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  • Is this the correct way to build a Perl hash that utilizes arrays?

    - by Structure
    This is the first time I have manipulated hashes and arrays in this way -- and it is working. Basically, for every key there are multiple values that I want to record and then print out in the form "key -- value -- value -- val..." My code is as follows. I am surprised that it works, so concerned that it works "by mistake". Is this the correct way to accomplish this task, or is there a more efficient or appropriate method? while ($source =~ m/(regex)/g) { #Get all key names from source $listkey = $1; #Set current list key to the current regex result. $list{$listkey} = ++$i unless $list{$listkey}; #Add the key to the hash unless it already exists. $list{$listkey} = [] unless exists $list{$listkey}; #Add an array for the hash unless the hash already exists. while ($loopcount==0) { if ($ifcount==0) { $listvalue=result_of_some_function_using_list_key; #Get the first list value from the list key. $ifcount++; #Increment so we only get the first list value once. } else { $listvalue=result_of_some_function_using_list_value; #Update the last list value. } if ($listvalue) { #If the function returned a value... push @{$list{$listkey}}, $listvalue; #...then add the value to the hash array for the key. } else { #There are no more values and we need a new key. $listkey=0; #Reset variable. $domain=0; #Reset variable. $loopcount++; #Increment loop counter to exit loop. } } $ifcount=0; #Reset count variable so the next listvalue can be generated from the new key. $loopcount=0; #Reset count variable so another loop can begin for a new key. } foreach $listkey (keys %list) { #For each key in the hash. print "$listkey --> "; #Print the key. @values = @{$list{$listkey}}; #Reference the arrays of the hash. print join ' --> ', @values; #Print the values. print "\n"; #Print new line. }

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  • How can I save/print values in my WATCH list in Visual Studio 2008?

    - by Rising Star
    When I attach the Visual Studio 2008 debugger to my web server process, I sometimes browse a large amount of data in my watch list. Suppose I have an array of string variable that I expand to show 20 entries. It seems that the only way to save these values is to copy and paste them one at a time. I have gone so far as to do a screen-shot in order to have a record of what the values were (to refer to later or print a hard copy). Is there an easy way to save and print these values? I am familiar with the new "IntelliTrace" feature in Visual Studio 2010 Ultimate, but it seems overkill for this purpose. I just want to take something like an array of strings and save it for later reference once I've stopped the debugger. What's a good way to do this?

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  • PHP, how can I produce a string, a unique list of values up to three items, for use after IN in a query?

    - by Jules
    I need to produce a string for use in an query e.g. SELECT whatever from Keywords.word IN (here); At the moment I have string which could be $search = "one word or four"; or $search = "one"; or $search = "one one"; I need to validate this into some acceptable for my query. I want a unique list of words, separated with a comma up to a maximum of three. This is what I have so far. $array = explode(" ",$search); $unique = array_unique ($array); I'm sure there must be a quicker way than evaluating each of the items for blank and selecting the first three.

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  • What is the most efficient way to pass data (list of pairs of [Integer + Double]) between two Google App Engine instances?

    - by ruslan
    What is the most efficient way to pass data (list of pairs of [Integer, Double]) between two Google App Engine instances ? Currently I use Java binary serialization. Frontend servlet receives data from the client in JSON format. I convert it to byte[] using ObjectOutput.writeObject and then send it to backend servlet via HTTP POST. It's not in production yet. Should I just pass client's JSON as it is to backend? It seems more logical. But it's bigger in size. Or should I use Google Protocol Buffers as stated in this benchmark article ? Thank you!!!

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  • JQuery not removeing added element

    - by Scott
    What I want to do is add and remove list items. I have got it to add new items to the list and I can remove existing ones but not the ones that have been added. It seem like it would work but it doesn't. Any help would be appreciated! Here the code: JQuery: <script type="text/javascript"> $(function(){ $('a#add').click(function(){ $('<li><a href="#" id="remove">--</a>List item</li>').appendTo('ul#list'); }); $('a#remove').click(function(){ $(this).parent().remove(); }); }); </script> HTML: <a href="#" id="add">Add List Item</a> <ul id="list"> <li><a href="#" id="remove">--</a> List item</li> <li><a href="#" id="remove">--</a> List item</li> <li><a href="#" id="remove">--</a> List item</li> <li><a href="#" id="remove">--</a> List item</li> </ul>

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  • how i insert values from list of Data Grid View,current time ,EmployeeID using button click event (C

    - by Six fourty
    hi, it show me this error Incorrect syntax near the keyword 'Select' to make to clear Employee ID in this case is FK in the table (Attendance detail) and the other thing is i am using Data Grid View from another table(Employee information) to Show the list of the staff in my form. then i want to transfer each selected cell value from Data Grid View to attendance detail table. 10q private void time_in_Click(object sender, EventArgs e) { employee_InformationDataGridView.SelectedCells[0].Style.ForeColor = Color.Green; time_in.Enabled = false; time_out.Enabled = true; con = new SqlConnection(GlobalClass.conn); con.Open(); SqlCommand cmd = new SqlCommand("Insert into Attendancedetail Values(" + "Select from EmployeeInformation(EmployeeID)" + ",'" + employee_InformationDataGridView.SelectedCells[0] + "','" + DateTime.Now.ToLongDateString() + "','" + null + "','" + null + "','" + DateTime.Now.ToLongTimeString() + "'," + null + ")", con); int i = cmd.ExecuteNonQuery(); MessageBox.Show(i.ToString() + " record inserted"); }

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  • The data structure of libev watchers

    - by changchang
    Libev uses three data structures to storage different watchers. Heap: for watchers that sorted by time, such as ev_timer and ev_periodic. Linked list: such as ev_io, ev_signal, ev_child and etc. Array: such as ev_prepare, ev_check, ev_async and etc. There is no doubt about that uses heap to store timer watcher. But what is the criteria of selecting linked list and array? The data structure that stores ev_io watchers seems a little complex. It first is an array that with fd as its index and the element in the array is a linked list of ev_io watcher. It is more convenient to allocate space for array if use linked list as element. Is it the reason? Or just because of the insert or remove operation of ev_io is more frequently and the ev_prepare seems more stable? Or any other reasons?

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  • Is it possible to combine a list of torrents into one torrent with many files, keeping the seeds?

    - by Zequez
    Let's say you have all the episodes of FOO series that you downloaded as they were out, so you have like 20 torrents. Now let's say you want to make a bundle torrent with all the files, call it "FOO Season 1", and then send it to someone. One way would be to create a new torrent with all the episodes, but you would lose all the seeds from the current torrents, and you also couldn't seed people that want to download single episodes. Is this possible with the BitTorrent protocol?

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  • After upgrading to 2.6.35-24 kernel, why does adb no longer list devices?

