CODEWITHSUNDEEP
c#multithreadingbackgroundworker
Jed I
Jed I

Reputation: 1018

progressbar not progressing using backgroundworker

I am using a background worker to update some tables in sqlserver. the progressbar max is getting set to the correct value, the progressbar value is being incremented, the backgroundworker progresschanged is being called correctly with correct value, yet the bar is not progressing.

here is the code for the form in the background_dowork method there is a loop which calls updateProgressBarValue which works with correct values.

public InterfaceConvertLonLat()
{
    InitializeComponent();
    Shown += new EventHandler(Form1_Shown);
    backgroundWorker1.WorkerReportsProgress = true;
    backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
    backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
}

public void ConvertLonLat_Load(object sender, EventArgs e)
{ 
}

public void updateProgressBarValue()
{
    progressBar1.Value++;
    backgroundWorker1.ReportProgress(progressBar1.Value);
}

public void setProgressBarMax(int max)
{
    progressBar1.Maximum = max;
    MessageBox.Show("setprogressbarmax " + max);
}

public void Form1_Shown(object sender, EventArgs e)
{     
    backgroundWorker1.RunWorkerAsync();
}

public void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    convert.OSGB36ToWGS84("paf");
}

public void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    progressBar1.Value = e.ProgressPercentage;
}

here is the loop contained in another class which calls updateprogressbarvalue, this is being fired and as stated backgroundworker1_progressChanged is being fired but the bar is not moving.

con.setProgressBarMax(address.Tables[0].Rows.Count); 

foreach (DataRow LonLat in address.Tables[0].Rows)
{
    con.updateProgressBarValue();
    Double lon = 0;
    Double lat = 0;
    lat = Convert.ToDouble(LonLat["LTO"]);
    lon = Convert.ToDouble(LonLat["LGO"]);
    LocalToWGS84(ref lat, ref lon, OGB_M);

    cmd1.Parameters["@LTW"].Value = lat;
    cmd1.Parameters["@LGW"].Value = lon;

    string dbQuery1 = "update " + tableName + " set LTW = @LTW, LGW = @LGW";

    cmd1.CommandText = (dbQuery1);
    cmd1.CommandType = CommandType.Text;
    cmd1.Connection = conn;
    cmd1.ExecuteNonQuery();
}
}
catch (Exception e)
{
    MessageBox.Show("error converting: " + e.Message);
}
finally
{
    conn.Close();
}

Upvotes: 1

Views: 6087

Answers (5)

Charan Gourishetty
Charan Gourishetty

Reputation: 109

private void Form1_Load(object sender, System.EventArgs e)
{
    // Start the BackgroundWorker.
    backgroundWorker1.RunWorkerAsync();
}

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    for (int i = 1; i <= 100; i++)
    {
    // Wait 100 milliseconds.
    Thread.Sleep(100);
    // Report progress.
    backgroundWorker1.ReportProgress(i);
    }
}

private void backgroundWorker1_ProgressChanged(object sender, progress e)
{
    // Change the value of the ProgressBar to the BackgroundWorker progress.
    progressBar1.Value = e.ProgressPercentage;
    // Set the text.
    this.Text = e.ProgressPercentage.ToString();
}

Upvotes: 0

Henk Holterman
Henk Holterman

Reputation: 273244

The following is seriously wrong:

public void updateProgressBarValue()
{
    progressBar1.Value++;   // not thread-safe
    backgroundWorker1.ReportProgress(progressBar1.Value);

}

ReportProgress() is intended to be called form DoWork, it should not even read a Control property.
You should maintain a counter in the foreach loop and feed that to the progress mechanism.

Now this does not directly indicate why it doesn't move but you do not have a Completed handler. Are you sure the process finishes at all?

If an exception escapes your DoWork you will never know what happened.

Upvotes: 1

Basic
Basic

Reputation: 26766

You've got a number of issues - Your UpdateprogressBarValue() just increases the value of the progress bar but doesn't keep track of how many times its been called / what the current value is - so if you call it 101 times (assuming a range of 0-100), you'll get an OutOfRangeException

Your DoWork() method doesn't seem to call the update at all (either directly or by raising an event).

You can use events to do this but you're better off using delegates or perhaps anonymous functions. Something like...

public void setProgress(int value) {
    progressBar1.invoke(delegate{ progressBar1.Value = value; }
}

then just call setProgress(0) through setProgress(progressBar1.MaxValue) from your DoWork() method

Upvotes: 1

InContext
InContext

Reputation: 2501

When reporting progress you need to fire an event from the background worker to tell the progressbar it needs updating. This can be done using the below:

backgroundWorker1.ReportProgress(10);

Change the value to what you need to demonstrate increased progress in your code. The progress changed event will mostly run on the same thread as your GUI so you should have no cross thread issues. One exception is if your form is being called from Excel via addin in which case Excel will be on the main thread.

Upvotes: 2

Christoffer
Christoffer

Reputation: 2125

I think this might be caused by the fact that the UI in windows forms is running in its own thread/context. In this case you probably need to use Invoke to make adjustments to the UI.

Something like this:

public void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    Invoke(new ProgressDelegate(UpdateProgress), e.ProgressPercentage);
}

delegate void ProgressDelegate(decimal value);

private void UpdateProgress(decimal value)
{
    progressBar1.Value = value;
}

Upvotes: -2

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