I writing a WPF desktop application and I used async await to keep my UI update.
its works OK for 5 or 6 sec but after that UI freezing but background code is running normally.
await Task.Run(() =>
{
result = index.lucene_index(filepath, filename, fileContent);
if (result) {
updateResultTextBox(filename);
Task.Delay(1000);
}
});
and updateResultTextBox is
private void updateResultTextBox(string _filename)
{
sync.Post(new SendOrPostCallback(o =>
{
result_tbx.Text += "Indexed \t" + (string)o + "\n";
result_tbx.ScrollToEnd();
}), _filename);
}
Your question is less then clear. So I have to guess. My only guess at this time: GUI write overhead.
Writing the GUI is not cheap. If you only do it once per user triggered event, you do not notice it. But once you do it in a loop - even one that runs in a seperate task or thread - you will notice it. I wrote this simple Windows Forms example to showcase the difference:
using System;
using System.Windows.Forms;
namespace UIWriteOverhead
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
int[] getNumbers(int upperLimit)
{
int[] ReturnValue = new int[upperLimit];
for (int i = 0; i < ReturnValue.Length; i++)
ReturnValue[i] = i;
return ReturnValue;
}
void printWithBuffer(int[] Values)
{
textBox1.Text = "";
string buffer = "";
foreach (int Number in Values)
buffer += Number.ToString() + Environment.NewLine;
textBox1.Text = buffer;
}
void printDirectly(int[] Values){
textBox1.Text = "";
foreach (int Number in Values)
textBox1.Text += Number.ToString() + Environment.NewLine;
}
private void btnPrintBuffer_Click(object sender, EventArgs e)
{
MessageBox.Show("Generating Numbers");
int[] temp = getNumbers(10000);
MessageBox.Show("Printing with buffer");
printWithBuffer(temp);
MessageBox.Show("Printing done");
}
private void btnPrintDirect_Click(object sender, EventArgs e)
{
MessageBox.Show("Generating Numbers");
int[] temp = getNumbers(1000);
MessageBox.Show("Printing directly");
printDirectly(temp);
MessageBox.Show("Printing done");
}
}
}
If you start a lot of those tasks and they suddenly all return 5-6 seconds in the process, you might just plain overload the GUI thread with the sheer amount of write operations.
I actually had that issue with my very first attempt at Multithreading. I did proper Multthreading, but I still overloaded the GUI thread wich made it appear I had failed.
there is something very strange on this code. Anyway, here are my two cents:
var text = await Task.Run(() =>
{
result = index.lucene_index(filepath, filename, fileContent);
if (result) {
return filename;
}
return string.Empty;
});
if (!string.IsNullOrEmpty(text)) {
result_tbx.Text += $"Indexed \t {text} {Environment.NewLine}";
result_tbx.ScrollToEnd();
}
Still a code smell...
Related
static List<int> sharedCollection = new List<int>();
static readonly Object obj = new Object();
static void Main(string[] args)`enter code here`
{
var writeThread = new Thread(() =>
{
for (int i = 0; i < 10; i++)
{
lock (obj)
{
Write();
}
}
});
var readThread = new Thread(() =>
{
for (int i = 0; i < 10; i++)
{
lock (obj)
{
Read();
}
}
});
writeThread.Start();
readThread.Start();
Console.ReadLine();
}
static void Read()
{
Console.Write("Current collection state: ");
sharedCollection.ForEach((e) => Console.Write($"{e} "));
Console.WriteLine();
}
static void Write()
{
Random generator = new Random();
var addedValue = generator.Next(1, 20);
sharedCollection.Add(addedValue);
Console.WriteLine($"Added value is: {addedValue}");
}
I spend a lot of time trying to understand why I receive this:
console result
Could someone explain to me what is wrong with this code?
Mutex works fine but I need to illustrate lock statement too...
I expect that after every adding in 1st thread I obtain a collection state from the 2nd thread. Like this:
Added value: 1
Collection state: 1
Added value: 15
Collection state: 1 15
Added value: 4
Collection state: 1 15 4
I understand you expeected those threasd to run somewhat in paralell, but instead they executed sequentially. You expectation is correct.
