I am currently writing a simple WPF 3.5 application that utilizes the SharePoint COM to make calls to SharePoint sites and generate Group and User information. Since this process takes awhile I want to show a ProgressBar while the groups are being generated. The desired process is as follows:
User enters url and clicks button to fetch site data.
ProgressBar begins animation
Groups are generated and names are added to a ListView
Upon completion ProgressBar animation ends
The problem I am running into is that the UI is never updated. Neither the ProgressBar or the ListView makes any changes. If anyone has any ideas to help with the code below it would be greatly appreciated.
private void GetGroupsAndUsersButton_Click(object sender, RoutedEventArgs e)
{
siteUrl = "";
if (SiteURLTextBox.Text.Length > 0)
{
FetchDataProgressBar.IsIndeterminate = true;
mWorker = new BackgroundWorker();
mWorker.DoWork += new DoWorkEventHandler(worker_DoWork);
mWorker.WorkerSupportsCancellation = true;
mWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
mWorker.RunWorkerAsync();
}
else
{
System.Windows.MessageBox.Show("Please enter a URL for the SharePoint site you wish to retrieve data");
}
}
private void worker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
siteUrl = SiteURLTextBox.Text;
GroupListView.ItemsSource = null;
try
{
using (SPSite site = new SPSite(siteUrl))
{
SPWeb web = site.OpenWeb();
SPGroupCollection collGroups = web.SiteGroups;
if (GroupNames == null)
GroupNames = new List<string>();
foreach (SPGroup oGroup in collGroups)
{
GroupListView.Items.Add(new ListViewItem() { Content = oGroup.Name });
}
foreach (ListViewItem item in GroupListView.Items)
{
item.MouseLeftButtonUp += item_MouseLeftButtonUp;
}
}
}
catch (Exception ex)
{
System.Windows.MessageBox.Show("Unable to locate a SharePoint site at: " + siteUrl);
}
}
private void worker_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
FetchDataProgressBar.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal,
new Action(
delegate()
{
FetchDataProgressBar.IsIndeterminate = false;
}
));
}
At first you need to support ProgressChanged events.
Update your BackgroundWorker initialization to:
GroupListView.ItemSource = null;
mWorker = new BackgroundWorker();
mWorker.DoWork += new DoWorkEventHandler(worker_DoWork);
mWorker.WorkerSupportsCancellation = true;
mWorker.WorkerReportsProgress = true;
mWorker.ProgressChanged += OnProgressChanged;
mWorker.RunWorkerCompleted +=
new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
mWorker.RunWorkerAsync(SiteURLTextBox.Text);
After that you have to add a OnProgressChanged handler:
private void OnProgressChanged(object sender, ProgressChangedEventArgs e)
{
FetchDataProgressBar.Value = e.ProgressPercentage;
ListViewItem toAdd = (ListViewItem)e.UserState;
toAdd.MouseLeftButtonUp += item_MouseLeftButtonUp;
GroupListView.Items.Add(toAdd);
}
Therefore you have to change your DoWork:
private void worker_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
BackgroundWorker worker = (BackgroundWorker)sender;
try
{
using (SPSite site = new SPSite((String)e.Argument))
{
SPWeb web = site.OpenWeb();
SPGroupCollection collGroups = web.SiteGroups;
if(GroupNames == null)
GroupNames = new List<string>();
int added = 0;
foreach(SPGroup oGroup in collGroups)
{
added++;
ListViewItem tmp = new ListViewItem() {
Content = oGroup.Name
};
worker.ReportProgress((added * 100)/collGroups.Count,tmp);
}
}
}
catch (Exception ex)
{
MessageBox.Show("Unable to locate a SharePoint site at: " + siteUrl);
}
}
That's because you're not allowed to change GUI on DoWork.
After that, each ListViewItem is added separately to your ListView. I would also recommend, that your URL is passed as an argument to RunWorkerAsync.
Edit: Add percentage to OnProgressChanged.
In your DoWork method, you are manipulating WPF controls in code on a background thread, which you are not supposed to do. Actually, you should receive errors like "Cannot access control from other thread". Probably those exceptions are caught by your catch-all error handler, and maybe even the MessageBox doesn't work from the background thread.
As a quick fix, you would have to make siteURL and collGroups class fields, move everything before the using block to your GetGroupsAndUsersButton_Click method, and everything starting with the first foreach loop to the RunworkerCompleted event, so that all code which accesses controls runs on the UI thread.
