Loading Views with UserControl

Topics: Prism v4 - WPF 4
Feb 10, 2012 at 11:31 AM

HI All,

I am navigating to particular view that contains userControls in it. I have checked the Loaded Event of the UserControl which is in the view that is called twice. Any suggestion in this when i loading the Views UserControl get loaded twice. How to avoid this?

Thanks and Regards,

Satkhi

Developer
Feb 10, 2012 at 4:36 PM

Hi Satkhi,

So far with the information you provided, I couldn't think of a reason for why you view is being loaded twice. Hence, it would be helpful if you could provide us with more information regarding your scenario, so that we can help you further with this.

Thanks,

Agustin Adami
http://blogs.southworks.net/aadami


 

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Accent 2" /> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 2 Accent 2" /> <w:LsdException Locked="false" Priority="65" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 1 Accent 2" /> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 2" /> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 2" /> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 2" /> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 2" /> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 2" /> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 2" /> <w:LsdException 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<w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 4" /> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 4" /> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 4" /> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 4" /> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 4" /> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading Accent 5" /> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List Accent 5" /> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid Accent 5" /> <w:LsdException Locked="false" Priority="63" 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List 1 Accent 6" /> <w:LsdException Locked="false" Priority="66" SemiHidden="false" UnhideWhenUsed="false" Name="Medium List 2 Accent 6" /> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 6" /> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 6" /> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 6" /> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 6" /> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 6" /> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 6" /> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 6" /> <w:LsdException 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Ø  so that we can help you further with this.

Feb 11, 2012 at 4:23 PM
Edited Feb 11, 2012 at 4:23 PM

You have provided very little context here, but some easy checks are to ensure that you are not adding he view twice in code. Meaning, is it possible you are adding a view to an IRegion or ContentControl via binding in more than one place or possibly in response to more than one event? Or multiple subscriptions to a single event that initiates the View injection or registration? 

How are you showing your view? What technique is used to initiate the "navigation" you mention above?

Feb 13, 2012 at 3:43 AM

Hi Jones,

Thank you for your reply.

<extab:CustomTabItem x:Class="PCSchool.Library.Views.LibraryPatronSubModuleView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" AllowDelete="True" CloseButtonClick="CustomTabItem_CloseButtonClick"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:extab="clr-namespace:Wpf.Controls;assembly=Wpf.TabControl"
             mc:Ignorable="d" xmlns:local="clr-namespace:PCSchool.Library.UserControls"  Header="Patrons" >
    <extab:CustomTabItem.Icon>
        <Image Source="Images/ModuleIcon/authority.png" Height="16" Width="16"></Image>
    </extab:CustomTabItem.Icon>
    <Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="20*"></ColumnDefinition>
        <ColumnDefinition Width="Auto"></ColumnDefinition>
    </Grid.ColumnDefinitions>
        <local:AuthorityLink Grid.Column="1" Margin="0,5,0,0"></local:AuthorityLink>
        <local:Patrons Grid.Column="0"></local:Patrons>
    </Grid>
</extab:CustomTabItem>

Above code represents my View. i am using user control inside the view.

I am loading this view to IUnityContainer  ==> var container = ServiceLocator.Current.GetInstance<IUnityContainer>();

      container.RegisterType<Object, LibraryPatronSubModuleView>("LibraryPatronSubModuleView");

Also i am loading this module on Demand as follows :

Type libraryModule = typeof(PCSchool.Library.LibraryModule);

catalog.AddModule(new ModuleInfo { ModuleName = libraryModule.Name, ModuleType = libraryModule.AssemblyQualifiedName, InitializationMode    InitializationMode.OnDemand });

I am using ViewModel DelegateCommandBinding for Navigating the View :

 private static Uri modulePatronViewUri = new Uri("LibraryPatronSubModuleView", UriKind.Relative);

 var regionManager = ServiceLocator.Current.GetInstance<IRegionManager>();

 regionManager.RequestNavigate(RegionNames.MainViewRegion, modulePatronViewUri);

Please review the provided information and update me the valuable solution.

Thanks and Regards,

Sakthi

Developer
Feb 13, 2012 at 8:10 PM
Edited Feb 13, 2012 at 8:11 PM

Hi,

So far, I couldn't find the cause of your problem, within the code snippets you provided. The suggestions provided by jesjones are a good starting point to check why this might be happening. On the other hand, if you have already check all these, perhaps you could provide us with a repro sample application so that we can analyze this in more depth.

Thanks,

Agustin Adami
http://blogs.southworks.net/aadami


Jun 29, 2012 at 3:06 AM

Did you ever find out what was going on here?

I have a similar problem.