I do not think it has anything to do with lock, however. lock will only prevent a read and a write from happening at the same time, not produce this behavior. Try it without the lock to verify. (However due to things like the JiT Compiler, CPU cache invalidations and Optimisations, results may still differet if there is a lock, even if it has no direct effect).
My best bet is that the read thread is simply so slow, it does not finish once before the write is through all it's itteartions. Writing the UI is expensive, even on something as trivial as the console. Or even especially there. I do a lot of backups of userprofiles using robocopy. And if it hits a lot of very small files, just writing the Console becomes the actuall programm bottleneck, ever over disk access. And something out-bottlenecking disk acess is not something that happens often.
If you write the UI only once per user triggerd event, you will not notice the cost. But do it from any form of loop - especially one running in another thread - and you will start to notice it. I was particualry informed that a foreach is apparently half as slow at ittearting as a for loop.
I even made a example for this, albeit in a Windows Forms Environment:
using System;
using System.Windows.Forms;
namespace UIWriteOverhead
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
int[] getNumbers(int upperLimit)
{
int[] ReturnValue = new int[upperLimit];
for (int i = 0; i < ReturnValue.Length; i++)
ReturnValue[i] = i;
return ReturnValue;
}
void printWithBuffer(int[] Values)
{
textBox1.Text = "";
string buffer = "";
foreach (int Number in Values)
buffer += Number.ToString() + Environment.NewLine;
textBox1.Text = buffer;
}
void printDirectly(int[] Values){
textBox1.Text = "";
foreach (int Number in Values)
textBox1.Text += Number.ToString() + Environment.NewLine;
}
private void btnPrintBuffer_Click(object sender, EventArgs e)
{
MessageBox.Show("Generating Numbers");
int[] temp = getNumbers(10000);
MessageBox.Show("Printing with buffer");
printWithBuffer(temp);
MessageBox.Show("Printing done");
}
private void btnPrintDirect_Click(object sender, EventArgs e)
{
MessageBox.Show("Generating Numbers");
int[] temp = getNumbers(1000);
MessageBox.Show("Printing directly");
printDirectly(temp);
MessageBox.Show("Printing done");
}
}
}
But even this overhead is pretty unlikey to have a presistent result. At some time the read thread should get the lock first, blocking write. But still, there are too many variables to say for sure. You should propably try a simpler example, with more consistent (and a whole lot less) writework. What about writing "A" and "B" to the console, instead of complex stuff like this?
I am trying to create a console application similar to speedsum site. The speedsum is a website which is really useful and fun to test our own mathematical ability in 30s.
After giving few try-s I was just thought to create one small C# console application with same concept.
Following is my code which is working fine. But I could not display countdown ?!
My code:
static void Main(string[] args)
{
int testCount = 0;
Console.Write("\n Get.. Set... Go.... : This is a 30s test.. " +
"Once each problem is completed the time finished will be shown \n Good Luck.. :) \n \n");
Stopwatch watch = new Stopwatch();
watch.Start();
for (int i = 1; i < 100000; i++)
{
if (watch.Elapsed.TotalSeconds >= 30)
break;
TimeSpan timeSpan = TimeSpan.FromSeconds(Convert.ToInt32(watch.Elapsed.TotalSeconds));
Console.Write($"\n {timeSpan.ToString("c")}" );
Random r = new Random();
int number1 = r.Next(10);
int number2 = r.Next(10);
int operation = r.Next(4);
var method = (operation > 2) ? '+' : '*';
int result = 0;
result = method == '+' ? (number1 + number2) : (number1 * number2);
Console.Write($" \n {number1} {method} {number2} = ");
var getAnswer = Convert.ToInt32(Console.ReadLine());
if (result == getAnswer)
{
testCount++;
continue;
}
else
break;
}
watch.Stop();
if(testCount >= 1 && testCount <=5)
Console.Write($"\n No Worries!! Try Hard ... \n you have solved {testCount} problems \n");
else if(testCount >=6 && testCount <=10)
Console.Write($"\n Good!! You can do well next time ... \n you have solved {testCount} problems \n");
else
Console.Write($"\n Awesome!! You are really a Genius ... \n you have solved {testCount} problems \n");
Console.Write("\n Thank you for playing with me... \n Enter a key to exit");
Console.Read();
}
I would like to get the countdown from 30s to 0s at,
Get.. Set... Go.... : This is a 30s test.. Once each problem is completed the time finished will be shown
Good Luck.. :)
<<Timer Should go here>> (30, 29... 0)
5 * 5 = 25 ...
