I am writing a piece of code that takes a user through a guided script. The user will have a few seconds to answer before the answer will be displayed.
So far, my code looks like this:
GuidedExercise3 exercise3 = new GuidedExercise3();
string AntonioAnswer = string.Empty; // expected answer
int upperBound = exercise3.Script.Count - 1; // zero-based counting
for(int i = 0; i < upperBound; i += 2)
{
labelInstructions.Text = exercise3.Script[i].TextToSpeak;
AntonioAnswer = exercise3.Script[i+1].TextToSpeak; // answer
SetTimer(AntonioAnswer, txtAntonio); // set timer sending in the answer and the TextBox object.
sysTimer.Start();
}
The odd lines of a List contain the question and the even lines contain the expected answer. My question is how do I display the question for X seconds and then get the user's answer in this WinForms app and then display the answer when the timer elapses, keeping the user from going to the next step of the script but allowing them to answer the question (which is in a Textbox).
I examined this StackOverflow question, but it doesn't match: Implementing a loop using a timer in C#
Here's how I would handle something like this:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
MoveNextQuestion();
timerAnswer.Interval = 5000;
timerAnswer.Start();
}
private string[] _questionsAndAnswers = new[]
{
"What colour is the sky?",
"Blue",
"What do chickens lay?",
"Eggs",
};
private int _currentIndex = -2;
private void timerAnswer_Tick(object sender, EventArgs e)
{
MoveNextQuestion();
}
private void buttonAnswer_Click(object sender, EventArgs e)
{
MoveNextQuestion();
}
private void MoveNextQuestion()
{
_currentIndex += 2;
if (_currentIndex < _questionsAndAnswers.Length)
{
labelQuestion.Text = _questionsAndAnswers[_currentIndex];
}
else
{
timerAnswer.Stop();
}
}
}
I was able to get this working fairly easily with a BackgroundWorker object. See the following article at MSDN for the exact coding. BackgroundWorker Class. In particular they have two examples in the documentation and the first example is sufficient. The BackgroundWorker class is allowing my UI to continue to accept user input while waiting on a timed answer. It displays the correct answer on the RunWorkerComplete event. So the BackgroundWorker's RunAsync gets called in my for loop.
I've run into the additional issue of the BackgroundWorker not returning control to my loop. I'm looking into that problem separately.
Related
When I clicked button starts for loop from i=0 and I want to see on the label value of i. However I only see last values of i.
public partial class Form1 : Form
{
int i;
public Form1()
{
InitializeComponent();
}
private void btnclick_Click(object sender, EventArgs e)
{
for ( i = 0; i < 3; i++)
{
lblForLoopExample.Text = i.ToString();
System.Threading.Thread.Sleep(1000);
}
}
}
when I run the my code I only see on the label ; 2 .
I want to see such a like below;
When the started For loop, i = 0, I must see the 0 on the Label.Text. An then when the i = 1, I must see 1 on the label.Text. And when i = 2, I must see 2 on the Label.Text.
I added Thread.Sleep(1000) however, result didn't change.
Where I am make mistake?
Please help me,
if you help me , I will appreciate you.
Thanks,
You need to append the lbl to get all the values. Right now, it finishes the loop and give you the last value in your label
public partial class Form1 : Form
{
int i;
public Form1()
{
InitializeComponent();
}
private void btnclick_Click(object sender, EventArgs e)
{
for ( i = 0; i < 3; i++)
{
lblForLoopExample.Text + = i.ToString();
}
}
}
Your problem is that you're doing work on the UI thread while expecting the UI thread to update your form.
While you process your loop, the UI thread is actually executing this code. The UI thread is therefore unable to update the form with the intermediate values you are setting within the loop. Once your code completes, the UI thread is then free to update the form. That's why you see the last value only.
You can see this better if you updated your code to loop ten million times instead of 3. Your form will become unresponsive and will appear locked up. That's because Windows knows your UI thread is locked in an intensive process and is unable to update the UI.
The solution is to use a background thread to run your process and synchronize updates with the UI thread. You'll also have to slow your loop down to see the changes, as others have suggested.
To learn more about how the UI thread works, and how to synchronize background threads with it, read this article (it's about WPF, but it covers the general case).
Each loop you re-write the string. Instead of saying
lblForLoopExample.Text = i.ToString();
You need to add to the string on each iteration. I'd create a variable to hold the value, and so something like this:
string myString = string.Empty;
for(i=0;i < 3; i++)
{
myString += i.ToString() + ", ";
}
lblForLoopExample.Text = myString.substring(0, (myString.length - 1));
substring is just so you don't have that trailing comma. It's kind of dirty code, but it will work.
