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• How Does One Differentiate Between Routes POSTed To In Asp.Net MVC?

  - by Laz

  I have two actions, one that accepts a ViewModel and one that accepts two parameters a string and an int, when I try to post to the action, it gives me an error telling me that the current request is ambiguous between the two actions. Is it possible to indicate to the routing system which action is the relevant one, and if it is how is it done?

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• Dispatcher.CurrentDispatcher?

  - by Mark

  If I do this... public PriorityQueue(Dispatcher dispatcher = null) { this.dispatcher = dispatcher ?? Dispatcher.CurrentDispatcher; } And then use it in a ViewModel (without passing any args) that is created through the XAML, this.dispatcher will point to the UI thread right?

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• Block temporarily interaction during wcf call!

  - by Muhammad Jamal Shaikh

  hi , Silverlight version : 4 Silverlight patter :MVVM Visual Studio template :Silverlight navigation application How do I block main navigation on (mainpage.xaml) as in any silverlight navigation application and block page's controls ( i.e whichever page is it in ) during async webservice calls in my viewmodel? Any best practices?

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• KnockoutJS radio buttons not changing like checkboxes do

  - by Gaui

  I have the same data structure for checkboxes and radio buttons. When checking the checkboxes, they return correct boolean value ('chosen' variable). However, when I check the radio buttons, 'chosen' always changes to the 'value' (integer). Also the radio buttons don't get "checked" in the beginning, even though 'chosen' == true Javascript: function attributeValueViewModel(data) { var self = this; self.id = ko.observable(data.id); self.attributeID = ko.observable(data.attributeID); self.value = ko.observable(data.value); self.chosen = ko.observable(data.chosen); } function viewModel() { var self = this; self.attributeValues1 = ko.observableArray([]); self.attributeValues2 = ko.observableArray([]); self.addToList = function(data) { ko.utils.arrayForEach(data, function(item) { self.attributeValues1.push(new attributeValueViewModel(item)); self.attributeValues2.push(new attributeValueViewModel(item)); }); }; } var arr = [ { "id": 55, "attributeID": 28, "value": "Yes", "chosen": false, }, { "id": 56, "attributeID": 28, "value": "No", "chosen": true, }, { "id": 62, "attributeID": 28, "value": "Maybe", "chosen": false, } ]; var vm = new viewModel(); ko.applyBindings(vm); vm.addToList(arr); HTML <b>Checkbox:</b> <div id="test1"> <span data-bind="foreach: attributeValues1()"> <input type="checkbox" data-bind="value: id(), checked: chosen, attr: { name: 'test1' }" /> <span data-bind="text: value()"></span> <span data-bind="text: chosen()"></span> </span> </div> <br /> <b>Radio:</b> <div id="test2"> <span data-bind="foreach: attributeValues2()"> <input type="radio" data-bind="value: id(), checked: chosen, attr: { name: 'test2' }" /> <span data-bind="text: value()"></span> <span data-bind="text: chosen()"></span> </span> </div>? Here is my fiddle: http://jsfiddle.net/SN7Vn/1/ Can you please explain this behavior and why the radio buttons don't update boolean (like checkboxes do)?

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• PropertyChanged Event of ObservableCollection

  - by developer

  Hi All, I have a observable collection of viewmodel objects. How can I subscribe to the Property Changed event of each view model in my collection as they are created and track which ones have been changed, so that I can updated them to my database. List<DomainObject> objectsToSave = new List<DomainObject>(); foreach (Test val in dirtyObjs) { objectsToSave.AddRange(val.GetObjectsToSave()); } //DB changes bool saveSucceeded = DataServices.SaveMultiple(objectsToSave);

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• Is it ok to reference .Net assemblies liberally?

  - by panamack

  I'm building a WPF application and working with the MVVM pattern. I have 4 projects in my solution, 3 class libraries, Data, Model and ViewModel and the WPF executable View. Is there anything wrong with the Model referencing WindowsBase so that I can use ObservableCollection<T> for example or can I just make use of what I intuitively feel I need without worrying about the original purposes of the class in the framework e.g. collection databinding.

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• Modifying an observable collection bound to a ListBox

  - by Rohit Kandhal

  I've a collection in viewmodel binded to listbox. I want to hide a particular type from the collection. Here is the code: public ObservableCollection [YZModeModelView] YZModeModelView { return this.XModelVIew.YZModelViewCollection; } I want to a particular type of model view's from YZModelViewCollection. eg. ModelView's with property abc set to null. Any suggestions ...

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• WPF XAML Bind Grid

  - by Jon Archway

  I have a custom user control that is based on a Grid control. I have a ViewModel that exposes this as a property. I would like the XAML on the view to bind to this. I am sure this must be easy but I am quite new to WPF. How is this achieved? Many thanks in advance

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• MVVM Tutorial/Example Code with internet connectivity

  - by SpikeX

  I understand the View and ViewModel portions of MVVM, but what I'm still really fuzzy on is how you connect your application to data sources on the Internet (say you're grabbing some XML or JSON from the web), and specifically, where that code goes in your application. Can someone provide or link to some example code or a tutorial that walks you through setting up a simple WPF (or Silverlight) application that fetches data from the Web?

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• MVVM in Silverlight - Where does async service logic go?

  - by joeldow

  I have the beginnings of my first Silverlight MVVM app and need to know where I should put business logic including async service calls. Does it go on the page hosting the view? Do I simply set a property of the ViewModel which updates the view?

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• MVVM,WPF: How to set a item as selected in a combobox

  - by msfanboy

  It seems nobody has yet found a way to set the comboboxitem as selected with a SelectedItem="Binding Property". Is the solution to use a IsSelected Property in the ViewModel object within the combobox itemssource ?