This SO Question Showing how to get countdown into our program, But I am confused at how I can do both parallely countdown and giving problems.
Any suggestion would be helpful to me.
It looks like you want to use BackgroundWorker. Then, DoWork event will decrement amount of seconds left, while ProgressChanged event will report current progress. The advantage of this solution is that background worker is running async, so you will not block your main thread allowing the user to enter answer anytime they want.
private static int secondsLeft;
private static BackgroundWorker bgWorker;
static void Main(string[] args)
{
secondsLeft = 30;
bgWorker = new BackgroundWorker();
bgWorker.DoWork += bgWorker_DoWork;
bgWorker.ProgressChanged += bgWorker_ProgressChanged;
bgWorker.WorkerReportsProgress = true;
bgWorker.RunWorkerAsync();
Console.ReadLine();
}
private static void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
while (secondsLeft >= 0)
{
bgWorker.ReportProgress(secondsLeft);
Thread.Sleep(1000);
secondsLeft--;
}
}
private static void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
Console.WriteLine($"Seconds left: {e.ProgressPercentage}");
}
This question already has an answer here:
get barcode reader value form background monitoring
(1 answer)
Closed 4 years ago.
I am scanning in a value from a barcode to a form, but it is not being entered into a textbox. I would like to "build" a string from the values returned by KeyPress so that I can parse the barcode later. I'm not sure how to set up a loop to capture all the characters from the barcode.
private string input;
private void MESMenu_KeyPress(object sender, KeyPressEventArgs e)
{
input += e.KeyChar;
MessageBox.Show(input);
}
Key Press looks like a event. One the one hand there is a loop - the Event Queue. On the other hand, there is no loop you can use directly (as you get no counting variable).
There are workarounds but they all have the same problem: You need to figure out when one barcode is "done" and can be processed. And thus the next one can begin. Or when the input of a barcode failed (propably due to some number not being readable) and thus should be repeated.
Aside from that, you are on the right track: You need a Variable outside of the Event that you append to. This can be a string, a List, List (a lot of single Character strings) or a Stringbuilder.
String is often good enough for short cases. If you do a lot of assignments, there is a bit of overhead in string connaction. It comes from the Inmubtability of the string and the fact that there is features like string interning to save memory. Just to get around those optimisations/issues, StringBuilder was added.
One thing you should avoid is using any GUI Element as teh outside variable. Writing the GUI causes considerable overhead. Not a issue if you do it once per user triggered event. But from any kind of loop the effects can be massive:
using System;
using System.Windows.Forms;
namespace UIWriteOverhead
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
int[] getNumbers(int upperLimit)
{
int[] ReturnValue = new int[upperLimit];
for (int i = 0; i < ReturnValue.Length; i++)
ReturnValue[i] = i;
return ReturnValue;
}
void printWithBuffer(int[] Values)
{
textBox1.Text = "";
string buffer = "";
foreach (int Number in Values)
buffer += Number.ToString() + Environment.NewLine;
textBox1.Text = buffer;
}
void printDirectly(int[] Values){
textBox1.Text = "";
foreach (int Number in Values)
textBox1.Text += Number.ToString() + Environment.NewLine;
}
private void btnPrintBuffer_Click(object sender, EventArgs e)
{
MessageBox.Show("Generating Numbers");
int[] temp = getNumbers(10000);
MessageBox.Show("Printing with buffer");
printWithBuffer(temp);
MessageBox.Show("Printing done");
}
private void btnPrintDirect_Click(object sender, EventArgs e)
{
MessageBox.Show("Generating Numbers");
int[] temp = getNumbers(1000);
MessageBox.Show("Printing directly");
printDirectly(temp);
MessageBox.Show("Printing done");
}
}
}
I get some problems with c# windows form.
