We Keep Coding

C# Update labels on custom progress bar windows form

I'm creating a form which simulates a progress bar.
The form has a progress bar, a label with a title and another label showing the progress percentage.
The idea is that before starting a loop I create an instance of the form using that loop's element count. Each iteration of the loop a method is called to update the progress bar, and the percentage label.
The progress bar is being updated fine, but the title and percentage labels are not being updated. I've read that's because everything is executed in the same thread, and the UI is not being updated.
This is my code:
Main program
...
MyProgressBar_Form pb = new MyProgressBar_Form("Test of progress bar", selectionBudget.Count);
pb.Show();
foreach (SelectedObject obj in selectionBudget) {
pb.meterProgress();
...
}
pb.Close();
...
Form class
public partial class MyProgressBar_Form : Form {
public MyProgressBar_Form(string title, int elems) {
InitializeComponent();
titleLbl.Text = title;
progressBar1.Minimum = 0;
progressBar1.Maximum = elems;
progressBar1.Step = 1;
this.Refresh();
}
public void meterProgress() {
if (progressBar1.Value < progressBar1.Maximum) {
progressBar1.Value++;
double percentage = Math.Round((double)(progressBar1.Value / progressBar1.Maximum * 100), 2);
progressLbl.Text = $"{percentage}%";
this.Refresh();
}
}
}

Try Application.DoEvents() inside the loop.

Adding percentage text to progressbar C#

I have a method that shows when a process bar is in execution and when is successfully completed.
I worked fine, but I would like to add a percentage showing a 100% if is complete and less if it got stuck some where.
I have made several research online but I could not adapt anything to the solution that I am looking for.
This is my code:
private void progressBar()
{
int i;
progressBar1.Minimum = 0;
progressBar1.Maximum = 100;
for (i = 0; i <= 100; i++)
{
progressBar1.Value = i;
}
}
I use the method call on my execution button by calling it with the follow:
progressBar();
Thanks

I have adjust the prograssBar method with the following lines.
The solution works.
Thanks
int percent = (int)(((double)progressBar1.Value / (double)progressBar1.Maximum) * 100);
progressBar1.Refresh();
progressBar1.CreateGraphics().DrawString(percent.ToString() + "%",
new Font("Arial", (float)8.25, FontStyle.Regular),
Brushes.Black,
new PointF(progressBar1.Width / 2 - 10, progressBar1.Height / 2 - 7));

In order to implement the progress in your operation, the operation's length must be calculated first. if it's not possible, you can't show a progress bar for that operation. (maybe only a loading gif)
but if so, There is an interface (IProgress) which can help you implement the progress reports.
First thing you should know, You must do the main task on another thread, and report the progress to the UI Thread. a simple example of this work would be something like this.
Progress.cs
public class Progress<T> : IProgress<T>
{
private readonly Action<T> _progressAction;
public Progress(Action<T> action)
{
_progressAction = action;
}
public void Report(T value)
{
_progressAction?.Invoke(value);
}
}
Your code would be like this, in which the task starts after you click a button named ButtonBase
Progress<int> MyProgressObject { get; set; }
private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
{
MyProgressObject = new Progress<int>(ProgressAction);
ThreadPool.QueueUserWorkItem(TimeConsumingTask);
}
public void TimeConsumingTask(object state)
{
for (int i = 0; i < 100; i++)
{
Thread.Sleep(100);
MyProgressBar.Dispatcher.Invoke(() => ProgressAction(i));
}
}
public void ProgressAction(int progress)
{
MyProgressBar.Value = progress;
}
I know It might look difficult but this is the proper way of doing time consuming tasks and prevent UI block

If you use it as a part of backgroundworker it works perfectly
I added a Label in the middle of the progressbar
And i added last row in my bgw_ProgressChanged method
private void bgw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
p_bar.Value = e.ProgressPercentage;
fnameLbl.Text = e.UserState.ToString();
percentLbl.Text = "%" + (e.ProgressPercentage).ToString();
}
ProgressPercentagevalue comes from the method below
foreach (var item in filebox1)
{
System.IO.File.Move(item, Path.Combine(destdir, Path.GetFileName(item)));
++counter;
int tmp = (int)((counter* 100) / totfiles);
bgw.ReportProgress(tmp, "File transfered : " + Path.GetFileName(item));
Thread.Sleep(100);
}
Totfiles is the number of files that I get from server.
Thread.Sleep(100) let's you see for a short time what is displayed with fnameLbl.Text

int total = ;
int val = ;
double createDivider = total / 100;
int percent = val / createDivider;
this value (percent) is the right percent '%' of total

