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  • how to update off screen pivot item

    - by Yama moto
    I want to have a pivot with many PivotItems. However, doing so will impact memory. So I bind pivot to my ViewModel, which has 3 item, and pivot will generate 3 PivotItems. My ViewModel is of type ObservableCollection and my item does implement INotifyPropertyChanged. This works fine. But when I update my ViewModel, only the current PivotItem, and the right PivotItem is updated. The left PivotItem, which is off screen, is not updated. You can see it when you drag pivot to the left. How to fix this? Or WP7 doesnot update off screen PivotItem ?

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  • Should I use ObservableCollections in my Model in M-V-VM

    - by Bill Jeeves
    I'm completely new to M-V-VM and very new to Silverlight, just reading about it for the first time today. As a sample, I am creating a model containing a list of items. My (Silverlight 4) View contains a listbox and my ViewModel will look to the model to retrieve the collection that the listbox will bind to. My question is this. I think it would be good to use an ObservableCollection to hold the items that the listbox binds to. This would be an ObseravleCollection in the ViewModel. Should I also use this type of collection in the model, or should I use another collection type and do smoe conversion between model and viewmodel?

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  • Silverlight Cream for March 08, 2010 -- #809

    - by Dave Campbell
    In this Issue: Michael Washington, Tim Greenfield, Bobby Diaz(-2-), Glenn Block(-2-), Nikhil Kothari, Jianqiang Bao(-2-), and Christopher Bennage. Shoutouts: Adam Kinney announced a Big update for the Project Rosetta site today Arpit Gupta has opened a new blog with a great logo: I think therefore I am dangerous :) From SilverlightCream.com: DotNetNuke Silverlight Traffic Module If it's DNN and Silverlight, it has to be my buddy Michael Washington :) ... Michael has combined those stunning gauges you've seen with website traffic... just too cool!... grab the code and display yours too! Cool demonstration of Silverlight VideoBrush This is a no-code post by Tim Greenfield, but I like the UX on this Jigsaw Puzzle page... and you can make your own. Introducing the Earthquake Locator – A Bing Maps Silverlight Application, part 1 Bobby Diaz has an informative post up on combining earthquake data with BingMaps in Silverlight 3... check it out, the grab the recently posted Live Demo and Source Code Adding Volcanos and Options - Earthquake Locator, part 2 Bobby Diaz also added volcanic activity to his earthquake BinMaps app, and updated the downloadable code and live demo. Building Hello MEF – Part IV – DeploymentCatalog Glenn Block posted a pair of MEF posts yesterday... made me think I missed one :) .. the first one is about the DeploymentCatalog. Note he is going to be using the CodePlex bits in his posts. Building HelloMEF – Part V – Refactoring to ViewModel Glenn Block's part V is about MEF and MVVM -- no, really! ... he is refactoring MVVM into the app with a nod to Josh Smith and Laurent Bugnion... get your head around this... The Case for ViewModel Nikhil Kothari has a post up about the ViewModel, and how it facilitates designer/developer workflow, jumpstarts development, improves scaling, and makes asynch programming development simpler MMORPG programming in Silverlight Tutorial (12)Map Instance (Part I) Jianqiang Bao has part 12 of his MMORPG game up... this one is showing how to deal with obstuctions on maps. MMORPG programming in Silverlight Tutorial (13)Perfect moving mechanism Jianqiang Bao also has part 13 up, and this second one is about sprite movement around the obstructions. 1 Simple Step for Commanding in Silverlight Christopher Bennage blogged about Commanding in Silverlight, he begins with a blog post about commands in Silverlight 4 then goes on to demonstrate the Caliburn way of doing commanding. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    MIX10

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  • ASP.NET Web API - Screencast series Part 4: Paging and Querying

