i am new in C# so please be patient with me .
i want to make progress bar work with any functions i make in my program
i have class to check if INTERNET available and the connection of database status
and i have "progressBar1" , style is "Marquee"
i just want to indicate that there is a process work "Function" in the program and i don't need to have step or timer to increment it
just make the progress work until the function finish its code and the functions will work in button event (when i push button)
this is my code
class checkInternet
{
[DllImport("wininet.dll")]
private extern static bool InternetGetConnectedState(out int Description, int ReservedValue);
public bool checkInternetAvailable()
{
int Desc;
bool result = false;
if (InternetGetConnectedState(out Desc, 0) == true)
{
try
{
dbConnection StartConn = new dbConnection();
SqlConnection MyConnetion = StartConn.GetConnection();
MyConnetion.Open();
if (MyConnetion.State == ConnectionState.Open)
{
result = true;
}
MyConnetion.Close();
}
catch (Exception)
{
result = false;
MessageBox.Show("The database connection does not available, May be because of this reasons: \n\n1- there is a new version of the program avalible. \n2- database has some maintenance. \n\n Please check later :)", "Conection status");
}
}
else
{
result = false;
MessageBox.Show("No internet connection avalible , Please check later :) \nThanks.", "Conection status");
}
return result;
}
}
and this is what i have in my button event
private void button1_Click(object sender, EventArgs e)
{
checkInternet check = new checkInternet();
progressBar1.Value = 0;
do
{
progressBar1.PerformStep();
} while (check.checkInternetAvailable());
}
how can i implement that ?
thanks
As I understand you want user to see progressbar while your check connection task executes in background. checkInternetAvailable would be your background operation and I wouldn't suggest showing messages directly form it. Instead return a custom struct :
public struct ConnectionCheckResult
{
public bool Success;
public string Message;
}
And this will be your button click event handler :
private void button1_Click(object sender, EventArgs e)
{
progressBar1.Style = ProgressBarStyle.Marquee;
progressBar1.Visible = true;
//add code here to be executed on UI thread before connection check
Task.Run(new Action(() =>
{
//Task.Run this code on the thread pool instead of your UI thread. So your code is checking connection while progress bar is still rendering
ConnectionCheckResult res = new checkInternet().checkInternetAvailable();
this.Invoke(new Action(() =>
{
//this.Invoke executes following delegate on UI thread. All UI changes - like progressBar1.Visible = false; need to be made in UI thread.
//add code here to be executed on the UI thread after connection check.
progressBar1.Visible = false;
if (!string.IsNullOrEmpty(res.Message))
MessageBox.Show(res.Message);
}));
}));
//add code to be executed on UI thread at the same time as connection check
}
I know multi-threading is difficult to wrap your head around at first, here's good tutorial with code samples.
Also when your progressbar style is Marquee you don't need to call PerformStep. It will just roll by itself.
EDIT: You should also modify checkInternetAvailable() like so :
public ConnectionCheckResult checkInternetAvailable()
{
int Desc;
ConnectionCheckResult result = new ConnectionCheckResult();
if (InternetGetConnectedState(out Desc, 0) == true)
{
try
{
dbConnection StartConn = new dbConnection();
SqlConnection MyConnetion = StartConn.GetConnection();
MyConnetion.Open();
if (MyConnetion.State == ConnectionState.Open)
{
result.Success = true;
}
MyConnetion.Close();
}
catch (Exception)
{
result.Success = false;
result.Message = "The database connection does not available, May be because of this reasons: \n\n1- there is a new version of the program available. \n2- database has some maintenance. \n\n Please check later :)";
}
}
else
{
result.Success = false;
result.Message = "No internet connection available , Please check later :) \nThanks.";
}
return result;
}
Related
I have code
private void AbrirConexao(string strConexao)
{
try
{
conexao = new NpgsqlConnection(strConexao);
conexao.Open();
}
catch (Exception)
{
ReconectarDB(null, strConexao);
}
}
public bool ReconectarDB(string strConexao)
{
bool erroConexao = false;
BackgroundWorker bw = new BackgroundWorker();
bw.DoWork += (obj, ea) =>
{
int erro = 0;
while (erro <= 4)
{
Thread.Sleep(1000);
try
{
conexao = new NpgsqlConnection(strConexao);
conexao.Open();
erroConexao = false;
break;
}
catch
{
erro++;
erroConexao = true;
}
}
};
bw.RunWorkerCompleted += (obj, ea) =>
{
if (erroConexao)
DialogReconectando.AlterarTela(ErroConexao.SemConexao);
else
DialogReconectando.Close();
};
bw.RunWorkerAsync();
Application.Current.Dispatcher.Invoke(new Action(() =>
{
if (DialogReconectando == null || Conexao.DialogReconectando.IsLoaded == false)
DialogReconectando = new DialogErroConexao(ErroConexao.Reconectando);
if(DialogReconectando.ShowActivated)
{
DialogReconectando.ShowActivated = true;
DialogReconectando.ShowDialog();
}
}));
return erroConexao;
}
I am using the Open Connection method to connect to the database. and when the connection fails, ReconnectDB is trying to reconnect with the database. If it fails, a Window is opened that there are two buttons, Retry and Abort the System.
