c# - Updating GUI (WPF) using a different thread

Question

Just have a problem here that I have no idea how to fix. I am doing a small project which involves a GUI and serial data. The GUI is being run by the main thread and since the data variables that hold my incoming serial data need to be updated continuously, these are being updated in a second thread. The problem is when I need to update some textboxes on the GUI, these need to be updated with data from the secondary thread and that is where my problem lies. I can't update them directly from the secondary thread and I have no idea how I would transfer data from my secondary thread and work out a system of updating them from main thread. I have put my code below:

Any help would be great.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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.IO;
using System.IO.Ports;
using System.Threading;

namespace GUIBike
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public static string inputdata;
        public static int MaximumSpeed, maximumRiderInput, RiderInput, Time, CurrentSpeed, DistanceTravelled, MaximumMotorOutput, MotorOutput, InputSpeed;
        public static string SaveDataString;
        public Thread Serial;
        public static SerialPort SerialData;
        public static string[] portlist = SerialPort.GetPortNames();
        public static string[] SaveData = new string[4];
        public static string directory = "C:";

        public MainWindow()
        {
            Serial = new Thread(ReadData);
            InitializeComponent();
            int Count = 0;
            for (Count = 0; Count < portlist.Length; Count++)
            {
                ComPortCombo.Items.Add(portlist[Count]);
            }
        }

        private void StartDataButton_Click(object sender, RoutedEventArgs e)
        {
            SerialData = new SerialPort(ComPortCombo.Text, 19200, Parity.None, 8, StopBits.One);
            SerialData.Open();
            SerialData.WriteLine("P");
            Serial.Start();
            StartDataButton.IsEnabled = false;
            EndDataButton.IsEnabled = true;
            ComPortCombo.IsEnabled = false;
            CurrentSpeed = 0;
            MaximumSpeed = 0;
            Time = 0;
            DistanceTravelled = 0;
            MotorOutput = 0;
            RiderInput = 0;
            SaveData[0] = "";
            SaveData[1] = "";
            SaveData[2] = "";
            SaveData[3] = "";
            SaveDataButton.IsEnabled = false;
            if (SerialData.IsOpen)
            {
                ComPortStatusLabel.Content = "OPEN";
                SerialData.NewLine = "/n";
                SerialData.WriteLine("0");
                SerialData.WriteLine("/n");
            }
        }

        private void EndDataButton_Click(object sender, RoutedEventArgs e)
        {
            SerialData.Close();
            SaveDataButton.IsEnabled = true;
            SerialData.WriteLine("1");
            SerialData.WriteLine("0");
            if (!SerialData.IsOpen)
            {
                ComPortStatusLabel.Content = "CLOSED";
            }
            int i = 0;
            for (i = 0; i < 4; i++)
            {
                if (i == 0)
                {
                    SaveDataString = "MaximumSpeed during the Ride was = " + Convert.ToString(MaximumSpeed) + "m/h";
                    SaveData[i] = SaveDataString;
                }
                if (i == 1)
                {
                    SaveDataString = "Total Distance Travelled = " + Convert.ToString(DistanceTravelled) + "m";
                    SaveData[i] = SaveDataString;
                }
                if (i == 2)
                {
                    SaveDataString = "Maximum Rider Input Power = " + Convert.ToString(maximumRiderInput) + "Watts";
                    SaveData[i] = SaveDataString;
                }
                if (i == 3)
                {
                    SaveDataString = "Maximum Motor Output Power = " + Convert.ToString(MaximumMotorOutput) + "Watts";
                    SaveData[i] = SaveDataString;
                }
            }
        }

        private void SaveDataButton_Click(object sender, RoutedEventArgs e)
        {
            //File.WriteAllBytes(directory + "image" + imageNO + ".txt", ); //saves the file to Disk    
            File.WriteAllLines(directory + "BikeData.txt", SaveData);
        }

        public void ReadData()
        {
            int counter = 0;

            while (SerialData.IsOpen)
            {
                if (counter == 0)
                {
                    //try
                    //{
                        InputSpeed = Convert.ToInt16(SerialData.ReadChar());
                        CurrentSpeed = InputSpeed;
                        if (CurrentSpeed > MaximumSpeed)
                        {
                            MaximumSpeed = CurrentSpeed;
                        }
                        SpeedTextBox.Text = "Current Wheel Speed = " + Convert.ToString(CurrentSpeed) + "Km/h";
                        DistanceTravelled = DistanceTravelled + (Convert.ToInt16(CurrentSpeed) * Time);
                        DistanceTravelledTextBox.Text = "Total Distance Travelled = " + Convert.ToString(DistanceTravelled) + "Km";
                    //}
                    //catch (Exception) { }
                }
                if (counter == 1)
                {
                    try
                    {
                        RiderInput = Convert.ToInt16(SerialData.ReadLine());
                        if (RiderInput > maximumRiderInput)
                        {
                            maximumRiderInput = RiderInput;
                        }
                        RiderInputTextBox.Text = "Current Rider Input Power =" + Convert.ToString(RiderInput) + "Watts";
                    }
                    catch (Exception) { }
                }
                if (counter == 2)
                {
                    try
                    {
                        MotorOutput = Convert.ToInt16(SerialData.ReadLine());
                        if (MotorOutput > MaximumMotorOutput)
                        {
                            MaximumMotorOutput = MotorOutput;
                        }

                        MotorOutputTextBox.Text = "Current Motor Output = " + Convert.ToString(MotorOutput) + "Watts";
                    }
                    catch (Exception) { }
                }
                counter++;
                if (counter == 3)
                {
                    counter = 0;
                }
            }
        }

        private void ComPortCombo_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            StartDataButton.IsEnabled = true;
        }


        private void Window_Closed(object sender, RoutedEventArgs e)
        {
            if (SerialData.IsOpen)
            {
                SerialData.Close();
            }
        }

Answer 1

You can use Dispatcher.Invoke to update your GUI from a secondary thread.

Here is an example:

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        new Thread(DoSomething).Start();
    }
    public void DoSomething()
    {
        for (int i = 0; i < 100000000; i++)
        {
               this.Dispatcher.Invoke(()=>{
               textbox.Text=i.ToString();
               });    
        } 
    }