Another thing you should change is that you should not create ListViewItems in code, but use a DataTemplate instead... this is not connected to your problem, though.
You'll need:
mWorker.WorkerReportsProgress = true;
mWorker.ProgressChanged +=
new ProgressChangedEventHandler(worker_ProgressChanged);
Then in your DoWork you'll need to call:
var worker = (BackgroundWorker)sender;
worker.ReportProgress(progressAmount);
Good worked example here: http://msdn.microsoft.com/en-us/library/cc221403(v=vs.95).aspx
Related
first off I'd like to say I'm brand new to C# so I am not too aware with how the background worker is supposed to be implemented. I have a GUI program that basically pings a domain a returns the response to a textbox. I am able to get it to work normally, however, it freezes the code because it is running on the same thread which is why I am trying to implement a background worker.
Here is the basic setup
private void button1_Click(object sender, EventArgs e)
{
url = textBox1.Text;
button1.Enabled = false;
button2.Enabled = true;
bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
bgWorker.RunWorkerAsync();
}
private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
do
{
if (bgWorker.CancellationPending)
break;
Invoke((MethodInvoker)delegate { monitor(); });
} while (true);
}
public void monitor()
{
textBox2.AppendText("Status of: " + url + "\n");
Status(url);
System.Threading.Thread.Sleep(30000);
}
private void Status(string url)
{
// This method does all the ping work and also appends the status to the Text box as it goes through , as OK or down
}
I have not worked with bgworkers before and as you can imagine it's confusing. I've looked at tons of other articles and I can't seem to get it. Sorry if the code looks crazy, I'm trying to learn.
Use Microsoft's Reactive Framework (NuGet "System.Reactive.Windows.Forms" and add using System.Reactive.Linq;) and then you can do this:
private void button1_Click(object sender, EventArgs e)
{
var url = textBox1.Text;
Observable
.Interval(TimeSpan.FromMinutes(0.5))
.SelectMany(_ => Observable.Start(() => Status(url)))
.ObserveOn(this)
.Subscribe(status => textBox2.AppendText("Status of: " + status + "\n"));
}
You then just need to change Status to have this signature: string Status(string url).
That's it. No background worker. No invoking. And Status is nicely run on a background thread.
You've got several mistakes. First,
Invoke((MethodInvoker)delegate
{
monitor();
});
will call monitor() on your UI thread. In almost all cases you should not call methods on other threads. You especially should not call methods that block or do anything that takes more than a few milliseconds on your UI thread, and that is what this does:
System.Threading.Thread.Sleep(30000);
Instead of calling a method on another thread; submit immutable data to the other thread and let the thread decide when to handle it. There is an event already built in to BackgroundWorker which does that. Before you call bgWorker.RunWorkerAsync() do this:
url = new Uri(something);
bgWorker.WorkerReportsProgress = true;
bgWorker.WorkerSupportsCancellation = true;
bgWorker.ProgressChanged += Bgw_ProgressChanged;
private void Bgw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
textBox2.AppendText("Status of: " + url + ": " + e.UserState.ToString()
+ Environment.NewLine);
}
Your bgWorker_DoWork should look more like this:
void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
while (!bgw.CancellationPending)
{
System.Threading.Thread.Sleep(new TimeSpan(0, 0, 30));
var status = ResultOfPing(e.Argument as Uri);
bgw.ReportProgress(0, status);
}
e.Cancel = true;
}
and you should call it like this:
bgWorker.RunWorkerAsync(url);
You've got a second problem. BackgroundWorker creates a thread, and your thread is going to spend most of its time blocked on a timer or waiting for network responses. That is a poor use of a thread. You would be better off using completion callbacks or async/await.
The background worker is running on a thread pool thread, but your call to Status and Sleep is running on the UI thread. You need to move that stuff back into bgWorker_DoWork.
