin-left: 12px; } .pagertext { border: none; margin-left: 30px; font-weight: bold; } .pagerbutton a { text-decoration: none; } .pagerbutton:hover { background-color: maroon; color: cornsilk; } .pagerbutton-prev { background-image: url(images/prev.png); background-position: 2px center; background-repeat: no-repeat; width: 35px; padding-left: 20px; } .pagerbutton-next { background-image: url(images/next.png); background-position: 40px center; background-repeat: no-repeat; width: 35px; padding-right: 20px; margin-right: 0px; } Yup that’s a lot of styling settings although not all of them are required. The key ones are pagerbutton, pager and pager selection. The others (which are implicitly created by the control based on the pagerbutton style) are for custom markup of the ‘special’ buttons. In my apps I tend to have two kinds of pages: Those that are associated with typical ‘grid’ displays that display purely tabular data and those that have a more looser list like layout. The two pagers shown above represent these two views and the pager and gridpager styles in my standard style sheet reflect these two styles. Configuring the Pager with Code Finally lets look at what it takes to hook up the pager. As mentioned in the highlights the Pager control is completely independent of other controls so if you just want to display a pager on its own it’s as simple as dropping the control and assigning the PageSize, ActivePage and either TotalPages or TotalItems. So for this markup: <ww:Pager runat="server" id="ItemPagerManual" PageSize="5" MaxPagesToDisplay="6" /> I can use code as simple as: ItemPagerManual.PageSize = 3; ItemPagerManual.ActivePage = 4;ItemPagerManual.TotalItems = 20; Note that ActivePage is not required - it will automatically use any Page=x query string value and assign it, although you can override it as I did above. TotalItems can be any value that you retrieve from a result set or manually assign as I did above. A more realistic scenario based on a LINQ to SQL IQueryable result is even easier. In this example, I have a UserControl that contains a ListView control that renders IQueryable data. I use a User Control here because there are different views the user can choose from with each view being a different user control. This incidentally also highlights one of the nice features of the pager: Because the pager is independent of the control I can put the pager on the host page instead of into each of the user controls. IOW, there’s only one Pager control, but there are potentially many user controls/listviews that hold the actual display data. The following code demonstrates how to use the Pager with an IQueryable that loads only the records it displays: protected voidPage_Load(objectsender, EventArgs e) {     Category = Request.Params["Category"] ?? string.Empty;     IQueryable<wws_Item> ItemList = ItemRepository.GetItemsByCategory(Category);     // Update the page and filter the list down     ItemList = ItemPager.FilterIQueryable<wws_Item>(ItemList); // Render user control with a list view Control ulItemList = LoadControl("~/usercontrols/" + App.Configuration.ItemListType + ".ascx"); ((IInventoryItemListControl)ulItemList).InventoryItemList = ItemList; phItemList.Controls.Add(ulItemList); // placeholder } The code uses a business object to retrieve Items by category as an IQueryable which means that the result is only an expression tree that hasn’t execute SQL yet and can be further filtered. I then pass this IQueryable to the FilterIQueryable() helper method of the control which does two main things: Filters the IQueryable to retrieve only the data displayed on the active page Sets the Totaltems property and calculates TotalPages on the Pager and that’s it! When the Pager renders it uses those values, plus the PageSize and ActivePage properties to render the Pager. In addition to IQueryable there are also filter methods for IEnumerable<T> and DataTable, but these versions just filter the data by removing rows/items from the entire already retrieved data. Output Generated and Paging Links The output generated creates pager links as plain href links. Here’s what the output looks like: <div id="ItemPager" class="pagercontainer"> <div class="pager"> <span class="pagertext">Pages: </span><a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=1" class="pagerbutton" />1</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=2" class="pagerbutton" />2</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=3" class="pagerbutton" />3</a> <span class="pagerbutton-selected">4</span> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=5" class="pagerbutton" />5</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=6" class="pagerbutton" />6</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=20" class="pagerbutton pagerbutton-last" />20</a>&nbsp;<a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=3" class="pagerbutton pagerbutton-prev" />Prev</a>&nbsp;<a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=5" class="pagerbutton pagerbutton-next" />Next</a></div> <br clear="all" /> </div> </div> The links point back to the current page and simply append a Page= page link into the page. When the page gets reloaded with the new page number the pager automatically detects the page number and automatically assigns the ActivePage property which results in the appropriate page to be displayed. The code shown in the previous section is all that’s needed to handle paging. Note that HTTP