Re: WPF / MVVM - Modular Design Question - WPF Discussion Boards

What is best technology choice (WCF/WPF, WebSockets, Rest) to share webcam video amongst up to 8 users?

10-Mar-13 15:08

So I have a data template... one of the properties is a bool? (nullable bool -- not a typo). When I go into the VS XAML editor, I see the prop fine and it says I can set false, true or {x:Null}. False & true work correctly. When I try to set {x:Null}. I get:

error MC4104: The property 'IsChecked' cannot be set as a property element on template. Only Triggers and Storyboards are allowed as property elements. Line 16 Position 60.

I guess the property is null by default, so I guess don't need to explicitly set it, just wondering why that doesn't work? And want to have an answer ready for users of my control.

Prism and FluidKit

DXXL10-Mar-13 2:46

DXXL

10-Mar-13 2:46

Hi guys

Im quite new to WPF but have managed to a modular application working using Prism Unity.

What I want to be able to do is use animated transitions between views in modules. I came across the FluidKit but im struggling to get it to work within Prism.

Has anyone ever used the FluidKit successfully in Prism?

Any help will be highly appreciated!

Paga Cession9-Mar-13 16:57

Paga Cession

9-Mar-13 16:57

I am starting a project that requires one person to stream their video to up to 8 others, and each of those 8 others stream back to the one.

I started this as a WinForm in C# with the form acting as sender, or receiver, but I am expending the thought to now use a server (either AWS or Azure of which I am signed up for both) to operate this as a hub & spoke type architecture instead of peer to peer.

I have experience in Silverlight and Lightswitch and thought it might be cool to use Lightswitch's new HTML server release, but there is usually something that stands in the way, whenever I take on a LS project, so then I thought a WebForm of WPF App might be better. I have some database needs and have used WCF/EF on other projects, and figured it would work well if I chose WPF since I did some RIA work before.

But, I have almost no knowledge of streaming video, and I am really stuck on what might be the best architecture to use.

Any thoughts along these lines, or outside the box are completely welcome. Thanks so much.

Dan "Paga Cession"

modified 14-Mar-13 15:47pm.

Auto complete text box problem

columbos149277-Mar-13 19:50

columbos14927

7-Mar-13 19:50

Hello,
Im using the

System.Windows.Controls.AutoCompleteBox

Here is my XAML code:

XML

<Window x:Class="auotocomplitetrial.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:toolkit="clr-  namespace:System.Windows.Controls;assembly=System.Windows.Controls.Input.Toolkit"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <toolkit:AutoCompleteBox Name="autocompleteBox"  Height="50" Width="300"
                                 ItemsSource="{Binding MyList}"
                                 IsTextCompletionEnabled="True">
        </toolkit:AutoCompleteBox>
    </Grid>
</Window>

And here is my code behind the XAML:

public partial class MainWindow : Window
 {
     private List<string> myList;

     public List<string> MyList
     {
         get { return myList; }
     }

     public MainWindow()
     {
         InitializeComponent();

         myList = new List<string>
                          {
                              "Macedonia",
                              "Madagascar",
                              "Malawi",
                              "Malaysia",
                              "Maldives",
                              "Mali",
                              "Malta",
                              "Marshall Islands",
                              "Mauritania",
                              "Mauritius",
                              "Mexico",
                              "Micronesia",
                              "Moldova",
                              "Monaco",
                              "Mongolia",
                              "Montenegro",
                              "Morocco",
                              "Mozambique",
                              "Myanmar"
                          };
         //autocompleteBox.ItemsSource = myList;
     }
 }

When i ran this code the auto complete text box doesn't auto completes.
But when i uncomment this line:

//autocompleteBox.ItemsSource = myList;

And removed this one:

XML

ItemsSource="{Binding MyList}"

From the XAML, the auto complete text box works fine.

What i'm missing?

Thanks

Re: Auto complete text box problem

Richard Deeming8-Mar-13 1:25

Richard Deeming

8-Mar-13 1:25

You don't appear to be setting the DataContext[^] anywhere.

In the constructor, after you've created the list, try adding:

DataContext = this;

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

WPF / MVVM - Modular Design Question

Kevin Marois7-Mar-13 7:27

7-Mar-13 7:27

I am working on this[^] application.