    - by nbolton
    When I first installed Ubuntu 10.10 64-bit, I was able to see a physical Android device (connected via USB) in the Android Device Chooser (launched from Eclipse). But, after upgrading my kernel from 2.6.35-22-generic to 2.6.35-24-generic, no devices are listed any more, and I am unable to see any results when running adb devices like so: $ ./adb devices List of devices attached $ I have tried booting in the previous kernel version, but I get some udev error, so I was hoping I could get it working with the newer kernel version. I figured SO was the best place for this question, as it seems more developer related.

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  • Easily view a list of changes of upgraded packages.

    - by D Connors
    So, let's say I run sudo apt-get upgrade on my Lucid Lynx and it upgrades a couple of packages I'm interested in. Is there a command to run that will open some kind of info or manual that tells me what changes were made in this new version of the package? For instance, if run the apt-get upgrade and it installs a new version of empathy. Do I have to go over to their site to review the changes made in this version, or is there a quicker command line way?

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  • How does java.util.Collections.contains() perform faster than a linear search?

    - by The111
    I've been fooling around with a bunch of different ways of searching collections, collections of collections, etc. Doing lots of stupid little tests to verify my understanding. Here is one which boggles me (source code further below). In short, I am generating N random integers and adding them to a list. The list is NOT sorted. I then use Collections.contains() to look for a value in the list. I intentionally look for a value that I know won't be there, because I want to ensure that the entire list space is probed. I time this search. I then do another linear search manually, iterating through each element of the list and checking if it matches my target. I also time this search. On average, the second search takes 33% longer than the first one. By my logic, the first search must also be linear, because the list is unsorted. The only possibility I could think of (which I immediately discard) is that Java is making a sorted copy of my list just for the search, but (1) I did not authorize that usage of memory space and (2) I would think that would result in MUCH more significant time savings with such a large N. So if both searches are linear, they should both take the same amount of time. Somehow the Collections class has optimized this search, but I can't figure out how. So... what am I missing? import java.util.*; public class ListSearch { public static void main(String[] args) { int N = 10000000; // number of ints to add to the list int high = 100; // upper limit for random int generation List<Integer> ints; int target = -1; // target will not be found, forces search of entire list space long start; long end; ints = new ArrayList<Integer>(); start = System.currentTimeMillis(); System.out.print("Generating new list... "); for (int i = 0; i < N; i++) { ints.add(((int) (Math.random() * high)) + 1); } end = System.currentTimeMillis(); System.out.println("took " + (end-start) + "ms."); start = System.currentTimeMillis(); System.out.print("Searching list for target (method 1)... "); if (ints.contains(target)) { // nothing } end = System.currentTimeMillis(); System.out.println(" Took " + (end-start) + "ms."); System.out.println(); ints = new ArrayList<Integer>(); start = System.currentTimeMillis(); System.out.print("Generating new list... "); for (int i = 0; i < N; i++) { ints.add(((int) (Math.random() * high)) + 1); } end = System.currentTimeMillis(); System.out.println("took " + (end-start) + "ms."); start = System.currentTimeMillis(); System.out.print("Searching list for target (method 2)... "); for (Integer i : ints) { // nothing } end = System.currentTimeMillis(); System.out.println(" Took " + (end-start) + "ms."); } }

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  • Show different product image in new.phtml vs. list

    - by user1907662
    $collection = $this->_addProductAttributesAndPrices($collection) ->addStoreFilter() ->addAttributeToFilter('is_discontinued', array('neq' => 1) ) ->addAttributeToFilter('collection_id', array('neq' => 'LKG') ) ->addAttributeToFilter('media_gallery_label', array('eq' => 'Home Page Image') ) //->addAttributeToSort('entity_id', 'desc') ->addAttributeToSort('news_from_date', 'desc') For the media_gallery_label field, I need to be able to filter by any gallery images, and if the label of any of the images is "Home Page Image", it needs to display instead of the default "small" image. I need this to work only in new.phtml file, and not in the list.phtml.

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  • Does C# 4's covariance support nesting of generics?

    - by Scott Bilas
    I don't understand why 'x' below converts, but 'y' and 'z' do not. var list = new List<List<int>>(); IEnumerable<List<int>> x = list; List<IEnumerable<int>> y = list; IEnumerable<IEnumerable<int>> z = list; Does the new covariance feature simply not work on generics of generics or am I doing something wrong? (I'd like to avoid using .Cast< to make y and z work.)

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  • How to write a query get all infomation from one table to another one

    - by Dave
    I am building access database that will get data from a outside source and place it in a table that is link to the data source. As we all know that you are not allowed to recinfigure that linked table. What I want to do is take that data from that that linked table and make another table that I will be able to add additional new fields and snyc the out that gets put into the linked table. Please Help

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  • Use Python to search one .txt file for a list of words or phrases (and show the context)

    - by prupert
    Basically as the question states. I am fairly new to Python and like to learn by seeing and doing. I would like to create a script that searches through a text document (say the text copied and pasted from a news article for example) for certain words or phrases. Ideally, the list of words and phrases would be stored in a separate file. When getting the results, it would be great to get the context of the results. So maybe it could print out the 50 characters in the text file before and after each search term that has been found. It'd be cool if it also showed what line the search term was found on. Any pointers on how to code this, or even code examples would be much appreciated.

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  • jQuery Templates and Data Linking (and Microsoft contributing to jQuery)