    - by Jon Galloway
    We're continuing a six part series on ASP.NET Web API that accompanies the getting started screencast series. This is an introductory screencast series that walks through from File / New Project to some more advanced scenarios like Custom Validation and Authorization. The screencast videos are all short (3-5 minutes) and the sample code for the series is both available for download and browsable online. I did the screencasts, but the samples were written by the ASP.NET Web API team. In Part 1 we looked at what ASP.NET Web API is, why you'd care, did the File / New Project thing, and did some basic HTTP testing using browser F12 developer tools. In Part 2 we started to build up a sample that returns data from a repository in JSON format via GET methods. In Part 3, we modified data on the server using DELETE and POST methods. In Part 4, we'll extend on our simple querying methods form Part 2, adding in support for paging and querying. This part shows two approaches to querying data (paging really just being a specific querying case) - you can do it yourself using parameters passed in via querystring (as well as headers, other route parameters, cookies, etc.). You're welcome to do that if you'd like. What I think is more interesting here is that Web API actions that return IQueryable automatically support OData query syntax, making it really easy to support some common query use cases like paging and filtering. A few important things to note: This is just support for OData query syntax - you're not getting back data in OData format. The screencast demonstrates this by showing the GET methods are continuing to return the same JSON they did previously. So you don't have to "buy in" to the whole OData thing, you're just able to use the query syntax if you'd like. This isn't full OData query support - full OData query syntax includes a lot of operations and features - but it is a pretty good subset: filter, orderby, skip, and top. All you have to do to enable this OData query syntax is return an IQueryable rather than an IEnumerable. Often, that could be as simple as using the AsQueryable() extension method on your IEnumerable. Query composition support lets you layer queries intelligently. If, for instance, you had an action that showed products by category using a query in your repository, you could also support paging on top of that. The result is an expression tree that's evaluated on-demand and includes both the Web API query and the underlying query. So with all those bullet points and big words, you'd think this would be hard to hook up. Nope, all I did was change the return type from IEnumerable<Comment> to IQueryable<Comment> and convert the Get() method's IEnumerable result using the .AsQueryable() extension method. public IQueryable<Comment> GetComments() { return repository.Get().AsQueryable(); } You still need to build up the query to provide the $top and $skip on the client, but you'd need to do that regardless. Here's how that looks: $(function () { //--------------------------------------------------------- // Using Queryable to page //--------------------------------------------------------- $("#getCommentsQueryable").click(function () { viewModel.comments([]); var pageSize = $('#pageSize').val(); var pageIndex = $('#pageIndex').val(); var url = "/api/comments?$top=" + pageSize + '&$skip=' + (pageIndex * pageSize); $.getJSON(url, function (data) { // Update the Knockout model (and thus the UI) with the comments received back // from the Web API call. viewModel.comments(data); }); return false; }); }); And the neat thing is that - without any modification to our server-side code - we can modify the above jQuery call to request the comments be sorted by author: $(function () { //--------------------------------------------------------- // Using Queryable to page //--------------------------------------------------------- $("#getCommentsQueryable").click(function () { viewModel.comments([]); var pageSize = $('#pageSize').val(); var pageIndex = $('#pageIndex').val(); var url = "/api/comments?$top=" + pageSize + '&$skip=' + (pageIndex * pageSize) + '&$orderby=Author'; $.getJSON(url, function (data) { // Update the Knockout model (and thus the UI) with the comments received back // from the Web API call. viewModel.comments(data); }); return false; }); }); So if you want to make use of OData query syntax, you can. If you don't like it, you're free to hook up your filtering and paging however you think is best. Neat. In Part 5, we'll add on support for Data Annotation based validation using an Action Filter.

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  • Security Issues with Single Page Apps