GET based paging is different than the Postback paging ASP.NET uses by default. Postback paging preserves modified page content when clicking on pager buttons, but this control will simply load a new page – no page preservation at this time. The advantage of not using Postback paging is that the URLs generated are plain HTML links that a search engine can follow where __doPostback() links are not. Pager with a Grid The pager also works in combination with grid controls so it’s easy to bypass the grid control’s paging features if desired. In the following example I use a gridView control and binds it to a DataTable result which is also filterable by the Pager control. The very basic plain vanilla ASP.NET grid markup looks like this: <div style="width: 600px; margin: 0 auto;padding: 20px; "> <asp:DataGrid runat="server" AutoGenerateColumns="True" ID="gdItems" CssClass="blackborder" style="width: 600px;"> <AlternatingItemStyle CssClass="gridalternate" /> <HeaderStyle CssClass="gridheader" /> </asp:DataGrid> <ww:Pager runat="server" ID="Pager" CssClass="gridpager" ContainerDivCssClass="gridpagercontainer" PageLinkCssClass="gridpagerbutton" SelectedPageCssClass="gridpagerbutton-selected" PageSize="8" RenderContainerDiv="true" MaxPagesToDisplay="6" /> </div> and looks like this when rendered: using custom set of CSS styles. The code behind for this code is also very simple: protected void Page_Load(object sender, EventArgs e) { string category = Request.Params["category"] ?? ""; busItem itemRep = WebStoreFactory.GetItem(); var items = itemRep.GetItemsByCategory(category) .Select(itm => new {Sku = itm.Sku, Description = itm.Description}); // run query into a DataTable for demonstration DataTable dt = itemRep.Converter.ToDataTable(items,"TItems"); // Remove all items not on the current page dt = Pager.FilterDataTable(dt,0); // bind and display gdItems.DataSource = dt; gdItems.DataBind(); } A little contrived I suppose since the list could already be bound from the list of elements, but this is to demonstrate that you can also bind against a DataTable if your business layer returns those. Unfortunately there’s no way to filter a DataReader as it’s a one way forward only reader and the reader is required by the DataSource to perform the bindings.  However, you can still use a DataReader as long as your business logic filters the data prior to rendering and provides a total item count (most likely as a second query). Control Creation The control itself is a pretty brute force ASP.NET control. Nothing clever about this other than some basic rendering logic and some simple calculations and update routines to determine which buttons need to be shown. You can take a look at the full code from the West Wind Web Toolkit’s Repository (note there are a few dependencies). To give you an idea how the control works here is the Render() method: /// <summary> /// overridden to handle custom pager rendering for runtime and design time /// </summary> /// <param name="writer"></param> protected override void Render(HtmlTextWriter writer) { base.Render(writer); if (TotalPages == 0 && TotalItems > 0) TotalPages = CalculateTotalPagesFromTotalItems(); if (DesignMode) TotalPages = 10; // don't render pager if there's only one page if (TotalPages < 2) return; if (RenderContainerDiv) { if (!string.IsNullOrEmpty(ContainerDivCssClass)) writer.AddAttribute("class", ContainerDivCssClass); writer.RenderBeginTag("div"); } // main pager wrapper writer.WriteBeginTag("div"); writer.AddAttribute("id", this.ClientID); if (!string.IsNullOrEmpty(CssClass)) writer.WriteAttribute("class", this.CssClass); writer.Write(HtmlTextWriter.TagRightChar + "\r\n"); // Pages Text writer.WriteBeginTag("span"); if (!string.IsNullOrEmpty(PagesTextCssClass)) writer.WriteAttribute("class", PagesTextCssClass); writer.Write(HtmlTextWriter.TagRightChar); writer.Write(this.PagesText); writer.WriteEndTag("span"); // if the base url is empty use the current URL FixupBaseUrl(); // set _startPage and _endPage ConfigurePagesToRender(); // write out first page link if (ShowFirstAndLastPageLinks && _startPage != 1) { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-first"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write("1"); writer.WriteEndTag("a"); writer.Write("&nbsp;"); } // write out all the page links for (int i = _startPage; i < _endPage + 1; i++) { if (i == ActivePage) { writer.WriteBeginTag("span"); if (!string.IsNullOrEmpty(SelectedPageCssClass)) writer.WriteAttribute("class", SelectedPageCssClass); writer.Write(HtmlTextWriter.TagRightChar); writer.Write(i.ToString()); writer.WriteEndTag("span"); } else { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, i.ToString()).TrimEnd('&'); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(i.ToString()); writer.WriteEndTag("a"); } writer.Write("\r\n"); } // write out last page link if (ShowFirstAndLastPageLinks && _endPage < TotalPages) { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, TotalPages.ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-last"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(TotalPages.ToString()); writer.WriteEndTag("a"); } // Previous link if (ShowPreviousNextLinks && !string.IsNullOrEmpty(PreviousText) && ActivePage > 1) { writer.Write("&nbsp;"); writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (ActivePage - 1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-prev"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(PreviousText); writer.WriteEndTag("a"); } // Next link if (ShowPreviousNextLinks && !string.IsNullOrEmpty(NextText) && ActivePage < TotalPages) { writer.Write("&nbsp;"); writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (ActivePage + 1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-next"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(NextText); writer.WriteEndTag("a"); } writer.WriteEndTag("div"); if (RenderContainerDiv) { if (RenderContainerDivBreak) writer.Write("<br clear=\"all\" />\r\n"); writer.WriteEndTag("div"); } } As I said pretty much brute force rendering based on the control’s property settings of which there are quite a few: You can also see the pager in the designer above. unfortunately the VS designer (both 2010 and 2008) fails to render the float: left CSS styles properly and starts wrapping after margins are applied in the special buttons. Not a big deal since VS does at least respect the spacing (the floated elements overlay). Then again I’m not using the designer anyway :-}. Filtering Data What makes the Pager easy to use is the filter methods built into the control. While this functionality is clearly not the most politically correct design choice as it violates separation of concerns, it’s very useful for typical pager operation. While I actually have filter methods that do something similar in my business layer, having it exposed on the control makes the control a lot more useful for typical databinding scenarios. Of course these methods are optional – if you have a business layer that can provide filtered page queries for you can use that instead and assign the TotalItems property manually. There are three filter method types available for IQueryable, IEnumerable and for DataTable which tend to be the most common use cases in my apps old and new. The IQueryable version is pretty simple as it can simply rely on on .Skip() and .Take() with LINQ: /// <summary> /// <summary> /// Queries the database for the ActivePage applied manually /// or from the Request["page"] variable. This routine /// figures out and sets TotalPages, ActivePage and /// returns a filtered subset IQueryable that contains /// only the items from the ActivePage. /// </summary> /// <param name="query"></param> /// <param name="activePage"> /// The page you want to display. Sets the ActivePage property when passed. /// Pass 0 or smaller to use ActivePage setting. /// </param> /// <returns></returns> public IQueryable<T> FilterIQueryable<T>(IQueryable<T> query, int activePage) where T : class, new() { ActivePage = activePage < 1 ? ActivePage : activePage; if (ActivePage < 1) ActivePage = 1; TotalItems = query.Count(); if (TotalItems <= PageSize) { ActivePage = 1; TotalPages = 1; return query; } int skip = ActivePage - 1; if (skip > 0) query = query.Skip(skip * PageSize); _TotalPages = CalculateTotalPagesFromTotalItems(); return query.Take(PageSize); } The IEnumerable<T> version simply  converts the IEnumerable to an IQuerable and calls back into this method for filtering. The DataTable version requires a little more work to manually parse and filter records (I didn’t want to add the Linq DataSetExtensions assembly just for this): /// <summary> /// Filters a data table for an ActivePage. /// /// Note: Modifies the data set permanently by remove DataRows /// </summary> /// <param name="dt">Full result DataTable</param> /// <param name="activePage">Page to display. 0 to use ActivePage property </param> /// <returns></returns> public DataTable FilterDataTable(DataTable dt, int activePage) { ActivePage = activePage < 1 ? ActivePage : activePage; if (ActivePage < 1) ActivePage = 1; TotalItems = dt.Rows.Count; if (TotalItems <= PageSize) { ActivePage = 1; TotalPages = 1; return dt; } int skip = ActivePage - 1; if (skip > 0) { for (int i = 0; i < skip * PageSize; i++ ) dt.Rows.RemoveAt(0); } while(dt.Rows.Count > PageSize) dt.Rows.RemoveAt(PageSize); return dt; } Using the Pager Control The pager as it is is a first cut I built a couple of weeks ago and since then have been tweaking a little as part of an internal project I’m working on. I’ve replaced a bunch of pagers on various older pages with this pager without any issues and have what now feels like a more consistent user interface where paging looks and feels the same across different controls. As a bonus I’m only loading the data from the database that I need to display a single page. With the preset class tags applied too adding a pager is now as easy as dropping the control and adding the style sheet for styling to be consistent – no fuss, no muss. Schweet. Hopefully some of you may find this as useful as I have or at least as a baseline to build ontop of… Resources The Pager is part of the West Wind Web & Ajax Toolkit Pager.cs Source Code (some toolkit dependencies) Westwind.css base stylesheet with .pager and .gridpager styles Pager Example Page © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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  • CQRS &ndash; Questions and Concerns

    - by Dylan Smith