My layout is as follows

Shell Window

  - Master Region

     - User Control A

           - RegionA

           - RegionB

I then fire a navigation event to navigate my master region to User Control B so my layout should look like this

  - Master REgion

     - User Control B

        - Region C

        - Region D

 

While this works on navigating Master Region from User Control A to User Control B my views registered inside Region C and Region D load twice. My views registered inside A and B load once as you would expect. I tried switching it so User Control B loads by default and I navigate to User Control A and in that scenario RegionA and REgionB controls load twice.

It is as if when navigating a region to a control with sub-regions the sub-regions get loaded twice for some reason. Is very bizarre.

Jun 29, 2012 at 3:31 AM

OK.

So if I made the following change I do not get the double-loading thing any more.

Switch from initialising the views in my region from the module init

regionManager.RegisterViewWithRegion(Regions.C, typeof(RegionCView))

regionManager.RegisterViewWithRegion(Regions.D, typeof(RegionDView))

to explicitly navigating in my User Control B like so

            this.Loaded += (sender, e) =>
            {
		regionManager.RequestNavigate(Regions.C,new Uri(RegionCView, UriKind.Relative));
regionManager.RequestNavigate(Regions.D,new Uri(RegionDView, UriKind.Relative));

            };

In the end this works out the same for me but it is more code I had to add to my view code-behind I would rather not add. Any idea why this would be happening?

Jun 29, 2012 at 11:06 AM

We actually do not like to use the RegionManager directly due to our need to filter the navigation request and “ask” the existing View if it can be closed or if it has pending changes.

Try this:

Create an IView interface:

public interface IView

{

bool CanClose { get; }

}

Ensure that all of your “Views” implement this interface. Also the View that is defining the implementing code for CanClose is responsible for prompting the user of pending changes while returning false as the result of the method call (see Controller Example below).

Create a controller class that is registered with Unity as a singleton and holds a local instance of the RegionManager.

· Expose a public method named something like RequestNavagation(IView V)… You will see that an IView is the expected parameter.

· In this method you will handle all requests by first casting the View in place as IView to see if it can be closed.

o Ex: if (currentView as IView).CanClose{...inject the passed in IView object…} else {…inform the user of pending changes…}

View Example (one line of code)

RequestMainContentView(UC.Resolve<MyMISView>());

Controller Example (you will notice that we also define a Refresh() method on our IView interface):

void RequestMainContentView(IView V)

{

// MainContent is an IView reference pointing to the current View in place.

// As discussed object in place is responsible for returning false and displaying prompts to notify the user why it cannot be closed.

if (MainContent.CanClose)

{

try

{

MainContent = V; // Inject your view at this point (we have a custom binding, but just know that you are injecting a view here)

NotifyPropertyChanged("MainContent", true);

ThreadPool.QueueUserWorkItem((f) => { V.Refresh(); });

EA.GetEvent<SuiteManagerRequestMainView_Rs>().Publish(true);

}

catch(Exception ex){

SynapsysMessage.Show("Cannot Load Requested View: [" + V.ToString() + "]", "IView Cannot Load", ex.Message);

}

}

}

Have fun!

From: bertnz [email removed]
Sent: Thursday, June 28, 2012 11:13 PM
To: Jesse Jones
Subject: Re: Loading Views with UserControl [CompositeWPF:302980]

From: bertnz

OK.

So if I made the following change I do not get the double-loading thing any more.

Switch from initialising the views in my region from the module init

regionManager.RegisterViewWithRegion(Regions.C, typeof(RegionCView))
regionManager.RegisterViewWithRegion(Regions.D, typeof(RegionDView))
to explicitly navigating in my User Control B like so
            this.Loaded += (sender, e) =>
            {
           regionManager.RequestNavigate(Regions.C,new Uri(RegionCView, UriKind.Relative));
regionManager.RequestNavigate(Regions.D,new Uri(RegionDView, UriKind.Relative));
 
            };

In the end this works out the same for me but it is more code I had to add to my view code-behind I would rather not add. Any idea why this would be happening?

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Developer
Jun 29, 2012 at 8:38 PM

Hi bertnz,

I am glad you have found a possible workaround for your problem.

However, we were unable to reproduce the issue you are mentioning with the information you provided so far. It would be helpful if you could provide us with a repro-sample application that isolates this behavior so that we can help you find the cause of this problem.

Regards,

Damian Cherubini
http://blogs.southworks.net/dcherubini

May 7, 2013 at 9:33 AM
Over a year after @jesjones suggestion, but thank you, or rather THANK YOU! I was getting this double-load problem and had carefully checked through the code for a few hours without success, came here and as soon as you mentioned "binding" was able to find and fix the problem :)