    - by ScottGu
    The jQuery library has a passionate community of developers, and it is now the most widely used JavaScript library on the web today. Two years ago I announced that Microsoft would begin offering product support for jQuery, and that we’d be including it in new versions of Visual Studio going forward. By default, when you create new ASP.NET Web Forms and ASP.NET MVC projects with VS 2010 you’ll find jQuery automatically added to your project. A few weeks ago during my second keynote at the MIX 2010 conference I announced that Microsoft would also begin contributing to the jQuery project.  During the talk, John Resig -- the creator of the jQuery library and leader of the jQuery developer team – talked a little about our participation and discussed an early prototype of a new client templating API for jQuery. In this blog post, I’m going to talk a little about how my team is starting to contribute to the jQuery project, and discuss some of the specific features that we are working on such as client-side templating and data linking (data-binding). Contributing to jQuery jQuery has a fantastic developer community, and a very open way to propose suggestions and make contributions.  Microsoft is following the same process to contribute to jQuery as any other member of the community. As an example, when working with the jQuery community to improve support for templating to jQuery my team followed the following steps: We created a proposal for templating and posted the proposal to the jQuery developer forum (http://forum.jquery.com/topic/jquery-templates-proposal and http://forum.jquery.com/topic/templating-syntax ). After receiving feedback on the forums, the jQuery team created a prototype for templating and posted the prototype at the Github code repository (http://github.com/jquery/jquery-tmpl ). We iterated on the prototype, creating a new fork on Github of the templating prototype, to suggest design improvements. Several other members of the community also provided design feedback by forking the templating code. There has been an amazing amount of participation by the jQuery community in response to the original templating proposal (over 100 posts in the jQuery forum), and the design of the templating proposal has evolved significantly based on community feedback. The jQuery team is the ultimate determiner on what happens with the templating proposal – they might include it in jQuery core, or make it an official plugin, or reject it entirely.  My team is excited to be able to participate in the open source process, and make suggestions and contributions the same way as any other member of the community. jQuery Template Support Client-side templates enable jQuery developers to easily generate and render HTML UI on the client.  Templates support a simple syntax that enables either developers or designers to declaratively specify the HTML they want to generate.  Developers can then programmatically invoke the templates on the client, and pass JavaScript objects to them to make the content rendered completely data driven.  These JavaScript objects can optionally be based on data retrieved from a server. Because the jQuery templating proposal is still evolving in response to community feedback, the final version might look very different than the version below. This blog post gives you a sense of how you can try out and use templating as it exists today (you can download the prototype by the jQuery core team at http://github.com/jquery/jquery-tmpl or the latest submission from my team at http://github.com/nje/jquery-tmpl).  jQuery Client Templates You create client-side jQuery templates by embedding content within a <script type="text/html"> tag.  For example, the HTML below contains a <div> template container, as well as a client-side jQuery “contactTemplate” template (within the <script type="text/html"> element) that can be used to dynamically display a list of contacts: The {{= name }} and {{= phone }} expressions are used within the contact template above to display the names and phone numbers of “contact” objects passed to the template. We can use the template to display either an array of JavaScript objects or a single object. The JavaScript code below demonstrates how you can render a JavaScript array of “contact” object using the above template. The render() method renders the data into a string and appends the string to the “contactContainer” DIV element: When the page is loaded, the list of contacts is rendered by the template.  All of this template rendering is happening on the client-side within the browser:   Templating Commands and Conditional Display Logic The current templating proposal supports a small set of template commands - including if, else, and each statements. The number of template commands was deliberately kept small to encourage people to place more complicated logic outside of their templates. Even this small set of template commands is very useful though. Imagine, for example, that each contact can have zero or more phone numbers. The contacts could be represented by the JavaScript array below: The template below demonstrates how you can use the if and each template commands to conditionally display and loop the phone numbers for each contact: If a contact has one or more phone numbers then each of the phone numbers is displayed by iterating through the phone numbers with the each template command: The jQuery team designed the template commands so that they are extensible. If you have a need for a new template command then you can easily add new template commands to the default set of commands. Support for Client Data-Linking The ASP.NET team recently submitted another proposal and prototype to the jQuery forums (http://forum.jquery.com/topic/proposal-for-adding-data-linking-to-jquery). This proposal describes a new feature named data linking. Data Linking enables you to link a property of one object to a property of another object - so that when one property changes the other property changes.  Data linking enables you to easily keep your UI and data objects synchronized within a page. If you are familiar with the concept of data-binding then you will be familiar with data linking (in the proposal, we call the feature data linking because jQuery already includes a bind() method that has nothing to do with data-binding). Imagine, for example, that you have a page with the following HTML <input> elements: The following JavaScript code links the two INPUT elements above to the properties of a JavaScript “contact” object that has a “name” and “phone” property: When you execute this code, the value of the first INPUT element (#name) is set to the value of the contact name property, and the value of the second INPUT element (#phone) is set to the value of the contact phone property. The properties of the contact object and the properties of the INPUT elements are also linked – so that changes to one are also reflected in the other. Because the contact object is linked to the INPUT element, when you request the page, the values of the contact properties are displayed: More interesting, the values of the linked INPUT elements will change automatically whenever you update the properties of the contact object they are linked to. For example, we could programmatically modify the properties of the “contact” object using the jQuery attr() method like below: Because our two INPUT elements are linked to the “contact” object, the INPUT element values will be updated automatically (without us having to write any code to modify the UI elements): Note that we updated the contact object above using the jQuery attr() method. In order for data linking to work, you must use jQuery methods to modify the property values. Two Way Linking The linkBoth() method enables two-way data linking. The contact object and INPUT elements are linked in both directions. When you modify the value of the INPUT element, the contact object is also updated automatically. For example, the following code adds a client-side JavaScript click handler to an HTML button element. When you click the button, the property values of the contact object are displayed using an alert() dialog: The following demonstrates what happens when you change the value of the Name INPUT element and click the Save button. Notice that the name property of the “contact” object that the INPUT element was linked to was updated automatically: The above example is obviously trivially simple.  Instead of displaying the new values of the contact object with a JavaScript alert, you can imagine instead calling a web-service to save the object to a database. The benefit of data linking is that it enables you to focus on your data and frees you from the mechanics of keeping your UI and data in sync. Converters The current data linking proposal also supports a feature called converters. A converter enables you to easily convert the value of a property during data linking. For example, imagine that you want to represent phone numbers in a standard way with the “contact” object phone property. In particular, you don’t want to include special characters such as ()- in the phone number - instead you only want digits and nothing else. In that case, you can wire-up a converter to convert the value of an INPUT element into this format using the code below: Notice above how a converter function is being passed to the linkFrom() method used to link the phone property of the “contact” object with the value of the phone INPUT element. This convertor function strips any non-numeric characters from the INPUT element before updating the phone property.  Now, if you enter the phone number (206) 555-9999 into the phone input field then the value 2065559999 is assigned to the phone property of the contact object: You can also use a converter in the opposite direction also. For example, you can apply a standard phone format string when displaying a phone number from a phone property. Combining Templating and Data Linking Our goal in submitting these two proposals for templating and data linking is to make it easier to work with data when building websites and applications with jQuery. Templating makes it easier to display a list of database records retrieved from a database through an Ajax call. Data linking makes it easier to keep the data and user interface in sync for update scenarios. Currently, we are working on an extension of the data linking proposal to support declarative data linking. We want to make it easy to take advantage of data linking when using a template to display data. For example, imagine that you are using the following template to display an array of product objects: Notice the {{link name}} and {{link price}} expressions. These expressions enable declarative data linking between the SPAN elements and properties of the product objects. The current jQuery templating prototype supports extending its syntax with custom template commands. In this case, we are extending the default templating syntax with a custom template command named “link”. The benefit of using data linking with the above template is that the SPAN elements will be automatically updated whenever the underlying “product” data is updated.  Declarative data linking also makes it easier to create edit and insert forms. For example, you could create a form for editing a product by using declarative data linking like this: Whenever you change the value of the INPUT elements in a template that uses declarative data linking, the underlying JavaScript data object is automatically updated. Instead of needing to write code to scrape the HTML form to get updated values, you can instead work with the underlying data directly – making your client-side code much cleaner and simpler. Downloading Working Code Examples of the Above Scenarios You can download this .zip file to get with working code examples of the above scenarios.  The .zip file includes 4 static HTML page: Listing1_Templating.htm – Illustrates basic templating. Listing2_TemplatingConditionals.htm – Illustrates templating with the use of the if and each template commands. Listing3_DataLinking.htm – Illustrates data linking. Listing4_Converters.htm – Illustrates using a converter with data linking. You can un-zip the file to the file-system and then run each page to see the concepts in action. Summary We are excited to be able to begin participating within the open-source jQuery project.  We’ve received lots of encouraging feedback in response to our first two proposals, and we will continue to actively contribute going forward.  These features will hopefully make it easier for all developers (including ASP.NET developers) to build great Ajax applications. Hope this helps, Scott P.S. [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu]