First of all, your code won't compile as you are missing the exact format of the ToString() method in i.ToString along with the ;
lblForLoopExample.Text = i.ToString();
^^^
As per your code, you should try this:
for ( i = 0; i < 3; i++)
{
lblForLoopExample.Text += i.ToString() + ", ";
}
I am struggling to workout how to create something that essentially pauses my while loop until my button1 is pressed, I know about the event handler button1_Click but I don't think that will work in this situation as I have lots of loops nested in each other on my form_load.
Any help would be highly appreciated!
This is a snipped of my code where I want the loop to be 'paused' with the notes:
while (reader2.Read())
{
QuestionSpace = Convert.ToString(reader2["Question Space"]);
label1.Text = QuestionSpace;
if (button1.Click = true) // if the button is clicked)
{
// continue with the while loop (I am going to add an INSERT SQL query in here later)
}
else
{
// pause until the button is pressed
}
}
My whole code for the form:
public partial class CurrentlySetTestForm : Form
{
private int QuestionID { get; set; }
private string QuestionSpace { get; set; }
public CurrentlySetTestForm()
{
InitializeComponent();
}
private void CurrentlySetTestForm_Load(object sender, EventArgs e)
{
string y = GlobalVariableClass.Signedinteacher;
MessageBox.Show(y);
Convert.ToInt32(y);
string connectionString = ConfigurationManager.ConnectionStrings["myconnectionstring"].ConnectionString;
SqlConnection connect = new SqlConnection(connectionString);
connect.Open();
SqlCommand command18 = new SqlCommand("SELECT [QuestionID] FROM QuestionStudentAssociation WHERE ( [StudentID]=#Signedinstudent)", connect);
command18.Parameters.AddWithValue("#Signedinstudent", y);
var reader = command18.ExecuteReader();
while (reader.Read())
{
QuestionID = Convert.ToInt32(reader["QuestionID"]);
SqlCommand command19 = new SqlCommand(#"SELECT [Question Space] FROM Questions WHERE ( [QuestionID] = #currentQID )", connect);
command19.Parameters.AddWithValue("#currentQID", QuestionID);
try
{
var reader2 = command19.ExecuteReader();
while (reader2.Read())
{
QuestionSpace = Convert.ToString(reader2["Question Space"]);
label1.Text = QuestionSpace;
if (button1.Click = true) // if the button is clicked)
{
// continue with the while loop (I am going to add an INSERT SQL query in here later)
}
else
{
// pause until the button is pressed
}
}
}
catch (SyntaxErrorException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
MessageBox.Show("Done one loop");
}
}
}
}
Sounds like your not ready to learn TPL
So maybe a BackgroundWorker , you can paint it on the form
To make the click cancel the background worker have a look at Cancel backgroundworker
I would some time to learn TPL as its going to create a simpler and more elegant solution.
As for pausing I would refactor the code, you should not keep the reader open waiting on the user.
You do want event-driven response to UI events, always. However, I guess that you don't want to split your logic into a state machine by hand (where each event triggers progress to the next state). Well, you're in luck, the C# compiler has some keywords to build state machines automagically so you don't have to manage the details.
There are actually two different mechanisms for continuation-passing style implemented in C#. The old one, yield return, works great if your UI events are pretty much interchangeable (or you're only interested in one). Works like this:
IEnumerator<int> Coroutine;
// this could be a Form_Load, but don't you need to get the user information before making the database connection?
void BeginQuiz_Click( object sender, EventArgs unused )
{
Coroutine = RunQA();
}
IEnumerator<int> RunQA()
{
// connect to DB
// show first question on UI
return ContinueQA();
}
IEnumerator<int> ContinueQA()
{
// you can use a while loop instead if you really want
for( int question = 0; question < questionCount; ++question )
{
// check answer
if (/* too many wrong answers*/) {
// report failure in DB
yield break;
}
// get next question from DB
// show new question on the UI
// wait for UI action
yield return question;
}
// report score in DB
// update UI with completion certificate
}
void AnswerButton_Click( object sender, EventArgs unused )
{
answer = sender;
Coroutine.MoveNext(); // MAGIC HAPPENS HERE
}
void TimeoutTimer_Tick( object sender, EventArgs unused )
{
answer = TimeoutTimer;
Coroutine.MoveNext();
}
The magic comes from yield return. Every time the function reaches yield return, the compiler saves what you were doing. When the button click event comes and calls MoveNext, the compiler generates code that starts where yield return paused everything, and keeps going from there until the next yield return.