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• Using the HTML5 &lt;input type=&quot;file&quot; multiple=&quot;multiple&quot;&gt; Tag in ASP.NET

  - by Rick Strahl

  Per HTML5 spec the <input type="file" /> tag allows for multiple files to be picked from a single File upload button. This is actually a very subtle change that's very useful as it makes it much easier to send multiple files to the server without using complex uploader controls. Please understand though, that even though you can send multiple files using the <input type="file" /> tag, the process of how those files are sent hasn't really changed - there's still no progress information or other hooks that allow you to automatically make for a nicer upload experience without additional libraries or code. For that you will still need some sort of library (I'll post an example in my next blog post using plUpload). All the new features allow for is to make it easier to select multiple images from disk in one operation. Where you might have required many file upload controls before to upload several files, one File control can potentially do the job. How it works To create a file input box that allows with multiple file support you can simply do:<form method="post" enctype="multipart/form-data"> <label>Upload Images:</label> <input type="file" multiple="multiple" name="File1" id="File1" accept="image/*" /> <hr /> <input type="submit" id="btnUpload" value="Upload Images" /> </form> Now when the file open dialog pops up - depending on the browser and whether the browser supports it - you can pick multiple files. Here I'm using Firefox using the thumbnail preview I can easily pick images to upload on a form: Note that I can select multiple images in the dialog all of which get stored in the file textbox. The UI for this can be different in some browsers. For example Chrome displays 3 files selected as text next to the Browse… button when I choose three rather than showing any files in the textbox. Most other browsers display the standard file input box and display the multiple filenames as a comma delimited list in the textbox. Note that you can also specify the accept attribute in the <input> tag, which specifies a mime-type to specify what type of content to allow.Here I'm only allowing images (image/*) and the browser complies by just showing me image files to display. Likewise I could use text/* for all text formats registered on the machine or text/xml to only show XML files (which would include xml,xst,xsd etc.). Capturing Files on the Server with ASP.NET When you upload files to an ASP.NET server there are a couple of things to be aware of. When multiple files are uploaded from a single file control, they are assigned the same name. In other words if I select 3 files to upload on the File1 control shown above I get three file form variables named File1. This means I can't easily retrieve files by their name:HttpPostedFileBase file = Request.Files["File1"]; because there will be multiple files for a given name. The above only selects the first file. Instead you can only reliably retrieve files by their index. Below is an example I use in app to capture a number of images uploaded and store them into a database using a business object and EF 4.2.for (int i = 0; i < Request.Files.Count; i++) { HttpPostedFileBase file = Request.Files[i]; if (file.ContentLength == 0) continue; if (file.ContentLength > App.Configuration.MaxImageUploadSize) { ErrorDisplay.ShowError("File " + file.FileName + " is too large. Max upload size is: " + App.Configuration.MaxImageUploadSize); return View("UploadClassic",model); } var image = new ClassifiedsBusiness.Image(); var ms = new MemoryStream(16498); file.InputStream.CopyTo(ms); image.Entered = DateTime.Now; image.EntryId = model.Entry.Id; image.ContentType = "image/jpeg"; image.ImageData = ms.ToArray(); ms.Seek(0, SeekOrigin.Begin); // resize image if necessary and turn into jpeg Bitmap bmp = Imaging.ResizeImage(ms.ToArray(), App.Configuration.MaxImageWidth, App.Configuration.MaxImageHeight); ms.Close(); ms = new MemoryStream(); bmp.Save(ms,ImageFormat.Jpeg); image.ImageData = ms.ToArray(); bmp.Dispose(); ms.Close(); model.Entry.Images.Add(image); } This works great and also allows you to capture input from multiple input controls if you are dealing with browsers that don't support multiple file selections in the file upload control. The important thing here is that I iterate over the files by index, rather than using a foreach loop over the Request.Files collection. The files collection returns key name strings, rather than the actual files (who thought that was good idea at Microsoft?), and so that isn't going to work since you end up getting multiple keys with the same name. Instead a plain for loop has to be used to loop over all files. Another Option in ASP.NET MVC If you're using ASP.NET MVC you can use the code above as well, but you have yet another option to capture multiple uploaded files by using a parameter for your post action method.public ActionResult Save(HttpPostedFileBase[] file1) { foreach (var file in file1) { if (file.ContentLength < 0) continue; // do something with the file }} Note that in order for this to work you have to specify each posted file variable individually in the parameter list. This works great if you have a single file upload to deal with. You can also pass this in addition to your main model to separate out a ViewModel and a set of uploaded files:public ActionResult Edit(EntryViewModel model,HttpPostedFileBase[] uploadedFile) You can also make the uploaded files part of the ViewModel itself - just make sure you use the appropriate naming for the variable name in the HTML document (since there's Html.FileFor() extension). Browser Support You knew this was coming, right? The feature is really nice, but unfortunately not supported universally yet. Once again Internet Explorer is the problem: No shipping version of Internet Explorer supports multiple file uploads. IE10 supposedly will, but even IE9 does not. All other major browsers - Chrome, Firefox, Safari and Opera - support multi-file uploads in their latest versions. So how can you handle this? If you need to provide multiple file uploads you can simply add multiple file selection boxes and let people either select multiple files with a single upload file box or use multiples. Alternately you can do some browser detection and if IE is used simply show the extra file upload boxes. It's not ideal, but either one of these approaches makes life easier for folks that use a decent browser and leaves you with a functional interface for those that don't. Here's a UI I recently built as an alternate uploader with multiple file upload buttons: I say this is my 'alternate' uploader - for my primary uploader I continue to use an add-in solution. Specifically I use plUpload and I'll discuss how that's implemented in my next post. Although I think that plUpload (and many of the other packaged JavaScript upload solutions) are a better choice especially for large uploads, for simple one file uploads input boxes work well enough. The advantage of this solution is that it's very easy to handle on the server side. Any of the JavaScript controls require special handling for uploads which I'll also discuss in my next post.© Rick Strahl, West Wind Technologies, 2005-2012Posted in HTML5  ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• ASP.NET MVC 3 Hosting :: MVC 2 Strongly Typed HTML Helper and Enhanced Validation Sample