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  • Do’s and Don’ts Building SharePoint Applications

    - by Bil Simser
    SharePoint is a great platform for building quick LOB applications. Simple things from employee time trackers to server and software inventory to full blown Help Desks can be crafted up using SharePoint from just customizing Lists. No programming necessary. However there are a few tricks I’ve painfully learned over the years that you can use for your own solutions. DO What’s In A Name? When you create a new list, column, or view you’ll commonly name it something like “Expense Reports”. However this has the ugly effect of creating a url to the list as “Expense%20Reports”. Or worse, an internal field name of “Expense_x0x0020_Reports” which is not only cryptic but hard to remember when you’re trying to find the column by internal name. While “Expense Reports 2011” is user friendly, “ExpenseReports2011” is not (unless you’re a programmer). So that’s not the solution. Well, not entirely. Instead when you create your column or list or view use the scrunched up name (I can’t think of the technical term for it right now) of “ExpenseReports2011”, “WomenAtTheOfficeThatAreMen” or “KoalaMeatIsGoodWhenBroiled”. After you’ve created it, go back and change the name to the more friendly “Silly Expense Reports That Nobody Reads”. The original internal name will be the url and code friendly one without spaces while the one used on data entry forms and view headers will be the human version. Smart Columns When building a view include columns that make sense. By default when you add a column the “Add to default view” is checked. Resist the urge to be lazy and leave it checked. Uncheck that puppy and decide consciously what columns should be included in the view. Pick columns that make sense to what the user is trying to do. This means you have to talk to the user. Yes, I know. That can be trying at times and even painful. Go ahead, talk to them. You might learn something. Find out what’s important to them and why. If they’re doing something repetitively as part of their job, try to make their life easier by including what’s most important to them. Do they really need to see the Created *and* Modified date of a document or do they just need the title and author? You’ll only find out after talking to them (or getting them drunk in a bar and leaving them in the back alley handcuffed to a garbage bin, don’t ask). Gotta Keep it Separated Hey, views are there for a reason. Use them. While “All Items” is a fine way to present a list of well, all items, it’s hardly sufficient to present a list of servers built before the Y2K bug hit. You’ll be scrolling the list for hours finally arriving at Page 387 of 12,591 and cursing that SharePoint guy for convincing you that putting your hardware into a list would be of any use to anyone. Next to collecting the data, presenting it is just as important. Views are often overlooked and many times ignored or misused. They’re the way you can slice and dice the data up so that you’re not trying to consume 3,000 years of human evolution on a single web page. Remember views can be filtered so feel free to create a view for each status or one for each operating system or one for each species of Information Worker you might be putting in that list or document library. Not only will it reduce the number of items someone sees at one time, it’ll also make the information that much more relevant. Also remember that each view is a separate page. Use it in navigation by creating a menu on the Quick Launch to each view. The discoverability of the Views menu isn’t overly obvious and if you violate the rule of columns (see Horizontally Scrolling below) the view menu doesn’t even show up until you shuffle the scroll bar to the left. Navigation links, big giant buttons, a screaming flashing “CLICK ME NOW” will help your users find their way. Sort It! Views are great so we’re building nice, rich views for the user. Awesomesauce. However sort is not very discoverable by the user. For example when you’re looking at a view how do you know if it’s ascending or descending and what is it sorted on. Maybe it’s sorted using two fields so what’s that all about? Help your users by letting them know the information they’re looking at is sorted. Maybe you name the view something appropriate like “Bogus Expense Claims Sorted By Deadbeats”. If you use the naming strategy just make sure you keep the name consistent with the description. In the previous example their better be a Deadbeat column so I can see the sort in action. Having a “Loser” column, while equally correct, is a little obtuse to the average Information Worker. Remember, they usually don’t use acronyms and even if they knew how to, it’s not immediately obvious to them that’s what you’re trying to convey. Another option is to simply drop a Content Editor Web Part above the list and explain exactly the view they’re looking at. Each view is it’s own page so one CEWP won’t be used across the board. Be descriptive in what the user is seeing but try to keep it brief. Dumping the first chapter of I, Claudius might be informative to the data but can gobble up screen real estate and miss the point of having the list. DO NOT Useless Attachments The attachments column is, in a word, useless. For the most part. Sure it indicates there’s an attachment on the list item but in the grand scheme of things that’s not overly informative. Maybe it is and by all means, if it makes sense to you include it. Colour it. Make it shine and stand like the Return of Clippy on every SharePoint list. Without it being functional it can be boring. EndUserSharePoint.com has an article to make the son of Clippy that much more useful so feel free to head over and check out this blog post by Paul Grenier on the task (Warning code ahead! Danger Will Robinson!) In any case, I would suggest you remove it from your views. Again if it’s important then include it but consider the jQuery solution above to make it functional. It’s added by default to views and one of things that people forget to clean up. Horizontal Scrolling Screen real estate is premium so building a list that contains 8,000 columns and stretches horizontally across 15 screens probably isn’t the most user friendly experience. Most users can’t figure out how to scroll vertically let alone horizontally so don’t make it even that more confusing for them. Take the Steve Krug approach in your view designs and try not to make the user think. Again views are your friend. Consider splitting up the data into views where one view contains 10 columns and other view contains the other 10. Okay, maybe your information doesn’t work that way but humans can only process 7 pieces of data at a time, 10 at most (then their heads explode and you don’t want to clean that mess up, especially on a Friday night before the big dance). It drives me batshit crazy when I see a view with 80 columns of data. I often ask the user “So what do you do with all this information”. The response is usually “With this data [the first 10 columns] I decide if I’m going to fire everyone, and with this data [the next 10 columns] I decide if I’m going to set the building on fire and collect the insurance”. It’s at that point I show them how to create two new views “People Who Are About To Get The Axe” and “Beach Time For The Executives”. Again, talk to your users and try to reason with them on cutting down the number of columns they see at once. Vertical Scrolling Another big faux pas I find is the use of multi-line comment fields in views. It’s not so bad when you have a statement like this in your view: “I really like, oh my god, thought I was going to scream when I saw this turtle then I decided what I was going to have for dinner and frankly I hate having to work late so when I was talking to the customer I thought, oh my god, what if the customer has turtles and then it appeared to me that I really was hungry so I'm going to have lunch now.” It’s fine if that’s the only column along with two or three others, but once you slap those 20 columns of data into the list, the comment field wraps and forms a new multi-page novel that takes up your entire screen. Do everyone a favour and just avoid adding the column to views. Train the user to just click through to the item if they need to see the contents. Duplicate Information Duplication is never good. Views and great as you can group data together. For example create a view of project status reports grouped by author. Then you can see what project manager is being a dip and not submitting their report. However if you group by author do you really need the Created By field as well in the view? Or if the view is grouped by Project then Author do you need both. Horizontal real estate is always at a premium so try not to clutter up the view with duplicate data like this. Oh  yeah, if you’re scratching your head saying “But Bil, if I don’t include the Project name in the view and I have a lot of items then how do I know which one I’m looking at”. That’s a hint that your grouping is too vague or you have too much data in the view based on that criteria. Filter it down a notch, create some views, and try to keep the group down to a single screen where you can see the group header at the top of the page. Again it’s just managing the information you have. Redundant, See Redundant This partially relates to duplicate information and smart columns but basically remember to not include the obvious in a view. Remember, don’t make me think. If you’ve gone to the trouble (and it was a lot of trouble wasn’t it?) to create separate views of your data by creating a “September Zombie Brain Sales”, “October Zombie Brain Sales”, etc. then please for the love of all that is holy do not include the Month and Product columns in your view. Similarly if you create a “My” view of anything (“My Favourite Brands of Spandex”, “My Co-Workers I Find The Urge To Disinfect”) then again, do not include the owner or author field (or whatever field you use to identify “My”). That’s just silly. Hope that helps! Happy customizing!