Try this code:
public partial class Form1 : Form
{
bool cancel;
public Form1()
{
InitializeComponent();
}
public void StartPinging()
{
this.cancel = false;
startButton.Enabled = false;
stopButton.Enabled = true;
responseBox.Clear();
responseBox.AppendText("Starting to ping server.");
responseBox.AppendText(Environment.NewLine);
var bw = new BackgroundWorker
{
WorkerReportsProgress = false,
WorkerSupportsCancellation = true
};
bw.DoWork += (obj, ev) =>
{
while (!cancel)
{
// Ping Server Here
string response = Server.PingServer();
this.Invoke(new UiMethod(() =>
{
responseBox.AppendText(response);
responseBox.AppendText(Environment.NewLine);
}));
}
};
bw.RunWorkerCompleted += (obj, ev) =>
{
this.Invoke(new UiMethod(() =>
{
responseBox.AppendText("Stopped pinging the server.");
responseBox.AppendText(Environment.NewLine);
startButton.Enabled = true;
stopButton.Enabled = false;
}));
};
bw.RunWorkerAsync();
}
delegate void UiMethod();
private void startButton_Click(object sender, EventArgs e)
{
StartPinging();
}
private void stopButton_Click(object sender, EventArgs e)
{
responseBox.AppendText("Cancelation Pressed.");
responseBox.AppendText(Environment.NewLine);
cancel = true;
}
}
public class Server
{
static Random rng = new Random();
public static string PingServer()
{
int time = 1200 + rng.Next(2400);
Thread.Sleep(time);
return $"{time} ms";
}
}
Erwin, when dealing with C# - threads and UI elements usually you will come across cross-thread operations i.e. Background thread with UI threads. This interaction needs to be done in thread safe way with the help of Invoke to avoid invalid operations.
Please look into below resource: InvokeRequired section.
https://learn.microsoft.com/en-us/dotnet/framework/winforms/controls/how-to-make-thread-safe-calls-to-windows-forms-controls
I recently attempted to thread a foreach loop because it was freezing the UI when it ran. This loop looks through a bunch of log files and retrieves information from them line by line, then adds it to a listView(also prints something to a richtextBox). The issue I'm having is that after threading this loop, it seems that neither the listView nor the richTextBox update anymore. I know for a fact that the method is being called, because when I put a MessageBox after that 'if statement', it opens just fine but everything else refuses to work.
public void searchForAll(object sender, DoWorkEventArgs e)
{
if (//argument)
{
listViewEx1.Items.Clear();
int logcount = 0;
richTextBoxEx1.Text += "Print something";
richTextBoxEx1.Text += "\n";
richTextBoxEx1.SelectionStart = richTextBoxEx1.Text.Length;
richTextBoxEx1.ScrollToCaret();
foreach (User user in s.Friends)
{
foreach (string log in Directory.GetFiles(path, "*.log"))
{
string[] fileToRead = File.ReadAllLines(log);
foreach (string line in fileToRead)
{
if (line.Contains(user.Handle) && line.Contains("-r"))
{
if (!isDuplicate(c))
{
listViewEx1.Items.Add(new ListViewItem(user.Handle)
{
SubItems = { c }
});
dupCheck.Add(c);
logcount++;
}
}
}
}
dupCheck.Clear();
Thread.Sleep(1000);
}
richTextBoxEx1.Text += "Print something";
}
}
}
It isn't recommended to directly change parts of the UI from within a BackgroundWorker.DoWork event, instead I recommend using BackgroundWorker.ReportProgress and editing the UI inside THAT method.
Here is an example of how I would implement changing a textbox's value to 'x':
public void searchForAll(object sender, DoWorkEventArgs e)
{
//Define background worker
var MyBack = (BackgroundWorker)sender;
for(...)
{
//Send some data to ReportProgress
MyBack.ReportProgress(0, "any object of any form goes here");
}
}
Then in the report progress method:
private void backgroundWorker1_ProgressChanged(object sender,
ProgressChangedEventArgs e)
{
textBox1.Text = e.UserState.ToString();
}
Please note that you have to set Backgroundworker1.WorkerReportsProgress = true; otherwise the worker won't be able to report the progress.
in my application i want to add files into my list box.
if my file isn't pcap extension i want to send the file path to my class and convet it to pcap extension and then add this file to my Listbox.
in case i am choose to add namy files the GUI not responding until my application finish to add or convert this file and i wonder how to add the option to do all this via threads.