    - by Stephen.Walther
    Last week, I was asked to do a code review of a Single Page App built using the ASP.NET Web API, Durandal, and Knockout (good stuff!). In particular, I was asked to investigate whether there any special security issues associated with building a Single Page App which are not present in the case of a traditional server-side ASP.NET application. In this blog entry, I discuss two areas in which you need to exercise extra caution when building a Single Page App. I discuss how Single Page Apps are extra vulnerable to both Cross-Site Scripting (XSS) attacks and Cross-Site Request Forgery (CSRF) attacks. This goal of this blog post is NOT to persuade you to avoid writing Single Page Apps. I’m a big fan of Single Page Apps. Instead, the goal is to ensure that you are fully aware of some of the security issues related to Single Page Apps and ensure that you know how to guard against them. Cross-Site Scripting (XSS) Attacks According to WhiteHat Security, over 65% of public websites are open to XSS attacks. That’s bad. By taking advantage of XSS holes in a website, a hacker can steal your credit cards, passwords, or bank account information. Any website that redisplays untrusted information is open to XSS attacks. Let me give you a simple example. Imagine that you want to display the name of the current user on a page. To do this, you create the following server-side ASP.NET page located at http://MajorBank.com/SomePage.aspx: <%@Page Language="C#" %> <html> <head> <title>Some Page</title> </head> <body> Welcome <%= Request["username"] %> </body> </html> Nothing fancy here. Notice that the page displays the current username by using Request[“username”]. Using Request[“username”] displays the username regardless of whether the username is present in a cookie, a form field, or a query string variable. Unfortunately, by using Request[“username”] to redisplay untrusted information, you have now opened your website to XSS attacks. Here’s how. Imagine that an evil hacker creates the following link on another website (hackers.com): <a href="/SomePage.aspx?username=<script src=Evil.js></script>">Visit MajorBank</a> Notice that the link includes a query string variable named username and the value of the username variable is an HTML <SCRIPT> tag which points to a JavaScript file named Evil.js. When anyone clicks on the link, the <SCRIPT> tag will be injected into SomePage.aspx and the Evil.js script will be loaded and executed. What can a hacker do in the Evil.js script? Anything the hacker wants. For example, the hacker could display a popup dialog on the MajorBank.com site which asks the user to enter their password. The script could then post the password back to hackers.com and now the evil hacker has your secret password. ASP.NET Web Forms and ASP.NET MVC have two automatic safeguards against this type of attack: Request Validation and Automatic HTML Encoding. Protecting Coming In (Request Validation) In a server-side ASP.NET app, you are protected against the XSS attack described above by a feature named Request Validation. If you attempt to submit “potentially dangerous” content — such as a JavaScript <SCRIPT> tag — in a form field or query string variable then you get an exception. Unfortunately, Request Validation only applies to server-side apps. Request Validation does not help in the case of a Single Page App. In particular, the ASP.NET Web API does not pay attention to Request Validation. You can post any content you want – including <SCRIPT> tags – to an ASP.NET Web API action. For example, the following HTML page contains a form. When you submit the form, the form data is submitted to an ASP.NET Web API controller on the server using an Ajax request: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> </head> <body> <form data-bind="submit:submit"> <div> <label> User Name: <input data-bind="value:user.userName" /> </label> </div> <div> <label> Email: <input data-bind="value:user.email" /> </label> </div> <div> <input type="submit" value="Submit" /> </div> </form> <script src="Scripts/jquery-1.7.1.js"></script> <script src="Scripts/knockout-2.1.0.js"></script> <script> var viewModel = { user: { userName: ko.observable(), email: ko.observable() }, submit: function () { $.post("/api/users", ko.toJS(this.user)); } }; ko.applyBindings(viewModel); </script> </body> </html> The form above is using Knockout to bind the form fields to a view model. When you submit the form, the view model is submitted to an ASP.NET Web API action on the server. Here’s the server-side ASP.NET Web API controller and model class: public class UsersController : ApiController { public HttpResponseMessage Post(UserViewModel user) { var userName = user.UserName; return Request.CreateResponse(HttpStatusCode.OK); } } public class UserViewModel { public string UserName { get; set; } public string Email { get; set; } } If you submit the HTML form, you don’t get an error. The “potentially dangerous” content is passed to the server without any exception being thrown. In the screenshot below, you can see that I was able to post a username form field with the value “<script>alert(‘boo’)</script”. So what this means is that you do not get automatic Request Validation in the case of a Single Page App. You need to be extra careful in a Single Page App about ensuring that you do not display untrusted content because you don’t have the Request Validation safety net which you have in a traditional server-side ASP.NET app. Protecting Going Out (Automatic HTML Encoding) Server-side ASP.NET also protects you from XSS attacks when you render content. By default, all content rendered by the razor view engine is HTML encoded. For example, the following razor view displays the text “<b>Hello!</b>” instead of the text “Hello!” in bold: @{ var message = "<b>Hello!</b>"; } @message   If you don’t want to render content as HTML encoded in razor then you need to take the extra step of using the @Html.Raw() helper. In a Web Form page, if you use <%: %> instead of <%= %> then you get automatic HTML Encoding: <%@ Page Language="C#" %> <% var message = "<b>Hello!</b>"; %> <%: message %> This automatic HTML Encoding will prevent many types of XSS attacks. It prevents <script> tags from being rendered and only allows &lt;script&gt; tags to be rendered which are useless for executing JavaScript. (This automatic HTML encoding does not protect you from all forms of XSS attacks. For example, you can assign the value “javascript:alert(‘evil’)” to the Hyperlink control’s NavigateUrl property and execute the JavaScript). The situation with Knockout is more complicated. If you use the Knockout TEXT binding then you get HTML encoded content. On the other hand, if you use the HTML binding then you do not: <!-- This JavaScript DOES NOT execute --> <div data-bind="text:someProp"></div> <!-- This Javacript DOES execute --> <div data-bind="html:someProp"></div> <script src="Scripts/jquery-1.7.1.js"></script> <script src="Scripts/knockout-2.1.0.js"></script> <script> var viewModel = { someProp : "<script>alert('Evil!')<" + "/script>" }; ko.applyBindings(viewModel); </script>   So, in the page above, the DIV element which uses the TEXT binding is safe from XSS attacks. According to the Knockout documentation: “Since this binding sets your text value using a text node, it’s safe to set any string value without risking HTML or script injection.” Just like server-side HTML encoding, Knockout does not protect you from all types of XSS attacks. For example, there is nothing in Knockout which prevents you from binding JavaScript to a hyperlink like this: <a data-bind="attr:{href:homePageUrl}">Go</a> <script src="Scripts/jquery-1.7.1.min.js"></script> <script src="Scripts/knockout-2.1.0.js"></script> <script> var viewModel = { homePageUrl: "javascript:alert('evil!')" }; ko.applyBindings(viewModel); </script> In the page above, the value “javascript:alert(‘evil’)” is bound to the HREF attribute using Knockout. When you click the link, the JavaScript executes. Cross-Site Request Forgery (CSRF) Attacks Cross-Site Request Forgery (CSRF) attacks rely on the fact that a session cookie does not expire until you close your browser. In particular, if you visit and login to MajorBank.com and then you navigate to Hackers.com then you will still be authenticated against MajorBank.com even after you navigate to Hackers.com. Because MajorBank.com cannot tell whether a request is coming from MajorBank.com or Hackers.com, Hackers.com can submit requests to MajorBank.com pretending to be you. For