Form Changing Before Other Commands Are Executed

Question

So I have this little bit of code here...

private void button1_Click(object sender, EventArgs e)
    {
        if (textBox2.Text==("Tim The Enchanter") && textBox1.Text==("cave100"))
        {
            label2.Visible = true;
            label2.Text = ("Correct");
            label2.ForeColor = System.Drawing.Color.Green;
            System.Threading.Thread.Sleep(1000);
            this.Hide();
            Form2 form2 = new Form2();
            form2.Visible = true;

        }
    }

It is basically a very primitive login screen!

Everything works except for the fact that the form changes to form2 before the label2 text can be seen. I tried to fix this by adding a system wait comand but instead this comes through before the text can be displayed. Once again I am back to where I started.

Any help would be appreciated!

score 4 · Accepted Answer · edited May 23 '17 at 11:58

Never use Thread.Sleep for waiting purposes in WinForms.
It blocks GUI thread and your label is not updated / seen by a user.

Of course, there are many workarounds to do it, you can read it here.

The easiest one is to use C# 5.0 async / await functionality:

private async void button1_Click(object sender, EventArgs e)
{
    if (textBox2.Text==("Tim The Enchanter") && textBox1.Text==("cave100"))
    {
        label2.Visible = true;
        label2.Text = ("Correct");
        label2.ForeColor = System.Drawing.Color.Green;
        await Task.Delay(1000);
        this.Hide();
        Form2 form2 = new Form2();
        form2.Visible = true;
    }
}

score 0 · Answer 2 · answered Jun 20 '16 at 04:11

You shouldn't call Thread.Sleep from the UI thread in winforms.

A click event handler needs to do its work and return quickly, because all the form drawing, responding to resize events, responding to user-input, etc is all happening on the same thread. This is the reason you don't see the form repaint itself - it doesn't get a chance, because you suspended the thread it would use to do that.

You need to do this in a more "event-driven" way. For example, you could add a Timer control to the form, with a timeout of 1000ms, and an Elapsed handler that shows/hides the forms.

Then your button handler just sets the timer Enabled to true, and exits.

Remember to stop the timer in the timer's event handler though!

score 0 · Answer 3 · answered Jun 20 '16 at 04:12

Try this:

private void button1_Click(object sender, EventArgs e)
    {
        if (textBox2.Text==("Tim The Enchanter") && textBox1.Text==("cave100"))
        {
            label2.Visible = true;
            label2.Text = ("Correct");
            label2.ForeColor = System.Drawing.Color.Green;

            new Timer{Enabled=true,Interval=100}.Tick += (s,e) =>
            {
              ((Timer)s).Dispose();
              this.Hide();
              Form2 form2 = new Form2();
              form2.Visible = true;
            }
        }
    }

It will give the OS a chance to make modifications to the UI before it shows the instance of Form2

Yeldar Kurmangaliyev's answer is probably the best, although my answer might be needed if you don't have C# 5.0. — Alastair Brown, Jun 20 '16 at 04:24

Form Changing Before Other Commands Are Executed

3 Answers3