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  • Java MVC project - either I can't update the drawing, or I can't see it

    - by user1881164
    I've got a project based around the Model-View-Controller paradigm, and I've been having a lot of trouble with getting it to work properly. The program has 4 panels, which are supposed to allow me to modify an oval drawn on the screen in various ways. These seem to work fine, and after considerable trouble I was able to get them to display in the JFrame which holds the whole shebang. I've managed to get them to display by breaking away from the provided instructions, but when I do that, I can't seem to get the oval to update. However, if I follow the directions to the letter, I only ever see an empty frame. The project had pretty specific directions, which I followed up to a point, but some of the documentation was unclear. I think what I'm missing must be something simple, since nothing is jumping out at me as not making sense. I have to admit though that my Java experience is limited and my experience with GUI design/paradigms is even more so. Anyway, I've been searching the web and this site extensively trying to figure out what's wrong, but this is a somewhat specific example and honestly I just don't know enough about this to generalize any of the answers I've found online and figure out what's missing. I've been poring over this code for far too long now so I'm really hoping someone can help me out. public class Model { private Controller controller; private View view; private MvcFrame mvcFrame; private int radius = 44; private Color color = Color.BLUE; private boolean solid = true; //bunch of mutators and accessors for the above variables public Model() { controller = new Controller(this); view = new View(this); mvcFrame = new MvcFrame(this); } } Here's the model class. This seems to be fairly simple. I think my understanding of what's going on here is solid, and nothing seems to be wrong. Included mostly for context. public class Controller extends JPanel{ private Model model; public Controller(Model model) { this.model = model; setBorder(BorderFactory.createLineBorder(Color.GREEN)); setLayout(new GridLayout(4,1)); add(new RadiusPanel(model)); add(new ColorPanel(model)); add(new SolidPanel(model)); add(new TitlePanel(model)); } } This is the Controller class. As far as I can tell, the setBorder, setLayout, and series of adds do nothing here. I had them commented out, but this is the way that the instructions told me to do things, so either there's a mistake there or something about my setup is wrong. However, when I did it this way, I would get an empty window (JFrame) but none of the panels would show up in it. What I did to fix this is put those add functions in the mvcFrame class: public class MvcFrame extends JFrame { private Model model; public MvcFrame(Model model){ this.model = model; //setLayout(new GridLayout(4,1)); //add(new RadiusPanel(model)); //add(new ColorPanel(model)); //add(new SolidPanel(model)); //add(new TitlePanel(model)); //add(new View(model)); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setLocationRelativeTo(null); setSize(800,600); setVisible(true); } } So here's where things kind of started getting weird. The first block of commented out code is the same as what's in the Controller class. The reason I have it commented out is because that was just a lucky guess - it's not supposed to be like that according to the instructions. However, this did work for getting the panels to show up - but at that point I was still tearing my hair out trying to get the oval to display. The other commented line ( add(new View(model)); ) was a different attempt at making things work. In this case, I put those add functions in the View class (see commented out code below). This actually worked to display both the oval and the panels, but that method wouldn't allow me to update the oval. Also, though I just had the oval displaying, I can't seem to figure out what exactly made that happen, and I can't seem to make it come back. public class View extends JPanel{ private Model model; public View(Model model) { this.model = model; //setLayout(new GridLayout(4,1)); //add(new RadiusPanel(model)); //add(new ColorPanel(model)); //add(new SolidPanel(model)); //add(new TitlePanel(model)); repaint(); } @Override protected void paintComponent(Graphics g){ super.paintComponent(g); //center of view panel, in pixels: int xCenter = getWidth()/2; int yCenter = getHeight()/2; int radius = model.getRadius(); int xStart = xCenter - radius; int yStart = yCenter - radius; int xWidth = 2 * radius; int yHeight = 2 * radius; g.setColor(model.getColor()); g.clearRect(0, 0, getWidth(), getHeight()); if (model.isSolid()){ g.fillOval(xStart, yStart, xWidth, yHeight); } else { g.drawOval(xStart, yStart, xWidth, yHeight); } } } Kinda same idea as before - the commented out code is stuff I added to try to get things working, but is not based on the provided directions. In the case where that stuff was uncommented, I had the add(new View(model)); line from the mvcFrame line uncommented as well. The various panel classes (SolidPanel, ColorPanel, etc) simply extend a class called ControlPanel which extends JPanel. These all seem to work as expected, not having much issue with them. There is also a driver which launches the GUI. This also seems to work as expected. The main problem I'm having is that I can't get the oval to show up, and the one time I could make it show up, none of the options for changing it seemed to work. I feel like I'm close but I'm just at a loss for other things to try out at this point. Anyone who can help will have my sincerest gratitude.

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  • Adding multiple views to a listview.

    - by hwrdprkns
    Hey guys, I tried to add these views to list view using this kind of factory but everytime I try and add the view to a ListActivity, it comes up with nothing. What am I doing wrong? I set my list views like so: List<View> views = new ArrayList<View>(); for(int x =0;x<tagg_views.size();x++) { lv.addHeaderView(views.get(x)); }

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  • iAd banner gives warning when pushed off screen by navController

    - by James Dunay
    I have a iAd that seems to be correctly displaying but when push a new view controller into the view i get a warning from the iAd that says it has been: WARNING A banner view (0x490fd0) has an ad but may be obscured. This message is only printed once per banner view. But the ad still runs fine so should i pay attention to this? I just tried adding self.adBannerView = nil; [adBannerView release];` just before i push the viewController but i still get that error

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  • Fix buttons at the bottom of the screen.

    - by Wilson
    I am a beginner in Android programming. I want to build a simple application with a main list view in the screen and two buttons at the bottom of the screen. When more items are added to the list view, the list view should scroll without increasing the overall length of the list view.

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  • asp.net mvc checkbox hierarchy

    - by mazhar
    I want to create a checkboxes hierarchy like this in mvc2.How would I be able to achieve this in the most simplest manner. Administrator Manage User Add Edit Delete View Manage Feature Add Edit Delete View Moderator Manage User Add Edit Delete View Manage Feature Add Edit Delete View

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  • problem in presentmodelviewcontroller?

    - by Bala
    i am using tabbarcontroller. In tabbar having one view.In that tab i call one function using Nstimer it open another viewcontroller. First * sVC = [[First alloc] initWithNibName:@"First" bundle:[NSBundle mainBundle]]; [self presentModalViewController:sVC animated:YES]; Opened viewcontrller having one button.when user click that button i want to close the view and call Nstimer. [self dismissModalViewControllerAnimated:NO] The problem is first the view opened and closed but second time view could not open.

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  • How to configure a URL with 3 levels in ASP.NET MVC?

    - by MCardinale
    Using ASP.NET MVC, I need to configure my URLs like this: www.foo.com/company : render View Company www.foo.com/company/about : render View Company www.foo.com/company/about/mission : render View Mission If "company" is my controller and "about" is my action, what should be "mission"? For every "folder" (company, about and mission) I have to render a different View. Anyone knows how can I do that? Thanks!

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  • Rails object based permission/authorization engine?

    - by Vlad
    Hi I want to add "Sharing documents" feature to my app, like in google documents service. As i see: User can: can list/view/create/edit/delete own documents share own document to everyone - its a public document share own document to another user with read-only access share own document to another user with read-write access view list of own documents and users to whom he gave permission to read and write view list of foreign documents view/edit foreign document with read/write permissions Please tell me, which permission/authorization solution is preffered for my task?

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  • Large memory chunk not garbage collected

    - by Niels
    In a hunt for a memory-leak in my app I chased down a behaviour I can't understand. I allocate a large memory block, but it doesn't get garbage-collected resulting in a OOM, unless I explicit null the reference in onDestroy. In this example I have two almost identical activities that switch between each others. Both have a single button. On pressing the button MainActivity starts OOMActivity and OOMActivity returns by calling finish(). After pressing the buttons a few times, Android throws a OOMException. If i add the the onDestroy to OOMActivity and explicit null the reference to the memory chunk, I can see in the log that the memory is correctly freed. Why doesn't the memory get freed automatically without the nulling? MainActivity: package com.example.oom; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; public class MainActivity extends Activity implements OnClickListener { private int buttonId; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); System.gc(); Button OOMButton = new Button(this); OOMButton.setText("OOM"); buttonId = OOMButton.getId(); setContentView(OOMButton); OOMButton.setOnClickListener(this); } @Override public void onClick(View v) { if (v.getId() == buttonId) { Intent leakIntent = new Intent(this, OOMActivity.class); startActivity(leakIntent); } } } OOMActivity: public class OOMActivity extends Activity implements OnClickListener { private static final int WASTE_SIZE = 20000000; private byte[] waste; private int buttonId; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Button BackButton = new Button(this); BackButton.setText("Back"); buttonId = BackButton.getId(); setContentView(BackButton); BackButton.setOnClickListener(this); waste = new byte[WASTE_SIZE]; } public void onClick(View view) { if (view.getId() == buttonId) { finish(); } } }

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  • How to get password html helper to render password on failed validation

    - by Max Schmeling
    I have a form for creating a new account and it has a password field in it. I'm using view models to pass data to the controller action and back to the form view. When the user enters their details in, and clicks submit, if validation fails and it returns them to the same view passing back in the view model, it won't default the password to what they entered. How can I get it to do this? Or should I even try?

