Working on a customized Task Manager in WPF .NET Framework, how do I prevent processes from duplicating?

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Diagnostics;
using System.IO;

namespace CustomizedWPFTaskManager
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            //Load Function
            OnLoad();
        }

        private void OnLoad()
        {
            System.Windows.Threading.DispatcherTimer dispatcherTimer = new          System.Windows.Threading.DispatcherTimer();
            dispatcherTimer.Tick += dispatcherTimer_Tick;
            dispatcherTimer.Interval = new TimeSpan(0, 0, 2);
            dispatcherTimer.Start();
        }

        private void dispatcherTimer_Tick(object sender, EventArgs e)
        {
            //- Refresh process list
            Process pList = new Process();
            List<String> procList = new List<string>(new string[] { "" });


            foreach (Process p in Process.GetProcesses())
            {
                try
                {
                    FileInfo fi = new FileInfo(p.MainModule.FileName);

                    procList.Add(fi.Name);
                    TaskViewBox1.Items.Add(fi.Name);
                }
                catch { }
            }

            countLabel.Content = TaskViewBox1.Items.Count + " PROCESSES    RUNNING";
        }
    }
}

This is what I have so far, but my problem is processes will keep adding even though they are already their (duplicates). Also I am new to this, my boss has been teaching me to help out around the shop. He wanted me to learn WPF as well. This was what I thought a good first project, any help on how to remove duplicates? Also if its not to much can you explain what you did a little but so I am not just copying the code but actually learning it for next time.

Answer 1

Let's take a look at a very basic example that makes use of the MVVM achitectural pattern.

First the view model. It has a Processes property, which is an ObservableCollection<Process> and a Tick event handler of a DispatcherTimer, which updates the collection.

public class ViewModel
{
    public ObservableCollection<Process> Processes { get; }
        = new ObservableCollection<Process>();

    public ViewModel()
    {
        var timer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(2) };
        timer.Tick += UpdateProcesses;
        timer.Start();
    }

    private void UpdateProcesses(object sender, EventArgs e)
    {
        var currentIds = Processes.Select(p => p.Id).ToList();

        foreach (var p in Process.GetProcesses())
        {
            if (!currentIds.Remove(p.Id)) // it's a new process id
            {
                Processes.Add(p);
            }
        }

        foreach (var id in currentIds) // these do not exist any more
        {
            Processes.Remove(Processes.First(p => p.Id == id));
        }
    }
}

Now the view. It is a simple ListBox that shows the Id and ProcessName of the collection of Processes. Its ItemsSource is bound to the Processes property of the view model.

<ListBox ItemsSource="{Binding Processes}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Id}" Width="50"/>
                <TextBlock Text="{Binding ProcessName}"/>
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Finally, an instance of the view model has to be assigned to the DataContext of the MainWindow. This can be done in XAML

<Window.DataContext>
    <local:ViewModel/>
</Window.DataContext>

or in code behind

public MainWindow()
{
    InitializeComponent();
    DataContext = new ViewModel();
}