My goal is to slice a big file(maybe>5GB) into files,and each file contains a million lines.
According to the code below,I have no idea why it will be out of memory.
Thanks.
StreamReader readfile = new StreamReader(...);
StreamWriter writefile = new StreamWriter(...);
string content;
while ((content = readfile.ReadLine()) != null)
{
writefile.Write(content + "\r\n");
i++;
if (i % 1000000 == 0)
{
index++;
writefile.Close();
writefile.Dispose();
writefile = new StreamWriter(...);
}
label5.Text = i.ToString();
label5.Update();
}
The error is probably in the
label5.Text = i.ToString();
label5.Update();
just to make a test I've written something like:
for (int i = 0; i < int.MaxValue; i++)
{
label1.Text = i.ToString();
label1.Update();
}
The app freezes around 16000-18000 (Windows 7 Pro SP1 x64, the app running both x86 and x64).
What probably happens is that by running your long operation in the main thread of the app, you stall the message queue of the window, and at a certain point it freezes. You can see that this is the problem by adding a
Application.DoEvents();
instead of the
label5.Update();
But even this is a false solution. The correct solution is moving the copying on another thread and updating the control every x milliseconds, using the Invoke method (because you are on a secondary thread),
For example:
public void Copy(string source, string dest)
{
const int updateMilliseconds = 100;
int index = 0;
int i = 0;
StreamWriter writefile = null;
try
{
using (StreamReader readfile = new StreamReader(source))
{
writefile = new StreamWriter(dest + index);
// Initial value "back in time". Forces initial update
int milliseconds = unchecked(Environment.TickCount - updateMilliseconds);
string content;
while ((content = readfile.ReadLine()) != null)
{
writefile.Write(content);
writefile.Write("\r\n"); // Splitted to remove a string concatenation
i++;
if (i % 1000000 == 0)
{
index++;
writefile.Dispose();
writefile = new StreamWriter(dest + index);
// Force update
milliseconds = unchecked(milliseconds - updateMilliseconds);
}
int milliseconds2 = Environment.TickCount;
int diff = unchecked(milliseconds2 - milliseconds);
if (diff >= updateMilliseconds)
{
milliseconds = milliseconds2;
Invoke((Action)(() => label5.Text = string.Format("File {0}, line {1}", index, i)));
}
}
}
}
finally
{
if (writefile != null)
{
writefile.Dispose();
}
}
// Last update
Invoke((Action)(() => label5.Text = string.Format("File {0}, line {1} Finished", index, i)));
}
and call it with:
var thread = new Thread(() => Copy(#"C:\Temp\lst.txt", #"C:\Temp\output"));
thread.Start();
Note how it will write the label5 every 100 milliseconds, plus once at the beginning (by setting the initial value of milliseconds "back in time"), each time the output file is changed (by setting the value of milliseconds "back in time") and after having disposed everything.
An even more correct example can be written by using the BackgroundWorker class, that exists explicitly for this scenario. It has an event, ProgressChanged, that can be subscribed to update the window.