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  • Portrait video to landscape

    - by dappa
    I am aware questions like this one may already be out there but for the sake of others like me I will go ahead and ask I have a app that is set to only allow portrait orientation but this setting affects my videos as I would like only the videos to be able to play in landscape also. Is there a method I can add unto my .m file to make this work? Here is my code; #import "BIDVideosViewController.h" @interface BIDVideosViewController () @end @implementation BIDVideosViewController @synthesize moviePlayer ; @synthesize tableList; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // Custom initialization } return self; } - (void)viewDidLoad { [super viewDidLoad]; UITableView *table = [[UITableView alloc]initWithFrame:self.view.bounds]; [table setDelegate:self]; [table setDataSource:self]; [self.view addSubview:table]; tableList = [[NSMutableArray alloc] initWithObjects:@"Gangan",@"SwimGood",@"German Ice", nil]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [tableList count]; } -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *DisclosureButtonIdentifier = @"DisclosurebutotonIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:DisclosureButtonIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:DisclosureButtonIdentifier]; } NSInteger row = [indexPath row]; NSString *rowString = [tableList objectAtIndex:row]; cell.textLabel.text = rowString; return cell; } -(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { { NSBundle *str = [tableList objectAtIndex:indexPath.row]; if ([str isEqual:@"Gangan"]) { NSBundle *bundle = [NSBundle mainBundle]; NSString *thePath = [bundle pathForResource:@"Gangan" ofType:@"mp4"]; NSURL *theurl = [NSURL fileURLWithPath:thePath]; moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:theurl]; [moviePlayer setMovieSourceType:MPMovieSourceTypeFile]; [self.view addSubview:moviePlayer.view]; [moviePlayer setFullscreen:YES]; [moviePlayer play]; } else if ([str isEqual:@"SwimGood"]) { NSBundle *bundle = [NSBundle mainBundle]; NSString *thePath = [bundle pathForResource:@"SwimGood" ofType:@"mp4"]; NSURL *theurl = [NSURL fileURLWithPath:thePath]; moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:theurl]; [moviePlayer setMovieSourceType:MPMovieSourceTypeFile]; [self.view addSubview:moviePlayer.view]; [moviePlayer setFullscreen:YES]; [moviePlayer play]; } else if ([str isEqual:@"German Ice"]) { NSBundle *bundle = [NSBundle mainBundle]; NSString *thePath = [bundle pathForResource:@"German Ice" ofType:@"mp4"]; NSURL *theurl = [NSURL fileURLWithPath:thePath]; moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:theurl]; [moviePlayer setMovieSourceType:MPMovieSourceTypeFile]; [self.view addSubview:moviePlayer.view]; [moviePlayer setFullscreen:YES]; [moviePlayer play]; } } } @end

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  • SQL Syntax for testing objects before creating views & functions

    - by Scott Weinstein
    I'm trying to figure out the syntax for creating a view (or function) but only if a dependent CLR assembly exits. I've tried both IF EXISTS (SELECT name FROM sys.assemblies WHERE name = 'MyCLRAssembly') begin create view dbo.MyView as select GETDATE() as C1 end and IF EXISTS (SELECT name FROM sys.assemblies WHERE name = 'MyCLRAssembly') create view dbo.MyView as select GETDATE() as C1 go Neither work. I get Msg 156, Level 15, State 1, Line 2 Incorrect syntax near the keyword 'view'. How can this be done?

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  • How to add a UIView above the current UITableViewController

    - by user558096
    I'm have difficulty adding a subview UIView from within the viewDidLoad method of a UITableViewController This works: [self.view addSubview:self.progView]; But you can see the table cell lines bleed through the UIView progView. I've tried this approach: [self.view.superview insertSubview:self.progView aboveSubview:self.view]; Which is an attempt to add the progView UIView to the superview, above the current view. When I try this I get this the UIView never appears.

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  • ...Welche DB-Hintergrundprozesse sind für was zuständig?... wie ging das nochmal? Und wie heisst noch diese eine wichtige Data Dictionary View? ...

    - by britta.wolf
    ...Gab es da nicht mal ein gutes Oracle-Poster, wo man schnell nachschauen konnte und einen guten Überblick bekam? Viele Datenbankadministratoren haben das besagte Poster, das die Architektur und Prozesse sowie die Data Dictionary-Struktur der Oracle Datenbank beschreibt, vermisst! Daher wurde nun eine handliche kleine Flash-Applikation mit erweitertem Inhalt entwickelt - Oracle Database 11g: Interactive Quick Reference - die man sich hier downloaden kann (einfach auf den Button "Download now" klicken (Größe der Zip-Datei: 4.6 MB). Ist genial, muss man haben!!! :-)

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  • Creating vCard action result

    - by DigiMortal
    I added support for vCards to one of my ASP.NET MVC applications. I worked vCard support out as very simple and intelligent solution that fits perfectly to ASP.NET MVC applications. In this posting I will show you how to send vCards out as response to ASP.NET MVC request. We need three things: some vCard class, vCard action result, controller method to test vCard action result. Everything is very simple, let’s get hands on. vCard class As first thing we need vCard class. Last year I introduced vCard class that supports also images. Let’s take this class because it is easy to use and some dirty work is already done for us. NB! Take a look at ASP.NET example in the blog posting referred above. We need it later when we close the topic. Now think about how useful blogging and information sharing with others can be. With this class available at public I saved pretty much time now. :) vCardResult As we have vCard it is now time to write action result that we can use in our controllers. Here’s the code. public class vCardResult : ActionResult {     private vCard _card;       protected vCardResult() { }       public vCardResult(vCard card)     {         _card = card;     }       public override void ExecuteResult(ControllerContext context)     {         var response = context.HttpContext.Response;         response.ContentType = "text/vcard";         response.AddHeader("Content-Disposition", "attachment; fileName=" + _card.FirstName + " " + _card.LastName + ".vcf");           var cardString = _card.ToString();         var inputEncoding = Encoding.Default;         var outputEncoding = Encoding.GetEncoding("windows-1257");         var cardBytes = inputEncoding.GetBytes(cardString);           var outputBytes = Encoding.Convert(inputEncoding,                                 outputEncoding, cardBytes);           response.OutputStream.Write(outputBytes, 0, outputBytes.Length);     } } And we are done. Some notes: vCard is sent to browser as downloadable file (user can save or open it with Outlook or any other e-mail client that supports vCards), File name is made of first and last name of contact. Encoding is important because Outlook may not understand vCards otherwise (don’t know if this problem is solved in Outlook 2010). Using vCardResult in controller Now let’s tale a look at simple controller method that accepts person ID and returns vCardResult. public class ContactsController : Controller {       // ... other controller methods ...       public vCardResult vCard(int id)     {         var person = _partyRepository.GetPersonById(id);         var card = new vCard                 {                     FirstName=person.FirstName,                     LastName = person.LastName,                     StreetAddress = person.StreetAddress,                     City = person.City,                     CountryName = person.Country.Name,                       Mobile = person.Mobile,                     Phone = person.Phone,                     Email = person.Email,                 };           return new vCardResult(card);     } } Now you can run Visual Studio and check out how your vCard is moving from your web application to your e-mail client. Conclusion We took old code that worked well with ASP.NET Forms and we divided it into action result and controller method that uses vCard as bridge between our controller and action result. All functionality is located where it should be and we did nothing complex. We wrote only couple of lines of very easy code to achieve our goal. Do you understand now why I love ASP.NET MVC? :)

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  • How to present a stable data model in a public API that allows internal data structures to be changed without breaking the public view of the data?