private void btnAddfiles_Click(object sender, EventArgs e)
{
System.IO.Stream stream;
OpenFileDialog thisDialog = new OpenFileDialog();
thisDialog.InitialDirectory = (lastPath.Length > 0 ? lastPath : "c:\\");
thisDialog.Filter = "(*.snoop, *.pcap, *.cap, *.net, *.pcapng, *.5vw, *.bfr, *.erf, *.tr1)" +
"|*.snoop; *.pcap; *.cap; *.net; *.pcapng; *.5vw; *.bfr; *.erf; *.tr1|" + "All files (*.*)|*.*";
thisDialog.FilterIndex = 1;
thisDialog.RestoreDirectory = false;
thisDialog.Multiselect = true;
thisDialog.Title = "Please Select Source File";
if (thisDialog.ShowDialog() == DialogResult.OK)
{
if (thisDialog.FileNames.Length > 0)
{
lastPath = Path.GetDirectoryName(thisDialog.FileNames[0]);
}
foreach (String file in thisDialog.FileNames)
{
try
{
if ((stream = thisDialog.OpenFile()) != null)
{
using (stream)
{
string fileToAdd = string.Empty;
Editcap editcap = new Editcap();
BackgroundWorker backgroundWorker = new BackgroundWorker();
backgroundWorker.WorkerReportsProgress = true;
backgroundWorker.DoWork += new DoWorkEventHandler(
(s3, e3) =>
{
if (!editcap.isLibpcapFormat(file))
{
fileToAdd = editcap.getNewFileName(file);
}
else
{
listBoxFiles.Items.Add(file);
}
});
backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(
(s3, e3) =>
{
listBoxFiles.Items.Add(fileToAdd);
});
backgroundWorker.RunWorkerAsync();
lastPath = Path.GetDirectoryName(thisDialog.FileNames[0]);
}
}
}
catch (Exception ex)
{
MessageBox.Show("Error: Could not read file from disk. Original error: " + ex.Message);
}
}
}
}
Your application is freezing because you're doing a lot of work in the UI thread. You need to move the long running tasks to a background thread and then just update the UI in the UI thread.
The first thing that you need to do, in order to do that, is seperate out your long running task from your UI manipulation. Currently you're intermingliing the two, which is what's causing your confusion as to how to map it to a BackgroundWorker.
As long as you don't need to be updating the listbox iteratively and it's okay to just add all of the items at the end all at once (that's what I would expect out of a listbox) you can simply do your file IO in one place, adding the results into a collection of some sort (List is likely appropriate here) and then, separately, you can add all of the items in the list to your ListBox (or use data binding).
Once you make that change the move to using something like a BackgroundWorker is quite easy. The IO work that populates the List goes in the DoWork, runs in the background, and then sets the Result. The RunWorkerCompleted event then takes that lists and adds the items to the ListBox.
If you have a compelling need to add the items to the listbox as you go, so you see one item, then the next, etc. over time, then just think of it as "reporting progress" and use the relevant progress reporting functionality built into BackgroundWorker. Update the progress inside of the loop, and in the progress reported event handler take the value given to you and put it in the ListBox.
Here is an implementation:
private void btnAddfiles_Click(object sender, EventArgs e)
{
System.IO.Stream stream;
OpenFileDialog thisDialog = new OpenFileDialog();
thisDialog.InitialDirectory = (lastPath.Length > 0 ? lastPath : "c:\\");
thisDialog.Filter = "(*.snoop, *.pcap, *.cap, *.net, *.pcapng, *.5vw, *.bfr, *.erf, *.tr1)" +
"|*.snoop; *.pcap; *.cap; *.net; *.pcapng; *.5vw; *.bfr; *.erf; *.tr1|" + "All files (*.*)|*.*";
thisDialog.FilterIndex = 1;
thisDialog.RestoreDirectory = false;
thisDialog.Multiselect = true;
thisDialog.Title = "Please Select Source File";
if (thisDialog.ShowDialog() == DialogResult.OK)
{
if (thisDialog.FileNames.Length > 0)
{
lastPath = Path.GetDirectoryName(thisDialog.FileNames[0]);
}
BackgroundWorker backgroundWorker = new BackgroundWorker();
backgroundWorker.WorkerReportsProgress = true;
backgroundWorker.DoWork +=
(s3, e3) =>
{
//TODO consider moving everything inside of the `DoWork` handler to another method
//it's a bit long for an anonymous method
foreach (String file in thisDialog.FileNames)
{
try
{
if ((stream = thisDialog.OpenFile()) != null)
{
using (stream)
{
Editcap editcap = new Editcap();
if (!editcap.isLibpcapFormat(file))
{
string fileToAdd = editcap.getNewFileName(file);
backgroundWorker.ReportProgress(0, fileToAdd);
}
else
{
backgroundWorker.ReportProgress(0, file);
}
lastPath = Path.GetDirectoryName(thisDialog.FileNames[0]);
}
}
}
catch (Exception ex)
{
MessageBox.Show("Error: Could not read file from disk. Original error: " + ex.Message);
}
}
};
backgroundWorker.ProgressChanged +=
(s3, arguments) =>
{
listBoxFiles.Items.Add(arguments.UserState);
};
backgroundWorker.RunWorkerAsync();
}
}
You can do it with BackgroundWorker:
Add a backgroundWorker to your form via the Toolbox.
