Problem With MultiThreading

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Hi, I'm developing a database software. I have many forms there and I also have a class and a method to retrieve data from database into ListView. So, I don't need to write methods anymore when I need to fill ListView with data. Here I'm using multi threads to avoid "Not Responding Program" when getting huge data. Unfortunately, this method has an error "cross-thread operation not valid accessed from a thread other than the thread it was created on"

C#

public class DatabaseListView
{
    bmtfunc.Databases d = new Databases();

    Int32 listViewRow = 0;
    Int32 listViewCol = 0;

    DataTable dataTable = new DataTable();

    //retrieving data to Listview
    public void RetrieveToListView(string SqlQuery, ListView Lv)
    {
        d.RetrieveToDataTable(SqlQuery, dataTable);

        ParameterizedThreadStart paramThread = delegate { this.ListViewRows(SqlQuery, Lv); };
        new Thread(paramThread).Start();

        //new Thread(new ParameterizedThreadStart(this.ListViewRows)).Start(SqlQuery);

    }

    private void ListViewRows(object SqlQuery, ListView listView)
    {
        if (dataTable.Rows.Count < 1)
            return;

        if (listView.InvokeRequired)
            listView.Invoke(new MethodInvoker(delegate { ListViewRows(SqlQuery, listView); }));

        for (listViewRow = 0; listViewRow < dataTable.Rows.Count -1; listViewRow++) //loop for rows
        {

            Thread.Sleep(50);
            ListViewItem listViewItem = listView.Items.Add(dataTable.Rows[listViewRow][0].ToString());
            for (listViewCol = 1; listViewCol < dataTable.Columns.Count; listViewCol++) //loop for columns
                listViewItem.SubItems.Add(dataTable.Rows[listViewRow][listViewCol].ToString());
        }

    }
}

Help me correct my code, please. Thanks in advance.

Posted 6-May-12 8:46am

derodevil

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OriginalGriff · Accepted Answer · 2012-05-06T08:52:00

You can only access GUI objects from the thread they were created on - if you try to access them from a different thread, you get the cross-thread error you are talking about. So you have correctly checked for invoke, and invoked if you need it.

Unfortunately, the same goes for creating controls - they can only be created on the UI thread.
So, try adding an else condition:

C#

private void ListViewRows(object SqlQuery, ListView listView)
{
    if (dataTable.Rows.Count < 1)
        return;

    if (listView.InvokeRequired)
        listView.Invoke(new MethodInvoker(delegate { ListViewRows(SqlQuery, listView); }));
    else
    {
        for (listViewRow = 0; listViewRow < dataTable.Rows.Count -1; listViewRow++) //loop for rows
        {
            Thread.Sleep(50);
            ListViewItem listViewItem = listView.Items.Add(dataTable.Rows[listViewRow][0].ToString());
            for (listViewCol = 1; listViewCol < dataTable.Columns.Count; listViewCol++) //loop for columns
                listViewItem.SubItems.Add(dataTable.Rows[listViewRow][listViewCol].ToString());
        }
    }
}