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  • MVVM - implementing 'IsDirty' functionality to a ModelView in order to save data

    - by Brendan
    Hi, Being new to WPF & MVVM I struggling with some basic functionality. Let me first explain what I am after, and then attach some example code... I have a screen showing a list of users, and I display the details of the selected user on the right-hand side with editable textboxes. I then have a Save button which is DataBound, but I would only like this button to display when data has actually changed. ie - I need to check for "dirty data". I have a fully MVVM example in which I have a Model called User: namespace Test.Model { class User { public string UserName { get; set; } public string Surname { get; set; } public string Firstname { get; set; } } } Then, the ViewModel looks like this: using System.Collections.ObjectModel; using System.Collections.Specialized; using System.Windows.Input; using Test.Model; namespace Test.ViewModel { class UserViewModel : ViewModelBase { //Private variables private ObservableCollection<User> _users; RelayCommand _userSave; //Properties public ObservableCollection<User> User { get { if (_users == null) { _users = new ObservableCollection<User>(); //I assume I need this Handler, but I am stuggling to implement it successfully //_users.CollectionChanged += HandleChange; //Populate with users _users.Add(new User {UserName = "Bob", Firstname="Bob", Surname="Smith"}); _users.Add(new User {UserName = "Smob", Firstname="John", Surname="Davy"}); } return _users; } } //Not sure what to do with this?!?! //private void HandleChange(object sender, NotifyCollectionChangedEventArgs e) //{ // if (e.Action == NotifyCollectionChangedAction.Remove) // { // foreach (TestViewModel item in e.NewItems) // { // //Removed items // } // } // else if (e.Action == NotifyCollectionChangedAction.Add) // { // foreach (TestViewModel item in e.NewItems) // { // //Added items // } // } //} //Commands public ICommand UserSave { get { if (_userSave == null) { _userSave = new RelayCommand(param => this.UserSaveExecute(), param => this.UserSaveCanExecute); } return _userSave; } } void UserSaveExecute() { //Here I will call my DataAccess to actually save the data } bool UserSaveCanExecute { get { //This is where I would like to know whether the currently selected item has been edited and is thus "dirty" return false; } } //constructor public UserViewModel() { } } } The "RelayCommand" is just a simple wrapper class, as is the "ViewModelBase". (I'll attach the latter though just for clarity) using System; using System.ComponentModel; namespace Test.ViewModel { public abstract class ViewModelBase : INotifyPropertyChanged, IDisposable { protected ViewModelBase() { } public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string propertyName) { PropertyChangedEventHandler handler = this.PropertyChanged; if (handler != null) { var e = new PropertyChangedEventArgs(propertyName); handler(this, e); } } public void Dispose() { this.OnDispose(); } protected virtual void OnDispose() { } } } Finally - the XAML <Window x:Class="Test.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:vm="clr-namespace:Test.ViewModel" Title="MainWindow" Height="350" Width="525"> <Window.DataContext> <vm:UserViewModel/> </Window.DataContext> <Grid> <ListBox Height="238" HorizontalAlignment="Left" Margin="12,12,0,0" Name="listBox1" VerticalAlignment="Top" Width="197" ItemsSource="{Binding Path=User}" IsSynchronizedWithCurrentItem="True"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel> <TextBlock Text="{Binding Path=Firstname}"/> <TextBlock Text="{Binding Path=Surname}"/> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> <Label Content="Username" Height="28" HorizontalAlignment="Left" Margin="232,16,0,0" Name="label1" VerticalAlignment="Top" /> <TextBox Height="23" HorizontalAlignment="Left" Margin="323,21,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" Text="{Binding Path=User/UserName}" /> <Label Content="Surname" Height="28" HorizontalAlignment="Left" Margin="232,50,0,0" Name="label2" VerticalAlignment="Top" /> <TextBox Height="23" HorizontalAlignment="Left" Margin="323,52,0,0" Name="textBox2" VerticalAlignment="Top" Width="120" Text="{Binding Path=User/Surname}" /> <Label Content="Firstname" Height="28" HorizontalAlignment="Left" Margin="232,84,0,0" Name="label3" VerticalAlignment="Top" /> <TextBox Height="23" HorizontalAlignment="Left" Margin="323,86,0,0" Name="textBox3" VerticalAlignment="Top" Width="120" Text="{Binding Path=User/Firstname}" /> <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="368,159,0,0" Name="button1" VerticalAlignment="Top" Width="75" Command="{Binding Path=UserSave}" /> </Grid> </Window> So basically, when I edit a surname, the Save button should be enabled; and if I undo my edit - well then it should be Disabled again as nothing has changed. I have seen this in many examples, but have not yet found out how to do it. Any help would be much appreciated! Brendan

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  • How to traverse the item in the collection in a List or Observable collection?