Important note, the code inside ContinueQA doesn't start when RunQA() does return ContinueQA(); It actually starts on the first MoveNext(). So split your code between RunQA() and ContinueQA accordingly.
If you need different pause reasons at different places in your code, then async/await will be more helpful.
A better way to handle this would be the use of a timer. This would allow the form to draw it's controls and handle all input, such as clicking the button.
Adjust the timer interval (ms) to your needs.
Another way of doing this would be, as Mehrzad Chehraz said, to use multi-threading.
On a side note, I would strongly recommend condition checks over the try/catch checks if possible.
Enable/Disable the timer using the button and call the loop when the timer ticks.
Example:
Timer loopTimer = new Timer();
private void Form1_Load(object sender, EventArgs e)
{
loopTimer.Interval = 100;
loopTimer.Tick += loopTimer_Tick;
loopTimer.Enabled = true;
}
void loopTimer_Tick(object sender, EventArgs e)
{
//perform the loop here at the set interval
}
private void button1_Click(object sender, EventArgs e)
{
//pause/play the loop
loopTimer.Enabled = !loopTimer.Enabled;
}
So, I'm trying to develop a simple application in visual C# which gets data from serial port and displays it in a textbox (to monitor temperature). I'm acquiring and displaying the data successfully, using the DataReceived event to update a global string variable and a timer to update the text field on my text box, as shown:
private void port_DataReceived_1(object sender, SerialDataReceivedEventArgs e)
{
try
{
globalVar.updateTemp = port.ReadLine(); //This is my global string
}
catch (IOException)
{
}
catch (InvalidOperationException)
{
}
catch (TimeoutException)
{
}
}
private void timer1_Tick(object sender, EventArgs e)
{
tempDisplayBox.Text = globalVar.updateTemp; //This is my textbox updating
}
The only issue I have is that the value shown in the textbox keeps flashing, making it hard to read. My timer is set to trigger every 10 ms (which should be fast enough, right?). Is there any way to make it more stable? I realize this may be a newb question, but to be fair I am a newb :) Any help is appreciated! Thanks!
Do you really need it updating every 10ms? What about every 500 ms or if not that then 100ms. 100ms will require your update method run 10 times less and therefore update 10 times less. The flickering you are expiriencing is due to the refresh speed. You could create custom method which will only update the temp only when target Label or textBox value is different than source port. But that will only sort the flickering when temp is steady, when temp will start vary it will bring back the flickering. Good luck ;-)
UPDATE
Hi I tried to reproduce the conditions and could not make my textbox nor Label flash. The way I tested it was by assigning int ntick = 0; and then increment the ++ntick; inside of the timer_tick method. The results didn't make any of the controls flash and were updated even every milisecond at some point. I also tried string.Format to put some load on the method. Is your app responsive?
The trick is to use double buffering. This way the operating system will redraw the Control off-screen, and only show the control when it is fully redrawn.
I have had the same problem, and solved it by extending the TextBox control like this:
public FastLogBox()
{
InitializeComponent();
_logBoxText = new StringBuilder(150000);
timer1.Interval = 20;
timer1.Tick += timer1_Tick;
timer1.Start();
SetStyle(ControlStyles.DoubleBuffer, true);
}
void timer1_Tick(object sender, EventArgs e)
{
if (_timeToClear)
{
_logBoxText.Clear();
_timeToClear = false;
}
if (_logQueue.Count <= 0) return;
while (!_logQueue.IsEmpty)
{
string element;
if (!_logQueue.TryDequeue(out element)) continue;
{
_logBoxText.Insert(0, element + "\r\n");
}
}
if (_logBoxText.Length > 150000)
{
_logBoxText.Remove(150000, _logBoxText.Length - 150001);
}
Text = _logBoxText.ToString();
}
public new void Clear()
{
_timeToClear = true;
while (!_logQueue.IsEmpty)
{
string element;
_logQueue.TryDequeue(out element);
}
}
public void AddToQueue(string message)
{
_logQueue.Enqueue(message);
}
}
I also use a timer and a concurrentQueue to avoid using Invoke to update the control from another thread. I also use a StringBuilder to prepare the string before putting it into the TextBox. StringBuilder is faster when building larger strings.
You can use ReadExisting() to read the whole data at a time.