  - by mbridge

  In lue of the off the official release of ASP.NET MVC 2 RTM, I decided I would put together a quick sample of the enhanced HTML.Helpers and validation controls. I am going to use my sample event site where I will have a form so a user can search for information about a certain events. So when the Search page loads the Search action is fired return my strongly typed model. to the view.    1: [HttpGet]    2: public ViewResult Search(): public ViewResult Search()    3: {    4:     IList<EventsModel> result = _eventsService.GetEventList();    5:     var viewModel = new EventSearchModel    6:                         {    7:                             EventList = new SelectList(result, "EventCode","EventName","Select Event")    8:                         };    9:     return View(viewModel);  10: } Nothing special here, although I did want to show how to load up a strongly typed drop down list because that hung me up for a little bit. So to that, I am going to pass back a SelectList to the view and my HTML helper should no how to load this. So lets take a look at the mark up for the view.    1: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master"    2: Inherits="System.Web.Mvc.ViewPage<EventsSample.Models.EventSearchModel>" %>    3:     4: <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">    5:     Search    6: </asp:Content>    7:     8: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">    9:   10:     <h2>Search for Events</h2>  11:   12:     <% using (Html.BeginForm("Search","Events")) {%>  13:         <%= Html.ValidationSummary(true) %>  14:          15:         <fieldset>  16:             <legend>Fields</legend>  17:              18:             <div class="editor-label">  19:                 <%= Html.LabelFor(model => model.EventNumber) %>  20:             </div>  21:             <div class="editor-field">  22:                 <%= Html.TextBoxFor(model => model.EventNumber) %>  23:                 <%= Html.ValidationMessageFor(model => model.EventNumber) %>  24:             </div>  25:              26:             <div class="editor-label">  27:                 <%= Html.LabelFor(model => model.GuestLastName) %>  28:             </div>  29:             <div class="editor-field">  30:                 <%= Html.TextBoxFor(model => model.GuestLastName) %>  31:                 <%= Html.ValidationMessageFor(model => model.GuestLastName) %>  32:             </div>  33:              34:             <div class="editor-label">  35:                 <%= Html.LabelFor(model => model.EventName) %>  36:             </div>  37:             <div class="editor-field">  38:                 <%= Html.DropDownListFor(model => model.EventName, Model.EventList,"Select Event") %>  39:                 <%= Html.ValidationMessageFor(model => model.EventName) %>  40:             </div>  41:              42:             <p>  43:                 <input type="submit" value="Save" />  44:             </p>  45:         </fieldset>  46:   47:     <% } %>  48:   49:     <div>  50:         <%= Html.ActionLink("Back to List", "Index") %>  51:     </div>  52:   53: </asp:Content> A nice feature is the scaffolding that MVC has to generate code. I simply right clicked inside my Search() action, inside the EventsController and selected “Add View” and then I selected my strongly typed object that I wanted to pass to the view and also selected that I wanted the content type be “Edit”. With that the aspx page was completely generated, although I did have to go back in and change the textbox for the Event Names to a drop down list of the names to select from. The new feature with MVC 2 are the strongly typed HTML helpers. So now, my textboxes, drop down list, and validation helpers are all strongly typed to my model.  This features gives you the benefits of intellisense and also makes it easier to debug. “The Gu” has a great post about the feature in case you want more details. The DropDownListFor function to generate the drop down list was a little tricky for me. You first need to use a Lanbda expression to pass in the property you want the selected value assigned to in your model, and then you need to pass in the list directly from the model. Validations To validate the form, you can use the strongly type validation HTML helpers which will inspect your model and return errors if the validation fails. The definitions of these rules are set directly on the Model itself so lets take a look.    1: using System.ComponentModel.DataAnnotations;    2: using System.Web.Mvc;    3:     4: namespace EventsSample.Models    5: {    6:     public class EventSearchModel    7:     {    8:         [Required(ErrorMessage = "Please enter the event number.")]    9:         [RegularExpression(@"\w{6}",  10:             ErrorMessage = "The Event Number must be 6 letters and/or numbers.")]  11:         public string EventNumber { get; set; }  12:   13:         [Required(ErrorMessage = "Please enter the guest's last name.")]  14:         [RegularExpression(@"^[A-Za-zÀ-ÖØ-öø-ÿ1-9 '\-\.]{1,22}$",  15:             ErrorMessage = "The gueest's last name must 1 to 20 characters.")]  16:         public string GuestLastName { get; set; }  17:   18:         public string EventName { get; set; }  19:         public SelectList EventList { get; set; }  20:     }  21: } Pretty cool! Okay, the only thing left to do is perform the validation in the POST action.    1: [HttpPost]    2: public ViewResult Search(EventSearchModel eventSearchModel)    3: {    4:     if (ModelState.IsValid) return View("SearchResults");    5:     else    6:     {    7:          IList<EventsModel> result = _eventsService.GetEventList();    8:         eventSearchModel.EventList = new SelectList(result, "EVentCode","EventName");   9:   10:         return View(eventSearchModel);  11:     }  12: }  13:     } If the form entries are valid, here I am simply displaying the SearchResult, but in a real world sample I would also go out get the results first. You get the idea though. In my case, when the form is not valid, I also had to reload my SelectList with the event names before I loaded the page again. Remember this is MVC, no _VieState here :) So that’s it. Now my form is validating the data and when it fails it looks like this.

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• Silverlight MVVM Confusion: Updating Image Based on State