    - by Ashish Ashu
    I have a collection that is binded to my Listview. I have provided options to user to "move up" "move down" the selected item in the list view. I have binded the selected item of the listview to my viewmodel, hence I get the item in the collection on which user want to do the operation. I have attached "move up" "move down" commands in my viewmodel. I want what is the best way to move up and down in the collection in the collection which is reflected in the list view. Please suggest.

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  • WPF ComboBox SelectedItem - change to previous value

    - by Taylor
    Hello, I have a ComboBox that has the SelectedItem bound to the ViewModel. <ComboBox SelectedItem="{Binding SelItem, Mode=TwoWay}" ItemsSource="{Binding MyItems}"> When the user selects a new Item in the View ComboBox, I want to display a prompt and verify that they want to make the change. In the SetItem Property setter in the View Model, I display a Dialog to confirm the selection. When they say yes, it works fine. My problem is, when the user clicks on "No" I am not sure who to get the ComboBox to revert back to the previous value. The Property in the ViewModel has the correct older value, however in the View the ComboBox displays the newly Selected Value. I want the user to select an item, confirm they want to go ahead with it, and if they decide not to, I want the ComboBox to revert back to the previous item. How can I accomplish this? Thanks!

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  • DataTemplate defautl visibility for ContentControls

    - by bitbonk
    In my MVVM based WPF application I have a lot of different ViewModel types that dynamically loaded into ContentControls or ContentPresenters. Therefor I need to explictly set what DataTemplate is to be used in XAML: <ContentControl Content={Binding SomePropertyOfTypeViewModel} ContentTemplate={StaticResource someTemplate} /> Now my problem is that the content control is displaying the UI of someTemplate even if the ContentControl is bound to nothing (i.e ViewModel.SomePropertyOfTypeViewModel is null) Is there a quick and easy way to make all ContentControls display nothing if they are currently bound to nothing? When I use implicit DataTemplates everything works as expected. Unfortunately I can't use this mechanism here.

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  • Following Domain Driven Design with MVVM/WPF

    - by msfanboy
    Hello, I have plain POCOs here and as INotifyPropertyChanged is a Interface for the Views need its implemented in the ViewModel not the Model. Now I want to show validation errors in the View beside every textbox the user typed in data. I do not want to implemented the IDataErrorInfo interface in my Models because lets assume I am not allowed to touch them as they come from another Service/Supplier. I do not want to put my IsCustomerFirstNameLenthValid Method into the Model because I could not have access to it or I just dont want to pollute my Models with interface`s having nothing to do there! How can I validate my naked POCO`s in the ViewModel and forward the results to the View by showing validation errors ?

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  • problem in basic implementation of MVVM pattern - Services

    - by netmajor
    I watch some video and read articles about MVVM pattern and start thinking how should I implement it in my Silverlight app. So at first I create Silverlight application. I think that for clear view I create 3 folders: View - for each user control page in my app, ViewModel - for c# class which will querying date and Model- Entity Data Model of my SQL Server or Oracle Database. And now I am confused, cause I want to implement *WCF/RIA Services/Web services* in my project. In which folder should I put in class of services? I see in examples that Services take date and filtering it and then output data was binding in View - so It looks as ViewModel. But I was sure that someone use Services in Model and that I want to do. But how? Can someone explain me implementing Services as Model? Is my point of view at MVVM is correctly?

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  • TextBox.TextChanged & ICommandSource

    - by Brad Leach
    I am following the M-V-VM pattern for my WPF UI. I would like to hook up a command to the TextChanged event of a TextBox to a command that is in my ViewModel class. The only way I can conceive of completing this task is to inherit from the TextBox control, and implement ICommandSource. I can then instruct the command to be fired from the TextChanged event. This seems to be too much work for something which appears to be so simple. Is there an easier way (than subclassing the TextBox and implementing ICommandSource) to hook up the TextChanged event to my ViewModel class?

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  • TabItems from View collection

    - by byte
    I am using MVVM. I have a tab control. I will have a collection of items. I want to display each of this item in the collection as a tab item. The view in each tab item is different and may have its own viewmodel. How do I achieve this? E.g. I have 3 items in the collection. The Tab item template contains an ItemControl. I would like to now have 3 Tabs created and the ItemControls inside each tabitem may be showing different views. One way I could do is have a single view and viewmodel for each item. Now based on some condition the View will display different UI elements and behave differently. But I am afraide this will make the view quite complex over a period of time.

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  • Where should I put WPF specific code when using MVVM?

