CODEWITHSUNDEEP
c#multithreading
m1m6
m1m6

Reputation: 69

InvalidCastException when using webbrowser and threads in c#

when i trying to use webBrowser component inside the backgroundWorker.DoWork function , i got this exception :

System.InvalidCastException was unhandled by user code

https://i.sstatic.net/EJFT3.jpg

here's my code :

void m_oWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        //NOTE : Never play with the UI thread here...
        string line;

        //time consuming operation
        while ((line=sr.ReadLine()) != null ){

            int index = line.IndexOf(":");
            HtmlDocument doc = web.Document;
            Thread.Sleep(1000);
            m_oWorker.ReportProgress(cnt);

            //If cancel button was pressed while the execution is in progress
            //Change the state from cancellation ---> cancel'ed
            if (m_oWorker.CancellationPending)
            {
                e.Cancel = true;
                m_oWorker.ReportProgress(0);
                return;
            }

            cnt++;
        }

        //Report 100% completion on operation completed
        m_oWorker.ReportProgress(100);
    }

or is their another way to use thread in c# ?

cause when i use Thread.sleep method in the main the gui freezes !!

Upvotes: 1

Views: 714

Answers (1)

Idle_Mind
Idle_Mind

Reputation: 39122

The WebBrowser doesn't like being accessed from other threads. Try passing it in to RunWorkerAsync() like this:

    private void button1_Click(object sender, EventArgs e)
    {
        HtmlDocument doc = web.Document;
        m_oWorker.RunWorkerAsync(doc);
    }

    void m_oWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        HtmlDocument doc = (HtmlDocument)e.Argument;

        //NOTE : Never play with the UI thread here...
        string line;

        //time consuming operation
        while ((line = sr.ReadLine()) != null)
        {
            int index = line.IndexOf(":");

            Thread.Sleep(1000);
            m_oWorker.ReportProgress(cnt);

            //If cancel button was pressed while the execution is in progress
            //Change the state from cancellation ---> cancel'ed
            if (m_oWorker.CancellationPending)
            {
                e.Cancel = true;
                m_oWorker.ReportProgress(0);
                return;
            }

            cnt++;
        }

        //Report 100% completion on operation completed
        m_oWorker.ReportProgress(100);
    }

Upvotes: 1

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