example, Hackers.com can post an HTML form from Hackers.com to MajorBank.com and change your email address at MajorBank.com. Hackers.com can post a form to MajorBank.com using your authentication cookie. After your email address has been changed, by using a password reset page at MajorBank.com, a hacker can access your bank account. To prevent CSRF attacks, you need some mechanism for detecting whether a request is coming from a page loaded from your website or whether the request is coming from some other website. The recommended way of preventing Cross-Site Request Forgery attacks is to use the “Synchronizer Token Pattern” as described here: https://www.owasp.org/index.php/Cross-Site_Request_Forgery_%28CSRF%29_Prevention_Cheat_Sheet When using the Synchronizer Token Pattern, you include a hidden input field which contains a random token whenever you display an HTML form. When the user opens the form, you add a cookie to the user’s browser with the same random token. When the user posts the form, you verify that the hidden form token and the cookie token match. Preventing Cross-Site Request Forgery Attacks with ASP.NET MVC ASP.NET gives you a helper and an action filter which you can use to thwart Cross-Site Request Forgery attacks. For example, the following razor form for creating a product shows how you use the @Html.AntiForgeryToken() helper: @model MvcApplication2.Models.Product <h2>Create Product</h2> @using (Html.BeginForm()) { @Html.AntiForgeryToken(); <div> @Html.LabelFor( p => p.Name, "Product Name:") @Html.TextBoxFor( p => p.Name) </div> <div> @Html.LabelFor( p => p.Price, "Product Price:") @Html.TextBoxFor( p => p.Price) </div> <input type="submit" /> } The @Html.AntiForgeryToken() helper generates a random token and assigns a serialized version of the same random token to both a cookie and a hidden form field. (Actually, if you dive into the source code, the AntiForgeryToken() does something a little more complex because it takes advantage of a user’s identity when generating the token). Here’s what the hidden form field looks like: <input name=”__RequestVerificationToken” type=”hidden” value=”NqqZGAmlDHh6fPTNR_mti3nYGUDgpIkCiJHnEEL59S7FNToyyeSo7v4AfzF2i67Cv0qTB1TgmZcqiVtgdkW2NnXgEcBc-iBts0x6WAIShtM1″ /> And here’s what the cookie looks like using the Google Chrome developer toolbar: You use the [ValidateAntiForgeryToken] action filter on the controller action which is the recipient of the form post to validate that the token in the hidden form field matches the token in the cookie. If the tokens don’t match then validation fails and you can’t post the form: public ActionResult Create() { return View(); } [ValidateAntiForgeryToken] [HttpPost] public ActionResult Create(Product productToCreate) { if (ModelState.IsValid) { // save product to db return RedirectToAction("Index"); } return View(); } How does this all work? Let’s imagine that a hacker has copied the Create Product page from MajorBank.com to Hackers.com – the hacker grabs the HTML source and places it at Hackers.com. Now, imagine that the hacker trick you into submitting the Create Product form from Hackers.com to MajorBank.com. You’ll get the following exception: The Cross-Site Request Forgery attack is blocked because the anti-forgery token included in the Create Product form at Hackers.com won’t match the anti-forgery token stored in the cookie in your browser. The tokens were generated at different times for different users so the attack fails. Preventing Cross-Site Request Forgery Attacks with a Single Page App In a Single Page App, you can’t prevent Cross-Site Request Forgery attacks using the same method as a server-side ASP.NET MVC app. In a Single Page App, HTML forms are not generated on the server. Instead, in a Single Page App, forms are loaded dynamically in the browser. Phil Haack has a blog post on this topic where he discusses passing the anti-forgery token in an Ajax header instead of a hidden form field. He also describes how you can create a custom anti-forgery token attribute to compare the token in the Ajax header and the token in the cookie. See: http://haacked.com/archive/2011/10/10/preventing-csrf-with-ajax.aspx Also, take a look at Johan’s update to Phil Haack’s original post: http://johan.driessen.se/posts/Updated-Anti-XSRF-Validation-for-ASP.NET-MVC-4-RC (Other server frameworks such as Rails and Django do something similar. For example, Rails uses an X-CSRF-Token to prevent CSRF attacks which you generate on the server – see http://excid3.com/blog/rails-tip-2-include-csrf-token-with-every-ajax-request/#.UTFtgDDkvL8 ). For example, if you are creating a Durandal app, then you can use the following razor view for your one and only server-side page: @{ Layout = null; } <!DOCTYPE html> <html> <head> <title>Index</title> </head> <body> @Html.AntiForgeryToken() <div id="applicationHost"> Loading app.... </div> @Scripts.Render("~/scripts/vendor") <script type="text/javascript" src="~/App/durandal/amd/require.js" data-main="/App/main"></script> </body> </html> Notice that this page includes a call to @Html.AntiForgeryToken() to generate the anti-forgery token. Then, whenever you make an Ajax request in the Durandal app, you can retrieve the anti-forgery token from the razor view and pass the token as a header: var csrfToken = $("input[name='__RequestVerificationToken']").val(); $.ajax({ headers: { __RequestVerificationToken: csrfToken }, type: "POST", dataType: "json", contentType: 'application/json; charset=utf-8', url: "/api/products", data: JSON.stringify({ name: "Milk", price: 2.33 }), statusCode: { 200: function () { alert("Success!"); } } }); Use the following code to create an action filter which you can use to match the header and cookie tokens: using System.Linq; using System.Net.Http; using System.Web.Helpers; using System.Web.Http.Controllers; namespace MvcApplication2.Infrastructure { public class ValidateAjaxAntiForgeryToken : System.Web.Http.AuthorizeAttribute { protected override bool IsAuthorized(HttpActionContext actionContext) { var headerToken = actionContext .Request .Headers .GetValues("__RequestVerificationToken") .FirstOrDefault(); ; var cookieToken = actionContext .Request .Headers .GetCookies() .Select(c => c[AntiForgeryConfig.CookieName]) .FirstOrDefault(); // check for missing cookie or header if (cookieToken == null || headerToken == null) { return false; } // ensure that the cookie matches the header try { AntiForgery.Validate(cookieToken.Value, headerToken); } catch { return false; } return base.IsAuthorized(actionContext); } } } Notice that the action filter derives from the base AuthorizeAttribute. The ValidateAjaxAntiForgeryToken only works when the user is authenticated and it will not work for anonymous requests. Add the action filter to your ASP.NET Web API controller actions like this: [ValidateAjaxAntiForgeryToken] public HttpResponseMessage PostProduct(Product productToCreate) { // add product to db return Request.CreateResponse(HttpStatusCode.OK); } After you complete these steps, it won’t be possible for a hacker to pretend to be you at Hackers.com and submit a form to MajorBank.com. The header token used in the Ajax request won’t travel to Hackers.com. This approach works, but I am not entirely happy with it. The one thing that I don’t like about this approach is that it creates a hard dependency on using razor. Your single page in your Single Page App must be generated from a server-side razor view. A better solution would be to generate the anti-forgery token in JavaScript. Unfortunately, until all browsers support a way to generate cryptographically strong random numbers – for example, by supporting the window.crypto.getRandomValues() method — there is no good way to generate anti-forgery tokens in JavaScript. So, at least right now, the best solution for generating the tokens is the server-side solution with the (regrettable) dependency on razor. Conclusion The goal of this blog entry was to explore some ways in which you need to handle security differently in the case of a Single Page App than in the case of a traditional server app. In particular, I focused on how to prevent Cross-Site Scripting and Cross-Site Request Forgery attacks in the case of a Single Page App. I want to emphasize that I am not suggesting that Single Page Apps are inherently less secure than server-side apps. Whatever type of web application you build – regardless of whether it is a Single Page App, an ASP.NET MVC app, an ASP.NET Web Forms app, or a Rails app – you must constantly guard against security vulnerabilities.

