gheff gheff - 1 year ago 139
C# Question

WPF, PRISM and EventAggregrator

I'm having some trouble with using EventAggregator within my application. The issue I am facing is that the UI will not update until the current processing has stopped. I was under the impression that EventAggregator ran in its own thread and therefore should be able to update the UI as soon as an event is published. Have I misunderstood this concept?

below is my code

Bootstrapper.cs

class Bootstraper : UnityBootstrapper
{
protected override DependencyObject CreateShell()
{
return ServiceLocator.Current.GetInstance<MainWindow>();
}

protected override void InitializeShell()
{
Application.Current.MainWindow.Show();
}
}


App.xmal.cs

public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);

var bs = new Bootstraper();
bs.Run();
}
}


MainWindow.xmal

<Window x:Class="TransactionAutomationTool.Views.MainWindow"
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:local="clr-namespace:TransactionAutomationTool"
xmlns:views="clr-namespace:TransactionAutomationTool.Views"
xmlns:prism="http://prismlibrary.com/"
prism:ViewModelLocator.AutoWireViewModel="True"
mc:Ignorable="d"
Title="MainWindow" Height="600" Width="800">
<Grid>
<views:HeaderView x:Name="HeaderViewCntl" Margin="20,21,10,0" Height="70" Width="740" HorizontalAlignment="Left" VerticalAlignment="Top" />
<views:ProcessSelectionView x:Name="ProcessSelectionViewControl" Margin="20,105,0,0" Height="144" Width="257" HorizontalAlignment="Left" VerticalAlignment="Top" />
<views:ProcessInputView x:Name="ProcessInputViewControl" Margin="20,280,0,0" Height="218" Width="257" HorizontalAlignment="Left" VerticalAlignment="Top"/>
<views:ProcessLogView x:Name="ProcessLogViewControl" Margin="298,105,0,0" Height="445" Width="462" HorizontalAlignment="Left" VerticalAlignment="Top" />
<views:ButtonsView x:Name="ButtonViewControl" Margin="0,513,0,0" Height="37" Width="300" HorizontalAlignment="Left" VerticalAlignment="Top" />
</Grid>




ProcessLogView.xaml

<UserControl x:Class="TransactionAutomationTool.Views.ProcessLogView"
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"
xmlns:local="clr-namespace:TransactionAutomationTool.Views"
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
xmlns:prism="http://prismlibrary.com/"
prism:ViewModelLocator.AutoWireViewModel="True"
mc:Ignorable="d"
d:DesignHeight="445" d:DesignWidth="462">
<UserControl.Resources>
<DataTemplate x:Key="TwoLinkMessage">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Message}" />
<TextBlock>
<Hyperlink NavigateUri="{Binding Link}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="HyperLinkClicked">
<ei:CallMethodAction MethodName="HyperLinkClicked" TargetObject="{Binding}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<TextBlock Text="{Binding Link}"/>
</Hyperlink>
</TextBlock>
<TextBlock>
<Hyperlink NavigateUri="{Binding SecondLink}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="HyperLinkClicked">
<ei:CallMethodAction MethodName="HyperLinkClicked" TargetObject="{Binding}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<TextBlock Text="{Binding SecondLink}"/>
</Hyperlink>
</TextBlock>
</StackPanel>
</DataTemplate>
<DataTemplate x:Key="LinkMessage">
<TextBlock>
<Hyperlink NavigateUri="{Binding Link}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="HyperLinkClicked">
<ei:CallMethodAction MethodName="HyperLinkClicked" TargetObject="{Binding}" />
</i:EventTrigger>
</i:Interaction.Triggers>
<TextBlock Text="{Binding Message}"/>
</Hyperlink>
</TextBlock>
</DataTemplate>
<DataTemplate x:Key="Default">
<TextBlock Text="{Binding Message}" />
</DataTemplate>
</UserControl.Resources>
<Border BorderBrush="Black" BorderThickness="1" CornerRadius="15">
<!--<ListBox x:Name="lbxProgress" HorizontalAlignment="Left" Height="408" Margin="5,5,0,0" VerticalAlignment="Top" Width="431" Foreground="Black" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding LogMessage}" BorderThickness="0" />-->
<ListView Name="lvProgress" ItemsSource="{Binding LogMessage}" Margin="9" BorderThickness="0">
<ListView.ItemContainerStyle>
<Style TargetType="{x:Type ListViewItem}">
<Setter Property="ContentTemplate" Value="{StaticResource Default}" />
<Style.Triggers>
<DataTrigger Binding="{Binding LinkNum}" Value="0">
<Setter Property="ContentTemplate" Value="{StaticResource Default}" />
</DataTrigger>
<DataTrigger Binding="{Binding LinkNum}" Value="1">
<Setter Property="ContentTemplate" Value="{StaticResource LinkMessage}" />
</DataTrigger>
<DataTrigger Binding="{Binding LinkNum}" Value="2">
<Setter Property="ContentTemplate" Value="{StaticResource TwoLinkMessage}" />
</DataTrigger>
</Style.Triggers>
</Style>
</ListView.ItemContainerStyle>
</ListView>
</Border>




