进度栏无法正常工作

Question

I just tried to write code for a progress bar with webclient Please see my code.

 private void button2_Click(object sender, EventArgs e)
    {
        if (textBox1.Text == "")
        {
            MessageBox.Show("Invalid Php Url");
        }
        else if (Uri.IsWellFormedUriString(textBox1.Text, UriKind.Absolute) == false)
        {
            MessageBox.Show("Invalid Php Url");
        }
        else
        {

            backgroundWorker1.RunWorkerAsync();

        }
    }

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        WebClient client = new WebClient();
        client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgressCallback);
        client.DownloadFileCompleted += new AsyncCompletedEventHandler(DownloadFileCallBack2);
        client.DownloadFile(textBox1.Text, @"D:\test\test.zip");

    }

    void DownloadProgressCallback(object sender, DownloadProgressChangedEventArgs e)
    {
        this.progressBar1.Value = e.ProgressPercentage;
        this.label6.Text = e.ProgressPercentage.ToString();
    }

    void DownloadFileCallBack2(object sender, AsyncCompletedEventArgs c)
    {
        MessageBox.Show("Download Completed");
    }

But the event is not calling why? is this because of the background worker or any other issues?

Please help me.

Best regards,

Answer 1

I think it is because the progress updated is called on a background thread and not the UI thread. Try passing in the webclient to the DoWork thread:

WebClient client = new WebClient(); 
client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgressCallback); 
client.DownloadFileCompleted += new AsyncCompletedEventHandler(DownloadFileCallBack2);
backgroundWorker1.RunWorkerAsync(client); 


private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)   
{   
    WebClient client = (WebClient)e.Argument;   
    client.DownloadFile(textBox1.Text, @"D:\test\test.zip");   

}   

Answer 2

Your Progress Bar must be of the following conditions :

-Accurate -Responsive and smooth -Precise -Appropriate