Textbox delay events

Question

I have an option form where the user has to enter parameters for a mini-game, going from 8 to 32. My problem is that as soon as I start typing, if I insert a number under 8 (I want to put 20, for example), the event activates as soon as I type 2 and turn it into 8.

private void TXBheight_TextChanged(object sender, EventArgs e)
    {

        if(int.Parse(TXBheight.Text) < 8)
        {
            TXBheight.Text = "8";
        }
        else if (int.Parse(TXBheight.Text) > 32)
        {
            TXBheight.Text = "32";
        }
    }

Is there any easy way to make a delay, or wait until I finish typing?

For those who identify this question as a possible duplicate, i took a look, and the possible answers are from 6 years ago. During that time, languages and compilers evolve, so maybe there is something new we can all learn from

Answer 1

Instead of using a TextChanged event, use the TextBox _Validating event and the _Validated event. The _Validating event is fired only when the text box loses focus, i.e., when the user clicks on another control, e.g., a Button or another TextBox. When this happens, the _Validating event is fired and you test the value in the text box. If it's invalid, you cancel the _Validating event. If its valid, you DON'T cancel the _Validating event, and as a a result the _Validated event is fired. In the _Validated event, you do what you neeed to do when the input data is valid. Use an errorprovider to inform the user when the input data is invalid.

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        errorProvider1.SetError(TXBheight, "");

        //NEW NEW NEW
        buttonCancel.CausesValidation = false;
    }

    private void Button1_Click(object sender, EventArgs e)
    {
        // do what is needed when the button is clicked
    }

    private void TXBheight_Validating(object sender, CancelEventArgs e)
    {

        errorProvider1.SetError(TXBheight, "");

        if (String.IsNullOrEmpty(TXBheight.Text))
        {
            errorProvider1.SetError(TXBheight, "Height is a required field");
            e.Cancel = true;
            return;
        }

        if (int.Parse(TXBheight.Text) < 8)
        {
            errorProvider1.SetError(TXBheight, "Height must be GE 8");
            e.Cancel = true;
            return;
        }

        if (int.Parse(TXBheight.Text) > 32)
        {
            errorProvider1.SetError(TXBheight, "Height must be LE 32");
            e.Cancel = true;
            return;
        }

    }

    private void TXBheight_Validated(object sender, EventArgs e)
    {
        //this event is fired when the data is valid, i.e., 
        // if e.Cancel in the _Validating method is NOT set to cancel

    }

    //NEW NEW NEW
    private void ButtonCancel_Click(object sender, EventArgs e)
    {
        AutoValidate = AutoValidate.Disable;
        Close();
    }

    // NEW #2

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        if (e.CloseReason == CloseReason.UserClosing)
        {
            DialogResult result = MessageBox.Show("Do you really want to exit?", "Dialog Title", MessageBoxButtons.YesNo);
            if (result == DialogResult.Yes)
            {
                Environment.Exit(0);
            }
            else
            {
                e.Cancel = true;
            }
        }
        else
        {
            e.Cancel = true;
        }
    }
}

Answer 2

The simple answer is: (C# 7 style)

public partial class Form1 : Form
{
  public Form1()
  {
    InitializeComponent();
    this.textBox1.TextChanged += TextBox1_TextChanged;
    this.textBox1.Leave += TextBox1_Leave;
  }

  private void TextBox1_TextChanged(object sender, EventArgs e)
  {
    string text = this.textBox1.Text;
    if (!int.TryParse(text, NumberStyles.Integer, CultureInfo.CurrentCulture, out int number))
    {
      this.textBox1.Text = "";
      return;
    }

    if (number > 32)
    {
      this.textBox1.Text = "32";
    }
  }

  private void TextBox1_Leave(object sender, EventArgs e)
  {
    string text = this.textBox1.Text;
    if (!int.TryParse(text, NumberStyles.Integer, CultureInfo.CurrentCulture, out int number))
    {
      this.textBox1.Text = "8";
      return;
    }

    if (number > 32)
    {
      this.textBox1.Text = "32";
    }

    if (number < 8)
    {
      this.textBox1.Text = "8";
    }
  }

I standardly do this with controlling the pressed keys and text changes (inclusive paste) to check correct content of the window. Unfortunately I have the code only for Borland C++ Builder and VS6 at work. Recreating this code is not that simple (too much code), therefore only the simple answer.

Answer 3

Use Microsoft's Reactive Framework and this becomes easy. Just do this:

private void Form1_Load(object sender, EventArgs e)
{
    IObservable<long> query =
        Observable
            .FromEventPattern<EventHandler, EventArgs>(
                h => TXBheight.TextChanged += h,
                h => TXBheight.TextChanged -= h)
            .Select(x => Observable.Timer(TimeSpan.FromMilliseconds(250.0)))
            .Switch()
            .ObserveOn(this);

    IDisposable subscription = query.Subscribe(ep =>
    {
        if (int.Parse(TXBheight.Text) < 8)
        {
            TXBheight.Text = "8";
        }
        else if (int.Parse(TXBheight.Text) > 32)
        {
            TXBheight.Text = "32";
        }
    });
}

Now there is a 250.0 millisecond delay after the last character is typed before your code runs. If a new character is typed before the 250.0 milliseconds is up then a new timer starts and the old one doesn't fire.

The .ObserveOn(this) code marshalls the timer back to the UI thread.

Just NuGet "System.Reactive" and "System.Reactive.Windows.Forms". Also add using System.Reactive.Linq; at the top of your class.

Answer 4

You can use the return as your breakpoint, when the user hit enter then you run your code.

You can use that with the KeypressEvent.

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    char ch = e.KeyChar; // Getting the Key that was pressed

    if (ch == 13) // Checking if it equal to 13 ASCII code for return 
    {
        if (int.Parse(textBox1.Text) < 8)
        {
            textBox1.Text = ""; // emptying the textbox
            textBox1.AppendText("8"); // using AppendText() to keep the cursor at the end
        }
        else if (int.Parse(textBox1.Text) > 32)
        {
            textBox1.Text = "";
            textBox1.AppendText("32");
        }
        e.Handled = true; // To say that the event was handled.
    }
}

Answer 5

Why not create task and check if it is completed before executing?

private Task task; //declare it at the top

private void TXBheight_TextChanged(object sender, EventArgs e)
{
   if(task?.Status == TaskStatus.Running) return;

   task =  Task.Run( () =>
   {
        if(int.Parse(TXBheight.Text) < 8)
        {
            TXBheight.Text = "8";
        }
        else if (int.Parse(TXBheight.Text) > 32)
        {
            TXBheight.Text = "32";
        } 
   });
}