The outter set of tabs is on the MainWindowView and the inner tabs are each on their own user control. IN the MainWindowViewMode I have a method called LoadView:

private void loadView(View View, _ArgsBase Args = null)
{
    ViewInfo tabInfo = new ViewInfo { View = View, EntityId = 0};

    // If the view is already open, then activate its tab
    if (TabManager.IsTabOpen(tabInfo))
    {
        TabManager.ActivateTab(tabInfo);
    }
    else
    {
        // Create an instance of the view and VM
        _DataEntryViewModelBase vm = null;
        UserControl view = null;
        string headerText = string.Empty;

        switch (View)
        {
            case View.Dashboard:
                headerText = "Dashboard";
                vm = new DashboardViewModel();
                view = new DashboardView();
                break;

            case View.JobCenter:
                headerText = "Job Center";
                vm = new JobCenterViewModel();
                view = new JobCenterView();
                break;

            case View.CompanyCenter:
                headerText = "Company Center";
                vm = new CompanyCenterViewModel();
                view = new CompanyCenterView();
                break;

            case View.MaterialsCenter:
                headerText = "Materials Center";
                vm = new MaterialsCenterViewModel();
                view = new MaterialsCenterView();
                break;
        }

        if (vm == null)
        {
            return;
        }

        // Load the vm's data and assign it to the view
        vm.Load(Args);
        view.DataContext = vm;

        // Cretae a tab and assign the view to it
        TabItem tabItem = new TabItem();

        tabItem.Header = headerText;
        tabItem.Content = view;
        tabItem.Tag = tabInfo;

        // Add the tab and activate it
        TabManager.AddTab(tabItem);
    }
}

The obvious problem here is that the MainWindowViewModel is now coupled to all the child views. What is the right way to do this?

If it's not broken, fix it until it is

SledgeHammer017-Mar-13 9:51

7-Mar-13 9:51

You'd have to know about the child views if you are creating them dynamically. What you DON'T have to know about is headerText and the vm.

Use a ViewLocator service or just specify it in the XAML. When the view is created, your VM will automatically be created and bound to the DataContext.

headerText should be specified in the XAML through data binding or hardcoded in the VM. The MainWindowViewModel certainly shouldn't know about it.

The real question is why you are getting a loadView method where you have access to the tab control itself. Big MVVM no-no.

TabControl should be in the main windows XAML and bound to an ItemsSource property. You shouldn't create tabs by hand, just add to the ItemsSource collection. That way you can do all the data binding in XAML.

Kevin Marois7-Mar-13 14:10

7-Mar-13 14:10

Ok, I get the ViewLocator part. The rest I don't get.

I don't understand what you mean by this:

SledgeHammer01 wrote:
The real question is why you are getting a loadView method where you have access
to the tab control itself.

The VM is trying to decide which view to open. Given the view type enum, how would the main window vm get a sub tab's view to open?

Can you point me to an example?

If it's not broken, fix it until it is

SledgeHammer017-Mar-13 15:07

7-Mar-13 15:07

If you want to be all MVVMy, you would derive your child VMs from a common base class:

public ChildViewModel1 : ChildViewModelBase (which is derived from ViewModelBase or whatever)
{
}

public ChildViewModel2 : ChildViewModelBase
{
}

then in your MainWindowVM, you would have:

public ObservableCollection<ChildViewModelBase> ChildViews
{
}

in your MainWindowVM, if you wanted to open a view, you'd new up a ChildViewModel1 for example and stick it in the list. Closing a view by removing it, etc.

The MainViewView.xaml's TabControl ItemsSource would bind to the ChildViews prop. You can have a Title property in ChildViewBase that specifies the tab text.

You wouldn't use a ViewLocator in this implementation because you are going the other way. You only new up the VMs.

You would map the VM back to a view by defining DataTemplates that say for a type ChildViewModel1, I want to instantiate ChildView1 or whatever.

That doesn't happen automatically, so you'd either derive from TabControl or use an attached property where you monitor the TabControl ItemSource collection and look up the DataTemplate for the type of VM and new up the view and set its DataContext to the content of the tab (the VM) and then the tab's content to the view.

Very slick and MVVMy once you get it set up.

Kevin Marois8-Mar-13 5:28

8-Mar-13 5:28

Ok, I et what you're saying, but how does binding the list of child views to the tab control item source actually render the view?

If it's not broken, fix it until it is

Wayne Gaylard8-Mar-13 6:10

Wayne Gaylard

8-Mar-13 6:10

You would have a resource dictionary, which would define data templates for each view/viewmodel

XML

<DataTemplate DataType="{x:type viewmodels:ChildViewModel1}">
    <views:ChildView1/>
</DataTemplate>

You would add this resource dicyionary to your App.xaml file

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

modified 9-Mar-13 5:00am.

Kevin Marois8-Mar-13 6:14

8-Mar-13 6:14

Ok, I see. I did this once a while back - back when I knew nothing about WPF. Someone showed it to me and I coded it. Didn't understand how it worked. It's all coming together now.