    - by Surfbutler
    I'm just getting up to speed on MVVM, but all the examples I've seen so far are binding View controls to simple non-WPF specific data types such as strings and ints. However in our app I want to be able to set a button's border brush based on a number in the Model. At the moment, I translate the number into a brush in the ViewModel to keep the View XAML only, but is that right? I don't like putting WPF specific code in the ViewModel, but equally I don't like the idea of putting code-behind on my View panel. Which is the best way? Thanks

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  • MVVM- View Model-View Model Communications

    - by user275561
    How do I go about having two view models communicate with one another using MVVM Light. I know how to use the messenger class and register etc.. Here is my Scenario A Settings View ---> a Settings View Model . . . A MainPage View ---> A MainPage ViewModel If something changes in the Settings View it will Message back to the Settings View Model. So then I want the Settings View Model to communicate to the MainPage View Model about what changed. THe MainPage ViewModel will then tell the View.

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  • What version of DataAnnotations is included with ASP.NET MVC 2 RTM

    - by Nick Thoresby
    I'm working on a project using Visual Studio 2008 and have moved from the the MVC 2 Preview to RTM version. We would like to use model validation such as: public class ViewModel { [Required(ErrorMessage="UserName is required.")] [StringLength(10, ErrorMessage="UserName cannot be greater than 10 chars.")] public string UserName { get; set; } } [HttpPost] public ActionResult Register(ViewModel model) { if (ModelState.IsValid){} // Always true } However the ModelState.IsValid always returns true. I have a suspicion that it might be something to do with the version of System.ComponentModel.DataAnnotations.dll that we are referencing, currently version 99.0.0.0, which seems rather odd. Does anyone know what version of this dll is included with the MVC 2 RTM for Visual Studio 2008?

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  • Adding global blank option to DroDownList in MVC

    - by Diegos Grace
    Is there a way of using a templated helper in mvc so that each and every select list in my project has a custom default 'Choose an option' with null value etc. The posts I have seen seem a little complex, is it possible to have a DropDownList.ascx file in shared view folder with something like this: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<IEnumerable<SelectListItem>>" %> <%= Html.DropDownList(selectlist name, selectlist value, "Choose an option")%> And then having a UIHint("DropDownList") for each dropdownlist in the ViewModel? Some guidance on syntax of parameters would be much appreciated, where name and value of the viewmodel dropdownlist plus the 'Choose an option' string are passed. Or is this all wishful thinking?

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  • MVVM and division of amongst multiple developers

    - by nlawalker
    Can anyone speak to the ease of dividing work amongst multiple developers when designing and building a medium- to large-complexity Silverlight or WPF application? My team is finding it difficult to cleanly split work when you've got, for example, a number of controls that provide different visualizations of a Model/ViewModel that's fairly complex and has a lot of properties and methods for interacting with data. It seems like a very big portion of the work ends up being the design and build of the Model/ViewModel, and much less inside each of the controls, which are naturally what are easy to ration out to multiple people.

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  • MVVM where does the code to load the data belong?

    - by cody
    As I wrap my head around the mvvm thing, the view is the view, and the viewmodel is 'a modal of a view' and the model are the entities we are dealing with (or at least that is my understanding). But I'm unclear as to what and when the model entities are populated. So for example: Lets say I have app that needs to create a new record in a DB. And that record should have default values to start with. Who is responsible for the new record, and getting the default values. Does this have anything to do with MVVM or is that part of a data access layer? Who calls the the viewmodel? Or for existing records when\where are the records retrieved? And saved if altered? Thanks

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  • ICOmmand - canexecute can not disable Button with image content.

    - by Anish
    Hi , I have a button control in my wpf-mvvm application. I use an ICommand property (defined in viewmodel) to bind the button click event to viewmodel. I have - execute and canexecute parameters for my ICommand implementation (RelayCommand). Even if CanExecute is false...button is not disabled...WHEN button CONTENT is IMAGE But, when button content is text..enable/disable works fine. <Button DockPanel.Dock="Top" Command="{Binding Path=MoveUpCommand}"> <Button.Content> <Image Source="/Resources/MoveUpArrow.png"></Image> </Button.Content> <Style> <Style.Triggers> <Trigger Property="IsEnabled" Value="False"> <Setter Property="Opacity" Value=".5" /> </Trigger> </Style.Triggers> </Style> </Button>

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  • ASP.NET MVC View Not posting back to Post method and expecting a parameterless Constructor?