    - by Max Palmer
    I am in the process of developing an application that allows users to write C# scripts. These scripts allow users to call selected methods and to access and manipulate data in a document. This works well, however, in the development version, scripts access the document's (internal) data structures directly. This means that if we were to change the internal data model/structure, there is a good chance that someone's script will no longer compile. We obviously want to prevent this breaking change from happening, but still want to allow the user to write sensible C# code (whilst not restricting how we develop our internal data model as a result). We therefore need to decouple our scripting API and its data structures from our internal methods and data structures. We've a few ideas as to how we might allow the user to access a what is effectively a stable public version of the document's internal data*, but I wanted to throw the question out there to someone who might have some real experience of this problem. NB our internal document's data structure is quite complex and it could be quite difficult to wrap. We know we want to expose as little as possible in our public API, especially as once it's out there, it's out there for good. Can anyone help? How do scripting languages / APIs decouple their public API and data structures from their internal data structures? Is there no real alternative to having to write a complex interaction layer? If we need to do this, what's a good approach or pattern for wrapping complex data structures that include nested objects, including collections? I've looked at the API facade pattern, which looks like it's trying to address these kinds of issues, but are there alternatives? *One idea is to build a data facade that is kept stable across versions of our application. The facade exposes a set of facade data objects that are used in the script code. These maintain backwards compatibility and wrap access to our internal document's data model.

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  • Using LINQ Distinct: With an Example on ASP.NET MVC SelectListItem

    - by Joe Mayo
    One of the things that might be surprising in the LINQ Distinct standard query operator is that it doesn’t automatically work properly on custom classes. There are reasons for this, which I’ll explain shortly. The example I’ll use in this post focuses on pulling a unique list of names to load into a drop-down list. I’ll explain the sample application, show you typical first shot at Distinct, explain why it won’t work as you expect, and then demonstrate a solution to make Distinct work with any custom class. The technologies I’m using are  LINQ to Twitter, LINQ to Objects, Telerik Extensions for ASP.NET MVC, ASP.NET MVC 2, and Visual Studio 2010. The function of the example program is to show a list of people that I follow.  In Twitter API vernacular, these people are called “Friends”; though I’ve never met most of them in real life. This is part of the ubiquitous language of social networking, and Twitter in particular, so you’ll see my objects named accordingly. Where Distinct comes into play is because I want to have a drop-down list with the names of the friends appearing in the list. Some friends are quite verbose, which means I can’t just extract names from each tweet and populate the drop-down; otherwise, I would end up with many duplicate names. Therefore, Distinct is the appropriate operator to eliminate the extra entries from my friends who tend to be enthusiastic tweeters. The sample doesn’t do anything with the drop-down list and I leave that up to imagination for what it’s practical purpose could be; perhaps a filter for the list if I only want to see a certain person’s tweets or maybe a quick list that I plan to combine with a TextBox and Button to reply to a friend. When the program runs, you’ll need to authenticate with Twitter, because I’m using OAuth (DotNetOpenAuth), for authentication, and then you’ll see the drop-down list of names above the grid with the most recent tweets from friends. Here’s what the application looks like when it runs: As you can see, there is a drop-down list above the grid. The drop-down list is where most of the focus of this article will be. There is some description of the code before we talk about the Distinct operator, but we’ll get there soon. This is an ASP.NET MVC2 application, written with VS 2010. Here’s the View that produces this screen: <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<TwitterFriendsViewModel>" %> <%@ Import Namespace="DistinctSelectList.Models" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">     Home Page </asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">     <fieldset>         <legend>Twitter Friends</legend>         <div>             <%= Html.DropDownListFor(                     twendVM => twendVM.FriendNames,                     Model.FriendNames,                     "<All Friends>") %>         </div>         <div>             <% Html.Telerik().Grid<TweetViewModel>(Model.Tweets)                    .Name("TwitterFriendsGrid")                    .Columns(cols =>                     {                         cols.Template(col =>                             { %>                                 <img src="<%= col.ImageUrl %>"                                      alt="<%= col.ScreenName %>" />                         <% });                         cols.Bound(col => col.ScreenName);                         cols.Bound(col => col.Tweet);                     })                    .Render(); %>         </div>     </fieldset> </asp:Content> As shown above, the Grid is from Telerik’s Extensions for ASP.NET MVC. The first column is a template that renders the user’s Avatar from a URL provided by the Twitter query. Both the Grid and DropDownListFor display properties that are collections from a TwitterFriendsViewModel class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { /// /// For finding friend info on screen /// public class TwitterFriendsViewModel { /// /// Display names of friends in drop-down list /// public List FriendNames { get; set; } /// /// Display tweets in grid /// public List Tweets { get; set; } } } I created the TwitterFreindsViewModel. The two Lists are what the View consumes to populate the DropDownListFor and Grid. Notice that FriendNames is a List of SelectListItem, which is an MVC class. Another custom class I created is the TweetViewModel (the type of the Tweets List), shown below: namespace DistinctSelectList.Models { /// /// Info on friend tweets /// public class TweetViewModel { /// /// User's avatar /// public string ImageUrl { get; set; } /// /// User's Twitter name /// public string ScreenName { get; set; } /// /// Text containing user's tweet /// public string Tweet { get; set; } } } The initial Twitter query returns much more information than we need for our purposes and this a special class for displaying info in the View.  Now you know about the View and how it’s constructed. Let’s look at the controller next. The controller for this demo performs authentication, data retrieval, data manipulation, and view selection. I’ll skip the description of the authentication because it’s a normal part of using OAuth with LINQ to Twitter. Instead, we’ll drill down and focus on the Distinct operator. However, I’ll show you the entire controller, below,  so that you can see how it all fits together: using System.Linq; using System.Web.Mvc; using DistinctSelectList.Models; using LinqToTwitter; namespace DistinctSelectList.Controllers { [HandleError] public class HomeController : Controller { private MvcOAuthAuthorization auth; private TwitterContext twitterCtx; /// /// Display a list of friends current tweets /// /// public ActionResult Index() { auth = new MvcOAuthAuthorization(InMemoryTokenManager.Instance, InMemoryTokenManager.AccessToken); string accessToken = auth.CompleteAuthorize(); if (accessToken != null) { InMemoryTokenManager.AccessToken = accessToken; } if (auth.CachedCredentialsAvailable) { auth.SignOn(); } else { return auth.BeginAuthorize(); } twitterCtx = new TwitterContext(auth); var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); var twendsVM = new TwitterFriendsViewModel { Tweets = friendTweets, FriendNames = friendNames }; return View(twendsVM); } public ActionResult About() { return View(); } } } The important part of the listing above are the LINQ to Twitter queries for friendTweets and friendNames. Both of these results are used in the subsequent population of the twendsVM instance that is passed to the view. Let’s dissect these two statements for clarification and focus on what is happening with Distinct. The query for friendTweets gets a list of the 20 most recent tweets (as specified by the Twitter API for friend queries) and performs a projection into the custom TweetViewModel class, repeated below for your convenience: var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); The LINQ to Twitter query above simplifies what we need to work with in the View and the reduces the amount of information we have to look at in subsequent queries. Given the friendTweets above, the next query performs another projection into an MVC SelectListItem, which is required for binding to the DropDownList.  This brings us to the focus of this blog post, writing a correct query that uses the Distinct operator. The query below uses LINQ to Objects, querying the friendTweets collection to get friendNames: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); The above implementation of Distinct seems normal, but it is deceptively incorrect. After running the query above, by executing the application, you’ll notice that the drop-down list contains many duplicates.  This will send you back to the code scratching your head, but there’s a reason why this happens. To understand the problem, we must examine how Distinct works in LINQ to Objects. Distinct has two overloads: one without parameters, as shown above, and another that takes a parameter of type IEqualityComparer<T>.  In the case above, no parameters, Distinct will call EqualityComparer<T>.Default behind the scenes to make comparisons as it iterates through the list. You don’t have problems with the built-in types, such as string, int, DateTime, etc, because they all implement IEquatable<T>. However, many .NET Framework classes, such as SelectListItem, don’t implement IEquatable<T>. So, what happens is that EqualityComparer<T>.Default results in a call to Object.Equals, which performs reference equality on reference type objects.  You don’t have this problem with value types because the default implementation of Object.Equals is bitwise equality. However, most of your projections that use Distinct are on classes, just like the SelectListItem used in this demo application. So, the reason why Distinct didn’t produce the results we wanted was because we used a type that doesn’t define its own equality and Distinct used the default reference equality. This resulted in all objects being included in the results because they are all separate instances in memory with unique references. As you might have guessed, the solution to the problem is to use the second overload of Distinct that accepts an IEqualityComparer<T> instance. If you were projecting into your own custom type, you could make that type implement IEqualityComparer<T>, but SelectListItem belongs to the .NET Framework Class Library.  Therefore, the solution is to create a custom type to implement IEqualityComparer<T>, as in the SelectListItemComparer class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { public class SelectListItemComparer : EqualityComparer { public override bool Equals(SelectListItem x, SelectListItem y) { return x.Value.Equals(y.Value); } public override int GetHashCode(SelectListItem obj) { return obj.Value.GetHashCode(); } } } The SelectListItemComparer class above doesn’t implement IEqualityComparer<SelectListItem>, but rather derives from EqualityComparer<SelectListItem>. Microsoft recommends this approach for consistency with the behavior of generic collection classes. However, if your custom type already derives from a base class, go ahead and implement IEqualityComparer<T>, which will still work. EqualityComparer is an abstract class, that implements IEqualityComparer<T> with Equals and GetHashCode abstract methods. For the purposes of this application, the SelectListItem.Value property is sufficient to determine if two items are equal.   Since SelectListItem.Value is type string, the code delegates equality to the string class. The code also delegates the GetHashCode operation to the string class.You might have other criteria in your own object and would need to define what it means for your object to be equal. Now that we have an IEqualityComparer<SelectListItem>, let’s fix the problem. The code below modifies the query where we want distinct values: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct(new SelectListItemComparer()) .ToList(); Notice how the code above passes a new instance of SelectListItemComparer as the parameter to the Distinct operator. Now, when you run the application, the drop-down list will behave as you expect, showing only a unique set of names. In addition to Distinct, other LINQ Standard Query Operators have overloads that accept IEqualityComparer<T>’s, You can use the same techniques as shown here, with SelectListItemComparer, with those other operators as well. Now you know how to resolve problems with getting Distinct to work properly and also have a way to fix problems with other operators that require equality comparisons. @JoeMayo