c# How to change/access WinForms controls from a different class

So I'm trying to change the text from a WinForms project, from another class than the Form class.
It should work like this:
But instead it does this:
The way I used to do it is pass along the object as a parameter to my other class and from that other class I could change the text. I do the same with the progressbar and it does work there, so it's weird that it works with the progressbar but not the label.
I use this method to change the progressbar:
public void IncreaseProgress(int progBarStepSize, String statusMsg, int currentProject=-1) {
if (currentProject != -1) {
lblStatus.Text = String.Format("Status: {0} | project {1} of {2}",statusMsg,currentProject,ProjectCount);
}
else {
lblStatus.Text = String.Format("Status: {0}",statusMsg);
}
pb.Increment(progBarStepSize);
}
And here is where I use the method:
public void InitialiseFile(List<string> filePaths, int eurojobType)
{
foreach (string sheet in outputSheets) {
switch (sheet) {
case "Summary":
for (int i = 0; i < filePaths.Count; i++) {
var filePath = filePaths[i];
IncreaseProgress(1, "Reading Summary", i);
worksheetIn = excelReader.ReadExcelSummary(filePath);
IncreaseProgress(1, "Writing Summary", i);
excelWriter.WriteExcelSummary(worksheetIn);
}
break;
case "Monthly_Cat1":
for (int i = 0; i < filePaths.Count; i++) {
var filePath = filePaths[i];
IncreaseProgress(1, "Reading Monthly", i);
worksheetIn = excelReader.ReadExcelMonthly(filePath);
IncreaseProgress(1, "Writing Monthly", i);
excelWriter.WriteExcelMonthly(worksheetIn);
}
break;
}
}
IncreaseProgress(1, "Completed!");
}
Now I know this code works because the progressbar increments. And it should jump in the first if-loop because i gets passed as a parameter, which is never -1.
//manager class
private Label lblStatus;
private ProgressBar pb;
public Manager(ProgressBar pb, Label lbl){
this.pb = pb;
lblStatus = lbl;
}
//Form class
Manager mgr = new Manager(progressBar1, lblStatus, projectFilePaths.Count, outputSheets.ToArray(), exportPath);
mgr.InitialiseFile(projectFilePaths, eurjobType);

You can call lblStatus.Refresh(); to force the control to be redrawn, after setting its Text.
But consider Slaks comment:
Don't do blocking work on the UI thread
You can consider using BackgroundWorker or Task.Run or async/await pattern instead.
As an example:
private async void button1_Click(object sender, EventArgs e)
{
await Task.Run(() =>
{
for (int i = 0; i < 10000; i++)
{
this.Invoke(new Action(() =>
{
label1.Text = i.ToString();
label1.Refresh();
}));
}
});
}
This way the numbers increase, the label refreshes and shows the new value, while the UI is responsive and for example you can move your form or click on other button.
You should put your UI related codes in an action fired by Invoke to prevent receiving cross thread operation exception.