    - by VJ
    Hi, I am trying to post back some data using a viewmodel i have created and it works for me for one of the projects.But I am doin this right now public ActionResult Foo(string userkey) { vm.Value="Xvalue"; return View(vm); } [HttpPost] public ActionResult Foo( MyViewModel vm) { // process input if (inputOK) string value=vm.Value return RedirectToAction("Index"); return View(); } public class MyViewModel { public string Value { get; set; } public SomeClass newobj {get;set;} } public class SomeClass { public int id{get;set;} public string str{get;set;} } So it on debugging never goes into the parameter method for Post although on the view i have added a form and a button that submits and the page inherits from the viewmodel.I get an error saying it expects a parameterless constructor how do I fix this ? . I wrote an post method with no parameters and it does go into that method

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  • Silverlight Bind to TextBlock from RIA Services

    - by DaRKoN_
    I've a TextBlock that looks like so: <TextBlock Text="{Binding Name}" /> This is inside a <Canvas> with the DataContext set to MyClient which is in the ViewModel: public Client MyClient { get; private set; } // This is a RIA Entity, hence supports INotifyPropertyChanged public ViewModel() { MyClient = new Client(); LoadOperation<Client> loadClient = RiaContext.Load<Client>(RiaContext.GetClientsQuery()); loadClient.Completed += new EventHandler(loadClient_Completed); } void loadClient_Completed(object sender, EventArgs e) { MyClient = DB.Clients.Single(); } Setting MyClient like the above does not raise the PropertyChanged event. As such the UI is never updated.

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  • Selecting the usercontrol to the relating datatemplate in mvvm

    - by msfanboy
    Hello, I have lets say a WeeklyViewUserControl.xaml and a DailyViewUserControl.xaml. Normally I used stuff like this to switch content: <DataTemplate DataType="{x:Type ViewModel:LessonPlannerViewModel}"> <View:LessonPlannerDailyUC/> </DataTemplate> This worked so far. But now I have still the WeeklyViewUC which uses 90 % of the LessonPlannerViewModel code so I want to make this additionally: <DataTemplate DataType="{x:Type ViewModel:LessonPlannerViewModel}"> <View:LessonPlannerWeeklyUC/> </DataTemplate> but this can not work, because from where does the ContentControl know that VM (LessonPlannerViewModel) should display a DailyViewUC or a WeeklyViewUC ? <ContentControl Content="{Binding VM}" />

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  • Where to put WPF specific code when using MVVM

    - by Surfbutler
    I'm just getting up to speed on MVVM, but all the examples I've seen so far are binding View controls to simple non-WPF specific data types such as strings and ints. However in our app I want to be able to set a button's border brush based on a number in the Model. At the moment, I translate the number into a brush in the ViewModel to keep the View XAML only, but is that right? I don't like putting WPF specific code in the ViewModel, but equally I don't like the idea of putting code-behind on my View panel. Which is the best way? Thanks

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  • Sharing state/changes across ViewModels

    - by joshperry
    I have an App which has a Tasks tab and a Projects tab. I decided to make a separate ViewModel for each of the tabs, TasksViewModel and ProjectsViewModel. The Tasks tab has a new task area with an associated project pulldown and the Projects tab (obviously) has a list of projects. What I'd like is for the pulldown on the Tasks tab to share the same collection as the Projects tab list so that any time I add or remove a project on the Projects tab the list on the Tasks tab is up to date automatically. This worked well with a single ViewModel but it was beginning to become quite unruly. Should I not have split into two ViewModels? Is there a common method of sharing data like this? Perhaps pass the same ObservableCollection<Project> into each of the ViewModels? Perhaps some type of notification back to the TasksViewModel along the lines of ICollectionChanged. Appreciate any insight/input!

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  • MVVM Binding To Property == Null

    - by LnDCobra
    I want to show some elements when a property is not null. What is the best way of achieving this? The following is my ViewModel: class ViewModel : ViewModelBase { public Trade Trade { get { return _trade; } set { SetField(ref _trade, value, () => Trade); } } private Trade _trade; } ViewModelBase inherits INotifyPropertyChanged and contains SetField() The Following is the Trade class: public class Trade : INotifyPropertyChaged { public virtual Company Company { get { return _company; } set { SetField(ref _company, value, () => Company); } } private Company _company; ...... } This is part of my View.xaml <GroupBox Visibility="{Binding Path=Trade.Company, Converter={StaticResource boolToVisConverter}}" /> I would like this groupbox to show only if Trade.Company is not null (so when a user selects a company). Would I need to create a custom converter to check for null and return the correct visibility or is there one in .NET?

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  • WPF textblock binding question.

    - by the empirical programmer
    I'm trying to get my head around the whole MVVM thing and binding. I have a ViewModel class which has a property that is another class. I want to bind to a (string) property of that class to the text of a textblock. I set the ViewModel as my data context for my window\page. And then do this: <TextBlock Text="{Binding ElementName=myAddressClass, Path=StreetName}" /> But this does not work. The text is empty. I can expose the StreetName directly as below and this works: <TextBlock Text="{Binding Path=StreetName}" /> So am I doing something wrong in the first example. It seems simple enough ... am I just confuse about what an elementname is or should be set to? thanks

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