  - by senfo

  I'm developing a Silverlight application and I'm trying to stick to the MVVM principals, but I'm running into some problems changing the source of an image based on the state of a property in the ViewModel. For all intents and purposes, you can think of the functionality I'm implementing as a play/pause button for an audio app. When in the "Play" mode, IsActive is true in the ViewModel and the "Pause.png" image on the button should be displayed. When paused, IsActive is false in the ViewModel and "Play.png" is displayed on the button. Naturally, there are two additional images to handle when the mouse hovers over the button. I thought I could use a Style Trigger, but apparently they're not supported in Silverlight. I've been reviewing a forum post with a question similar to mine where it's suggested to use the VisualStateManager. While this might help with changing the image for hover/normal states, the part missing (or I'm not understanding) is how this would work with a state set via the view model. The post seems to apply only to events rather than properties of the view model. Having said that, I also haven't successfully completed the normal/hover affects, either. Below is my Silverlight 4 XAML. It should also probably be noted I'm working with MVVM Light. <UserControl x:Class="Foo.Bar.MyUserControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity" mc:Ignorable="d" d:DesignHeight="100" d:DesignWidth="200"> <UserControl.Resources> <Style x:Key="MyButtonStyle" TargetType="Button"> <Setter Property="IsEnabled" Value="true"/> <Setter Property="IsTabStop" Value="true"/> <Setter Property="Background" Value="#FFA9A9A9"/> <Setter Property="Foreground" Value="#FF000000"/> <Setter Property="MinWidth" Value="5"/> <Setter Property="MinHeight" Value="5"/> <Setter Property="Margin" Value="0"/> <Setter Property="HorizontalAlignment" Value="Left" /> <Setter Property="HorizontalContentAlignment" Value="Center"/> <Setter Property="VerticalAlignment" Value="Top" /> <Setter Property="VerticalContentAlignment" Value="Center"/> <Setter Property="Cursor" Value="Hand"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="Button"> <Grid> <Image Source="/Foo.Bar;component/Resources/Icons/Bar/Play.png"> <VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="Active"> <VisualState x:Name="MouseOver"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Source" Storyboard.TargetName="/Foo.Bar;component/Resources/Icons/Bar/Play_Hover.png" /> </Storyboard> </VisualState> </VisualStateGroup> </VisualStateManager.VisualStateGroups> </Image> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> </UserControl.Resources> <Grid x:Name="LayoutRoot" Background="White"> <Button Style="{StaticResource MyButtonStyle}" Command="{Binding ChangeStatus}" Height="30" Width="30" /> </Grid> </UserControl> What is the proper way to update images on buttons with the state determined by the view model? Update I changed my Button to a ToggleButton hoping I could use the Checked state to differentiate between play/pause. I practically have it, but I ran into one additional problem. I need to account for two states at the same time. For example, Checked Normal/Hover and Unchecked Normal/Hover. Following is my updated XAML: <UserControl x:Class="Foo.Bar.MyUserControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity" mc:Ignorable="d" d:DesignHeight="100" d:DesignWidth="200"> <UserControl.Resources> <Style x:Key="MyButtonStyle" TargetType="ToggleButton"> <Setter Property="IsEnabled" Value="true"/> <Setter Property="IsTabStop" Value="true"/> <Setter Property="Background" Value="#FFA9A9A9"/> <Setter Property="Foreground" Value="#FF000000"/> <Setter Property="MinWidth" Value="5"/> <Setter Property="MinHeight" Value="5"/> <Setter Property="Margin" Value="0"/> <Setter Property="HorizontalAlignment" Value="Left" /> <Setter Property="HorizontalContentAlignment" Value="Center"/> <Setter Property="VerticalAlignment" Value="Top" /> <Setter Property="VerticalContentAlignment" Value="Center"/> <Setter Property="Cursor" Value="Hand"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="ToggleButton"> <Grid> <VisualStateManager.VisualStateGroups> <VisualStateGroup x:Name="CommonStates"> <VisualState x:Name="Normal"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="Pause"> <DiscreteObjectKeyFrame KeyTime="0"> <DiscreteObjectKeyFrame.Value> <Visibility>Collapsed</Visibility> </DiscreteObjectKeyFrame.Value> </DiscreteObjectKeyFrame> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> <VisualState x:Name="MouseOver"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="PlayHover"> <DiscreteObjectKeyFrame KeyTime="0"> <DiscreteObjectKeyFrame.Value> <Visibility>Visible</Visibility> </DiscreteObjectKeyFrame.Value> </DiscreteObjectKeyFrame> </ObjectAnimationUsingKeyFrames> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="Play"> <DiscreteObjectKeyFrame KeyTime="0"> <DiscreteObjectKeyFrame.Value> <Visibility>Collapsed</Visibility> </DiscreteObjectKeyFrame.Value> </DiscreteObjectKeyFrame> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> </VisualStateGroup> <VisualStateGroup x:Name="CheckStates"> <VisualState x:Name="Checked"> <Storyboard> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="Pause"> <DiscreteObjectKeyFrame KeyTime="0"> <DiscreteObjectKeyFrame.Value> <Visibility>Visible</Visibility> </DiscreteObjectKeyFrame.Value> </DiscreteObjectKeyFrame> </ObjectAnimationUsingKeyFrames> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="Play"> <DiscreteObjectKeyFrame KeyTime="0"> <DiscreteObjectKeyFrame.Value> <Visibility>Collapsed</Visibility> </DiscreteObjectKeyFrame.Value> </DiscreteObjectKeyFrame> </ObjectAnimationUsingKeyFrames> <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="PlayHover"> <DiscreteObjectKeyFrame KeyTime="0"> <DiscreteObjectKeyFrame.Value> <Visibility>Collapsed</Visibility> </DiscreteObjectKeyFrame.Value> </DiscreteObjectKeyFrame> </ObjectAnimationUsingKeyFrames> </Storyboard> </VisualState> <VisualState x:Name="Unchecked" /> </VisualStateGroup> </VisualStateManager.VisualStateGroups> <Image x:Name="Play" Source="/Foo.Bar;component/Resources/Icons/Bar/Play.png" /> <Image x:Name="Pause" Source="/Foo.Bar;component/Resources/Icons/Bar/Pause.png" Visibility="Collapsed" /> <Image x:Name="PlayHover" Source="/Foo.Bar;component/Resources/Icons/Bar/Play_Hover.png" Visibility="Collapsed" /> <Image x:Name="PauseHover" Source="/Foo.Bar;component/Resources/Icons/Bar/Pause_Hover.png" Visibility="Collapsed" /> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> </UserControl.Resources> <Grid x:Name="LayoutRoot" Background="White"> <ToggleButton Style="{StaticResource MyButtonStyle}" IsChecked="{Binding IsPlaying}" Command="{Binding ChangeStatus}" Height="30" Width="30" /> </Grid> </UserControl>

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• WPF TabControl - how to preserve control state within tab items (MVVM pattern)

  - by Tim Coulter

  I am a newcomer to WPF, attempting to build a project that follows the recommendations of Josh Smith's excellent article describing The Model-View-ViewModel Design Pattern. Using Josh's sample code as a base, I have created a simple application that contains a number of "workspaces", each represented by a tab in a TabControl. In my application, a workspace is a document editor that allows a hierarchical document to be manipulated via a TreeView control. Although I have succeeded in opening multiple workspaces and viewing their document content in the bound TreeView control, I find that the TreeView "forgets" its state when switching between tabs. For example, if the TreeView in Tab1 is partially expanded, it will be shown as fully collapsed after switching to Tab2 and returning to Tab1. This behaviour appears to apply to all aspects of control state for all controls. After some experimentation, I have realized that I can preserve state within a TabItem by explicitly binding each control state property to a dedicated property on the underlying ViewModel. However, this seems like a lot of additional work, when I simply want all my controls to remember their state when switching between workspaces. I assume I am missing something simple, but I am not sure where to look for the answer. Any guidance would be much appreciated. Thanks, Tim Update: As requested, I will attempt to post some code that demonstrates this problem. However, since the data that underlies the TreeView is complex, I will post a simplified example that exhibits the same symtoms. Here is the XAML from the main window: <TabControl IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding Path=Docs}"> <TabControl.ItemTemplate> <DataTemplate> <ContentPresenter Content="{Binding Path=Name}" /> </DataTemplate> </TabControl.ItemTemplate> <TabControl.ContentTemplate> <DataTemplate> <view:DocumentView /> </DataTemplate> </TabControl.ContentTemplate> </TabControl> The above XAML correctly binds to an ObservableCollection of DocumentViewModel, whereby each member is presented via a DocumentView. For the simplicity of this example, I have removed the TreeView (mentioned above) from the DocumentView and replaced it with a TabControl containing 3 fixed tabs: <TabControl> <TabItem Header="A" /> <TabItem Header="B" /> <TabItem Header="C" /> </TabControl> In this scenario, there is no binding between the DocumentView and the DocumentViewModel. When the code is run, the inner TabControl is unable to remember its selection when the outer TabControl is switched. However, if I explicitly bind the inner TabControl's SelectedIndex property ... <TabControl SelectedIndex="{Binding Path=SelectedDocumentIndex}"> <TabItem Header="A" /> <TabItem Header="B" /> <TabItem Header="C" /> </TabControl> ... to a corresponding dummy property on the DocumentViewModel ... public int SelecteDocumentIndex { get; set; } ... the inner tab is able to remember its selection. I understand that I can effectively solve my problem by applying this technique to every visual property of every control, but I am hoping there is a more elegant solution.

