用到了控件的 KeyPress 和 KeyUp事件。

KeyPress 中控制输入“点、空格，负号”；

KeyUp 中防止删空，以及防止输入超过最大值或最小值 。

        private void nudStart_KeyPress(object sender, KeyPressEventArgs e)
        {
            numericUpDownKeyPress(sender, e);
        }

        private void nudStart_KeyUp(object sender, KeyEventArgs e)
        {
            numericUpDownKeyUp(nudStart, sender, e);
        }

        private void numericUpDownKeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar == '.')
            {
                e.Handled = true;
            }
            else if (e.KeyChar == '-')
            {
                e.Handled = true;
            }
            else if (e.KeyChar == ' ')
            {
                e.Handled = true;
            }
        }

        private void numericUpDownKeyUp(NumericUpDown numericUpDown, object sender, KeyEventArgs e)
        {
            UpDownBase UpDowns = (UpDownBase)numericUpDown;
            if (UpDowns.Text == "")
            {
                numericUpDown.Text = numericUpDown.Value.ToString();
            }
            else
            {
                int value = Convert.ToInt32(UpDowns.Text);
                if (value > numericUpDown.Maximum)
                {
                    value = Convert.ToInt32(numericUpDown.Maximum);
                    numericUpDown.Value = value;
                    numericUpDown.Text = numericUpDown.Value.ToString();
                }
                else if (value < numericUpDown.Minimum)
                {
                    value = Convert.ToInt32(numericUpDown.Minimum);
                    numericUpDown.Value = value;
                    numericUpDown.Text = numericUpDown.Value.ToString();
                }
            }
        }