how to restrict contiguous values in NumericUpDown component c#

Question

Greetings,

Using Visual Studio 2019. Have created a c# solution using WinForms.

I have a numericUpDown component on Form1. I have set the minimum property to 0 and the maximum property to 127. If I wanted to prevent number 7,11 and 31 from being selected by the user, how do I accomplish this ?

Thanks in advance.

Answer 1

Here is a custom NumericUpDown

• Has a list property for disallowed values
• Prevents copy from Windows Clipboard
• Several overrides to prevent disallowed values
• Prevent beep on pressing enter key
• Property to get decimal Value as int
• overrides for DownButton and UpButton refinements of KO

using System.ComponentModel;

namespace TODO;

public class SpecialNumericUpDown : NumericUpDown
{
    public SpecialNumericUpDown()
    {
        TextAlign = HorizontalAlignment.Right;
        DisallowValues = new List<decimal>();
    }

    [Browsable(false)] public int AsInteger => (int)Value;

    public delegate void TriggerDelegate();

    public event TriggerDelegate TriggerEvent;
    protected override void OnKeyDown(KeyEventArgs e)
    {
        if (e.KeyCode == Keys.Return)
        {
            e.Handled = true;
            e.SuppressKeyPress = true;

            TriggerEvent?.Invoke();

            return;
        }

        base.OnKeyDown(e);
    }

    [Category("Custom")]
    [Description("Values not permitted")]
    public List<decimal> DisallowValues { get; set; }

    [Browsable(false)]
    public bool IsValid => DisallowValues.Contains(Value) == false;

    protected override void OnKeyUp(KeyEventArgs e)
    {
        if (DisallowValues.Contains(Value))
        {
            Value++;
            return;
        }

        base.OnKeyUp(e);
    }

    protected override void OnMouseUp(MouseEventArgs mevent)
    {

        if (DisallowValues.Contains(Value))
        {
            Value++;
            return;
        }

        base.OnMouseUp(mevent);
    }

    public override void DownButton()
    {
        base.DownButton();
        if (DisallowValues.Contains(Value))
        {
            Value--;
        }
    }

    public override void UpButton()
    {
        base.UpButton();
        if (DisallowValues.Contains(Value))
        {
            Value++;
        }
    }

    // code to prevent paste from clipboard

    Handler _handler;
    protected override void OnHandleCreated(EventArgs e)
    {
        base.OnHandleCreated(e);
        _handler = new Handler(Controls[1]);
    }
    protected override void Dispose(bool disposing)
    {
        if (_handler != null)
            _handler.DestroyHandle();
        base.Dispose(disposing);
    }
    private class Handler : NativeWindow
    {
        Control _control;
        public Handler(Control control)
        {
            _control = control;
            AssignHandle(_control.Handle);
        }
        protected override void WndProc(ref Message m)
        {
            if (m.Msg != 0x0302 /*WM_PASTE*/)
            {
                base.WndProc(ref m);
            }
            else
            {
                System.Media.SystemSounds.Beep.Play();
            }
        }
    }
}

Disallow property in form designer

Answer 2

the easiest to use on change event, and the value is 7,11, or 31 update with the desired value (+1?). you can not do at the keystroke or the user could not enter 110, 112, ...

Answer 3

If you create a new control by inheriting NumericUpdown, you can prevent button selection.

public class NumericUpDownEx : NumericUpDown
{

    private readonly TextBox textBox;

    public NumericUpDownEx() {
        textBox = Controls.Cast<Control>().OfType<TextBox>().FirstOrDefault();
    }

    public override void DownButton() {
        base.DownButton();
        switch (Value) {
            case 7:
            case 11:
            case 31:
                Value--;
                break;
        }
    }

    public override void UpButton() {
        base.UpButton();
        switch (Value) {
            case 7:
            case 11:
            case 31:
                Value++;
                break;
        }
    }
}

Also, when inputting directly into the TextBox part, you can apply restrictions to the TextBox control extracted using the code above.

https://learn.microsoft.com/en-us/answers/questions/1377768/help-value-of-text-not-updating-on-keypress-event