You need to handle DataReceived Event of SerialPort
serialPort1.ReadExisting();
Sample:
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
String myData=serialPort1.ReadExisting();
}
Example Code: Here i would like to show you the code to Read Data(RFID Tag Code which is basically of length 12)
String macid = "";
private void DoWork()
{
Invoke(
new SetTextDeleg(machineExe ),
new object[] { macid });
macid = "";
}
private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
string str1;
macid += serialPort1.ReadExisting();
if (macid.Length == 12)
{
macid = macid.Substring(0, 10);
Thread t = new Thread(new ThreadStart(DoWork));
t.Start();
}
}
public void machineExe(string text)
{
TextBox1.Text=text;
}
Thank you so much for the answers! I found a way to work around this issue:
Instead of replacing the contents of my textbox by rewriting the TextBox.Text property - which, as HenningNT implied, refreshes the control and causes the flickering - I'm now using the TextBox.AppendText method. Though, as I want to display only one line of data at a time, I use the textbox in multiline mode and the Environment.NewLine to jump to a new line before appending the text. As for the method of updating, I've gone back to using the timer because with the invoke method was crashing my application when I close the form, for some reason. Also, enabling double buffering didn't do me much good, although I guess I was doing it wrong... It still flickers a bit, but it's much better now :) I know this is not really a perfect solution (much more of a workaround), so I'll keep looking for it. If I find it, I'll be sure to update it here ;) My code:
private void timer1_Tick(object sender, EventArgs e) //Timer to update textbox
{
if (tempDisplayBox.Text != globalVar.updateTemp) //Only update if temperature is different
{
try
{
tempDisplayBox.AppendText(Environment.NewLine);
tempDisplayBox.AppendText(globalVar.updateTemp);
}
catch (NullReferenceException)
{
}
}
}
I am currently taking a beginner's class in c#. We missed 2 consecutive classes because the teacher couldn't be there. So we didn't really see what we needed to do this. He said to just go see on MSDN, but that is usually way too complicated for me. So here is my problem:
I have to create a "Simon Says" program. Here is my current code (sorry for the French variables):
public partial class Form1 : Form
{
const byte LIMITE = 255;
const byte LIMITEBOUTON = 5;
byte[] _abyBouton = new byte[LIMITE];
Random _rand = new Random();
public Form1()
{
InitializeComponent();
}
//Blinks the Button. Works correctly.
void AnimerBouton(Button btnBouton, Color Cocoleur)
{
btnBouton.BackColor = Color.Black;
btnBouton.ForeColor = Color.White;
Update();
System.Threading.Thread.Sleep(500); // C'est inscrit en miliseconde
btnBouton.BackColor = Cocoleur;
btnBouton.ForeColor = Color.Black;
Update();
System.Threading.Thread.Sleep(500); // C'est inscrit en miliseconde
}
private void btnDémarrer_Click(object sender, EventArgs e)
{
//Creates an array with the 255 eventual moves.
for (byte byIndex = 0; byIndex <= LIMITE - 1; byIndex++)
{
_abyBouton[byIndex] = (byte)_rand.Next(1, LIMITEBOUTON);
}
for (byte byIndex = 0; byIndex <= LIMITE - 1; byIndex++)
{
//Takes care of the current progress in the game.
for (byte byIndex2 = 0; byIndex2 <= byIndex; byIndex2++)
{
switch (_abyBouton[byIndex2])
{
case 1:
{
AnimerBouton(btn1, Color.Green);
}
break;
case 2:
{
AnimerBouton(btn2, Color.Red);
}
break;
case 3:
{
AnimerBouton(btn3, Color.Yellow);
}
break;
case 4:
{
AnimerBouton(btn4, Color.Cyan);
}
break;
}
//Wait to see if the click is correct. No idea how to do this.
}
}
}
}
So I have to wait for the user to click a button and see if it is the correct one. I looked around and it was talking about events, but I couldn't grasp what I needed to do. I would appreciate some help on how to do this.
Thanks!
In the designer, on the properties window, click the lightning bolt icon. You will get a list of events for the selected control. Make sure the btnBouton control is selected, and find the Click event in the list. You should see btnDemarrer_Click in the drop down list. Select it. Now when the button is clicked, it should call your btnDemarrer_Click handler.
When you have not already written a handler, you can double-click the event in the list, and it will generate the method skeleton for you automatically. You can also double-click the control itself to generate the default event handler for that control. (In the case of buttons, I think the default event is the click event.)
If you want a particular method to wait until some work is done, you could look into AutoResetEvent. An extremely simplified example might help you get on the right track:
using System.Threading;
public static AutoResetEvent arEvent = new AutoResetEvent(false);
static void Main()
{
DoWork();
arEvent.WaitOne(); //WaitOne() "pauses" Main and waits for some work to be done.