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  • Top things web developers should know about the Visual Studio 2013 release

    - by Jon Galloway
    ASP.NET and Web Tools for Visual Studio 2013 Release NotesASP.NET and Web Tools for Visual Studio 2013 Release NotesSummary for lazy readers: Visual Studio 2013 is now available for download on the Visual Studio site and on MSDN subscriber downloads) Visual Studio 2013 installs side by side with Visual Studio 2012 and supports round-tripping between Visual Studio versions, so you can try it out without committing to a switch Visual Studio 2013 ships with the new version of ASP.NET, which includes ASP.NET MVC 5, ASP.NET Web API 2, Razor 3, Entity Framework 6 and SignalR 2.0 The new releases ASP.NET focuses on One ASP.NET, so core features and web tools work the same across the platform (e.g. adding ASP.NET MVC controllers to a Web Forms application) New core features include new templates based on Bootstrap, a new scaffolding system, and a new identity system Visual Studio 2013 is an incredible editor for web files, including HTML, CSS, JavaScript, Markdown, LESS, Coffeescript, Handlebars, Angular, Ember, Knockdown, etc. Top links: Visual Studio 2013 content on the ASP.NET site are in the standard new releases area: http://www.asp.net/vnext ASP.NET and Web Tools for Visual Studio 2013 Release Notes Short intro videos on the new Visual Studio web editor features from Scott Hanselman and Mads Kristensen Announcing release of ASP.NET and Web Tools for Visual Studio 2013 post on the official .NET Web Development and Tools Blog Scott Guthrie's post: Announcing the Release of Visual Studio 2013 and Great Improvements to ASP.NET and Entity Framework Okay, for those of you who are still with me, let's dig in a bit. Quick web dev notes on downloading and installing Visual Studio 2013 I found Visual Studio 2013 to be a pretty fast install. According to Brian Harry's release post, installing over pre-release versions of Visual Studio is supported.  I've installed the release version over pre-release versions, and it worked fine. If you're only going to be doing web development, you can speed up the install if you just select Web Developer tools. Of course, as a good Microsoft employee, I'll mention that you might also want to install some of those other features, like the Store apps for Windows 8 and the Windows Phone 8.0 SDK, but they do download and install a lot of other stuff (e.g. the Windows Phone SDK sets up Hyper-V and downloads several GB's of VM's). So if you're planning just to do web development for now, you can pick just the Web Developer Tools and install the other stuff later. If you've got a fast internet connection, I recommend using the web installer instead of downloading the ISO. The ISO includes all the features, whereas the web installer just downloads what you're installing. Visual Studio 2013 development settings and color theme When you start up Visual Studio, it'll prompt you to pick some defaults. These are totally up to you -whatever suits your development style - and you can change them later. As I said, these are completely up to you. I recommend either the Web Development or Web Development (Code Only) settings. The only real difference is that Code Only hides the toolbars, and you can switch between them using Tools / Import and Export Settings / Reset. Web Development settings Web Development (code only) settings Usually I've just gone with Web Development (code only) in the past because I just want to focus on the code, although the Standard toolbar does make it easier to switch default web browsers. More on that later. Color theme Sigh. Okay, everyone's got their favorite colors. I alternate between Light and Dark depending on my mood, and I personally like how the low contrast on the window chrome in those themes puts the emphasis on my code rather than the tabs and toolbars. I know some people got pretty worked up over that, though, and wanted the blue theme back. I personally don't like it - it reminds me of ancient versions of Visual Studio that I don't want to think about anymore. So here's the thing: if you install Visual Studio Ultimate, it defaults to Blue. The other versions default to Light. If you use Blue, I won't criticize you - out loud, that is. You can change themes really easily - either Tools / Options / Environment / General, or the smart way: ctrl+q for quick launch, then type Theme and hit enter. Signing in During the first run, you'll be prompted to sign in. You don't have to - you can click the "Not now, maybe later" link at the bottom of that dialog. I recommend signing in, though. It's not hooked in with licensing or tracking the kind of code you write to sell you components. It is doing good things, like  syncing your Visual Studio settings between computers. More about that here. So, you don't have to, but I sure do. Overview of shiny new things in ASP.NET land There are a lot of good new things in ASP.NET. I'll list some of my favorite here, but you can read more on the ASP.NET site. One ASP.NET You've heard us talk about this for a while. The idea is that options are good, but choice can be a burden. When you start a new ASP.NET project, why should you have to make a tough decision - with long-term consequences - about how your application will work? If you want to use ASP.NET Web Forms, but have the option of adding in ASP.NET MVC later, why should that be hard? It's all ASP.NET, right? Ideally, you'd just decide that you want to use ASP.NET to build sites and services, and you could use the appropriate tools (the green blocks below) as you needed them. So, here it is. When you create a new ASP.NET application, you just create an ASP.NET application. Next, you can pick from some templates to get you started... but these are different. They're not "painful decision" templates, they're just some starting pieces. And, most importantly, you can mix and match. I can pick a "mostly" Web Forms template, but include MVC and Web API folders and core references. If you've tried to mix and match in the past, you're probably aware that it was possible, but not pleasant. ASP.NET MVC project files contained special project type GUIDs, so you'd only get controller scaffolding support in a Web Forms project if you manually edited the csproj file. Features in one stack didn't work in others. Project templates were painful choices. That's no longer the case. Hooray! I just did a demo in a presentation last week where I created a new Web Forms + MVC + Web API site, built a model, scaffolded MVC and Web API controllers with EF Code First, add data in the MVC view, viewed it in Web API, then added a GridView to the Web Forms Default.aspx page and bound it to the Model. In about 5 minutes. Sure, it's a simple example, but it's great to be able to share code and features across the whole ASP.NET family. Authentication In the past, authentication was built into the templates. So, for instance, there was an ASP.NET MVC 4 Intranet Project template which created a new ASP.NET MVC 4 application that was preconfigured for Windows Authentication. All of that authentication stuff was built into each template, so they varied between the stacks, and you couldn't reuse them. You didn't see a lot of changes to the authentication options, since they required big changes to a bunch of project templates. Now, the new project dialog includes a common authentication experience. When you hit the Change Authentication button, you get some common options that work the same way regardless of the template or reference settings you've made. These options work on all ASP.NET frameworks, and all hosting environments (IIS, IIS Express, or OWIN for self-host) The default is Individual User Accounts: This is the standard "create a local account, using username / password or OAuth" thing; however, it's all built on the new Identity system. More on that in a second. The one setting that has some configuration to it is Organizational Accounts, which lets you configure authentication using Active Directory, Windows Azure Active Directory, or Office 365. Identity There's a new identity system. We've taken the best parts of the previous ASP.NET Membership and Simple Identity systems, rolled in a lot of feedback and made big enhancements to support important developer concerns like unit testing and extensiblity. I've written long posts about ASP.NET identity, and I'll do it again. Soon. This is not that post. The short version is that I think we've finally got just the right Identity system. Some of my favorite features: There are simple, sensible defaults that work well - you can File / New / Run / Register / Login, and everything works. It supports standard username / password as well as external authentication (OAuth, etc.). It's easy to customize without having to re-implement an entire provider. It's built using pluggable pieces, rather than one large monolithic system. It's built using interfaces like IUser and IRole that allow for unit testing, dependency injection, etc. You can easily add user profile data (e.g. URL, twitter handle, birthday). You just add properties to your ApplicationUser model and they'll automatically be persisted. Complete control over how the identity data is persisted. By default, everything works with Entity Framework Code First, but it's built to support changes from small (modify the schema) to big (use another ORM, store your data in a document database or in the cloud or in XML or in the EXIF data of your desktop background or whatever). It's configured via OWIN. More on OWIN and Katana later, but the fact that it's built using OWIN means it's portable. You can find out more in the Authentication and Identity section of the ASP.NET site (and lots more content will be going up there soon). New Bootstrap based project templates The new project templates are built using Bootstrap 3. Bootstrap (formerly Twitter Bootstrap) is a front-end framework that brings a lot of nice benefits: It's responsive, so your projects will automatically scale to device width using CSS media queries. For example, menus are full size on a desktop browser, but on narrower screens you automatically get a mobile-friendly menu. The built-in Bootstrap styles make your standard page elements (headers, footers, buttons, form inputs, tables etc.) look