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  • Displaying device contacts with an indication that the contact is registered to the app

    - by Prasanna Aarthi
    We are developing a mobile app that needs to pick up device contacts, display them and indicate if the contact has already registered with this app. We have our DB in the server and the app fetches data using web services. What will be the best approach to implement the above scenario taking performance into consideration. Option 1: Every time user opens the app,fetch the contacts and send the list of email addresses to the server, check with the registered email ids and return the list of registered users in the contact list. In this approach whenever user opens the particular page, he needs to wait for few seconds to load data, but the contacts will be the latest from the device. Option 2: First time when the user opens the app, fetch contacts ,send the entire list of contacts and save it in the DB, retrieve list of registered users in the contacts then save this to local DB. From now on, data will be fetched from local DB and displayed. When a new user registers in the app, again check with records in central DB and send list of new users who are in your contacts that have registered to your app. This list will be added to local DB. and the process continues. In this case the new contacts added by user will not be updated in the app but retrieval and display of records would be quick. What would be the correct approach? In case there is a better way of doing this, please let me know.

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  • Redirecting to a dynamic page

    - by binarydev
    I have a page displaying blog posts (latest_posts.php) and another page that display single blog posts (blog.php) . I intend to link the image title in latest_posts.php so that it redirects to blog.php where it would display the particular post that was clicked. latest_posts.php: <!-- Header --> <h2 class="underline"> <span>What&#039;s new</span> <span></span> </h2> <!-- /Header --> <!-- Posts list --> <ul class="post-list post-list-1"> <?php /* Fetches Date/Time, Post Content and title */ include 'dbconnect.php'; $sql = "SELECT * FROM wp_posts"; $res = mysql_query($sql); while ( $row = mysql_fetch_array($res) ) { ?> <!-- Post #1 --> <li class="clear-fix"> <!-- Date --> <div class="post-list-date"> <div class="post-date-box"> <?php //Timestamp broken down to show accordingly $timestamp = $row['post_date']; $datetime = new DateTime($timestamp); $date = $datetime->format("d"); $month = $datetime->format("M"); ?> <h3> <?php echo $date; ?> </h3> <span> <?php echo $month; ?> </span> </div> </div> <!-- /Date --> <!-- Image + comments count --> <div class="post-list-image"> <!-- Image --> <div class="image image-overlay-url image-fancybox-url"> <a href="post.php" class="preloader-image"> <?php echo '<img src="', $row['image'], '" alt="' , $row['post_title'] , '\'s Blog Image" />'; ?> </a> </div> <!-- /Image --> </div> <!-- /Image + comments count --> <!-- Content --> <div class="post-list-content"> <div> <!-- Header --> <h4> <a href="post.php? . $row['ID'] . "> <?php echo $row['post_title']; ?> </a> </h4> <!-- /Header --> <!-- Excerpt --> <p> <?php echo $row ['post_content']; }?> </p> <!-- /Excerpt --> </div> </div> <!-- /Content --> </li> <!-- /Post #1 --> </ul> <!-- /Posts list --> <a href="blog.php" class="button-browse">Browse All Posts</a> </div> <?php require_once('include/twitter_user_timeline.php'); ?> blog.php: <?php require_once('include/header.php'); ?> <body class="blog"> <?php require_once('include/navigation_bar_blog.php'); ?> <div class="blog"> <div class="main"> <!-- Header --> <h2 class="underline"> <span>What&#039;s new</span> <span></span> </h2> <!-- /Header --> <!-- Layout 66x33 --> <div class="layout-p-66x33 clear-fix"> <!-- Left column --> <!-- <div class="column-left"> --> <!-- Posts list --> <ul class="post-list post-list-2"> <?php /* Fetches Date/Time, Post Content and title with Pagination */ include 'dbconnect.php'; //sets to default page if(empty($_GET['pn'])){ $page=1; } else { $page = $_GET['pn']; } // Index of the page $index = ($page-1)*3; $sql = "SELECT * FROM `wp_posts` ORDER BY `post_date` DESC LIMIT " . $index . " ,3"; $res = mysql_query($sql); //Loops through the values while ( $row = mysql_fetch_array($res) ) { ?> <!-- Post #1 --> <li class="clear-fix"> <!-- Date --> <div class="post-list-date"> <div class="post-date-box"> <?php //Timestamp broken down to show accordingly $timestamp = $row['post_date']; $datetime = new DateTime($timestamp); $date = $datetime->format("d"); $month = $datetime->format("M"); ?> <h3> <?php echo $date; ?> </h3> <span> <?php echo $month; ?> </span> </div> </div> <!-- /Date --> <!-- Image + comments count --> <div class="post-list-image"> <!-- Image --> <div class="image image-overlay-url image-fancybox-url"> <a href="post.php" class="preloader-image"> <?php echo '<img src="', $row['image'], '" alt="' , $row['post_title'] , '\'s Blog Image" />'; ?> </a> </div> <!-- /Image --> </div> <!-- /Image + comments count --> <!-- Content --> <div class="post-list-content"> <div> <?php $id = $_GET['ID']; $post = lookup_post_somehow($id); if($post) { // render post } else { echo 'blog post not found..'; } ?> <!-- Header --> <h4> <a href="post.php"> <?php echo $row['post_title']; ?> </a> </h4> <!-- /Header --> <!-- Excerpt --> <p> <?php echo $row ['post_content']; ?> </p> <!-- /Excerpt --> </div> </div> <!-- /Content --> </li> <!-- /Post #1 --> <?php } // close while loop ?> </ul> <!-- /Posts list --> <div><!-- Pagination --> <ul class="blog-pagination clear-fix"> <?php //Count the number of rows $numberofrows = mysql_query("SELECT COUNT(ID) FROM `wp_posts`"); //Do ciel() to round the result according to number of posts $postsperpage = 4; $numOfPages = ceil($numberofrows / $postsperpage); for($i=1; $i < $numOfPages; $i++) { //echos links for each page $paginationDisplay = '<li><a href="blog.php?pn=' . $i . '">' . $i . '</a></li>'; echo $paginationDisplay; } ?> <!-- <li><a href="#" class="selected">1</a></li> <li><a href="#">2</a></li> <li><a href="#">3</a></li> <li><a href="#">4</a></li> --> </ul> </div><!-- /Pagination --> <!-- /div> --> <!-- Left column --> </div> <!-- /Layout 66x33 --> </div> </div> <?php require_once('include/twitter_user_timeline.php'); ?> <?php require_once('include/footer_blog.php'); ?> How do I render?