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  • KISS and Tell - MVVM and the ViewModelLocator

    - by Bobby Diaz
    A popular topic that comes up when talking about MVVM is the use of a ViewModelLocator and the many different ways one can be implemented.  Rather than getting into the pros and cons on when or why you should use it, I decided I would just post my version of a simple ViewModelLocator and let those who like it use it, and those who don’t, well you know…  :) First, a disclaimer.  I have not used this code in a production application, it is just something I was tossing around while reading others’ posts on the subject. 1. MainView.xaml   2. MainViewModel.cs 3. ViewModelLocator.cs   I have a codepaste of the ViewModelLocator.cs file if you are interested but don’t feel like re-typing the 50 lines of code! Enjoy! Additional Resources Simple ViewModel Locator for MVVM: The Patients Have Left the Asylum - by John Papa ViewModel binding with the Managed Extensibility Framework - by Jeremy Likness MVVM Light Toolkit - by Laurent Bugnion

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  • Silverlight Cream for April 26, 2010 -- #848

    - by Dave Campbell
    In this Issue: Viktor Larsson, Mike Snow(-2-), Jeff Brand, Marlon Grech(-2-, -3-), Jonathan van de Veen, Phil Middlemiss. Shoutout: Justin Angel wants everyone to know he is Joining the Vertigo Team!... congratulations, Justin! From SilverlightCream.com: Learning Silverlight – Advanced Color Animations Viktor Larsson is demonstrating small pieces of Silverlight he's picked upon in the course of his work project. This first one is on ColorAnimations using KeyFrames Silverlight Tip of the Day #4 – Enabling Out of Browser Applications Mike Snow has Tip #4 up and it's all about OOB... from what you have to do to what your user sees, including how to check to see if you're running OOB... source project included. Silverlight Tip of the Day #5 – Debugging Out of Browser Applications Following a fine tradition he started with his first series, Mike Snow is putting out more than one Tip per day :) ... Number 5 is up and is all about debugging OOB apps. Simplifying Page Transitions in Windows Phone 7 Silverlight Applications Jeff Brand has a WP7 post up discussing Page Transitions. He first discusses the most common brute-force method, then moves into the TransitioningContentControl from the Toolkit. An introduction to MEFedMVVM – PART 1 Marlon Grech, Peter O’Hanlon, and Glenn Block worked together to produce an MEF and MVVM library that works for WPF and Silverlight and allows Design-time goodness and a loosely-coupled bridge between the View and ViewModel ... and it's on CodePlex ... they're also looking for comments/additions, so check it out. Leveraging MEFedMVVM ExportViewModel – MEFedMVVM Part 2 In Part 2, Marlon Grech demonstrates using MEFedMVVM and shows off some of the basics such as Importing services, Design-Time data and DataContextAware ViewModels IContextAware services to bridge the gap between the View and the ViewModel – MEFedMVVM Part 3 Marlon Grech's 3rd post about MEFedMVVM is about IContextAwareService -- bridging the gap betwen the View and ViewModel -- a service that knows about it's context. Building a Web Setup that configures your Silverlight application Jonathan van de Veen has a post up at SilverlightShow on using a Web Setup Project to configure your Silverlight when things startup... if you're not familiar with doing this... take note! A Chrome and Glass Theme - Part 4 Phil Middlemiss has part 4 of his great tutorial series up on creating a theme in Expression Blend ... this time tackling the listbox. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Databinding to an Entity Framework in WPF