The problem is that there are situations that I use other concurrent threads that makes requests with the database. In those cases, I would not want it to display a new Window. So if there is a Window open, I would like the Thread to lock until the Window is closed. I tried to solve the problem using EventWaitHandle. However, Window is also caught in this situation. Would you have any idea how you could solve this problem?
It depends on what you want the second thread to do. If you want the second thread to simply skip over showing the window, you can use a semaphore to ensure that only a single thread shows the window, like this:
SemaphoreSlim semaphore = new SemaphoreSlim(1, 1);
private void ShowWindowNonBlocking()
{
bool acquiredLock = false;
try
{
acquiredLock = semaphore.Wait(0);
if (acquiredLock)
{
// This thread now has exclusive access to the isWindowShown variable
var result = MessageBox.Show(
"Retry the connection?",
"Connection Failed",
MessageBoxButtons.RetryCancel);
if (result == DialogResult.Retry)
{
// Retry the connection
}
}
else
{
// Another thread is showing the window
}
}
finally
{
if (acquiredLock)
{
semaphore.Release();
}
}
}
Here is a good site that I refer back to from time to time on locking mechanisms: http://www.albahari.com/threading/part2.aspx#_Semaphore
If however, you want the second thread to block until the first window is finished (for example, if you want to know what the result of the window was in order to know whether to retry on the second thread), you can use a lock, like this:
private object windowLock = new object();
private void ShowWindowBlocking()
{
lock (windowLock)
{
var result = MessageBox.Show(
"Retry the connection?",
"Connection Failed",
MessageBoxButtons.RetryCancel);
if (result == DialogResult.Retry)
{
// Retry the connection
}
}
}
If you need further clarification, let me know and I will try to expand the answer.
I am working on signalR. I have a server (ASP .NET) and a client (C# WinForms).
In my client app I have a async method:
public async void conAsync()
{
HubConn = new HubConnection(serverURL);
HubPrx = HubConn.CreateHubProxy("myHUB");
try
{
await HubConn.Start();
richTextBox1.AppendText("connected");
button1.BackColor = Color.Green;
groupBox1.Enabled = true;
groupBox2.Enabled = true;
}
catch(Exception err)
{
// deactive comps
groupBox1.Enabled = false;
groupBox2.Enabled = false;
richTextBox1.AppendText(err.toString());
}
}
The Start Button executes the above method.
I want provide a Stop Button which stops the connection to the server. I read about CancellationToken but I got confused about how to use it in my case.
Actually my button is a CheckBox which acts like a ToggleButton.
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
if (checkBox1.Checked)
{
checkBox1.ForeColor = Color.Green;
conAsync();
}
else
{
//stop conAsync() here
}
}
HubConn.close() solved the problem and it stops the conAsync() ..... i think the cancellation token is not the solution here (i was wrong) but it may be alternative one for another case.
To get used to and get trained using Backgroundworker for my Project, i used a sample code which runs smoothly except when it comes to handling error condition it doesn't allow me to use (e.Error!=null) facility of RunWorkerCompletedEventArgs e.I want to handle error like the way cancel and successful completion works for me.
Suggestions please!
Following is the code:
private void DoWork(object sender, DoWorkEventArgs e)
{
Random rand = new Random();
for (int i = 0; i < 10; i++)
{
if (this.backgroundWorker.CancellationPending)
{
e.Cancel = true;
break;
}
// report progress
this.backgroundWorker.ReportProgress(-1, string.Format("Performing step {0}...", i + 1));
// simulate operation step
System.Threading.Thread.Sleep(rand.Next(1000, 10000));
//setting simulateError to true after inducing error(a button)
if (this.simulateError)
{
this.simulateError = false;
//needs a code to use (e.Error!=null) in
RunWorkerCompleted().
//A jump to RunWorkerCompleted is required here.