    I’ve been doing a lot of learning on CQRS and Event Sourcing over the last little while and I have a number of questions that I haven’t been able to answer. 1. What is the benefit of CQRS when compared to a typical DDD architecture that uses Event Sourcing and properly captures intent and behavior via verb-based commands? (other than Scalability) 2. When using CQRS what do you do with complex query-based logic? I’m going to elaborate on #1 in this blog post and I’ll do a follow-up post on #2. I watched through Greg Young’s video on the business benefits of CQRS + Event Sourcing and first let me say that I thought it was an excellent presentation that really drives home a lot of the benefits to this approach to architecture (I watched it twice in a row I enjoyed it so much!). But it didn’t answer some of my questions fully (I wish I had been there to ask these of Greg in person!). So let me pick apart some of the points he makes and how they relate to my first question above. I’m completely sold on the idea of event sourcing and have a clear understanding of the benefits that it brings to the table, so I’m not going to question that. But you can use event sourcing without going to a CQRS architecture, so my main question is around the benefits of CQRS + Event Sourcing vs Event Sourcing + Typical DDD architecture Architecture with Event Sourcing + Commands on Left, CQRS on Right Greg talks about how the stereotypical architecture doesn’t support DDD, but is that only because his diagram shows DTO’s coming up from the client. If we use the same diagram but allow the client to send commands doesn’t that remove a lot of the arguments that Greg makes against the stereotypical architecture? We can now introduce verbs into the system. We can capture intent now (storing it still requires event sourcing, but you can implement event sourcing without doing CQRS) We can create a rich domain model (as opposed to an anemic domain model) Scalability is obviously a benefit that CQRS brings to the table, but like Greg says, very few of the systems we create truly need significant scalability Greg talks about the ability to scale your development efforts. He says CQRS allows you to split the system into 3 parts (Client, Domain/Commands, Reads) and assign 3 teams of developers to work on them in parallel; letting you scale your development efforts by 3x with nearly linear gains. But in the stereotypical architecture don’t you already have 2 separate modules that you can split your dev efforts between: The client that sends commands/queries and receives DTO’s, and the Domain which accepts commands/queries, and generates events/DTO’s. If this is true it’s not really a 3x scaling you achieve with CQRS but merely a 1.5x scaling which while great doesn’t sound nearly as dramatic (“I can do it with 10 devs in 12 months – let me hire 5 more and we can have it done in 8 months”). Making the Query side “stupid simple” such that you can assign junior developers (or even outsource it) sounds like a valid benefit, but I have some concerns over what you do with complex query-based logic/behavior. I’m going to go into more detail on this in a follow-up blog post shortly. He also seemed to focus on how “stupid-simple” it is doing queries against the de-normalized data store, but I imagine there is still significant complexity in the event handlers that interpret the events and apply them to the de-normalized tables. It sounds like Greg suggests that because we’re doing CQRS that allows us to apply Event Sourcing when we otherwise wouldn’t be able to (~33:30 in the video). I don’t believe this is true. I don’t see why you wouldn’t be able to apply Event Sourcing without separating out the Commands and Queries. The queries would just operate against the domain model instead of the database. But you’d still get the benefits of Event Sourcing. Without CQRS the queries would only be able to operate against the current state rather than the event history, but even in CQRS the domain behaviors can only operate against the current state and I don’t see that being a big limiting factor. If some query needs to operate against something that is not captured by the current state you would just have to update the domain model to capture that information (no different than if that statement were made about a Command under CQRS). Some of the benefits I do see being applicable are that your domain model might end up being simpler/smaller since it only needs to represent the state needed to process commands and not worry about the reads (like the Deactivate Inventory Item and associated comment example that Greg provides). And also commands that can be handled in a Transaction Script style manner by the command handler simply generating events and not touching the domain model. It also makes it easier for your senior developers to focus on the command behavior and ignore the queries, which is usually going to be a better use of their time. And of course scalability. If anybody out there has any thoughts on this and can help educate me further, please either leave a comment or feel free to get in touch with me via email:

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  • Algorithmia Source Code released on CodePlex

    - by FransBouma