    - by King Chan
    Is it good to use databinding to Entity Framework's Entity in WPF? I created a singleton entity framework context: To have only one connection and it won't open and close all the time. So I can pass the Entity around to any class, and can modify the Entity and make changes to the database. All ViewModels getting the entity out from the same Context and databinding to the View saves me time from mapping new object, but now I imagine there is problem in not using the newest Context: A ViewModel databinding to a Entity, then someone else updated the data. The ViewModel will still display the old data, because the Context is never being dispose to refresh. I always create new Context and then dispose of it. If I want to pass the Entity around, then there will be conflicts between Context and Entity. What is the suggested way of doing this ?

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  • WPF: Setting DataContext of a UserControl with Binding not working in XAML

    - by Grant Crofton
    Hi, I'm trying to get my first WPF app working using MVVM, and I've hit a little binding problem. The setup is that I have a view & viewModel which holds User details (the parent), and to try and keep things simple I've put a section of that view into a separate view & viewModel (the child). The child view is defined as a UserControl. The issue I'm having is how to set the DataContext of the child view (the UserControl). My parent ViewModel has a property which exposes the child ViewModel, like so: class ParentViewModel: INotifyPropertyChanged { public ChildViewModel childViewModel { get; set; } //... } In the XAML for my parent view (which has it's DataContext set to the ParentViewModel), I try to set the DataContext of the child view as follows: <views:ChildView x:Name="ChildView" DataContext="{Binding childViewModel}"/> However, this doesn't work. The DataContext of the child view is set to the same DataContext as the parent view (i.e. the ParentViewModel), as if I wasn't setting it at all. I also tried setting the DataContext in the child view itself, which also doesn't work: <UserControl x:Class="DietRecorder.Client.View.ChildView" DataContext="childViewModel" I have found a couple of ways around this. In the child view, I can bind everything by including the ChildViewModel in the path: <SomeControl Visibility="{Binding Path=childViewModel.IsVisible}"> but I don't want the child view to have this level of awareness of the hierarchy. Setting the DataContext in code also works - however, I have to do this after showing the parent view, otherwise the DataContext just gets overwritten when I call Show(): parentView.Show(); parentView.ChildView.DataContext = parentViewModel.childViewModel; This code also makes me feel uneasy, what with the LOD violation and all. It's just the DataContext that seems to be the problem - I can bind other things in the child, for example I tried binding the FontSize to an int property just to test it: <views:ChildView x:Name="ChildView" FontSize="{Binding Path=someVal}"/> And that works fine. But I'm sure binding the DataContext should work - I've seen similar examples of this kind of thing. Have I missed something obvious here? Is there a reason this won't work? Is there a spelling mistake somewhere? (I renamed things for your benefit so you won't be able to help me there anyway). Any thoughts welcome. Thanks, Grant

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  • WPF DataGrid multiselect binding

    - by JZ
    I have a datagrid that is multi-select enabled. I need to change the selection in the viewmodel. However, the SelectedItems property is read only and can't be directly bound to a property in the viewmodel. So how do I signal to the view that the selection has changed?

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  • Having ObservableCollection Trigger an update

    - by user275561
    So i have something along the lines of private ObservableCollection<ViewModel> _internal; public ObservableCollection<ViewModel> BoundInternal{get;set}; //this is Binded in the Itemssource like ItemSource={Binding BoundInternal} Now In my code i do something like BoundInternal=_internal, However the problem is the BoundInternal isn't trigger any collectionChanged event. I have to use the Add method. So I am wondering if there is a solution to this.

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  • Silverlight4 disable textbox required validation when form loads with initial value (null)

    - by Jay
    I am trying to implement validation using IDataErrorInfo or INotifyDataErrorInfo but either way I am struggling to make it work only once user start entering data or clicking save button. Since I am using MVVM, I am setting my view's datacontext to ViewModel and my ViewModel is implementing IDataErrorInfo / INotifyDataErrorInfo. I need to make sure validation happens but not when form loads up. Anyone has got any suggestion how I can implement? Thanks

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  • how to reference drageventArgs in xaml as command parameter with silverlight

    - by Shaggy
    Hi, on my silverlight 4 app I am trying to link up the drop event on a list box to my viewmodel. I am using expression blend 4's event trigger and invokecommandaction to hook up the drop event. Setting break points on my viewmodel, I can see the relevant function is fired when I drag a file onto the list box, however I cant seem to get access to the drageventArgs. I tried sending the entire listbox as a command parameter, and that doesn't work. Any ideas? Thanks

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  • WPF MVVM Get Parent from VIEW MODEL

    - by dnndeveloper
    In a MVVM WPF application. How do you set a second windows parent from the ViewModel? example: view1 viewModel1 viewModel1's command calls: var view2 = new view2 view2.Owner = <----This is the problem area. How do I get view1 as the owner here from the viewModel? view2.Show() Thank you!