Start it with:
backgroundWorker.RunWorkerAsync(new string[] {parm1, parm2});
Add a events to backgroundWorker (Properties window)
Use DoWork to do your calculations. Then use RunWorkerCompleted to apply the settings.
Iam Unable to do this from past one week. I want to click on multiple links n multiple web pages using webBrowser in C# Following is the code please help me in this regard.
public void DoDelete()
{
int count = 0;
if (corruptList.Count > 0)
{
foreach (string listItem in corruptList)
{
var th = new Thread(() =>
{
try
{
WebBrowser webBrowser = new WebBrowser();
webBrowser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(webBroswer_DocumentCompleted);
webBrowser.Navigate(listItem);
Thread.Sleep(100);
webBrowser.Dispose();
}
catch (Exception ex)
{
throw ex;
}
this.Invoke(new MethodInvoker(delegate
{
dataGridView_CorruptLinks.Rows[count].Cells[2].Value = "Deleted";
}));
});
th.SetApartmentState(ApartmentState.STA);
th.Start();
Thread.Sleep(100);
}
count++;
}
}
void webBroswer_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
try
{
WebBrowser webBrowser = sender as WebBrowser;
HtmlElementCollection ec = webBrowser.Document.GetElementsByTagName("a");
foreach (HtmlElement item in ec)
{
if (item.InnerHtml == "Delete this invalid field")
{
item.InvokeMember("Click");
break;
}
}
}
catch (Exception exp)
{
}
}
Navigate is an asynchronous action and you're only giving it 1/10 of a second to complete before you call Dispose on the web browser object. Your navigation and clicks are probably taking longer than that to complete and so there is no web browser to act against... You're also "swallowing" all exceptions in the document complete handler. This is a very bad thing to do. You should at the very least be doing some debug logging there to help yourself diagnose the problem.
But, to keep the similar logic you should create a collection of web browsers at class level. Something like:
private List<WebBrowser> _myWebBrowsers;
Then add to this list in your loop but do not call Dispose. You should only dispose of the browser when you're done with it.
That should get you closer though there are a few other potential issues with your code. You're allocating a borser object and thread for every time through a loop. This could quickly become unwieldy. You should use a thread management mechanism to throttle this process.
Simplified class:
class WebRunner
{
private List<string> _corruptList = new List<string>();
private List<WebBrowser> _browsers = new List<WebBrowser>();
public void Run()
{
_corruptList.Add("http://google.com");
_corruptList.Add("http://yahoo.com");
_corruptList.Add("http://bing.com");
DoDelete();
Console.ReadKey();
}
public void DoDelete()
{
if (_corruptList.Count < 1) return;
int counter = 1;
foreach (string listItem in _corruptList)
{
WebBrowser webBrowser = new WebBrowser();
_browsers.Add(webBrowser);
webBrowser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(webBroswer_DocumentCompleted);
webBrowser.Navigated += new WebBrowserNavigatedEventHandler(webBrowser_Navigated);
webBrowser.Navigate(listItem);
if (counter % 10 == 0) Thread.Sleep(3000); // let app catch up every so often
counter++;
}
}
void webBrowser_Navigated(object sender, WebBrowserNavigatedEventArgs e)
{
Console.WriteLine("NAVIGATED: " + e.Url);
}
void webBroswer_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
{
Console.WriteLine("COMPLETED!");
try
{
WebBrowser webBrowser = sender as WebBrowser;
HtmlDocument doc = webBrowser.Document;
var button = doc.Body.Document.GetElementById("button");
button.InvokeMember("Click");
_browsers.Remove(webBrowser);
}
catch (Exception exp)
{
Console.WriteLine(exp.StackTrace);
MessageBox.Show(exp.Message);
}
}
}
You can access the WebBrowser document content using the following (you are missing body and need to type document to dynamic).
dynamic doc = browser.Document;
var button = doc.body.document.getElementById("button");
button.Click();
I found the solution very next day. Sorry for the late post by processing threads one by one by putting the statement after thread.sleep()
if (th.ThreadState == ThreadState.Aborted || th.ThreadState == ThreadState.Stopped)
I have written code to save an image which is generated by the application. The size of the image is around 32-35 MB. While saving the image to a BMB file, it is taking a long time, around 3-5 secs. For this purpose, I have used a background worker but when running the background worker, it shows an error like..."can't access the object as it is created on different thread".