Something like this:
private void button1_Click(object sender, EventArgs e)
{
BackgroundWorker backgroundWorker = new BackgroundWorker();
backgroundWorker.WorkerReportsProgress = true;
backgroundWorker.ProgressChanged += backgroundWorker_ProgressChanged;
backgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
backgroundWorker.DoWork += backgroundWorker_DoWork;
backgroundWorker.RunWorkerAsync(new string[] { #"C:\Temp\lst.txt", #"C:\Temp\output" });
}
private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
string[] arguments = (string[])e.Argument;
string source = arguments[0];
string dest = arguments[1];
const int updateMilliseconds = 100;
int index = 0;
int i = 0;
StreamWriter writefile = null;
try
{
using (StreamReader readfile = new StreamReader(source))
{
writefile = new StreamWriter(dest + index);
// Initial value "back in time". Forces initial update
int milliseconds = unchecked(Environment.TickCount - updateMilliseconds);
string content;
while ((content = readfile.ReadLine()) != null)
{
writefile.Write(content);
writefile.Write("\r\n"); // Splitted to remove a string concatenation
i++;
if (i % 1000000 == 0)
{
index++;
writefile.Dispose();
writefile = new StreamWriter(dest + index);
// Force update
milliseconds = unchecked(milliseconds - updateMilliseconds);
}
int milliseconds2 = Environment.TickCount;
int diff = unchecked(milliseconds2 - milliseconds);
if (diff >= updateMilliseconds)
{
milliseconds = milliseconds2;
worker.ReportProgress(0, new int[] { index, i });
}
}
}
}
finally
{
if (writefile != null)
{
writefile.Dispose();
}
}
// For the RunWorkerCompleted
e.Result = new int[] { index, i };
}
void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
int[] state = (int[])e.UserState;
label5.Text = string.Format("File {0}, line {1}", state[0], state[1]);
}
void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
int[] state = (int[])e.Result;
label5.Text = string.Format("File {0}, line {1} Finished", state[0], state[1]);
}
I am probably just doing it very wrong. I am currently working with MSMQ and Webservices. I wanted to learn how MSMQ worked so I found a school example of a Loan Broker.
To make a long story short, I need to be able to stress test my system, so I want to be able to make, say, 100 messages and send them through my messaging system. I want to do that from a Windows Form application, but here lies the problem. I have a form that looks like this:
On the left you see a custom control and on the right, my "console" window that tells me what's going on. When I press the Send button, it should use the data given in the fields above it, to send messages. But when I press the Send Button, the program freezes for a while and then hits the OutOfMemoryException. This is the Send method:
private void Send(List<SimpleRequest.LoanRequest> list)
{
int quantity = int.Parse(numericQuantity.Value.ToString());
int delay = int.Parse(numericDelay.Value.ToString());
if (list.Count == 1)
{
for (int threadnumber = 0; threadnumber < quantity; threadnumber++)
{
Task.Factory.StartNew(() => RequestLoanQuote(threadnumber, list[0]));
if (delay > 0)
{
Thread.Sleep(delay);
}
}
}
else
{
for (int threadnumber = 0; threadnumber < quantity; threadnumber++)
{
Task.Factory.StartNew(() => RequestLoanQuote(threadnumber, list[threadnumber]));
if (delay > 0)
{
Thread.Sleep(delay);
}
}
}
}
Here is the RequestLoanQuote method that the Send method is calling:
private void RequestLoanQuote(object state, SimpleRequest.LoanRequest loanRequest)
{
try
{
if (console.InvokeRequired)
{
SetText("Sending: " + loanRequest.SSN + "\n");
}
StringBuilder sb = new StringBuilder();
var threadnumber = (int)state;
using (var client = new LoanBrokerWS.LoanBrokerWSClient())
{
Utility_Tool.LoanBrokerWS.LoanQuote response = client.GetLoanQuote(loanRequest.SSN, loanRequest.LoanAmount, loanRequest.LoanDuration);
sb.Append(response.SSNk__BackingField + " returned: ");
sb.Append(response.interestRatek__BackingField + " | ");
sb.Append(response.BankNamek__BackingField + "\n");
SetText(sb.ToString());
}
}
catch (Exception e)
{
SetText(e.Message + "\n");
}
}
And finally, the SetText method:
private void SetText(String msg)
{
if (this.console.InvokeRequired)
{
SetTextCallback d = new SetTextCallback(SetText);
this.Invoke(d, new object[] { msg });
}
else
{
this.console.Text += msg;
}
}
So the Send method calls the RequestLoanQuote method which calls the SetText method. I cannot figure out where I went wrong but it's probably a deadlock.
Try using BeginInvoke and AppendText, like so:
public static void SetText(this RichTextBox textBox, string msg)
{
Action append = () => textBox.AppendText(msg);
if (textBox.InvokeRequired)
textBox.BeginInvoke(append);
else
append();
}