    Following the release of our BCL Extensions Library on CodePlex, we have now released the source-code of Algorithmia on CodePlex! Algorithmia is an algorithm and data-structures library for .NET 3.5 or higher and is one of the pillars LLBLGen Pro v3's designer is built on. The library contains many data-structures and algorithms, and the source-code is well documented and commented, often with links to official descriptions and papers of the algorithms and data-structures implemented. The source-code is shared using Mercurial on CodePlex and is licensed under the friendly BSD2 license. User documentation is not available at the moment but will be added soon. One of the main design goals of Algorithmia was to create a library which contains implementations of well-known algorithms which weren't already implemented in .NET itself. This way, more developers out there can enjoy the results of many years of what the field of Computer Science research has delivered. Some algorithms and datastructures are known in .NET but are re-implemented because the implementation in .NET isn't efficient for many situations or lacks features. An example is the linked list in .NET: it doesn't have an O(1) concat operation, as every node refers to the containing LinkedList object it's stored in. This is bad for algorithms which rely on O(1) concat operations, like the Fibonacci heap implementation in Algorithmia. Algorithmia therefore contains a linked list with an O(1) concat feature. The following functionality is available in Algorithmia: Command, Command management. This system is usable to build a fully undo/redo aware system by building your object graph using command-aware classes. The Command pattern is implemented using a system which allows transparent undo-redo and command grouping so you can use it to make a class undo/redo aware and set properties, use its contents without using commands at all. The Commands namespace is the namespace to start. Classes you'd want to look at are CommandifiedMember, CommandifiedList and KeyedCommandifiedList. See the CommandQueueTests in the test project for examples. Graphs, Graph algorithms. Algorithmia contains a sophisticated graph class hierarchy and algorithms implemented onto them: non-directed and directed graphs, as well as a subgraph view class, which can be used to create a view onto an existing graph class which can be self-maintaining. Algorithms include transitive closure, topological sorting and others. A feature rich depth-first search (DFS) crawler is available so DFS based algorithms can be implemented quickly. All graph classes are undo/redo aware, as they can be set to be 'commandified'. When a graph is 'commandified' it will do its housekeeping through commands, which makes it fully undo-redo aware, so you can remove, add and manipulate the graph and undo/redo the activity automatically without any extra code. If you define the properties of the class you set as the vertex type using CommandifiedMember, you can manipulate the properties of vertices and the graph contents with full undo/redo functionality without any extra code. Heaps. Heaps are data-structures which have the largest or smallest item stored in them always as the 'root'. Extracting the root from the heap makes the heap determine the next in line to be the 'maximum' or 'minimum' (max-heap vs. min-heap, all heaps in Algorithmia can do both). Algorithmia contains various heaps, among them an implementation of the Fibonacci heap, one of the most efficient heap datastructures known today, especially when you want to merge different instances into one. Priority queues. Priority queues are specializations of heaps. Algorithmia contains a couple of them. Sorting. What's an algorithm library without sort algorithms? Algorithmia implements a couple of sort algorithms which sort the data in-place. This aspect is important in situations where you want to sort the elements in a buffer/list/ICollection in-place, so all data stays in the data-structure it already is stored in. PropertyBag. It re-implements Tony Allowatt's original idea in .NET 3.5 specific syntax, which is to have a generic property bag and to be able to build an object in code at runtime which can be bound to a property grid for editing. This is handy for when you have data / settings stored in XML or other format, and want to create an editable form of it without creating many editors. IEditableObject/IDataErrorInfo implementations. It contains default implementations for IEditableObject and IDataErrorInfo (EditableObjectDataContainer for IEditableObject and ErrorContainer for IDataErrorInfo), which make it very easy to implement these interfaces (just a few lines of code) without having to worry about bookkeeping during databinding. They work seamlessly with CommandifiedMember as well, so your undo/redo aware code can use them out of the box. EventThrottler. It contains an event throttler, which can be used to filter out duplicate events in an event stream coming into an observer from an event. This can greatly enhance performance in your UI without needing to do anything other than hooking it up so it's placed between the event source and your real handler. If your UI is flooded with events from data-structures observed by your UI or a middle tier, you can use this class to filter out duplicates to avoid redundant updates to UI elements or to avoid having observers choke on many redundant events. Small, handy stuff. A MultiValueDictionary, which can store multiple unique values per key, instead of one with the default Dictionary, and is also merge-aware so you can merge two into one. A Pair class, to quickly group two elements together. Multiple interfaces for helping with building a de-coupled, observer based system, and some utility extension methods for the defined data-structures. We regularly update the library with new code. If you have ideas for new algorithms or want to share your contribution, feel free to discuss it on the project's Discussions page or send us a pull request. Enjoy!

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