nice and modern. Bootstrap is themeable, so you can reskin your whole site by dropping in a new Bootstrap theme. Since Bootstrap is pretty popular across the web development community, this gives you a large and rapidly growing variety of templates (free and paid) to choose from. Bootstrap also includes a lot of very useful things: components (like progress bars and badges), useful glyphicons, and some jQuery plugins for tooltips, dropdowns, carousels, etc.). Here's a look at how the responsive part works. When the page is full screen, the menu and header are optimized for a wide screen display: When I shrink the page down (this is all based on page width, not useragent sniffing) the menu turns into a nice mobile-friendly dropdown: For a quick example, I grabbed a new free theme off bootswatch.com. For simple themes, you just need to download the boostrap.css file and replace the /content/bootstrap.css file in your project. Now when I refresh the page, I've got a new theme: Scaffolding The big change in scaffolding is that it's one system that works across ASP.NET. You can create a new Empty Web project or Web Forms project and you'll get the Scaffold context menus. For release, we've got MVC 5 and Web API 2 controllers. We had a preview of Web Forms scaffolding in the preview releases, but they weren't fully baked for RTM. Look for them in a future update, expected pretty soon. This scaffolding system wasn't just changed to work across the ASP.NET frameworks, it's also built to enable future extensibility. That's not in this release, but should also hopefully be out soon. Project Readme page This is a small thing, but I really like it. When you create a new project, you get a Project_Readme.html page that's added to the root of your project and opens in the Visual Studio built-in browser. I love it. A long time ago, when you created a new project we just dumped it on you and left you scratching your head about what to do next. Not ideal. Then we started adding a bunch of Getting Started information to the new project templates. That told you what to do next, but you had to delete all of that stuff out of your website. It doesn't belong there. Not ideal. This is a simple HTML file that's not integrated into your project code at all. You can delete it if you want. But, it shows a lot of helpful links that are current for the project you just created. In the future, if we add new wacky project types, they can create readme docs with specific information on how to do appropriately wacky things. Side note: I really like that they used the internal browser in Visual Studio to show this content rather than popping open an HTML page in the default browser. I hate that. It's annoying. If you're doing that, I hope you'll stop. What if some unnamed person has 40 or 90 tabs saved in their browser session? When you pop open your "Thanks for installing my Visual Studio extension!" page, all eleventy billion tabs start up and I wish I'd never installed your thing. Be like these guys and pop stuff Visual Studio specific HTML docs in the Visual Studio browser. ASP.NET MVC 5 The biggest change with ASP.NET MVC 5 is that it's no longer a separate project type. It integrates well with the rest of ASP.NET. In addition to that and the other common features we've already looked at (Bootstrap templates, Identity, authentication), here's what's new for ASP.NET MVC. Attribute routing ASP.NET MVC now supports attribute routing, thanks to a contribution by Tim McCall, the author of http://attributerouting.net. With attribute routing you can specify your routes by annotating your actions and controllers. This supports some pretty complex, customized routing scenarios, and it allows you to keep your route information right with your controller actions if you'd like. Here's a controller that includes an action whose method name is Hiding, but I've used AttributeRouting to configure it to /spaghetti/with-nesting/where-is-waldo public class SampleController : Controller { [Route("spaghetti/with-nesting/where-is-waldo")] public string Hiding() { return "You found me!"; } } I enable that in my RouteConfig.cs, and I can use that in conjunction with my other MVC routes like this: public class RouteConfig { public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapMvcAttributeRoutes(); routes.MapRoute( name: "Default", url: "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional } ); } } You can read more about Attribute Routing in ASP.NET MVC 5 here. Filter enhancements There are two new additions to filters: Authentication Filters and Filter Overrides. Authentication filters are a new kind of filter in ASP.NET MVC that run prior to authorization filters in the ASP.NET MVC pipeline and allow you to specify authentication logic per-action, per-controller, or globally for all controllers. Authentication filters process credentials in the request and provide a corresponding principal. Authentication filters can also add authentication challenges in response to unauthorized requests. Override filters let you change which filters apply to a given action method or controller. Override filters specify a set of filter types that should not be run for a given scope (action or controller). This allows you to configure filters that apply globally but then exclude certain global filters from applying to specific actions or controllers. ASP.NET Web API 2 ASP.NET Web API 2 includes a lot of new features. Attribute Routing ASP.NET Web API supports the same attribute routing system that's in ASP.NET MVC 5. You can read more about the Attribute Routing features in Web API in this article. OAuth 2.0 ASP.NET Web API picks up OAuth 2.0 support, using security middleware running on OWIN (discussed below). This is great for features like authenticated Single Page Applications. OData Improvements ASP.NET Web API now has full OData support. That required adding in some of the most powerful operators: $select, $expand, $batch and $value. You can read more about OData operator support in this article by Mike Wasson. Lots more There's a huge list of other features, including CORS (cross-origin request sharing), IHttpActionResult, IHttpRequestContext, and more. I think the best overview is in the release notes. OWIN and Katana I've written about OWIN and Katana recently. I'm a big fan. OWIN is the Open Web Interfaces for .NET. It's a spec, like HTML or HTTP, so you can't install OWIN. The benefit of OWIN is that it's a community specification, so anyone who implements it can plug into the ASP.NET stack, either as middleware or as a host. Katana is the Microsoft implementation of OWIN. It leverages OWIN to wire up things like authentication, handlers, modules, IIS hosting, etc., so ASP.NET can host OWIN components and Katana components can run in someone else's OWIN implementation. Howard Dierking just wrote a cool article in MSDN magazine describing Katana in depth: Getting Started with the Katana Project. He had an interesting example showing an OWIN based pipeline which leveraged SignalR, ASP.NET Web API and NancyFx components in the same stack. If this kind of thing makes sense to you, that's great. If it doesn't, don't worry, but keep an eye on it. You're going to see some cool things happen as a result of ASP.NET becoming more and more pluggable. Visual Studio Web Tools Okay, this stuff's just crazy. Visual Studio has been adding some nice web dev features over the past few years, but they've really cranked it up for this release. Visual Studio is by far my favorite code editor for all web files: CSS, HTML, JavaScript, and lots of popular libraries. Stop thinking of Visual Studio as a big editor that you only use to write back-end code. Stop editing HTML and CSS in Notepad (or Sublime, Notepad++, etc.). Visual Studio starts up in under 2 seconds on a modern computer with an SSD. Misspelling HTML attributes or your CSS classes or jQuery or Angular syntax is stupid. It doesn't make you a better developer, it makes you a silly person who wastes time. Browser Link Browser Link is a real-time, two-way connection between Visual Studio and all connected browsers. It's only attached when you're running locally, in debug, but it applies to any and all connected browser, including emulators. You may have seen demos that showed the browsers refreshing based on changes in the editor, and I'll agree that's pretty cool. But it's really just the start. It's a two-way connection, and it's built for extensiblity. That means you can write extensions that push information from your running application (in IE, Chrome, a mobile emulator, etc.) back to Visual Studio. Mads and team have showed off some demonstrations where they enabled edit mode in the browser which updated the source HTML back on the browser. It's also possible to look at how the rendered HTML performs, check for compatibility issues, watch for unused CSS classes, the sky's the limit. New HTML editor The previous HTML editor had a lot of old code that didn't allow for improvements. The team rewrote the HTML editor to take advantage of the new(ish) extensibility features in Visual Studio, which then allowed them to add in all kinds of features - things like CSS Class and ID IntelliSense (so you type style="" and get a list of classes and ID's for your project), smart indent based on how your document is formatted, JavaScript reference auto-sync, etc. Here's a 3 minute tour from Mads Kristensen. The previous HTML editor had a lot of old code that didn't allow for improvements. The team rewrote the HTML editor to take advantage of the new(ish) extensibility features in Visual Studio, which then allowed them to add in all kinds of features - things like CSS Class and ID IntelliSense (so you type style="" and get a list of classes and ID's for your project), smart indent based on how your document is formatted, JavaScript reference auto-sync, etc. Lots more Visual Studio web dev features That's just a sampling - there's a ton of great features for JavaScript editing, CSS editing, publishing, and Page Inspector (which shows real-time rendering of your page inside Visual Studio). Here are some more short videos showing those features. Lots, lots more Okay, that's just a summary, and it's still quite a bit. Head on over to http://asp.net/vnext for more information, and download Visual Studio 2013 now to get started!

