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Question

I'm having an issue where a datagrid is not reflecting changes to its collection when attached to a view inside a view. More accurately, I have a SecondView within the MainView. On the SecondView I have a datagrid with autogeneratecolumns set to true; when the datagrid is first rendered, it displays the appropriate columns and headers. However, when I populate the list that is attached to it, no changes are reflected.

Here is the complete code for the two views and their respective viewmodels: MainWindowView:

<Window x:Class="MyApp.MainWindowView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:cal="http://www.caliburnproject.org"
    xmlns:views="clr-namespace:MyApp"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindowView" Height="300" Width="300">
<Grid>
    <DockPanel>
        <Menu DockPanel.Dock="Top">
            <MenuItem Header="File">
                <MenuItem Header="Open" x:Name="Open"/>
                <MenuItem Header="Exit" x:Name="Exit"/>
            </MenuItem>
        </Menu>
        <StackPanel DockPanel.Dock="Bottom">
            <views:SecondView/>
        </StackPanel>
    </DockPanel>
</Grid>

MainWindowViewModel:

namespace MyApp
{
[Export(typeof(IShell))]
internal class MainWindowViewModel : Screen, IShell
{
    Regex expression = new Regex(@"^N\d\.C\d\.D\d\.R\d:\s\s\s-\d"); //ex. "N1.C1.D2.R1:   -3"        
    SecondViewModel svm = new SecondViewModel();        
    public void Open()
    {
        Microsoft.Win32.OpenFileDialog openFile = new Microsoft.Win32.OpenFileDialog();
        openFile.Multiselect = true;
        openFile.Filter = "Text Files(*.txt)|*.txt|Log Files(*.log)|*.log|All Files(*.*)|*.*";
        openFile.Title = "Open File(s)";
        bool? userClickedOK = openFile.ShowDialog();
        string[] _fileNames = openFile.FileNames;
        if (userClickedOK == true)
        {
            if (_fileNames != null)
            {
                for (int i = 0; i < _fileNames.Length; i++)
                {
                    ValidFiles(_fileNames[i]);
                }
            }
        }
    }
    public void Exit()
    {
        App.Current.Shutdown();
    }
    /* ValidFiles() accepts a string containing a filename and creates a Streamreader that reads the file if it is not a Boxboro file.
     */
    public void ValidFiles(string filename)
    {
        string line;
        using (StreamReader sr = new StreamReader(filename))
        {
            while ((line = sr.ReadLine()) != null)
            {
                if (line.Contains("Mono Status"))
                {
                    Console.WriteLine("File(s) not supported by this parser. Please select a valid file.");
                    break;
                }
                else
                {
                    IsMatch(line);
                }
            }
        }
    }
    /* IsMatch() accepts a string "input" and determines which parsing method to send the string to, if any.
     * Strings not matching any of the initial criteria are not processed to limit overhead.
     */
    public void IsMatch(string input)
    {
        Match match = expression.Match(input);
        if (match.Success)
        {
            svm.GetData(input);
        }
    }
}

}

SecondWindowView:

<UserControl x:Class="MyApp.SecondView"
         xmlns:cal="http://www.caliburnproject.org"
         cal:Bind.Model="MyApp.SecondViewModel"
         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" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid>
    <StackPanel>
        <DataGrid x:Name="MyList"/>
    </StackPanel>
</Grid>

SecondWindowViewModel:

namespace MyApp
{
[Export(typeof(SecondViewModel))]
class SecondViewModel:Screen
{
    Parse parse = new Parse();
    BindableCollection<MyObject> myList = new BindableCollection<MyObject>();
    MyObject myObject;
    public MyObject MyObject
    {
        get { return myObject; }
        set
        {
            myObject = value;
            NotifyOfPropertyChange(() => MyList);
        }
    }
    public BindableCollection<MyObject> MyList
    {
        get { return myList; }
        set 
        { 
            MyList = value;
            NotifyOfPropertyChange(() => MyList);
        }
    }
    public void GetData(string input)
    {
        string[] tempArray = input.Split();
        List<int> tempList = new List<int>();
        for (int i = 1; i < tempArray.Length; i++)
        {
            if (!string.IsNullOrEmpty(tempArray[i]))
            {
                tempList.Add(Convert.ToInt32(tempArray[i]));
            }
        }
        int[] tempIntArray = tempList.ToArray();
        MyObject = new MyObject(tempArray[0], tempIntArray[0], tempIntArray[1], tempIntArray[2], tempIntArray[3]);
        this.MyList.Add(MyObject);