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  • Initialization of ComboBox in datagrid, Silverlight 4.0

    - by Budda
    I have datagrid with list of MyPlayer objects linked to ItemsSource, there are ComboBoxes inside of grid that are linked to a list of inner object, and binding works correctly: when I select one of the item then its value is pushed to data model and appropriately updated in other places, where it is used. The only problem: initial selections are not displayed in my ComboBoxes. I don't know why..? Instance of the ViewModel is assigned to view DataContext. Here is grid with ComboBoxes (grid is binded to the SquadPlayers property of ViewModel): <data:DataGrid ="True" AutoGenerateColumns="False" ItemsSource="{Binding SquadPlayers}"> <data:DataGrid.Columns> <data:DataGridTemplateColumn Header="Rig." Width="50"> <data:DataGridTemplateColumn.CellTemplate> <DataTemplate> <ComboBox SelectedItem="{Binding Rigid, Mode=TwoWay}" ItemsSource="{Binding IntLevels, Mode=TwoWay}"/> </DataTemplate> </data:DataGridTemplateColumn.CellTemplate> </data:DataGridTemplateColumn> </data:DataGrid.Columns> </data:DataGrid> Here is ViewModel class ('_model_DataReceivedEvent' method is called asynchronously, when data are received from server): public class SquadViewModel : ViewModelBase<SquadModel> { public SquadViewModel() { SquadPlayers = new ObservableCollection<SquadPlayer>(); } private void _model_DataReceivedEvent(List<SostavPlayerData> allReadyPlayers) { TeamTask task = new TeamTask { Rigid = 1 }; foreach (SostavPlayerData spd in allReadyPlayers) { SquadPlayer sp = new SquadPlayer(spd, task); SquadPlayers.Add(sp); } RaisePropertyChanged("SquadPlayers"); } And here is SquadPlayer class (it's objects are binded to the grid rows): public class SquadPlayer : INotifyPropertyChanged { public SquadPlayer(SostavPlayerData spd) { _spd = spd; Rigid = 2; } public event PropertyChangedEventHandler PropertyChanged; private int _rigid; public int Rigid { get { return _rigid; } set { _rigid = value; if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs("Rigid")); } } } private readonly ObservableCollection<int> _statIntLevels = new ObservableCollection<int> { 1, 2, 3, 4, 5 }; public ObservableCollection<int> IntLevels { get { return _statIntLevels; } } It is expected to have all "Rigid" comboboxes set to "2" value, but they are not selected (items are in the drop-down list, and if any value is selected it is going to ViewModel). What is wrong with this example? Any help will be welcome. Thanks.

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  • ASP.NET MVC Custom Error Pages with Magical Unicorn

    - by FLClover
    my question is regarding Pure.Kromes answer to this post. I tried implementing my pages' custom error messages using his method, yet there are some problems I can't quite explain. a) When I provoke a 404 Error by entering in invalid URL such as localhost:3001/NonexistantPage, it defaults to the ServerError() Action of my error controller even though it should go to NotFound(). Here is my ErrorController: public class ErrorController : Controller { public ActionResult NotFound() { Response.TrySkipIisCustomErrors = true; Response.StatusCode = (int)HttpStatusCode.NotFound; var viewModel = new ErrorViewModel() { ServerException = Server.GetLastError(), HTTPStatusCode = Response.StatusCode }; return View(viewModel); } public ActionResult ServerError() { Response.TrySkipIisCustomErrors = true; Response.StatusCode = (int)HttpStatusCode.InternalServerError; var viewModel = new ErrorViewModel() { ServerException = Server.GetLastError(), HTTPStatusCode = Response.StatusCode }; return View(viewModel); } } My error routes in Global.asax.cs: routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" }); routes.MapRoute( name: "Error - 404", url: "NotFound", defaults: new { controller = "Error", action = "NotFound" } ); routes.MapRoute( name: "Error - 500", url: "ServerError", defaults: new { controller = "Error", action = "ServerError" } ); And my web.config settings: <system.web> <customErrors mode="On" redirectMode="ResponseRewrite" defaultRedirect="/ServerError"> <error statusCode="404" redirect="/NotFound" /> </customErrors> ... </system.web> <system.webServer> <httpErrors errorMode="Custom" existingResponse="Replace"> <remove statusCode="404" subStatusCode="-1" /> <error statusCode="404" path="/NotFound" responseMode="ExecuteURL" /> <remove statusCode="500" subStatusCode="-1" /> <error statusCode="500" path="/ServerError" responseMode="ExecuteURL" /> </httpErrors> ... The Error views are located in /Views/Error/ as NotFound.cshtml and ServerError.cshtml. b) One funny thing is, When a server error occurs, it does in fact display the Server Error view I defined, however it also outputs a default error message as well saying that the Error page could not be found. Here's how it looks like: Do you have any advice how I could fix these two problems? I really like Pure.Kromes approach to implementing these error messages, but if there are better ways of achieving this don't hestitate to tell me. Thanks! *EDIT : * I can directly navigate to my views through the ErrorController by accessing /Error/NotFound or Error/ServerError. The views themselves only contain some text, no markup or anything. As I said, it actually works in some way, just not the way I intended it to work. There seems to be an issue with the redirect in the web.config, but I haven't been able to figure it out.

