Winfoms Label appears on Form with no text.

Question

I have a Winforms App in C# using VS 2022.

I have a Form1 that has a Label control on it and associated OpenFileDialog control.

In the code below, I put Text into the Label, Refresh the Label, Refresh the Form, cause the form to Show, Sleep for 5 secs, then cause the OpenFileDialog to pop up.

During the 5 sec Sleep, the Form and Label show up, but the label background is white with no text. The OpenFileDialog appears. Once the OpenFileDialog closes, the Form appears with the correct text in Black,

How can I make the Form with the Label, with the correct Text in Black appear before the 5-sec delay?

public Form1()
{
    InitializeComponent();
    label1.Text= "Please select file to Encrypt or Decrypt.";
    label1.Invalidate();
    label1.Refresh();
    this.Invalidate();
    this.Refresh();
    this.Show();
    Thread.Sleep(5000);
    openFileDialog1.ShowDialog();
}

Answer 1

It's time to learn a bit about async/await. Instead of calling Thread.Sleep which blocks the UI thread, you can use await Task.Delay. For example, assuming you have the using statement:

using System.Threading.Tasks;

Then put the loading code, in the Load event handler, like this:

private async void Form1_Load(object sender, EventArgs e)
{
    textBox1.Text = "Something ...";
    await Task.Delay(5000);
    MessageBox.Show("After 5 seconds!");
}

Here you do not need to call refresh or update or invalidate, and you do not need it in constructor. Just remember to handle the load event (assign the event handler using designer or using code).

Learn more

• Async/Await - Best Practices in Asynchronous Programming
• Asynchronous programming with async and await
• Task asynchronous programming model
• Show loading animation and loading data in another thread using a task

Answer 2

Don't use Sleep in the constructor

If you want to display an OpenFileDialog after 5 seconds, you can use a Timer, like in the MSDN sample

Answer 3

Hi

using System;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace DesktopAppasync
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
       
        private void button1_Click(object sender, EventArgs e)
        {
            MessageBox.Show("Thanks!");
        }
        private async void Form1_LoadAsync(object sender, EventArgs e)
        {
            textBox1.Text = "Do Something ...";
            await Task.Delay(5000);
            MessageBox.Show("After 5 seconds!");
        }
    }
}