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  • Using a WPF ListView as a DataGrid

    - by psheriff
    Many people like to view data in a grid format of rows and columns. WPF did not come with a data grid control that automatically creates rows and columns for you based on the object you pass it. However, the WPF Toolkit can be downloaded from CodePlex.com that does contain a DataGrid control. This DataGrid gives you the ability to pass it a DataTable or a Collection class and it will automatically figure out the columns or properties and create all the columns for you and display the data.The DataGrid control also supports editing and many other features that you might not always need. This means that the DataGrid does take a little more time to render the data. If you want to just display data (see Figure 1) in a grid format, then a ListView works quite well for this task. Of course, you will need to create the columns for the ListView, but with just a little generic code, you can create the columns on the fly just like the WPF Toolkit’s DataGrid. Figure 1: A List of Data using a ListView A Simple ListView ControlThe XAML below is what you would use to create the ListView shown in Figure 1. However, the problem with using XAML is you have to pre-define the columns. You cannot re-use this ListView except for “Product” data. <ListView x:Name="lstData"          ItemsSource="{Binding}">  <ListView.View>    <GridView>      <GridViewColumn Header="Product ID"                      Width="Auto"               DisplayMemberBinding="{Binding Path=ProductId}" />      <GridViewColumn Header="Product Name"                      Width="Auto"               DisplayMemberBinding="{Binding Path=ProductName}" />      <GridViewColumn Header="Price"                      Width="Auto"               DisplayMemberBinding="{Binding Path=Price}" />    </GridView>  </ListView.View></ListView> So, instead of creating the GridViewColumn’s in XAML, let’s learn to create them in code to create any amount of columns in a ListView. Create GridViewColumn’s From Data TableTo display multiple columns in a ListView control you need to set its View property to a GridView collection object. You add GridViewColumn objects to the GridView collection and assign the GridView to the View property. Each GridViewColumn object needs to be bound to a column or property name of the object that the ListView will be bound to. An ADO.NET DataTable object contains a collection of columns, and these columns have a ColumnName property which you use to bind to the GridViewColumn objects. Listing 1 shows a sample of reading and XML file into a DataSet object. After reading the data a GridView object is created. You can then loop through the DataTable columns collection and create a GridViewColumn object for each column in the DataTable. Notice the DisplayMemberBinding property is set to a new Binding to the ColumnName in the DataTable. C#private void FirstSample(){  // Read the data  DataSet ds = new DataSet();  ds.ReadXml(GetCurrentDirectory() + @"\Xml\Product.xml");    // Create the GridView  GridView gv = new GridView();   // Create the GridView Columns  foreach (DataColumn item in ds.Tables[0].Columns)  {    GridViewColumn gvc = new GridViewColumn();    gvc.DisplayMemberBinding = new Binding(item.ColumnName);    gvc.Header = item.ColumnName;    gvc.Width = Double.NaN;    gv.Columns.Add(gvc);  }   // Setup the GridView Columns  lstData.View = gv;  // Display the Data  lstData.DataContext = ds.Tables[0];} VB.NETPrivate Sub FirstSample()  ' Read the data  Dim ds As New DataSet()  ds.ReadXml(GetCurrentDirectory() & "\Xml\Product.xml")   ' Create the GridView  Dim gv As New GridView()   ' Create the GridView Columns  For Each item As DataColumn In ds.Tables(0).Columns    Dim gvc As New GridViewColumn()    gvc.DisplayMemberBinding = New Binding(item.ColumnName)    gvc.Header = item.ColumnName    gvc.Width = [Double].NaN    gv.Columns.Add(gvc)  Next   ' Setup the GridView Columns  lstData.View = gv  ' Display the Data  lstData.DataContext = ds.Tables(0)End SubListing 1: Loop through the DataTable columns collection to create GridViewColumn objects A Generic Method for Creating a GridViewInstead of having to write the code shown in Listing 1 for each ListView you wish to create, you can create a generic method that given any DataTable will return a GridView column collection. Listing 2 shows how you can simplify the code in Listing 1 by setting up a class called WPFListViewCommon and create a method called CreateGridViewColumns that returns your GridView. C#private void DataTableSample(){  // Read the data  DataSet ds = new DataSet();  ds.ReadXml(GetCurrentDirectory() + @"\Xml\Product.xml");   // Setup the GridView Columns  lstData.View =      WPFListViewCommon.CreateGridViewColumns(ds.Tables[0]);  lstData.DataContext = ds.Tables[0];} VB.NETPrivate Sub DataTableSample()  ' Read the data  Dim ds As New DataSet()  ds.ReadXml(GetCurrentDirectory() & "\Xml\Product.xml")   ' Setup the GridView Columns  lstData.View = _      WPFListViewCommon.CreateGridViewColumns(ds.Tables(0))  lstData.DataContext = ds.Tables(0)End SubListing 2: Call a generic method to create GridViewColumns. The CreateGridViewColumns MethodThe CreateGridViewColumns method will take a DataTable as a parameter and create a GridView object with a GridViewColumn object in its collection for each column in your DataTable. C#public static GridView CreateGridViewColumns(DataTable dt){  // Create the GridView  GridView gv = new GridView();  gv.AllowsColumnReorder = true;   // Create the GridView Columns  foreach (DataColumn item in dt.Columns)  {    GridViewColumn gvc = new GridViewColumn();    gvc.DisplayMemberBinding = new Binding(item.ColumnName);    gvc.Header = item.ColumnName;    gvc.Width = Double.NaN;    gv.Columns.Add(gvc);  }   return gv;} VB.NETPublic Shared Function CreateGridViewColumns _  (ByVal dt As DataTable) As GridView  ' Create the GridView  Dim gv As New GridView()  gv.AllowsColumnReorder = True   ' Create the GridView Columns  For Each item As DataColumn In dt.Columns    Dim gvc As New GridViewColumn()    gvc.DisplayMemberBinding = New Binding(item.ColumnName)    gvc.Header = item.ColumnName    gvc.Width = [Double].NaN    gv.Columns.Add(gvc)  Next   Return gvEnd FunctionListing 3: The CreateGridViewColumns method takes a DataTable and creates GridViewColumn objects in a GridView. By separating this method out into a class you can call this method anytime you want to create a ListView with a collection of columns from a DataTable. SummaryIn this blog you learned how to create a ListView that acts like a DataGrid. You are able to use a DataTable as both the source of the data, and for creating the columns for the ListView. In the next blog entry you will learn how to use the same technique, but for Collection classes. NOTE: You can download the complete sample code (in both VB and C#) at my website. http://www.pdsa.com/downloads. Choose Tips & Tricks, then "WPF ListView as a DataGrid" from the drop-down. Good Luck with your Coding,Paul Sheriff ** SPECIAL OFFER FOR MY BLOG READERS **Visit http://www.pdsa.com/Event/Blog for a free eBook on "Fundamentals of N-Tier".