ProcessLogViewModel.cs

class ProcessLogViewModel: EventsBase
{

private ObservableCollection<LogPayload> logMessage;

public ObservableCollection<LogPayload> LogMessage
{
get { return logMessage; }
set { SetProperty(ref logMessage, value); }
}

public ProcessLogViewModel()
{
//If statement is required for viewing the MainWindow in design mode otherwise errors are thrown
//as the ProcessLogViewModel has parameters which only resolve at runtime. I.E. events
if (!(bool)DesignerProperties.IsInDesignModeProperty.GetMetadata(typeof(DependencyObject)).DefaultValue)
{
events.GetEvent<LogUpdate>().Subscribe(UpdateProgressLog);
LogMessage = new ObservableCollection<LogPayload>();
}
}

public void HyperLinkClicked(object sender, RequestNavigateEventArgs e)
{
System.Diagnostics.Process.Start(e.Uri.AbsoluteUri);
}

private void UpdateProgressLog(LogPayload msg)
{
LogMessage.Add(msg);
}
}


EventsBase.cs

public class EventsBase: BindableBase
{
public static IServiceLocator svc = ServiceLocator.Current;
public static IEventAggregator events = svc.GetInstance<IEventAggregator>();
}


LogEvents.cs

public class LogUpdate : PubSubEvent { }

public class LogEvents : EventsBase
{
public static void UpdateProcessLogUI(LogPayload msg)
{
events.GetEvent<LogUpdate>().Publish(msg);
}
}


LogEvent struct

public struct LogPayload
{
public string Message { get; set; }
public int LinkNum { get; set; }
public string Link { get; set; }
public string SecondLink { get; set; }
}


Then if I drag and drop a spreadsheet on to the ProcessInputView the following code is hit within my ProcessInputViewModel.cs

public void FileDropped(object sender, DragEventArgs e)
{
string[] files;
string[] cols;
TextBox txtFileName = (TextBox)sender;
SpreadsheetCheck result = new SpreadsheetCheck();
DDQEnums.TranTypes tranType;
List<string> fileFormats = new List<string>();

fileFormats.Add(Constants.FileFormats.XLS);
fileFormats.Add(Constants.FileFormats.XLSX);

if (e.Data.GetDataPresent(DataFormats.FileDrop, true))
{
files = e.Data.GetData(DataFormats.FileDrop, true) as string[];

if (files.GetLength(0) > 1)
{
result.IsValid = false;
result.Message = "Only drop one file per input box";
}
else
{
result = Utils.CheckIfSpreadsheetIsValidForInput(files[0], fileFormats, (DDQEnums.TranTypes)txtFileName.Tag, out tranType);