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• Rendering a WPF Network Map/Graph layout - Manual? PathListBox? Something Else?

  - by Ben Von Handorf

  I'm writing code to present the user with a simplified network map. At any given time, the map is focused on a specific item... say a router or a server. Based on the focused item, other network entities are grouped into sets (i.e. subnets or domains) and then rendered around the focused item. Lines would represent connections and groups would be visually grouped inside a rectangle or ellipse. Panning and zooming are required features. An item can be selected to display more information in a "properties" style window. An item could also be double-clicked to re-focus the entire network map on that item. At that point, the entire map would be re-calculated. I am using MVVM without any framework, as of yet. Assume the logic for grouping items and determining what should be shown or not is all in place. I'm looking for the best way to approach the UI layout. So far, I'm aware of the following options: Use a canvas for layout (inside a ScrollViewer to handle the panning). Have my ViewModel make use of a Layout Manager type of class, which would handle assigning all the layout properties (Top, Left, etc.). Bind my set of display items to an ItemsControl and use Data Templates to handle the actual rendering. The drawbacks with this approach: Highly manual layout on my part. Lots of calculation. I have to handle item selection manually. Computation of connecting lines is manual. The Pros of this approach: I can draw additional lines between child subnets as appropriate (manually). Additional LayoutManagers could be added later to render the display differently. This could probably be wrapped up into some sort of a GraphLayout control to be re-used. Present the focused item at the center of the display and then use a PathListBox for layout of the additional items. Have my ViewModel expose a simple list of things to be drawn and bind them to the PathListBox. Override the ListBoxItem Template to also create a line geometry from the borders of the focused item (tricky) to the bound item. Use DataTemplates to handle the case where the item being bound is a subnet, in which case we would use another PathListBox in the template to display items inside the subnet. The drawbacks with this approach: Selected Item synchronization across multiple `PathListBox`es. Only one item on the whole graph can be selected at a time, but each child PathListBox maintains its own selection. Also, subnets cannot be selected, but would be selectable without additional work. Drawing the connecting lines is going to be a bit of trickery in the ListBoxItem template, since I need to know the correct side of the focused item to connect to. The pros of this approach: I get to stay out of the layout business, more. I'm looking for any advice or thoughts from others who have encountered similar issues or who have more WPF experience than I. I'm using WPF 4, so any new tricks are legal and encouraged.

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• Using bindings to control column order in a DataGrid

  - by DanM

  Problem I have a WPF Toolkit DataGrid, and I'd like to be able to switch among several preset column orders. This is an MVVM project, so the column orders are stored in a ViewModel. The problem is, I can't get bindings to work for the DisplayIndex property. No matter what I try, including the sweet method in this Josh Smith tutorial, I get: The DisplayIndex for the DataGridColumn with Header 'ID' is out of range. DisplayIndex must be greater than or equal to 0 and less than Columns.Count. Parameter name: displayIndex. Actual value was -1. Is there any workaround for this? I'm including my test code below. Please let me know if you see any problems with it. ViewModel code public class MainViewModel { public List<Plan> Plans { get; set; } public int IdDisplayIndex { get; set; } public int NameDisplayIndex { get; set; } public int DescriptionDisplayIndex { get; set; } public MainViewModel() { Initialize(); } private void Initialize() { IdDisplayIndex = 1; NameDisplayIndex = 2; DescriptionDisplayIndex = 0; Plans = new List<Plan> { new Plan { Id = 1, Name = "Primary", Description = "Likely to work." }, new Plan { Id = 2, Name = "Plan B", Description = "Backup plan." }, new Plan { Id = 3, Name = "Plan C", Description = "Last resort." } }; } } Plan Class public class Plan { public int Id { get; set; } public string Name { get; set; } public string Description { get; set; } } Window code - this uses Josh Smith's DataContextSpy <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" xmlns:mwc="http://schemas.microsoft.com/wpf/2008/toolkit" Title="Main Window" Height="300" Width="300"> <Grid> <mwc:DataGrid ItemsSource="{Binding Plans}" AutoGenerateColumns="False"> <mwc:DataGrid.Resources> <local:DataContextSpy x:Key="spy" /> </mwc:DataGrid.Resources> <mwc:DataGrid.Columns> <mwc:DataGridTextColumn Header="ID" Binding="{Binding Id}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.IdDisplayIndex}" /> <mwc:DataGridTextColumn Header="Name" Binding="{Binding Name}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.NameDisplayIndex}" /> <mwc:DataGridTextColumn Header="Description" Binding="{Binding Description}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.DescriptionDisplayIndex}" /> </mwc:DataGrid.Columns> </mwc:DataGrid> </Grid> </Window> Note: If I just use plain numbers for DisplayIndex, everything works fine, so the problem is definitely with the bindings. Update 5/1/2010 I was just doing a little maintenance on my project, and I noticed that when I ran it, the problem I discuss in this post had returned. I knew that it worked last time I ran it, so I eventually narrowed the problem down to the fact that I had installed a newer version of the WPF Toolkit (Feb '10). When I reverted to the June '09 version, everything worked fine again. So, I'm now doing something I should have done in this first place: I'm including the WPFToolkit.dll that works in my solution folder and checking it into version control. It's unfortunate, though, that the newer toolkit has a breaking change.

