Question

I’ve got a NumericUpDown control, and I want the value inside a seperate textbox to decrease or increase depending on which input the user inputes (up or down)

What event or code do I use to accomplish this?
I tried this but got an error while running

“Unable to cast object of type ‘System.Windows.Forms.NumericUpDown’ to type ‘System.IConvertible’.

  int UpDownNum;
  int NumBank;
  int TV = 0
  private void UpDown1_MouseUp(object sender, MouseEventArgs e)
    {
        UpDownNum = (Convert.ToInt32(UpDown1));
        NumBank = (Convert.ToInt32(NumTextbox.Text));

        TV = NumBank - UpDownNum;
        NumTextbox.Text = (Convert.ToString(TV));

Am I doing the wrong event? or is it some other problem?

Answer 1

The exception is caused by casting the NumericUpdown control to an integer. That doesn’t work. You need to use the NumericUpdown.Value property.

I assume that it’s the ValueChanged event that you’re looking for:

private decimal oldValue = 0;

private void numericUpDown1_ValueChanged(object sender, EventArgs e)
{
    NumericUpDown UpDown1 = (NumericUpDown)sender;
    decimal diff = UpDown1.Value - oldValue;
    oldValue = UpDown1.Value;
    int numBank = int.Parse(NumTextBox.Text);
    decimal newValue = numBank + diff;
    NumTextBox.Text = newValue.ToString();
}

Edit:

The only way i know to get the difference between the old and the new value of a NumericUpDown value is to save the old value manually(for example in a member variable) and change it in ValueChanged after you’ve calculated the difference (see edited code above).