Following is the code:
private void btnSaveDesign_Click(object sender, RoutedEventArgs e)
{
Microsoft.Win32.SaveFileDialog sfd = new Microsoft.Win32.SaveFileDialog();
sfd.Title = "Save design as...";
sfd.Filter = "BMP|*.bmp";
if (sfd.ShowDialog() == true)
{
ww = new winWait();
ww.Show();
System.ComponentModel.BackgroundWorker bw = new System.ComponentModel.BackgroundWorker();
bw.DoWork += new System.ComponentModel.DoWorkEventHandler(bw_DoWork);
bw.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
fName = sfd.FileName;
cache = new CachedBitmap((BitmapSource)imgOut.Source, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
bw.RunWorkerAsync();
}
}
void bw_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
ww.Close();
}
void bw_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
BmpBitmapEncoder encoder = new BmpBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(cache)); //here... it says cant access...
using (FileStream file = File.OpenWrite(fName))
{
encoder.Save(file);
}
}
I have declared "cache" as a global object. (A similar trick worked when I was programming in Windows Forms with VB.NET.)
ww is the wait window that I want to be displayed while the precess is being executed.
How to do this? Is there any other simple method for multi threading in WPF?
When WPF objects are created they are assigned to a Dispatcher object. This disallows any threads other than the creating thread to access the object. This can be circumvented by freezing the object by calling the freeze method. You would need to call Freeze on your bitmapsource object. Once you have frozen your object it becomes uneditable
Your problem comes about because you are accessing an object which is not created by the background worker thread. Normally this would happen if you access a UI control which is created in the main thread and accessed from different thread.
Use the code below.
Dispatcher.Invoke
(
new Action(
delegate()
{
BmpBitmapEncoder encoder = new BmpBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(cache));
using (FileStream file = File.OpenWrite(fName))
{
encoder.Save(file);
}
}
)
);
I think you have to pass cache as a parameter to the new thread:
bw.RunWorkerAsync(cache);
and get it from the DoWork method:
var cache=(CacheType) e.Argument;
.NET framework provides a simple way to get started in threading with
the BackgroundWorker component. This wraps much of the complexity and
makes spawning a background thread relatively safe. In addition, it
allows you to communicate between your background thread and your UI
thread without doing any special coding. You can use this component
with WinForms and WPF applications. The BackgroundWorker offers
several features which include spawning a background thread, the
ability to cancel the background process before it has completed, and
the chance to report the progress back to your UI.
public BackgroudWorker()
{
InitializeComponent();
backgroundWorker = ((BackgroundWorker)this.FindResource("backgroundWorker"));
}
private int DoSlowProcess(int iterations, BackgroundWorker worker, DoWorkEventArgs e)
{
int result = 0;
for (int i = 0; i <= iterations; i++)
{
if (worker != null)
{
if (worker.CancellationPending)
{
e.Cancel = true;
return result;
}
if (worker.WorkerReportsProgress)
{
int percentComplete =
(int)((float)i / (float)iterations * 100);
worker.ReportProgress(percentComplete);
}
}
Thread.Sleep(100);
result = i;
}
return result;
}
private void startButton_Click(object sender, RoutedEventArgs e)
{
int iterations = 0;
if (int.TryParse(inputBox.Text, out iterations))
{
backgroundWorker.RunWorkerAsync(iterations);
startButton.IsEnabled = false;
cancelButton.IsEnabled = true;
outputBox.Text = "";
}
}
private void cancelButton_Click(object sender, RoutedEventArgs e)
{
// TODO: Implement Cancel process
this.backgroundWorker.CancelAsync();
}
private void BackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
// e.Result = DoSlowProcess((int)e.Argument);
var bgw = sender as BackgroundWorker;
e.Result = DoSlowProcess((int)e.Argument, bgw, e);
}
private void BackgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
workerProgress.Value = e.ProgressPercentage;
}
private void BackgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
MessageBox.Show(e.Error.Message);
}
else if (e.Cancelled)
{
outputBox.Text = "Canceled";
workerProgress.Value = 0;
}
else
{
outputBox.Text = e.Result.ToString();
workerProgress.Value = 0;
}
startButton.IsEnabled = true;
cancelButton.IsEnabled = false;
}