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• ObjectContext.SaveChanges() fails with SQL CE

  - by David Veeneman

  I am creating a model-first Entity Framework 4 app that uses SQL CE as its data store. All is well until I call ObjectContext.SaveChanges() to save changes to the entities in the model. At that point, SaveChanges() throws a System.Data.UpdateException, with an inner exception message that reads as follows: Server-generated keys and server-generated values are not supported by SQL Server Compact. I am completely puzzled by this message. Any idea what is going on and how to fix it? Thanks. Here is the Exception dump: System.Data.UpdateException was unhandled Message=An error occurred while updating the entries. See the inner exception for details. Source=System.Data.Entity StackTrace: at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter) at System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache) at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options) at System.Data.Objects.ObjectContext.SaveChanges() at FsDocumentationBuilder.ViewModel.Commands.SaveFileCommand.Execute(Object parameter) in D:\Users\dcveeneman\Documents\Visual Studio 2010\Projects\FsDocumentationBuilder\FsDocumentationBuilder\ViewModel\Commands\SaveFileCommand.cs:line 68 at MS.Internal.Commands.CommandHelpers.CriticalExecuteCommandSource(ICommandSource commandSource, Boolean userInitiated) at System.Windows.Controls.Primitives.ButtonBase.OnClick() at System.Windows.Controls.Button.OnClick() at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e) at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e) at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target) at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent) at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e) at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target) at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args) at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args) at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted) at System.Windows.Input.InputManager.ProcessStagingArea() at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input) at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport) at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel) at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.Run() at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at FsDocumentationBuilder.App.Main() in D:\Users\dcveeneman\Documents\Visual Studio 2010\Projects\FsDocumentationBuilder\FsDocumentationBuilder\obj\x86\Debug\App.g.cs:line 50 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException: System.Data.EntityCommandCompilationException Message=An error occurred while preparing the command definition. See the inner exception for details. Source=System.Data.Entity StackTrace: at System.Data.Mapping.Update.Internal.UpdateTranslator.CreateCommand(DbModificationCommandTree commandTree) at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.CreateCommand(UpdateTranslator translator, Dictionary`2 identifierValues) at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary`2 identifierValues, List`1 generatedValues) at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter) InnerException: System.NotSupportedException Message=Server-generated keys and server-generated values are not supported by SQL Server Compact. Source=System.Data.SqlServerCe.Entity StackTrace: at System.Data.SqlServerCe.SqlGen.DmlSqlGenerator.GenerateReturningSql(StringBuilder commandText, DbModificationCommandTree tree, ExpressionTranslator translator, DbExpression returning) at System.Data.SqlServerCe.SqlGen.DmlSqlGenerator.GenerateInsertSql(DbInsertCommandTree tree, List`1& parameters, Boolean isLocalProvider) at System.Data.SqlServerCe.SqlGen.SqlGenerator.GenerateSql(DbCommandTree tree, List`1& parameters, CommandType& commandType, Boolean isLocalProvider) at System.Data.SqlServerCe.SqlCeProviderServices.CreateCommand(DbProviderManifest providerManifest, DbCommandTree commandTree) at System.Data.SqlServerCe.SqlCeProviderServices.CreateDbCommandDefinition(DbProviderManifest providerManifest, DbCommandTree commandTree) at System.Data.Common.DbProviderServices.CreateCommandDefinition(DbCommandTree commandTree) at System.Data.Common.DbProviderServices.CreateCommand(DbCommandTree commandTree) at System.Data.Mapping.Update.Internal.UpdateTranslator.CreateCommand(DbModificationCommandTree commandTree) InnerException:

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• Binding a property to change the listbox items foreground individually for each item

  - by Eyal-Shilony

  I'm trying to change the foreground color of the items in the ListBox individually for each item, I've already posted a similar question but this one is more concrete. I hoped that the state of the color is reserved for each item added to the ListBox, so I tried to create a property (in this case "HotkeysForeground"), bind it and change the color when the items are added in the "HotkeyManager_NewHotkey" event, the problem it's changing the foreground color for all the items in the ListBox. How can I do that per item ? Here is the ViewModel I use. namespace Monkey.Core.ViewModel { using System; using System.Collections.ObjectModel; using System.Windows.Media; using Monkey.Core.SystemMonitor.Accessibility; using Monkey.Core.SystemMonitor.Input; public class MainWindowViewModel : WorkspaceViewModel { private readonly FocusManager _focusManager; private readonly HotkeyManager _hotkeyManager; private readonly ObservableCollection<string> _hotkeys; private Color _foregroundColor; private string _title; public MainWindowViewModel() { _hotkeys = new ObservableCollection<string>(); _hotkeyManager = new HotkeyManager(); _hotkeyManager.NewHotkey += HotkeyManager_NewHotkey; _focusManager = new FocusManager(); _focusManager.Focus += FocusManager_Focus; } public Color HotkeysForeground { get { return _foregroundColor; } set { _foregroundColor = value; OnPropertyChanged(() => HotkeysForeground); } } public ReadOnlyObservableCollection<string> Hotkeys { get { return new ReadOnlyObservableCollection<string>(_hotkeys); } } public string Title { get { return _title; } set { _title = value; OnPropertyChanged(() => Title); } } protected override void OnDispose() { base.OnDispose(); _hotkeyManager.Dispose(); _focusManager.Dispose(); } private void FocusManager_Focus(object sender, FocusManagerEventArgs e) { Title = e.Title; } private void HotkeyManager_NewHotkey(object sender, EventArgs eventArgs) { HotkeysForeground = _hotkeys.Count <= 2 ? Colors.Blue : Colors.Brown; _hotkeys.Clear(); foreach (var hotkey in _hotkeyManager.GetHotkeys()) { _hotkeys.Add(hotkey); } } } } Here is the view. <Window x:Class="Monkey.View.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:System="clr-namespace:System;assembly=mscorlib" Title="{Binding Mode=OneWay, Path=Title, UpdateSourceTrigger=PropertyChanged}" Height="200" Width="200" ShowInTaskbar="False" WindowStyle="ToolWindow" Topmost="True" ResizeMode="CanResizeWithGrip" AllowsTransparency="False"> <Window.Resources> <SolidColorBrush Color="{Binding HotkeysForeground}" x:Key="HotkeysBrush"/> </Window.Resources> <ListBox Canvas.Left="110" Canvas.Top="74" Name="HotkeyList" Height="Auto" Width="Auto" HorizontalContentAlignment="Left" BorderThickness="0" ScrollViewer.CanContentScroll="False" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Disabled" ItemsSource="{Binding Path=Hotkeys}" VerticalAlignment="Stretch" VerticalContentAlignment="Center" FontSize="20"> <ListBox.ItemContainerStyle> <Style TargetType="ListBoxItem"> <Setter Property="IsEnabled" Value="False" /> </Style> </ListBox.ItemContainerStyle> <ListBox.ItemTemplate> <DataTemplate> <Label Content="{Binding}" Foreground="{StaticResource HotkeysBrush}"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Window> Thank you in advance.