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  • SignalR Auto Disconnect when Page Changed in AngularJS

    - by Shaun
    Originally posted on: http://geekswithblogs.net/shaunxu/archive/2014/05/30/signalr-auto-disconnect-when-page-changed-in-angularjs.aspxIf we are using SignalR, the connection lifecycle was handled by itself very well. For example when we connect to SignalR service from browser through SignalR JavaScript Client the connection will be established. And if we refresh the page, close the tab or browser, or navigate to another URL then the connection will be closed automatically. This information had been well documented here. In a browser, SignalR client code that maintains a SignalR connection runs in the JavaScript context of a web page. That's why the SignalR connection has to end when you navigate from one page to another, and that's why you have multiple connections with multiple connection IDs if you connect from multiple browser windows or tabs. When the user closes a browser window or tab, or navigates to a new page or refreshes the page, the SignalR connection immediately ends because SignalR client code handles that browser event for you and calls the "Stop" method. But unfortunately this behavior doesn't work if we are using SignalR with AngularJS. AngularJS is a single page application (SPA) framework created by Google. It hijacks browser's address change event, based on the route table user defined, launch proper view and controller. Hence in AngularJS we address was changed but the web page still there. All changes of the page content are triggered by Ajax. So there's no page unload and load events. This is the reason why SignalR cannot handle disconnect correctly when works with AngularJS. If we dig into the source code of SignalR JavaScript Client source code we will find something below. It monitors the browser page "unload" and "beforeunload" event and send the "stop" message to server to terminate connection. But in AngularJS page change events were hijacked, so SignalR will not receive them and will not stop the connection. 1: // wire the stop handler for when the user leaves the page 2: _pageWindow.bind("unload", function () { 3: connection.log("Window unloading, stopping the connection."); 4:  5: connection.stop(asyncAbort); 6: }); 7:  8: if (isFirefox11OrGreater) { 9: // Firefox does not fire cross-domain XHRs in the normal unload handler on tab close. 10: // #2400 11: _pageWindow.bind("beforeunload", function () { 12: // If connection.stop() runs runs in beforeunload and fails, it will also fail 13: // in unload unless connection.stop() runs after a timeout. 14: window.setTimeout(function () { 15: connection.stop(asyncAbort); 16: }, 0); 17: }); 18: }   Problem Reproduce In the codes below I created a very simple example to demonstrate this issue. Here is the SignalR server side code. 1: public class GreetingHub : Hub 2: { 3: public override Task OnConnected() 4: { 5: Debug.WriteLine(string.Format("Connected: {0}", Context.ConnectionId)); 6: return base.OnConnected(); 7: } 8:  9: public override Task OnDisconnected() 10: { 11: Debug.WriteLine(string.Format("Disconnected: {0}", Context.ConnectionId)); 12: return base.OnDisconnected(); 13: } 14:  15: public void Hello(string user) 16: { 17: Clients.All.hello(string.Format("Hello, {0}!", user)); 18: } 19: } Below is the configuration code which hosts SignalR hub in an ASP.NET WebAPI project with IIS Express. 1: public class Startup 2: { 3: public void Configuration(IAppBuilder app) 4: { 5: app.Map("/signalr", map => 6: { 7: map.UseCors(CorsOptions.AllowAll); 8: map.RunSignalR(new HubConfiguration() 9: { 10: EnableJavaScriptProxies = false 11: }); 12: }); 13: } 14: } Since we will host AngularJS application in Node.js in another process and port, the SignalR connection will be cross domain. So I need to enable CORS above. In client side I have a Node.js file to host AngularJS application as a web server. You can use any web server you like such as IIS, Apache, etc.. Below is the "index.html" page which contains a navigation bar so that I can change the page/state. As you can see I added jQuery, AngularJS, SignalR JavaScript Client Library as well as my AngularJS entry source file "app.js". 1: <html data-ng-app="demo"> 2: <head> 3: <script type="text/javascript" src="jquery-2.1.0.js"></script> 1:  2: <script type="text/javascript" src="angular.js"> 1: </script> 2: <script type="text/javascript" src="angular-ui-router.js"> 1: </script> 2: <script type="text/javascript" src="jquery.signalR-2.0.3.js"> 1: </script> 2: <script type="text/javascript" src="app.js"></script> 4: </head> 5: <body> 6: <h1>SignalR Auto Disconnect with AngularJS by Shaun</h1> 7: <div> 8: <a href="javascript:void(0)" data-ui-sref="view1">View 1</a> | 9: <a href="javascript:void(0)" data-ui-sref="view2">View 2</a> 10: </div> 11: <div data-ui-view></div> 12: </body> 13: </html> Below is the "app.js". My SignalR logic was in the "View1" page and it will connect to server once the controller was executed. User can specify a user name and send to server, all clients that located in this page will receive the server side greeting message through SignalR. 1: 'use strict'; 2:  3: var app = angular.module('demo', ['ui.router']); 4:  5: app.config(['$stateProvider', '$locationProvider', function ($stateProvider, $locationProvider) { 6: $stateProvider.state('view1', { 7: url: '/view1', 8: templateUrl: 'view1.html', 9: controller: 'View1Ctrl' }); 10:  11: $stateProvider.state('view2', { 12: url: '/view2', 13: templateUrl: 'view2.html', 14: controller: 'View2Ctrl' }); 15:  16: $locationProvider.html5Mode(true); 17: }]); 18:  19: app.value('$', $); 20: app.value('endpoint', 'http://localhost:60448'); 21: app.value('hub', 'GreetingHub'); 22:  23: app.controller('View1Ctrl', function ($scope, $, endpoint, hub) { 24: $scope.user = ''; 25: $scope.response = ''; 26:  27: $scope.greeting = function () { 28: proxy.invoke('Hello', $scope.user) 29: .done(function () {}) 30: .fail(function (error) { 31: console.log(error); 32: }); 33: }; 34:  35: var connection = $.hubConnection(endpoint); 36: var proxy = connection.createHubProxy(hub); 37: proxy.on('hello', function (response) { 38: $scope.$apply(function () { 39: $scope.response = response; 40: }); 41: }); 42: connection.start() 43: .done(function () { 44: console.log('signlar connection established'); 45: }) 46: .fail(function (error) { 47: console.log(error); 48: }); 49: }); 50:  51: app.controller('View2Ctrl', function ($scope, $) { 52: }); When we went to View1 the server side "OnConnect" method will be invoked as below. And in any page we send the message to server, all clients will got the response. If we close one of the client, the server side "OnDisconnect" method will be invoked which is correct. But is we click "View 2" link in the page "OnDisconnect" method will not be invoked even though the content and browser address had been changed. This might cause many SignalR connections remain between the client and server. Below is what happened after I clicked "View 1" and "View 2" links four times. As you can see there are 4 live connections.   Solution Since the reason of this issue is because, AngularJS hijacks the page event that SignalR need to stop the connection, we can handle AngularJS route or state change event and stop SignalR connect manually. In the code below I moved the "connection" variant to global scope, added a handler to "$stateChangeStart" and invoked "stop" method of "connection" if its state was not "disconnected". 1: var connection; 2: app.run(['$rootScope', function ($rootScope) { 3: $rootScope.$on('$stateChangeStart', function () { 4: if (connection && connection.state && connection.state !== 4 /* disconnected */) { 5: console.log('signlar connection abort'); 6: connection.stop(); 7: } 8: }); 9: }]); Now if we refresh the page and navigated to View 1, the connection will be opened. At this state if we clicked "View 2" link the content will be changed and the SignalR connection will be closed automatically.   Summary In this post I demonstrated an issue when we are using SignalR with AngularJS. The connection cannot be closed automatically when we navigate to other page/state in AngularJS. And the solution I mentioned below is to move the SignalR connection as a global variant and close it manually when AngularJS route/state changed. You can download the full sample code here. Moving the SignalR connection as a global variant might not be a best solution. It's just for easy to demo here. In production code I suggest wrapping all SignalR operations into an AngularJS factory. Since AngularJS factory is a singleton object, we can safely put the connection variant in the factory function scope.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Ajax Control Toolkit May 2012 Release

