NumericUpDown Control should fire ValueChanged Event only on scroll finished

Question

I have a numericUpDown control (Windows Forms).

I want to listen to the ValueChanged event.

I set it in the properties and it works.

But:

I want that i can "scroll" up or down. (If I make this longer it will be faster)

When I'm done with the "scroll", I want that the event xyz is fired now and not during the scrolling.

How can I do that?

Answer 1

Try using the mouseup event. It fires when you take your finger off of the left mouse button, so in theory it should solve your issue.

[Edited by James] Try this control on your form.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace Example.CustomControl
{
    /// <summary>
    /// Provides an extra event for the numericUpDown control that fires after the value stops scrolling.
    /// </summary>
    public class NumericDelayedChange : NumericUpDown
    {
        /// <summary>
        /// Flag that the value has actually changed.
        /// </summary>
        /// <devdoc>
        /// Just in case the control was clicked somewhere other than the up/down buttons.
        /// </devdoc>
        private bool valueHasChanged = false;

        /// <summary>
        /// Fires when the value has stopped being scrolled.
        /// </summary>
        public event EventHandler OnAfterScollValueChanged;

        /// <summary>
        /// Captures that value as having changed.
        /// </summary>
        /// <param name="e"></param>
        protected override void OnValueChanged(EventArgs e)
        {
            valueHasChanged = true;
            base.OnValueChanged(e);
        }

        /// <summary>
        /// Captures the mouse up event to identify scrolling stopped when used in combination with the value changed flag.
        /// </summary>
        /// <param name="mevent"></param>
        protected override void OnMouseUp(MouseEventArgs mevent)
        {
            base.OnMouseUp(mevent);
            if (mevent.Button == System.Windows.Forms.MouseButtons.Left)
            {
                PerformOnAfterScollValueChanged();
            }
        }

        /// <summary>
        /// Captures the key up/down events to identify scrolling stopped when used in combination with the value changed flag.
        /// </summary>
        /// <param name="mevent"></param>
        protected override void OnKeyUp(KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Up || e.KeyCode == Keys.Down)
            {
                PerformOnAfterScollValueChanged();
            }
            base.OnKeyUp(e);
        }

        /// <summary>
        /// Checks the value changed flag and fires the OnAfterScollValueChanged event.
        /// </summary>
        private void PerformOnAfterScollValueChanged()
        {
            if (valueHasChanged)
            {
                valueHasChanged = false;
                if (OnAfterScollValueChanged != null) { OnAfterScollValueChanged(this, new EventArgs()); }
            }
        }
    }
}

Answer 2

You need to define what is I'm done with the scroll. This could be removing the mouse from the scroll button, or a certain time passed since the last click. In any case, I don't think you can cause the event not to run, but you can do some checks in the event handler. For example:

private DateTime? lastClickTime;
public void MyUpDown_ValueChanged(object sender, EventArgs e)
{
    if (lastClickTime != null && DateTime.Now.Subtract(lastClickTime.Value).Seconds > someInterval)
    {
        // Do the work
    }

    lastClickTime = DateTime.Now
}

But, as I said, you need first to define what is I'm done. This code is not perfect.