}
}
}
private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// hide animation
this.pictureBox.Image = null;
// show result indication
if (e.Cancelled)
{
////works nice
this.labelProgress.Text = "Operation cancelled by the user!";
this.pictureBox.Image = Properties.Resources.WarningImage;
}
else
{
//doesn't execute at all....why?
if (e.Error != null)
{
this.labelProgress.Text = "Operation failed: " + e.Error.Message;
this.pictureBox.Image = Properties.Resources.ErrorImage;
}
else
{
//works nice
this.labelProgress.Text = "Operation finished successfuly!";
this.pictureBox.Image = Properties.Resources.InformationImage;
}
}
// restore button states
this.buttonStart.Enabled = true;
this.buttonCancel.Enabled = false;
this.buttonError.Enabled = false;
}
I induce error using simulateError ,for the purpose to show peculiar error message how should i use
if (e.Error != null)
{
this.labelProgress.Text = "Operation failed: " + e.Error.Message;
My Program isn't coming to private void RunWorkerCompleted(object sender, ,RunWorkerCompletedEventArgs e) in case of error. In other cases(cancellation,succesful completion) it executes right.
To get used to and get trained using Backgroundworker for my Project
Why would you do that? Task.Run() is better than BackgroundWorker in every way.
Now to your actual question: to cause an error in a BackgroundWorker, use the standard mechanism for that in .Net: exceptions:
if (this.simulateError)
{
this.simulateError = false;
throw new Exception("Simulating error.");
}
I want to synchronize my local and web database so i have written a stored procedure using linked server. My stored procedure executes fine and data synchronization is successful but the procedure takes around 7-10 minutes to get executed. The exact timing cannot be determined. So whenever the procedure runs on my windows application then the page seems as if it has become unresponsive though the process is still going on.
So i am having a "Data Sync" button on my page on click of which i want the progress bar to display the progress of the stored procedure. For the time being I am taking the average of last few execution timings to define the time duration for which the stored procedure runs. Now the problem is that when i click on the data sync button then the progress bar doesn't work. Kindly help me with this issue.
My code is as follows:-
namespace RMS
{
public partial class DataSync : Form
{
connection con = new connection();
SqlCommand cmd = new SqlCommand();
static int rowCount;
static int syncTime;
static int timeSlice;
public DataSync()
{
InitializeComponent();
}
private void btnDataSync_Click(object sender, EventArgs e)
{
// Start the asynchronous operation.
backgroundWorker1.RunWorkerAsync();
try
{
con.GetConnectLive();
con.GetConnect();
if (con.CnLive.State == ConnectionState.Open)
{
MessageBox.Show("Connection to Live Server Successful!!!...Data Synchronisation may take several minutes so do not cancel the operation while in execution mode");
btnDataSync.Enabled = false;
btnDataSync.Text = "Please Wait...";
string Str = "RMS_LocalToLive";
cmd = new SqlCommand(Str, con.Cn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandTimeout = 1200;
rowCount = cmd.ExecuteNonQuery();
if (rowCount > -1)
{
MessageBox.Show("Total no. of rows synchronised = " + rowCount);
btnDataSync.Text = "Success";
}
else
{
MessageBox.Show("Data Synchronisation couldn't be completed because of connection problem... Please try again!!!");
}
}
else
{
MessageBox.Show("Unable to connect to Live Server...Please check your internet connection and try again!!!");
}
con.GetDisConnect();
con.GetDisConnectLive();
}
catch (Exception ex)
{
MessageBox.Show("Please check your internet connection and try again!!!");
}
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
try
{
con.GetConnect();
string Str = "RMS_DataSyncTime";
cmd = new SqlCommand(Str, con.Cn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandTimeout = 1200;
syncTime = Convert.ToInt32(cmd.ExecuteScalar().ToString());
timeSlice = syncTime / 100;
con.GetDisConnect();
}
catch (Exception ex)
{
MessageBox.Show("Unable to retrieve last Data Synchronisation Timing");
}
for (int i = 1; i <= synctime; i=i+timeslice)
{
Thread.Sleep(timeslice);
// Report progress.
backgroundWorker1.ReportProgress(i);
}
}
private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// Change the value of the ProgressBar to the BackgroundWorker progress.
progressBar1.Value = e.ProgressPercentage;
// Set the text.
this.Text = e.ProgressPercentage.ToString() + "% Completed";
}
private void DataSync_Load(object sender, EventArgs e)
{
}
private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgse)
{
}
}
}
The main issue here is that, while you are executing your progress bar updates in the BackgroundWorker's thread, the ReportProgress() updates never make it to the UI thread, because you've blocked that thread with the main SQL operation.