Making an updating winform multi threaded

I have been breaking my head over this for a long time now and I can't seem to find how to solve this. Simply put I need to present Parallel programming to my class and i am making a demo that clearly shows the diffrence between single threaded and multi threaded.
First the program takes a screenshot and loads that in this class into a bitmap.
Then it loads the winform with a picturebox called screenshot. Next it does Form1_Load and loads the screenshot into the picturebox.
Then Form1_Shown Runs the for loop which just scrambles the pixels around based on a randomizer and updates the image from the left to the right.
example: http://gyazo.com/ab04583bb33de59d08407886da1c4870
This all works.
I now want to make it so that the screenshot is being updated from the left to the middle by the first thread, and from the middle to the right with the second thread.
But when i put it in 2 separate threads it says "An unhandled exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll"
The error implies I am making illegal cross thread calls. Particulary on screenshot and probably also on mybitmap.
Visual studio helps me by linking me to "How to: Make Thread-Safe Calls to Windows Forms Controls"
But i am not getting any wiser out of this information which is probably because i am not that fluent with the C# terminology yet.
How should i approach/fix this ?
This is the class where everything happens (except taking the screenshot):
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace ScreenOutput
{
public partial class Form1 : Form
{
PictureBox screenshot;
Bitmap myBitmap = new Bitmap(#".\screenshot.jpg");
public Form1()
{
InitializeComponent();
}
private int Xcount;
private int Ycount;
private int maxXValue = Screen.PrimaryScreen.Bounds.Width - 1;
private int maxXValueT1 = 960;
private int maxXValueT2 = 1919;
private int maxYValue = Screen.PrimaryScreen.Bounds.Height - 1;
private int maxYValueT1 = 539;
private int maxYValueT2 = 1079;
private void Form1_Load(object sender, EventArgs e)
{
screenshot.Image = myBitmap;
}
private void Form1_Shown(object sender, EventArgs e)
{
Thread startThread1 = new Thread(new ThreadStart(thread1));
Thread startThread2 = new Thread(new ThreadStart(thread2));
startThread1.Start();
startThread2.Start();
Thread.Sleep(10000); //waiting for completion
startThread1.Abort();
startThread2.Abort();
//this is how it would work without multithreading
/*Random random = new Random();
for (Xcount = 0; Xcount < maxXValue; Xcount++)
{
screenshot.Refresh();
for (Ycount = 0; Ycount < maxYValue; Ycount++)
{
int calculatedX = Xcount + random.Next(0, maxXValue);
if (calculatedX > maxXValue) calculatedX = maxXValue;
myBitmap.SetPixel(Xcount, Ycount, myBitmap.GetPixel(calculatedX, Ycount));
}
}
Thread.Sleep(2000);*/
Application.Exit();
}
public void thread1()
{
Random random = new Random();
for (Xcount = 0; Xcount < maxXValueT1; Xcount++)
{
screenshot.Refresh();
for (Ycount = 0; Ycount < maxYValueT1; Ycount++)
{
int calculatedX = Xcount + random.Next(0, maxXValueT1);
if (calculatedX > maxXValue) calculatedX = maxXValueT1;
myBitmap.SetPixel(Xcount, Ycount, myBitmap.GetPixel(calculatedX, Ycount));
}
}
}
public void thread2()
{
Random random = new Random();
for (Xcount = 0; Xcount < maxXValueT2; Xcount++)
{
screenshot.Refresh();
for (Ycount = 0; Ycount < maxYValueT2; Ycount++)
{
int calculatedX = Xcount + random.Next(0, maxXValueT2);
if (calculatedX > maxXValueT2) calculatedX = maxXValueT2;
myBitmap.SetPixel(Xcount, Ycount, myBitmap.GetPixel(calculatedX, Ycount));
}
}
}
}
}

You will need to Invoke the GUI thread.
I prefer the following solution.
Using a Form member ('screenshot' in this case) check to see if InvokeRequired = true. If so then Invoke a delegate using that members BeginInvoke() function as the following example demonstrates:
private void ScreenshotRefresh()
{
if(screenshot.InvokeRequired)
{
screenshot.BeginInvoke(new MethodInvoker(this.ScreenshotRefresh));
}
else
{
screenshot.Refresh();
}
}

The calling thread cannot access this object because a different thread owns it

So I am making a simple brick breaking game in c#/wpf. I am running into an issue using timers, I feel like it is probably a simple fix but here is whats happening. Whenever t_Elapsed is fired it attempts to call Update() but when it does its like OMG Im not in the right thread so I cant do that sir. How do I invoke the method from the Game from the proper thread? (And yes I know the code is ugly and has magic numbers but I just kinda chugged it out without putting a lot of effort in. And yes I have zero experience programming games)
public partial class Game : Grid
{
public bool running;
public Paddle p;
public Ball b;
Timer t;
public Game()
{
Width = 500;
Height = 400;
t = new Timer(20);
p = new Paddle();
b = new Ball();
for (int i = 15; i < 300; i += 15)
{
for (int j = 15; j < 455; j += 30)
{
Brick br = new Brick();
br.Margin = new Thickness(j, i, j + 30, i + 15);
Children.Add(br);
}
}
Children.Add(p);
Children.Add(b);
p.Focus();
t.AutoReset = true;
t.Start();
t.Elapsed += new ElapsedEventHandler(t_Elapsed);
}
void t_Elapsed(object sender, ElapsedEventArgs e)
{
if (running)
{
Update();
}
}
void Update()
{
b.Update(); //Error here when Update is called from t_Elapsed event
}
void Begin()
{
running = true;
b.Initiate();
}
}

You should use the DispatcherTimer object instead, it will ensure that the timer events are published to the correct thread.

Timer elapsed events fire on a thread from the thread pool (http://www.albahari.com/threading/part3.aspx#_Timers) and not on the UI thread. Your best approach is to invoke the control's dispatcher through a call like this:
yourControl.Dispatcher.BeginInvoke(
System.Windows.Threading.DispatcherPriority.Normal
, new System.Windows.Threading.DispatcherOperationCallback(delegate
{
// update your control here
return null;
}), null);

The calling thread cannot access this object because a different thread owns it
this.Dispatcher.Invoke((Action)(() =>
{
...// your code here.
}));