Thanks!

If it's not broken, fix it until it is

Wayne Gaylard8-Mar-13 6:35

Wayne Gaylard

8-Mar-13 6:35

Kevin Marois wrote:
Thanks!

Glad to help!

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

Kevin Marois11-Mar-13 8:39

11-Mar-13 8:39

By the way, do you know of any resources, book, articles, etc, that discuss this? I have been Googling, but I always get back fragments.

Thanks for your help.

If it's not broken, fix it until it is

SledgeHammer0111-Mar-13 10:20

11-Mar-13 10:20

Not really. Its mostly basic WPF concepts put together. Data templates, data binding, monitoring changes in a collection through INotifyCollectionChanged / OnItemsSourceChanged subscribing / unsubscribing to the collection changes.

As for doing the code that implements the add / remove tabs, you could do it via an attached property or deriving from the TabControl.

Concept is, if you get a new item in the collection, its going to be a ChildViewModelBase, it's going to be assigned to the tab content. So you'd do a GetType() on it and try to find a DataTemplate that is specified for that type, then you can create the child view automatically. You'd set that as the content and set the DataContext of the view as the VM.

Wayne Gaylard12-Mar-13 1:38

Wayne Gaylard

12-Mar-13 1:38

You should try to read Josh Smith's article on MSDN[^] that puts it all in one place. This article is where I learned most of my MVVM stuff from.

When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman

Abhinav S10-Mar-13 5:31

Abhinav S

10-Mar-13 5:31

I've used a separate 'controller' class for this kind of scenario.
Let the viewmodel know about this controller class and then let this 'controller' or 'loader' class decide which view needs to be loaded.

Decouples the viewmodel from all the views.

WP Apps - Color Search | Arctic | XKCD | Sound Meter | Speed Dial

SledgeHammer0111-Mar-13 14:52

11-Mar-13 14:52

MVVM doesn't have a controller. Also, it already has a mechanism for mapping VMs to Views... DataTemplates.

Abhinav S11-Mar-13 17:03

Abhinav S

11-Mar-13 17:03

SledgeHammer01 wrote:
MVVM doesn't have a controller

I agree. But you can always build one.
You can call it controller or view loader or whatever you like.

The idea is to decouple the viewmodel from the logic of instantiating the appropriate view.

WP Apps - Color Search | Arctic | XKCD | Sound Meter | Speed Dial

SledgeHammer0111-Mar-13 17:38

How to expand TreeViewItem programatically?

11-Mar-13 17:38

Yeah, thats what DataTemplates do Smile | :)

SledgeHammer013-Mar-13 19:16

Re: How to expand TreeViewItem programatically?

3-Mar-13 19:16

Been messing around with this all day and its not working for some reason. I know as you expand a node, you have to wait for the ItemContainerGenerator to do its thing, which is what I'm doing, but its only expanding one level for some reason:

    internal void ExpandAll(TreeViewItem tvi)
    {
        if (tvi.IsExpanded)
        {
            for (int nIndex = 0; nIndex < tvi.Items.Count; nIndex++)
            {
                TreeViewItem tviCurrent = tvi.ItemContainerGenerator.ContainerFromIndex(nIndex) as TreeViewItem;

                if ((object)tviCurrent != null)
                    ExpandAll(tviCurrent);
            }
        }
        else
        {
            if (tvi.ItemContainerGenerator.Status != GeneratorStatus.ContainersGenerated)
            {
                EventHandler handler = null;

                handler = new EventHandler(delegate
                {
                    if (tvi.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
                    {
// ONLY GETS IN HERE ONCE                       tvi.ItemContainerGenerator.StatusChanged -= handler;
                        ExpandAll(tvi);
                    }
                });

                tvi.ItemContainerGenerator.StatusChanged += handler;
            }

            tvi.SetCurrentValue(TreeViewItem.IsExpandedProperty, true);
        }
    }

So I only get inside the EventHandler one time. It doesn't get in there for the child nodes. If I expand the child node manually, THEN the handler code is called.

Also tried the built in .Net ExpandSubTree and it has the same issue. Only expands one level down.

I don't think I'm intercepting anything anywhere.

Mycroft Holmes4-Mar-13 11:49

Mycroft Holmes

4-Mar-13 11:49

I used this article [^]as the basis of my treeview item, it binds the IsExpanded to a property and that drives the tree. I extended it somewhat to meet my needs but it was an excellent concept and worked very well.

Never underestimate the power of human stupidity
RAH

Re: How to expand TreeViewItem programatically?

SledgeHammer014-Mar-13 12:09