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• ListBoxFor not populating with selected items

  - by user576838

  I've see this question asked a couple of other times, and I followed this after I tried things on my own with the MS music store demo to no avail, but I still can't get this to work. I've also noticed when I look at my MultiSelectList object in the viewmodel, it has the correct items in the selected items property, but if I expand the results view, it doesn't have any listboxitem with the selected value. What am I missing here? I feel like I'm taking crazy pills! Thanks in advance. model: public class Article { public int ArticleID { get; set; } public DateTime? DatePurchased { get; set; } public DateTime? LastWorn { get; set; } public string ThumbnailImg { get; set; } public string LargeImg { get; set; } public virtual List<Outfit> Outfits { get; set; } public virtual List<Tag> Tags { get; set; } } viewmodel: public class ArticleViewModel { public int ArticleID { get; set; } public List<Tag> Tags { get; set; } public MultiSelectList mslTags { get; set; } public virtual Article Article { get; set; } public ArticleViewModel(int ArticleID) { using (ctContext db = new ctContext()) { this.Article = db.Articles.Find(ArticleID); this.Tags = db.Tags.ToList(); this.mslTags = new MultiSelectList(this.Tags, "TagID", "Name", this.Article.Tags); } } } controller: public ActionResult Index() { ArticleIndexViewModel vm = new ArticleIndexViewModel(db); return View(vm); } view: @model ClosetTracker.ArticleViewModel @using (Html.BeginForm()) { <img id="bigImg" src="@Model.Article.ThumbnailImg" alt="img" /> @Html.HiddenFor(m => m.ArticleID); @Html.LabelFor(m => m.Article.Tags) @* @Html.ListBoxFor(m => m.Article.Tags, Model.Tags.Select(t => new SelectListItem { Text = t.Name, Value = t.TagID.ToString() }), new { Multiple = "multiple" }) *@ @Html.ListBoxFor(m => m.Article.Tags, Model.mslTags); @Html.LabelFor(m => m.Article.LastWorn) @Html.TextBoxFor(m => m.Article.LastWorn, new { @class = "datepicker" }) @Html.LabelFor(m => m.Article.DatePurchased) @Html.TextBoxFor(m => m.Article.DatePurchased, new { @class = "datepicker" }) <p> <input type="submit" value="Save" /> </p> } EDITED Ok, I changed around the constructor of the MultiSelectList to have a list of TagID in the selected value arg instead of a list of Tag objects. This shows the correct tags as selected in the results view when I watch the mslTags object in debug mode. However, it still isn't rendering correctly to the page. public class ArticleViewModel { public int ArticleID { get; set; } public List<Tag> Tags { get; set; } public MultiSelectList mslTags { get; set; } public virtual Article Article { get; set; } public ArticleViewModel(int ArticleID) { using (ctContext db = new ctContext()) { this.Article = db.Articles.Find(ArticleID); this.Tags = db.Tags.ToList(); this.mslTags = new MultiSelectList(this.Tags, "TagID", "Name", this.Article.Tags.Select(t => t.TagID).ToList()); } } }

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• How can I keep my MVC Views, models, and model binders as clean as possible?

  - by MBonig

  I'm rather new to MVC and as I'm getting into the whole framework more and more I'm finding the modelbinders are becoming tough to maintain. Let me explain... I am writing a basic CRUD-over-database app. My domain models are going to be very rich. In an attempt to keep my controllers as thin as possible I've set it up so that on Create/Edit commands the parameter for the action is a richly populated instance of my domain model. To do this I've implemented a custom model binder. As a result, though, this custom model binder is very specific to the view and the model. I've decided to just override the DefaultModelBinder that ships with MVC 2. In the case where the field being bound to my model is just a textbox (or something as simple), I just delegate to the base method. However, when I'm working with a dropdown or something more complex (the UI dictates that date and time are separate data entry fields but for the model it is one Property), I have to perform some checks and some manual data munging. The end result of this is that I have some pretty tight ties between the View and Binder. I'm architecturally fine with this but from a code maintenance standpoint, it's a nightmare. For example, my model I'm binding here is of type Log (this is the object I will get as a parameter on my Action). The "ServiceStateTime" is a property on Log. The form values of "log.ServiceStartDate" and "log.ServiceStartTime" are totally arbitrary and come from two textboxes on the form (Html.TextBox("log.ServiceStartTime",...)) protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder) { if (propertyDescriptor.Name == "ServiceStartTime") { string date = bindingContext.ValueProvider.GetValue("log.ServiceStartDate").ConvertTo(typeof (string)) as string; string time = bindingContext.ValueProvider.GetValue("log.ServiceStartTime").ConvertTo(typeof (string)) as string; DateTime dateTime = DateTime.Parse(date + " " + time); return dateTime; } if (propertyDescriptor.Name == "ServiceEndTime") { string date = bindingContext.ValueProvider.GetValue("log.ServiceEndDate").ConvertTo(typeof(string)) as string; string time = bindingContext.ValueProvider.GetValue("log.ServiceEndTime").ConvertTo(typeof(string)) as string; DateTime dateTime = DateTime.Parse(date + " " + time); return dateTime; } The Log.ServiceEndTime is a similar field. This doesn't feel very DRY to me. First, if I refactor the ServiceStartTime or ServiceEndTime into different field names, the text strings may get missed (although my refactoring tool of choice, R#, is pretty good at this sort of thing, it wouldn't cause a build-time failure and would only get caught by manual testing). Second, if I decided to arbitrarily change the descriptors "log.ServiceStartDate" and "log.ServiceStartTime", I would run into the same problem. To me, runtime silent errors are the worst kind of error out there. So, I see a couple of options to help here and would love to get some input from people who have come across some of these issues: Refactor any text strings in common between the view and model binders out into const strings attached to the ViewModel object I pass from controller to the aspx/ascx view. This pollutes the ViewModel object, though. Provide unit tests around all of the interactions. I'm a big proponent of unit tests and haven't started fleshing this option out but I've got a gut feeling that it won't save me from foot-shootings. If it matters, the Log and other entities in the system are persisted to the database using Fluent NHibernate. I really want to keep my controllers as thin as possible. So, any suggestions here are greatly welcomed! Thanks

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• Silverlight Cream for May 19, 2010 -- #865

  - by Dave Campbell

  In this Issue: Michael Washington, Mike Snow(-2-), Justin Angel(-2-), Jeremy Likness, and David Kelley. Shoutout: Erik Mork and crew have their latest up: Silverlight Week – Silverlight Android? From SilverlightCream.com: Simple Silverlight 4 Example Using oData and RX Extensions Michael Washington has a follow-on tutorial up on ViewModel, Rx, and lashed up to OData... good detailed tutorial with external links for more information. Silverlight Tip of the Day #21 – Animation Easing Mike Snow has a couple new tips up -- this first one is about easing... great diagrams to help visualize and a cool demo application to boot. Silverlight Tip of the Day #22 – Data Validation Mike Snow's second tip (#22) is about validation and again he has a great demo app on the post. Windows Phone 7 - Emulator Automation Justin Angel has a WP7 post up about Automating the emulator... and in the process, loading the emulator from something other than VS2010... lots of good information. TFS2010 WP7 Continuous Integration Justin Angel hinted at continuous integration for WP7 in the last post, and he pays off with this one... even without all the bits installed on the build server. Making the ScrollViewer Talk in Silverlight 4 Jeremy Likness tried to respond to a user query about knowing when a user scrolled to the bottom of a ScrollViewer... Jeremy resolved it by listening to the right property. MEF (Microsoft Extensibility Framework) made simple (ish) David Kelley is discussing MEF and using a real-world example while doing so. Good discussion and code available in his code browser app... check thecomments. 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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• Silverlight Cream for November 21, 2011 -- #1171