LogEvents.UpdateProcessLogUI(Utils.BuildLogPayload(string.Format("Checking {0} Spreadsheet Column Format", tranType)));
if (result.IsValid)
{
cols = Utils.GetSpreadsheetColumns(tranType);
if (cols.GetLength(0) > 0)
{
result = CheckSpreadsheetColumnFormat(files[0], cols, tranType);
txtFileName.Text = Path.GetFileName(files[0]);
}
else
{
result.IsValid = false;
result.Message = "Unable to get column definations to be used";
}
}
}
IsInputValid = result.IsValid;
LogEvents.UpdateProcessLogUI(Utils.BuildLogPayload(result.Message));
ProcessInputViewEventsPublish.SendInputValidStatus(IsInputValid, SelectedProcess, files[0]);
}
else
{
LogEvents.UpdateProcessLogUI(Utils.BuildLogPayload("Unable to get the file path for the dropped file"));
}
}


This all works fine except the ProcessLog listview is not updated until the FileDropped method has completed. This can been seen clearer by adding a thread.sleep into the FileDropped method just after the LogEvents.UpdateProcessLogUI method.

Have I implemented this incorrectly and if so how do I get real time updates in the ProcessLogView listview while using IEventAggregator?

Answer Source

OK, so turns out I was being pretty stupid. The FilesDropped method within my ProcessInputViewModel was running on the UI thread so of course the UI didn't update until after processing had finished.

I solved this by creating a new method FileDroppedBackground and running this on a new thread.

FileDropped method

    public void FileDropped(object sender, DragEventArgs e)
    {
        TextBox txtFileName = (TextBox)sender;
        DDQEnums.TranTypes tag = (DDQEnums.TranTypes)txtFileName.Tag;
        string fileName = string.Empty;

        new Thread(() => fileName = FileDroppedBackground(tag, e)).Start();
        txtFileName.Text = fileName;
    }

FileDroppedBackground method

    private string FileDroppedBackground(DDQEnums.TranTypes tag, DragEventArgs e)
    {
        string[] files;
        string[] cols;

        string returnValue = string.Empty;


        SpreadsheetCheck result = new SpreadsheetCheck();
        DDQEnums.TranTypes tranType;
        List<string> fileFormats = new List<string>();

        fileFormats.Add(Constants.FileFormats.XLS);
        fileFormats.Add(Constants.FileFormats.XLSX);

        if (e.Data.GetDataPresent(DataFormats.FileDrop, true))
        {
            files = e.Data.GetData(DataFormats.FileDrop, true) as string[];

            if (files.GetLength(0) > 1)
            {
                result.IsValid = false;
                result.Message = "Only drop one file per input box";
            }
            else
            {
                result = Utils.CheckIfSpreadsheetIsValidForInput(files[0], fileFormats, tag, out tranType);

                LogEvents.UpdateProcessLogUI(Utils.BuildLogPayload(string.Format("Checking {0} Spreadsheet Column Format", tranType)));
                Thread.Sleep(10000);

                if (result.IsValid)
                {
                    cols = Utils.GetSpreadsheetColumns(tranType);
                    if (cols.GetLength(0) > 0)
                    {
                        result = CheckSpreadsheetColumnFormat(files[0], cols, tranType);
                        returnValue = Path.GetFileName(files[0]);
                    }
                    else
                    {
                        result.IsValid = false;
                        result.Message = "Unable to get column definations to be used";
                    }
                }
            }
            IsInputValid = result.IsValid;
            LogEvents.UpdateProcessLogUI(Utils.BuildLogPayload(result.Message));
            ProcessInputViewEventsPublish.SendInputValidStatus(IsInputValid, SelectedProcess, files[0]);
        }
        else
        {
            LogEvents.UpdateProcessLogUI(Utils.BuildLogPayload("Unable to get the file path for the dropped file"));
        }

        return returnValue;
    }

This then caused an exception within the UpdateProgressLog method in my ProcessLogViewModel about the ObservableCollection not being able to be updated from another thread

so I updated this method as follows

    private void UpdateProgressLog(LogPayload msg)
    {
        dispatcher.Invoke(new Action(() => { LogMessage.Add(msg); }));
    }

I defined dispatcher as Dispatcher dispatcher = Dispatcher.CurrentDispatcher; at the top of my class.

Now when I run the application and drop a spreadsheet on to the ProcessInputView the log is updated in real-time and not when the method finishes processing

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