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  • Database Migration Scripts: Getting from place A to place B

    - by Phil Factor
    We’ll be looking at a typical database ‘migration’ script which uses an unusual technique to migrate existing ‘de-normalised’ data into a more correct form. So, the book-distribution business that uses the PUBS database has gradually grown organically, and has slipped into ‘de-normalisation’ habits. What’s this? A new column with a list of tags or ‘types’ assigned to books. Because books aren’t really in just one category, someone has ‘cured’ the mismatch between the database and the business requirements. This is fine, but it is now proving difficult for their new website that allows searches by tags. Any request for history book really has to look in the entire list of associated tags rather than the ‘Type’ field that only keeps the primary tag. We have other problems. The TypleList column has duplicates in there which will be affecting the reporting, and there is the danger of mis-spellings getting there. The reporting system can’t be persuaded to do reports based on the tags and the Database developers are complaining about the unCoddly things going on in their database. In your version of PUBS, this extra column doesn’t exist, so we’ve added it and put in 10,000 titles using SQL Data Generator. /* So how do we refactor this database? firstly, we create a table of all the tags. */IF  OBJECT_ID('TagName') IS NULL OR OBJECT_ID('TagTitle') IS NULL  BEGIN  CREATE TABLE  TagName (TagName_ID INT IDENTITY(1,1) PRIMARY KEY ,     Tag VARCHAR(20) NOT NULL UNIQUE)  /* ...and we insert into it all the tags from the list (remembering to take out any leading spaces */  INSERT INTO TagName (Tag)     SELECT DISTINCT LTRIM(x.y.value('.', 'Varchar(80)')) AS [Tag]     FROM     (SELECT  Title_ID,          CONVERT(XML, '<list><i>' + REPLACE(TypeList, ',', '</i><i>') + '</i></list>')          AS XMLkeywords          FROM   dbo.titles)g    CROSS APPLY XMLkeywords.nodes('/list/i/text()') AS x ( y )  /* we can then use this table to provide a table that relates tags to articles */  CREATE TABLE TagTitle   (TagTitle_ID INT IDENTITY(1, 1),   [title_id] [dbo].[tid] NOT NULL REFERENCES titles (Title_ID),   TagName_ID INT NOT NULL REFERENCES TagName (Tagname_ID)   CONSTRAINT [PK_TagTitle]       PRIMARY KEY CLUSTERED ([title_id] ASC, TagName_ID)       ON [PRIMARY])        CREATE NONCLUSTERED INDEX idxTagName_ID  ON  TagTitle (TagName_ID)  INCLUDE (TagTitle_ID,title_id)        /* ...and it is easy to fill this with the tags for each title ... */        INSERT INTO TagTitle (Title_ID, TagName_ID)    SELECT DISTINCT Title_ID, TagName_ID      FROM        (SELECT  Title_ID,          CONVERT(XML, '<list><i>' + REPLACE(TypeList, ',', '</i><i>') + '</i></list>')          AS XMLkeywords          FROM   dbo.titles)g    CROSS APPLY XMLkeywords.nodes('/list/i/text()') AS x ( y )    INNER JOIN TagName ON TagName.Tag=LTRIM(x.y.value('.', 'Varchar(80)'))    END    /* That's all there was to it. Now we can select all titles that have the military tag, just to try things out */SELECT Title FROM titles  INNER JOIN TagTitle ON titles.title_ID=TagTitle.Title_ID  INNER JOIN Tagname ON Tagname.TagName_ID=TagTitle.TagName_ID  WHERE tagname.tag='Military'/* and see the top ten most popular tags for titles */SELECT Tag, COUNT(*) FROM titles  INNER JOIN TagTitle ON titles.title_ID=TagTitle.Title_ID  INNER JOIN Tagname ON Tagname.TagName_ID=TagTitle.TagName_ID  GROUP BY Tag ORDER BY COUNT(*) DESC/* and if you still want your list of tags for each title, then here they are */SELECT title_ID, title, STUFF(  (SELECT ','+tagname.tag FROM titles thisTitle    INNER JOIN TagTitle ON titles.title_ID=TagTitle.Title_ID    INNER JOIN Tagname ON Tagname.TagName_ID=TagTitle.TagName_ID  WHERE ThisTitle.title_id=titles.title_ID  FOR XML PATH(''), TYPE).value('.', 'varchar(max)')  ,1,1,'')    FROM titles  ORDER BY title_ID So we’ve refactored our PUBS database without pain. We’ve even put in a check to prevent it being re-run once the new tables are created. Here is the diagram of the new tag relationship We’ve done both the DDL to create the tables and their associated components, and the DML to put the data in them. I could have also included the script to remove the de-normalised TypeList column, but I’d do a whole lot of tests first before doing that. Yes, I’ve left out the assertion tests too, which should check the edge cases and make sure the result is what you’d expect. One thing I can’t quite figure out is how to deal with an ordered list using this simple XML-based technique. We can ensure that, if we have to produce a list of tags, we can get the primary ‘type’ to be first in the list, but what if the entire order is significant? Thank goodness it isn’t in this case. If it were, we might have to revisit a string-splitter function that returns the ordinal position of each component in the sequence. You’ll see immediately that we can create a synchronisation script for deployment from a comparison tool such as SQL Compare, to change the schema (DDL). On the other hand, no tool could do the DML to stuff the data into the new table, since there is no way that any tool will be able to work out where the data should go. We used some pretty hairy code to deal with a slightly untypical problem. We would have to do this migration by hand, and it has to go into source control as a batch. If most of your database changes are to be deployed by an automated process, then there must be a way of over-riding this part of the data synchronisation process to do this part of the process taking the part of the script that fills the tables, Checking that the tables have not already been filled, and executing it as part of the transaction. Of course, you might prefer the approach I’ve taken with the script of creating the tables in the same batch as the data conversion process, and then using the presence of the tables to prevent the script from being re-run. The problem with scripting a refactoring change to a database is that it has to work both ways. If we install the new system and then have to rollback the changes, several books may have been added, or had their tags changed, in the meantime. Yes, you have to script any rollback! These have to be mercilessly tested, and put in source control just in case of the rollback of a deployment after it has been in place for any length of time. I’ve shown you how to do this with the part of the script .. /* and if you still want your list of tags for each title, then here they are */SELECT title_ID, title, STUFF(  (SELECT ','+tagname.tag FROM titles thisTitle    INNER JOIN TagTitle ON titles.title_ID=TagTitle.Title_ID    INNER JOIN Tagname ON Tagname.TagName_ID=TagTitle.TagName_ID  WHERE ThisTitle.title_id=titles.title_ID  FOR XML PATH(''), TYPE).value('.', 'varchar(max)')  ,1,1,'')    FROM titles  ORDER BY title_ID …which would be turned into an UPDATE … FROM script. UPDATE titles SET  typelist= ThisTaglistFROM     (SELECT title_ID, title, STUFF(    (SELECT ','+tagname.tag FROM titles thisTitle      INNER JOIN TagTitle ON titles.title_ID=TagTitle.Title_ID      INNER JOIN Tagname ON Tagname.TagName_ID=TagTitle.TagName_ID    WHERE ThisTitle.title_id=titles.title_ID    ORDER BY CASE WHEN tagname.tag=titles.[type] THEN 1 ELSE 0  END DESC    FOR XML PATH(''), TYPE).value('.', 'varchar(max)')    ,1,1,'')  AS ThisTagList  FROM titles)fINNER JOIN Titles ON f.title_ID=Titles.title_ID You’ll notice that it isn’t quite a round trip because the tags are in a different order, though we’ve managed to make sure that the primary tag is the first one as originally. So, we’ve improved the database for the poor book distributors using PUBS. It is not a major deal but you’ve got to be prepared to provide a migration script that will go both forwards and backwards. Ideally, database refactoring scripts should be able to go from any version to any other. Schema synchronization scripts can do this pretty easily, but no data synchronisation scripts can deal with serious refactoring jobs without the developers being able to specify how to deal with cases like this.

