CODEWITHSUNDEEP
c#multithreadingwinforms
user4671342
user4671342

Reputation:

Showing/hiding label by another thread

Someting doesn't work in my code so I wanted to ask if someone can help me. I have this so far:

private void searchList_TextChanged(object sender, EventArgs e)
    {
            Thread th = new Thread(new ThreadStart(setLabel));
            th.IsBackground = true;
            th.Start();

            //some code that needs time
  if (searchBox.Text == String.Empty)
        {
            listViewType.Items.Clear();
            fillListView();
        }

        else
        {

            listViewType.Items.Clear();
            var matchings = stringTypes.FindAll(delegate(string s) { return s.StartsWith(searchBox.Text); });

            for (int i = 0; i < matchings.Count; i++)
            {
                ListViewItem storeMatched = new ListViewItem(matchings[i]);
                storeMatched.SubItems.Add(matchings[i]);
                listViewType.Items.Add(storeMatched);

            }

            th.Abort();
            searchLabel.Visible = false;
}

     private void setLabel()
    {
        MethodInvoker set = () => searchLabel.Visible = true;
        searchLabel.BeginInvoke(set);
    }

So searchLabel is a label that I want to show/hide. I tried here to show the label before the operation begins and hide it after it finished. Somehow it gets shown AFTER the code was executed (//some code that needs time) and then stays visible. How to code that correctly?

Upvotes: 0

Views: 1412

Answers (2)

Steve Drake
Steve Drake

Reputation: 2048

You are doing work on the UI thread

Your

//some code that needs time

Will hang the UI thread so will not re-draw, you should use the new async / await stuff

Task.Run might not be right for your case but I would need to understand the 'some code' more.

private async void searchList_TextChanged(object sender, EventArgs e)
{
    searchLabel.Visible = true;

    await Task.Run(() =>
    {
        // code that needs time 
    });

    // simulate
    await Task.Delay(5000);

    searchLabel.Visible = false;
}

Upvotes: 1

Szer
Szer

Reputation: 3476

private void searchList_TextChanged(object sender, EventArgs e)
{
    searchLabel.Visible = false;
    backgroundWorker.RunWorkerAsync();
}

private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
    //some code that needs time
    Thread.Sleep(1000);
}

private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    SetLabelVisible(true);
}

private delegate void SetLabelVisibleDelegate(bool status);

private void SetLabelVisible(bool status)
{
    if (searchLabel.InvokeRequired)
        searchLabel.Invoke(new SetLabelVisibleDelegate(SetLabelVisible), status);
    else
        searchLabel.Visible = status;
}

Upvotes: 2

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