DoWork();
arEvent.WaitOne();
}
static void DoWork();
{
//Some work is done here.
arEvent.Set(); //This lets Main() continue where it left off.
}
Using this, you could have btnDémarrer_Click wait for the user input then continue on after the user has done his clicking.
Below is a method that I want to ship off into a background worker but I am struggling how to do it based on how created my method. As you can it doesn't return anything which is ok but it expects a directoryInfo object everytime it is recalled.
private void getSizeForTargetDirectory(DirectoryInfo dtar)
{
// generate a collection of objects. files comes first and then directories.
foreach (Object item in collection )
{
if (item == file)
{
track the size of the files as you encounter.
}
else if (item == directory)
{
// found a new directory, recall the method. !!!
}
}
}
This is my first time using a background worker so I'm a little stuck, I tried implementing something thanks to the help found here but got stuck when I realised my method was recursive.
How do I display progress during a busy loop?
I implemented a doWork event handler method but noticed that i needed to somehow recall the method if I had more files and folders to process on lower sub levels.
I have a simple button click event handler that calls my 'getSizeForTargetDirectory()' method when the current selected node is a directory.
private void retrieveInfoButton_Click(object sender, EventArgs e)
{
// check to see if the path is valid
// reset the labels and textfields.
string fullPath = treeDrives.SelectedNode.FullPath;
string sNodesName = treeDrives.SelectedNode.Text;
if (directory) // Enter here if its a directory.
{
string parentPath = treeDrives.SelectedNode.Parent.FullPath;
DirectoryInfo[] dirArray = populateFoldersArray(parentPath);
for (int i = 0; i < dirArray.Length; i++)
{
if (dirArray[i].Name == sNodesName)
{
getSizeForTargetDirectory(dirArray[i]);
// do work !
Hopefully that explains what I am trying to do and how I am doing it. Question is how can i use the report progress feature of the background worker class when the bulk of the work I am trying to ship is coming from a recursive method.
Through early testing I noticed that my getSize method was incredibly efficient after a few tweaks and reported size information for the current supplied folder very quickley but then again I use quite a powerful dev machine so this may not be true for all users.
Thanks For Reading, Hope someone can help !!!
I think it is much simpler to use the built-in methods on either Directory or DirectoryInfo to obtain all directories, or files, using the recursive search option:
public partial class Form1 : Form
{
private Action<float> updateProgMethod;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
updateProgMethod = UpdateProgress;
}
private void GetDirectorySizeAsync(string path)
{
backgroundWorker.RunWorkerAsync(path);
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
DirectoryInfo di = new DirectoryInfo((string)e.Argument);
di.GetTotalSize(ProgressCallback);
}
// Takes callbacks from the GetTotalSize() method
private void ProgressCallback(float p)
{
// Invokes update progress bar on GUI thread:
this.BeginInvoke(updateProgMethod, new object[] { p });
}
// Actually updates the progress bar:
private void UpdateProgress(float p)
{
progressBar.Value = (int)(p * (progressBar.Maximum - progressBar.Minimum)) + progressBar.Minimum;
}
}
public static class IOExtensions
{
public static long GetTotalSize(this DirectoryInfo directory, Action<float> progressCallback)
{
FileInfo[] files = directory.GetFiles("*.*", SearchOption.AllDirectories);
long sum = 0;
int countDown = 0;
for (int i = 0; i < files.Length; i++)
{
sum += files[i].Length;
countDown--;
if (progressCallback != null && countDown <= 0)
{
countDown = 100;
progressCallback((float)i / files.Length);
}
}
return sum;
}
}
It's hard to guess progress without knowing the number of files or folders first!
EDIT: I've improved the code a little.
If, when you call a method, you don't know how long the method is going to take or how many discrete steps are going to be involved, then there is no way to display a progress bar while the method is executing.
In my opinion, the purpose of a progress bar is not to give reliable information about when a task is going to be completed. Rather, the purpose is to keep the user from freaking out and cancelling the whole operation because they think your program has locked up and isn't doing anything at all.
Since you're iterating through directories and sub-directories, a simpler approach here might be to just display the current directory in a Label. This would give the user a relaxing sense that things are happening, and if the directories are all ordered alphabetically, they can even gauge for themselves the overall progress of the operation.
I would report how far you have gotten since you don't know the goal until you get there. I would do it once per invocation. Perhaps # of files and # of directories seen so far.