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  • MultiSelectChoice: How to get underlying values selected

    - by Vijay Mohan
    Let's say you include a multiselectchoice component in your jspx/jsff page, which has <f;selectItem> or <af:forEach> binded to a VO iterator to populate the multiselectchoice and the value property of which is binded to a List attribute binding.When the user selects some items in that choice List then u want the actual values to be posted.You can check the valuepassthrough flag to true , but many a times it doesn't help and you end up getting the indexes of multiselect values.Here is a way to get the actual values..Lets say in the bean u have a utility method to achieve this as follows..You can associate a valueChangeListener for the multiselectchoice as follows..public void onValueChangeOfLOV(ValueChangeEvent valueChangeEvent) { //get array of indexes of selected items in master list List valueIndexes = (List)valueChangeEvent.getNewValue(); String concatCodes = returnSelectmanyChoiceValues(valueIndexes,"YourIterator", "YourAttribute"); } public String returnSelectmanyChoiceValues(List valueIndexes,String iterName, String idAttrName){ DCBindingContainer dc = (DCBindingContainer)BindingContext.getCurrent().getCurrentBindingsEntry(); DCIteratorBinding iter = dc.findIteratorBinding(iterName); ViewObject vo = iter.getViewObject(); String codes = ""; for(Object index : valueIndexes){ String iIndex = (String)index; Row row = vo.getRowAtRangeIndex(Integer.parseInt(iIndex)); codes = codes +(String)row.getAttribute(idAttrName)+","; } //remove last "," if(codes.endsWith(",")) codes = codes.substring(0,codes.lastIndexOf(",")); return codes; }This will return u a comma separated values of the selected items. if you want thenYou can store it in a List.

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  • Trying to make a game with C++, using lists to store bullets and enemies, but they are not erased

    - by XD_dued
    I've been trying to make a pretty simple space shooter game with C++, and I have been having a lot of trouble trying to use lists to store enemies and bullets. Basically I followed the post here almost exactly to store my bullets: SDL Bullet Movement I've done something similar to store my enemies. However, when I call bullets.erase(it++), for some reason the bullet is not erased. When the bullet movement is run for the next frame, it tries to re delete the bullet and segfaults the program. When I comment out the erase line, it runs fine, but the bullets are then never erased from the list... Is there any reason why the elements of the list aren't being deleted? I also set it up to print the number of elements in the list for every iteration, and it does not go down after deleting. Thanks! EDIT: Here's the specific code I'm using to store my enemies and having them act: std::list<Grunt*> doGrunts(std::list<Grunt*> grunts) { for(std::list<Grunt*>::iterator it = grunts.begin(); it != grunts.end();) { if((*it)->getHull() == 0) { delete * it; grunts.erase(it++); } else { (**it).doUnit(grunts, it); ++it; } } } Grunt is my enemy class, and the list grunts is a global variable. Is that my problem? When I pass the global into the function it becomes local? I assumed lists would be a reference type so thought this wouldn't be a problem. Sorry if this was a dumb question, I'm very new to C++, this is the first major thing I'm working on.