    - by Stephen.Walther
    I’m happy to announce the May 2012 release of the Ajax Control Toolkit. This newest release of the Ajax Control Toolkit includes a new file upload control which displays file upload progress. We’ve also added several significant enhancements to the existing HtmlEditorExtender control such as support for uploading images and Source View. You can download and start using the newest version of the Ajax Control Toolkit by entering the following command in the Library Package Manager console in Visual Studio: Install-Package AjaxControlToolkit Alternatively, you can download the latest version of the Ajax Control Toolkit from CodePlex: http://AjaxControlToolkit.CodePlex.com The New Ajax File Upload Control The most requested new feature for the Ajax Control Toolkit (according to the CodePlex Issue Tracker) has been support for file upload with progress. We worked hard over the last few months to create an entirely new file upload control which displays upload progress. Here is a sample which illustrates how you can use the new AjaxFileUpload control: <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="01_FileUpload.aspx.cs" Inherits="WebApplication1._01_FileUpload" %> <html> <head runat="server"> <title>Simple File Upload</title> </head> <body> <form id="form1" runat="server"> <div> <ajaxToolkit:ToolkitScriptManager runat="server" /> <ajaxToolkit:AjaxFileUpload id="ajaxUpload1" OnUploadComplete="ajaxUpload1_OnUploadComplete" runat="server" /> </div> </form> </body> </html> The page above includes a ToolkitScriptManager control. This control is required to use any of the controls in the Ajax Control Toolkit because this control is responsible for loading all of the scripts required by a control. The page also contains an AjaxFileUpload control. The UploadComplete event is handled in the code-behind for the page: namespace WebApplication1 { public partial class _01_FileUpload : System.Web.UI.Page { protected void ajaxUpload1_OnUploadComplete(object sender, AjaxControlToolkit.AjaxFileUploadEventArgs e) { // Generate file path string filePath = "~/Images/" + e.FileName; // Save upload file to the file system ajaxUpload1.SaveAs(MapPath(filePath)); } } } The UploadComplete handler saves each uploaded file by calling the AjaxFileUpload control’s SaveAs() method with a full file path. Here’s a video which illustrates the process of uploading a file: Warning: in order to write to the Images folder on a production IIS server, you need Write permissions on the Images folder. You need to provide permissions for the IIS Application Pool account to write to the Images folder. To learn more, see: http://learn.iis.net/page.aspx/624/application-pool-identities/ Showing File Upload Progress The new AjaxFileUpload control takes advantage of HTML5 upload progress events (described in the XMLHttpRequest Level 2 standard). This standard is supported by Firefox 8+, Chrome 16+, Safari 5+, and Internet Explorer 10+. In other words, the standard is supported by the most recent versions of all browsers except for Internet Explorer which will support the standard with the release of Internet Explorer 10. The AjaxFileUpload control works with all browsers, even browsers which do not support the new XMLHttpRequest Level 2 standard. If you use the AjaxFileUpload control with a downlevel browser – such as Internet Explorer 9 — then you get a simple throbber image during a file upload instead of a progress indicator. Here’s how you specify a throbber image when declaring the AjaxFileUpload control: <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="02_FileUpload.aspx.cs" Inherits="WebApplication1._02_FileUpload" %> <html> <head id="Head1" runat="server"> <title>File Upload with Throbber</title> </head> <body> <form id="form1" runat="server"> <div> <ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server" /> <ajaxToolkit:AjaxFileUpload id="ajaxUpload1" OnUploadComplete="ajaxUpload1_OnUploadComplete" ThrobberID="MyThrobber" runat="server" /> <asp:Image id="MyThrobber" ImageUrl="ajax-loader.gif" Style="display:None" runat="server" /> </div> </form> </body> </html> Notice that the page above includes an image with the Id MyThrobber. This image is displayed while files are being uploaded. I use the website http://AjaxLoad.info to generate animated busy wait images. Drag-And-Drop File Upload If you are using an uplevel browser then you can drag-and-drop the files which you want to upload onto the AjaxFileUpload control. The following video illustrates how drag-and-drop works: Remember that drag-and-drop will not work on Internet Explorer 9 or older. Accepting Multiple Files By default, the AjaxFileUpload control enables you to upload multiple files at a time. When you open the file dialog, use the CTRL or SHIFT key to select multiple files. If you want to restrict the number of files that can be uploaded then use the MaximumNumberOfFiles property like this: <ajaxToolkit:AjaxFileUpload id="ajaxUpload1" OnUploadComplete="ajaxUpload1_OnUploadComplete" ThrobberID="throbber" MaximumNumberOfFiles="1" runat="server" /> In the code above, the maximum number of files which can be uploaded is restricted to a single file. Restricting Uploaded File Types You might want to allow only certain types of files to be uploaded. For example, you might want to accept only image uploads. In that case, you can use the AllowedFileTypes property to provide a list of allowed file types like this: <ajaxToolkit:AjaxFileUpload id="ajaxUpload1" OnUploadComplete="ajaxUpload1_OnUploadComplete" ThrobberID="throbber" AllowedFileTypes="jpg,jpeg,gif,png" runat="server" /> The code above prevents any files except jpeg, gif, and png files from being uploaded. Enhancements to the HTMLEditorExtender Over the past months, we spent a considerable amount of time making bug fixes and feature enhancements to the existing HtmlEditorExtender control. I want to focus on two of the most significant enhancements that we made to the control: support for Source View and support for uploading images. Adding Source View Support to the HtmlEditorExtender When you click the Source View tag, the HtmlEditorExtender changes modes and displays the HTML source of the contents contained in the TextBox being extended. You can use Source View to make fine-grain changes to HTML before submitting the HTML to the server. For reasons of backwards compatibility, the Source View tab is disabled by default. To enable Source View, you need to declare your HtmlEditorExtender with the DisplaySourceTab property like this: <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="05_SourceView.aspx.cs" Inherits="WebApplication1._05_SourceView" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head id="Head1" runat="server"> <title>HtmlEditorExtender with Source View</title> </head> <body> <form id="form1" runat="server"> <div> <ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server" /> <asp:TextBox id="txtComments" TextMode="MultiLine" Columns="60" Rows="10" Runat="server" /> <ajaxToolkit:HtmlEditorExtender id="HEE1" TargetControlID="txtComments" DisplaySourceTab="true" runat="server" /> </div> </form> </body> </html> The page above includes a ToolkitScriptManager, TextBox, and HtmlEditorExtender control. The HtmlEditorExtender extends the TextBox so that it supports rich text editing. Notice that the HtmlEditorExtender includes a DisplaySourceTab property. This property causes a button to appear at the bottom of the HtmlEditorExtender which enables you to switch to Source View: Note: when using the HtmlEditorExtender, we recommend that you set the DOCTYPE for the document. Otherwise, you can encounter weird formatting issues. Accepting Image Uploads We also enhanced the HtmlEditorExtender to support image uploads (another very highly requested feature at CodePlex). The following video illustrates the experience of adding an image to the editor: Once again, for backwards compatibility reasons, support for image uploads is disabled by default. Here’s how you can declare the HtmlEditorExtender so that it supports image uploads: <ajaxToolkit:HtmlEditorExtender id="MyHtmlEditorExtender" TargetControlID="txtComments" OnImageUploadComplete="MyHtmlEditorExtender_ImageUploadComplete" DisplaySourceTab="true" runat="server" > <Toolbar> <ajaxToolkit:Bold /> <ajaxToolkit:Italic /> <ajaxToolkit:Underline /> <ajaxToolkit:InsertImage /> </Toolbar> </ajaxToolkit:HtmlEditorExtender> There are two things that you should notice about the code above. First, notice that an InsertImage toolbar button is added to the HtmlEditorExtender toolbar. This HtmlEditorExtender will render toolbar buttons for bold, italic, underline, and insert image. Second, notice that the HtmlEditorExtender includes an event handler for the ImageUploadComplete event. The code for this event handler is below: using System.Web.UI; using AjaxControlToolkit; namespace WebApplication1 { public partial class _06_ImageUpload : System.Web.UI.Page { protected void MyHtmlEditorExtender_ImageUploadComplete(object sender, AjaxFileUploadEventArgs e) { // Generate file path string filePath = "~/Images/" + e.FileName; // Save uploaded file to the file system var ajaxFileUpload = (AjaxFileUpload)sender; ajaxFileUpload.SaveAs(MapPath(filePath)); // Update client with saved image path e.PostedUrl = Page.ResolveUrl(filePath); } } } Within the ImageUploadComplete event handler, you need to do two things: 1) Save the uploaded image (for example, to the file system, a database, or Azure storage) 2) Provide the URL to the saved image so the image can be displayed within the HtmlEditorExtender In the code above, the uploaded image is saved to the ~/Images folder. The path of the saved image is returned to the client by setting the AjaxFileUploadEventArgs PostedUrl property. Not surprisingly, under the covers, the HtmlEditorExtender uses the AjaxFileUpload. You can get a direct reference to the AjaxFileUpload control used by an HtmlEditorExtender by using the following code: void Page_Load() { var ajaxFileUpload = MyHtmlEditorExtender.AjaxFileUpload; ajaxFileUpload.AllowedFileTypes = "jpg,jpeg"; } The code above illustrates how you can restrict the types of images that can be uploaded to the HtmlEditorExtender. This code prevents anything but jpeg images from being uploaded. Summary This was the most difficult release of the Ajax Control Toolkit to date. We iterated through several designs for the AjaxFileUpload control – with each iteration, the goal was to make the AjaxFileUpload control easier for developers to use. My hope is that we were able to create a control which Web Forms developers will find very intuitive. I want to thank the developers on the Superexpert.com team for their hard work on this release.

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