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  • WPF MVVM View with varying number of objects. How to?

    - by 0xDEAD BEEF
    HI! I want to design view which will contain multiple objects in different locations. For example - it would be great if viewmodel could have field like list of objects (rectangles) and when i change/add members to list, new rectangles appear on view in specified positions. How do i create such view/viewmodel?

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  • Silverlight textblock binding question + MVVM

    - by AdrianDN
    Hello everyone, I'm trying to create a simple textblock control and I'm trying to insert a property from my ViewModel in the middle of the string. E.G. "Hello, My name is XX, bla, bla." (XX is a property from my ViewModel) <TextBlock Text="Hello, My name is {Binding SelectedUser.Name}, bla, bla." /> Is that possible? Regards, Adrian

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  • Defining a select list through controller and view model

    - by Ibrar Hussain
    I have a View Model that looks like this: public class SomeViewModel { public SomeViewModel(IEnumerable<SelectListItem> orderTemplatesListItems) { OrderTemplateListItems = orderTemplatesListItems; } public IEnumerable<SelectListItem> OrderTemplateListItems { get; set; } } I then have an Action in my Controller that does this: public ActionResult Index() { var items = _repository.GetTemplates(); var selectList = items.Select(i => new SelectListItem { Text = i.Name, Value = i.Id.ToString() }).ToList(); var viewModel = new SomeViewModel { OrderTemplateListItems = selectList }; return View(viewModel); } Lastly my view: @Html.DropDownListFor(n => n.OrderTemplateListItems, new SelectList(Model.OrderTemplateListItems, "value", "text"), "Please select an order template") The code works fine and my select list populates wonderfully. Next thing I need to do is set the selected value that will come from a Session["orderTemplateId"] which is set when the user selects a particular option from the list. Now after looking online the fourth parameter should allow me to set a selected value, so if I do this: @Html.DropDownListFor(n => n.OrderTemplateListItems, new SelectList(Model.OrderTemplateListItems, "value", "text", 56), "Please select an order template") 56 is the Id of the item that I want selected, but to no avail. I then thought why not do it in the Controller? As a final attempt I tried building up my select list items in my Controller and then passing the items into the View: public ActionResult Index() { var items = _repository.GetTemplates(); var orderTemplatesList = new List<SelectListItem>(); foreach (var item in items) { if (Session["orderTemplateId"] != null) { if (item.Id.ToString() == Session["orderTemplateId"].ToString()) { orderTemplatesList.Add(new SelectListItem { Text = item.Name, Value = item.Id.ToString(), Selected = true }); } else { orderTemplatesList.Add(new SelectListItem { Text = item.Name, Value = item.Id.ToString() }); } } else { orderTemplatesList.Add(new SelectListItem { Text = item.Name, Value = item.Id.ToString() }); } } var viewModel = new SomeViewModel { OrderTemplateListItems = orderTemplatesList }; return View(viewModel); } Leaving my View like so: @Html.DropDownListFor(n => n.OrderTemplateListItems, new SelectList(Model.OrderTemplateListItems, "value", "text"), "Please select an order template") Nothing! Why isn't this working for me?

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  • How to bind Listbox to two properties?

    - by Gabriel
    I have in Silverlight a Grid with DataContext set to class ViewModel. ViewModel contains list of items (each of them containing int ID and string Text) and an integer "ID", which identifies actually active item (not selected item). I would like to construct xaml with ListBox where activated item has another color. How can I do it?

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  • Viewmodels and Models, howto split them up

    - by molgan
    Hello I'm using asp.net mvc 2 and I'm not sure howto structure the models and viewmodels. In the nerddinner there is only 1 of each. Shall I have only 1 viewmodel of each entity (?) and then have 1 model for each form-modifing viewpage? So that viewmodel contains like all it ever would need, like: PagedFoo FooClass ..., FooClass, Foowithbunnies, FooClassStats... ? /M

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  • Silverlight and M-V-VM - Where should a timer live?

    - by Bill Jeeves
    I'm creating a simple monitoring tool in Silverlight. It talks to a web service to retrieve the status information and store it in the ViewModel. This needs to happen once per minute so I'm going to add a timer for this purpose (probably a DispatcherTimer). My question is, where should the timer go in an M-V-VM architecture? In the ViewModel or the View?

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