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  • Guest Post: Instantiate SharePoint Workflow On Item Deleted

    - by Brian Jackett
    In this post, guest author Lucas Eduardo Silva will walk you through the steps of instantiating a workflow using an item event receiver from a custom list.  The ItemDeleting event will require approval via the workflow. Foreword     As you may have read recently, I injured my right hand and have had it in a cast for the past 3 weeks.  Due to this I planned to reduce my blogging while my hand heals.  As luck would have it, I was actually approached by someone who asked if they could be a guest author on my blog.  I’ve never had a guest author, but considering my injury now seemed like as good a time as ever to try it out. About the Guest Author     Lucas Eduardo Silva (email) works for CPM Braxis, a sibling company to my employer Sogeti in the CapGemini family.  Lucas and I exchanged emails a few times after one of my  recent posts and continued into various topics.  When I posted that I had injured my hand, Lucas mentioned that he had a post idea that he would like to publish and asked if it could be published on my blog.  The below content is the result of that collaboration. The Problem     Lucas has a big problem.  He has a workflow that he wants to fire every time an item is deleted from a custom list. He has already created the association in the "item deleting event", but needs to approve the deletion but the workflow is finishing first. Lucas put an onWorkflowItemChanged wait for the change of status approval, but it is not being hit. The Solution Note: This solution assumes you have the Visual Studio Extensions for Windows SharePoint Services (VSeWSS) installed to access the SharePoint project templates within VIsual Studio. 1 - Create a workflow that will be activated by ItemEventReceiver. 2 - Create the list by Visual Studio clicking in File -> New -> Project. Select SharePoint, then List Definition. 3 - Select the type of document to be created. List, Document Library, Wiki, Tasks, etc.. 4 - Visual Studio creates the file ItemEventReceiver.cs with all possible events in a list. 5 – In the workflow project, open the workflow.xml and copy the ID. 6 - Uncomment the ItemDeleting and insert the following code by replacing the ID that you copied earlier.   //Cancel the Exclusion properties.Cancel = true;   //Activating Exclusion Workflow SPWorkflowManager workflowManager = properties.ListItem.Web.Site.WorkflowManager;   SPWorkflowAssociation wfAssociation = properties.ListItem.ParentList.WorkflowAssociations. GetAssociationByBaseID(new Guid("37b5aea8-792a-4ded-be25-d283d9fe1f9d"));   workflowManager.StartWorkflow(properties.ListItem, wfAssociation, wfAssociation.AssociationData, true);   properties.Status = SPEventReceiverStatus.CancelNoError;   7 - properties.Cancel cancels the event being activated and executes the code that is inside the event. In the example, it cancels the deletion of the item to start the workflow that will be active as an association list with the workflow ID. 8 - Create and deploy the workflow and the list for SharePoint. 9 - Create a list through the model that was created. 10 - Enable the workflow in the list and Congratulations! Every time you try to delete the item the workflow is activated. TIP: If you really want to delete the item after the workflow is done you will have to delete the item by the workflow.   this.workflowProperties.Site.AllowUnsafeUpdates = true; this.workflowProperties.Item.Delete(); this.workflowProperties.List.Update();   Conclusion     In this guest post Lucas took you through the steps of creating an item deletion approval workflow with an event receiver.  This was also the first time I’ve had a guest author on this blog.  Many thanks to Lucas for putting together this content and offering it.  I haven’t decided how I’d handle future guest authors, mostly because I don’t know if there are others who would want to submit content.  If you do have something that you would like to guest author on my blog feel free to drop me a line and we can discuss.  As a disclaimer, there are no guarantees that it will be published though.  For now enjoy Lucas’ post and look for my return to regular blogging soon.         -Frog Out   <Update 1> If you wish to contact Lucas you can reach him at [email protected] </Update 1>

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  • Using Delegates in C# (Part 1)

    - by rajbk
    This post provides a very basic introduction of delegates in C#. Part 2 of this post can be read here. A delegate is a class that is derived from System.Delegate.  It contains a list of one or more methods called an invocation list. When a delegate instance is “invoked” with the arguments as defined in the signature of the delegate, each of the methods in the invocation list gets invoked with the arguments. The code below shows example with static and instance methods respectively: Static Methods 1: using System; 2: using System.Linq; 3: using System.Collections.Generic; 4: 5: public delegate void SayName(string name); 6: 7: public class Program 8: { 9: [STAThread] 10: static void Main(string[] args) 11: { 12: SayName englishDelegate = new SayName(SayNameInEnglish); 13: SayName frenchDelegate = new SayName(SayNameInFrench); 14: SayName combinedDelegate =(SayName)Delegate.Combine(englishDelegate, frenchDelegate); 15: 16: combinedDelegate.Invoke("Tom"); 17: Console.ReadLine(); 18: } 19: 20: static void SayNameInFrench(string name) { 21: Console.WriteLine("J'ai m'appelle " + name); 22: } 23: 24: static void SayNameInEnglish(string name) { 25: Console.WriteLine("My name is " + name); 26: } 27: } We have declared a delegate of type SayName with return type of void and taking an input parameter of name of type string. On line 12, we create a new instance of this delegate which refers to a static method - SayNameInEnglish.  SayNameInEnglish has the same return type and parameter list as the delegate declaration.  Once a delegate is instantiated, the instance will always refer to the same target. Delegates are immutable. On line 13, we create a new instance of the delegate but point to a different static method. As you may recall, a delegate instance encapsulates an invocation list. You create an invocation list by combining delegates using the Delegate.Combine method (there is an easier syntax as you will see later). When two non null delegate instances are combined, their invocation lists get combined to form a new invocation list. This is done in line 14.  On line 16, we invoke the delegate with the Invoke method and pass in the required string parameter. Since the delegate has an invocation list with two entries, each of the method in the invocation list is invoked. If an unhandled exception occurs during the invocation of one of these methods, the exception gets bubbled up to the line where the invocation was made (line 16). If a delegate is null and you try to invoke it, you will get a System.NullReferenceException. We see the following output when the method is run: My name is TomJ'ai m'apelle Tom Instance Methods The code below outputs the same results as before. The only difference here is we are creating delegates that point to a target object (an instance of Translator) and instance methods which have the same signature as the delegate type. The target object can never be null. We also use the short cut syntax += to combine the delegates instead of Delegate.Combine. 1: public delegate void SayName(string name); 2: 3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: Translator translator = new Translator(); 9: SayName combinedDelegate = new SayName(translator.SayNameInEnglish); 10: combinedDelegate += new SayName(translator.SayNameInFrench); 11:  12: combinedDelegate.Invoke("Tom"); 13: Console.ReadLine(); 14: } 15: } 16: 17: public class Translator { 18: public void SayNameInFrench(string name) { 19: Console.WriteLine("J'ai m'appelle " + name); 20: } 21: 22: public void SayNameInEnglish(string name) { 23: Console.WriteLine("My name is " + name); 24: } 25: } A delegate can be removed from a combination of delegates by using the –= operator. Removing a delegate from an empty list or removing a delegate that does not exist in a non empty list will not result in an exception. Delegates are invoked synchronously using the Invoke method. We can also invoke them asynchronously using the BeginInvoke and EndInvoke methods which are compiler generated.

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