  - by Dave Campbell

  In this Issue: Colin Eberhardt, Sumit Dutta, Morten Nielsen, Jesse Liberty, Jeff Blankenburg(-2-), Brian Noyes, and Tony Champion. Above the Fold: Silverlight: "PV Basics : Client-side Collections" Tony Champion WP7: "Pushpin Clustering with the Windows Phone 7 Bing Map control" Colin Eberhardt Shoutouts: Michael Palermo's latest Desert Mountain Developers is up Michael Washington's latest Visual Studio #LightSwitch Daily is up From SilverlightCream.com: Pushpin Clustering with the Windows Phone 7 Bing Map control Colin Eberhardt is back discussing Pushpins for a BingMaps app on WP7 and provides a utility class that clusters pushpins, allowing you to render 1000s of pins on an app ... all the explanation and all the code Part 22 - Windows Phone 7 - Tile Push Notification Part 22 in Sumit Dutta's WP7 series is about Tile Push Notification... nice tutorial with all the code listed Correctly displaying your current location Morten Nielsen demonstrates formatting the information from the GPS on your WP7 into something intelligible and useful Spiking the Pomodoro Timer Jesse Liberty put up a quick and dirty version of a Pomodoro timer for WP7.1 to explore the technical challenges of the Full Stack Phase 2 he's cranking up 31 Days of Mango | Day #11: Network Jeff Blankenburg's Number 10 in his 31 Days quest of WP7.1 is about the NetworkInformation namespace which gives you all sorts of info on the user's device network connection availability, type, etc. 31 Days of Mango | Day #11: Live Tiles Jeff Blankenburg takes off on Live Tiles for Day 11... big topic for a 1 day post, but he takes off on it... updating and Live Tiles too Working with Prism 4 Part 2: MVVM Basics and Commands Brian Noyes has part 2 of his Prism/MVVM series up at SilverlightShow... very nice tutorial on the basics of getting a view and viewmodel up, and setting up an ICommand to launch an Edit View... plus the code to peruse. PV Basics : Client-side Collections Tony Champion is startig a series on Silverlight 5 and Pivot Viewer... First up is some basics in dealing with the control in SL5 and talking about Client-side Collections... great informative tutorial and all the code 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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• Silverlight Cream for March 13, 2010 -- #813

  - by Dave Campbell

  In this Issue: András Velvárt, Bobby Diaz, John Papa/Laurent Bugnion, Jesse Liberty, Christopher Bennage, Tim Greenfield, and Cameron Albert. Shoutouts: Svetla Stoycheva of SilverlightShow has an Interview with SilverlightShow Eco Contest Grand Prize Winner Daniel James Svetla Stoycheva of SilverlightShow also has an Interview with SilverlightShow Eco Contest Community Vote Winner Cigdem Patlak File this under #DoesHeEverSleep, Nokola has an EasyPainter Source Pack 1 Refresh And another filing in the same category by Nokola: EasyPainter Source Pack 2: Flickr, ComboCheckBox and more! In my last pre-#MIX10 'Cream post: From SilverlightCream.com: A Designer-friendly Approach to MVVM András Velvárt has an MVVM tutorial up on SilverlightShow from the Designer perspective of wiring up the View and ViewModel... good stuff my friend! Generate Strongly Typed Observable Events for the Reactive Extensions for .NET (Rx) In an effort to get more familiar with Rx, Bobby Diaz built a WhiteBoard app... there's a demo page plus the source... thanks Bobby! Silverlight TV 13: MVVM Light Toolkit My friend Laurent Bugnion is probably in the air flying to MIX10 right now, but at the MVP Summit last month, he recorded with John Papa and they produced an episode of Silverlight TV for Laurent's MVVM Light ... good stuff guys... see you tomorrow :) WCF Ria Services For Real Jesse Liberty has a great tutorial up on what it takes to get real data into your app ... you know... the stuff you have to get after reading a blog post that uses local stuff :) 1 Simple Step for Commanding in Silverlight Christopher Bennage is discussing Commanding and of course is using Caliburn for the example :) Use Silverlight Reactive Extensions (Rx) to build responsive UIs Tim Greenfield is beginning a two-parter on using Rx. In this first he has a comparison of with and without Rx... cool idea. General Purpose Sprite Class On the heels of Bill Reiss' Sprite posts, Cameron Albert has a General Purpose Sprite class post up using Bill's SilverSprite. 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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• Silverlight Cream for May 30, 2010 -- #873

  - by Dave Campbell

  In this Issue: Matthias Shapiro, Colin Blair(-2-), Mike Snow, Marlon Grech, Victor Gaudioso. Shoutout: If you're going to be anywhere near Mission Viejo, California on June 19th, set your calendar for this Victor Gaudioso event: New Speaking Event: Microsoft Book Signing/Silverlight 4 Presentation SilverLaw has another example of his Flexible surface app up: Drag & Drop Flexible Surface - Silverlight 4 From SilverlightCream.com: Silverlight 4 Binding and StringFormat in XAML Matthias Shapiro has a discussion posted about StringFormat binding in Silverlight 4 ... he dug in hard on this... well worth a read. View Model Collection Properties for WCF RIA Services Colin Blair is discussing some possibilities for exposing collections of entities from the ViewModel... his favorite: PagedCollectionView. The next post discusses this deeper. Advanced Paged Collection View Colin Blair continues in more depth on the PagedCollectionView, this time handling paging, sorting, and multiple loads. Silverlight Tip of the day #25 – Detecting Validation Errors on Submit Mike Snow's latest Tip of the Day is up and is about validation - specifically validating after your user has pressed "OK" INotifyPropertyChanged… I am fed up of handling events just to know when a property changed Marlon Grech has an Rx-less solution to code notifications of properties changing... this is a WPF and Silverlight solution and all the code is downloadable. New Silverlight Video Tutorial: How to Add Multiple BitmapEffects to One Object Victor Gaudioso's latest outing is in response to a query from a reader and is a video tutorial showing how to add multiple bitmap effects to one object. 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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