        Console.WriteLine("MyList has " + MyList.Count.ToString() + " elements.");
        //foreach (MyObject item in MyList)
        //{
        //    Console.WriteLine(item.Location);
        //}
    }
}

}

Boostrapper:

namespace MyApp
{
    internal class AppBootStrapper : Bootstrapper<IShell>
    {
        static AppBootStrapper()
        {
            //Initializes the logger for debugging, remove or comment out in release.
            LogManager.GetLog = type => new DebugLogger(type);
        }
        private CompositionContainer container;
        protected override void BuildUp(object instance)
        {
            this.container.SatisfyImportsOnce(instance);
        }
        protected override void Configure()
        {
            this.container = 
                new CompositionContainer(
                    new AggregateCatalog(
                        AssemblySource.Instance.Select(x => new AssemblyCatalog(x)).OfType<ComposablePartCatalog>()));
            var batch = new CompositionBatch();
            batch.AddExportedValue<IWindowManager>(new WindowManager());
            batch.AddExportedValue<IEventAggregator>(new EventAggregator());
            batch.AddExportedValue(this.container);
            this.container.Compose(batch);
        }
        protected override IEnumerable<object> GetAllInstances(Type serviceType)
        {
            return this.container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
        }
        //This method is required for the BootStrapper.cs to be discovered.
        protected override object GetInstance(Type serviceType, string key)
        {
            string contract = string.IsNullOrEmpty(key) ? AttributedModelServices.GetContractName(serviceType) : key;
            IEnumerable<object> exports = this.container.GetExportedValues<object>(contract);
            if (exports.Count() > 0)
            {
                return exports.First();
            }
            throw new Exception(string.Format("Could not locate any instances of contract {0}.", contract));
        }
    }
}

Based on my understanding of Caliburn.Micro, whenever the observablecollection MyList is updated (a new item added), the datagrid with x:name MyList should be updated. Even without a data template, I would think I would see a list of blank entries equivalent in length to the number of objects in MyList. When I use this same code in the MainViewModel, rather than in a usercontrol bound to the MainView, I have no issues rendering the list. It seems I'm missing something about updating a view within a view.

I should note, I can verify the list has objects in it by using Console.WriteLine(MyList.Count.ToString()) and watching the output window. I hate asking about these things, every time I do it ends up being a typo or something equally silly, but I've been stuck here for too long.

NOTE: Even with MyList.Refresh() thrown in on each iteration, no changes in the datagrid occur.

NOTE: It seems like this may answer my question, but I don't understand how to implement it. Perhaps if someone else understands it better, they could put the lines of code in the appropriate places in my code and explain why it works. Thanks in advance. Caliburn.Micro convention-based bindings not working in nested views?

Answer 1

Try this viewmodel first approach - I suspect your inner view isn't being bound (CM doesn't look across control boundaries when applying conventions eg it won't apply conventions to nested usercontrols)

<Window x:Class="MyApp.MainWindowView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:cal="http://www.caliburnproject.org"
    xmlns:views="clr-namespace:MyApp"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindowView" Height="300" Width="300">
<Grid>
    <DockPanel>
        <Menu DockPanel.Dock="Top">
            <MenuItem Header="File">
                <MenuItem Header="Open" x:Name="Open"/>
                <MenuItem Header="Exit" x:Name="Exit"/>
            </MenuItem>
        </Menu>
        <StackPanel DockPanel.Dock="Bottom">
            <!-- Use ContentControl for sub-views, CM will do it's magic if you bind to the VM property using the standard conventions -->
            <ContentControl x:Name="SecondView" />
        </StackPanel>
    </DockPanel>
</Grid>

Then in your main:

internal class MainWindowViewModel : Screen, IShell
{
    Regex expression = new Regex(@"^N\d\.C\d\.D\d\.R\d:\s\s\s-\d"); //ex. "N1.C1.D2.R1:   -3"      
    // Declare your second VM as a property so you can bind to it via CM conventions  
    public SecondViewModel SecondView 
    { 
        get { return _secondView; } 
        set 
        {
            _secondView = value;
            NotifyOfPropertyChange(() => SecondView);
        }
    }

    public MainWindowViewModel()
    {
        SecondView = new SecondViewModel();
    }

CM will automatically inject the right view into the content controls template and setup the datacontext

Alternatively, you can use Bind.Model to bind the VM instance to the view which is more a view-first approach

   <StackPanel DockPanel.Dock="Bottom">
        <views:SecondView cal:Bind.Model="{Binding SecondView}" />
    </StackPanel>

(I think it's Bind.Model and not View.Model but I often get the two mixed up, so failing Bind.Model try View.Model)