Instead of doing that, you should do something more like this:
private void btnDataSync_Click(object sender, EventArgs e)
{
// Start the asynchronous operation.
backgroundWorker1.RunWorkerAsync();
btnDataSync.Enabled = false;
btnDataSync.Text = "Please Wait...";
bool success = false;
try
{
// Execute the query asynchronously
success = await Task.Run(() => ExecuteLocalToLive());
}
catch (Exception ex)
{
MessageBox.Show("Please check your internet connection and try again!!!");
}
btnDataSync.Enabled = true;
btnDataSync.Text = success ? "Success" : "Failure";
}
private bool ExecuteLocalToLive()
{
bool success = false;
con.GetConnectLive();
con.GetConnect();
if (con.CnLive.State == ConnectionState.Open)
{
MessageBox.Show("Connection to Live Server Successful!!!...Data Synchronisation may take several minutes so do not cancel the operation while in execution mode");
string Str = "RMS_LocalToLive";
cmd = new SqlCommand(Str, con.Cn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandTimeout = 1200;
rowCount = cmd.ExecuteNonQuery();
if (rowCount > -1)
{
MessageBox.Show("Total no. of rows synchronised = " + rowCount);
success = true;
}
else
{
MessageBox.Show("Data Synchronisation couldn't be completed because of connection problem... Please try again!!!");
}
}
else
{
MessageBox.Show("Unable to connect to Live Server...Please check your internet connection and try again!!!");
}
con.GetDisConnect();
con.GetDisConnectLive();
return success;
}
I have rearranged the code that handles the button state and text, so that it's still executed in the UI thread where it belongs, even though the method itself is not. You also never appeared to set the button back to the enabled state; it's not clear to me whether that was intentional or not, so I went ahead and added a line to do that.
Finally, I will strongly recommend you figure out a better way to report status to the user than the calls to MessageBox.Show() you have now. The biggest issue is that you don't even start doing any work until after the user dismisses the initial message, which immediately puts your progress bar out of sync with the actual work. But it's also better to keep all your UI in the UI thread, and to keep UI separate from non-UI logic (i.e. the SQL operation).
All, I have successfully used ADO.NET to make use of asynchronous SQL queries similar to the example below. In the example shown the method ExecNonQuery is being invoked from the UI thread. This works well, but I wondered how I would handle the callback if I were to call ExecNonQuery from a non-UI thread?
Note. Clearly, in such a case I would amend ExecNonQuery, so that such things as this.toolStripStatusLabel1.Text were dealt with accordingly, or removed.
public bool ExecNonQuery(string strCmd, string strUserMsg = "")
{
try
{
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.CommandText = strCmd;
cmd.CommandTimeout = 0;
bIsExecuting = true;
AsyncCallback callback = new AsyncCallback(HandleCallback);
cmd.BeginExecuteNonQuery(callback, cmd);
return true;
}
catch (Exception Ex)
{
bIsExecuting = false;
this.toolStripStatusLabel1.Text = String.Format("Ready (last error: {0})", Ex.Message);
if (conn != null)
conn.Close();
}
return false;
}
private delegate void DisplayInfoDelegate(string Text);
private void HandleCallback(IAsyncResult result)
{
try
{
// Retrieve the original command object, passed
// to this procedure in the AsyncState property
// of the IAsyncResult parameter.
SqlCommand command = (SqlCommand)result.AsyncState;
int rowCount = command.EndExecuteNonQuery(result);
string rowText = " rows affected.";
if (rowCount == 1)
rowText = " row affected.";
rowText = rowCount + rowText;
// Call the procedure from the form's thread.
DisplayInfoDelegate del = new DisplayInfoDelegate(DisplayResults);
this.Invoke(del, rowText);
}
catch (Exception ex)
{
// Because you are now running code in a separate thread,
// if you do not handle the exception here, none of your other
// code catches the exception.
// You can create the delegate instance as you
// invoke it, like this:
this.Invoke(new DisplayInfoDelegate(DisplayResults),
String.Format("Ready(last error: {0}", ex.Message));
}
finally
{
bIsExecuting = false;
if (conn != null)
conn.Close();
}
}
private void DisplayResults(string Text)
{
this.toolStripStatusLabel1.Text = Text;
this.toolStripProgressBar1.Style = ProgressBarStyle.Blocks;
this.toolStripProgressBar1.Value = 100;
}
Thanks for you time.
It makes no difference to your callback which thread runs ExecNonQuery - HandleCallback will still be run on a thread pool thread.
You have already spotted the change you need to make: don't access UI controls directly in ExecNonQuery if it is not being run on the UI thread.
Nick