Determine If Changed Event Occurred from User Input Or Not

Question

In C#, the Changed event for a control (say, a numericupdown) gets fired whether the value was change directly by the user or if it was changed programatically as the result of some other event.

Is there a way to determine whether the event occurred as a result of user input? For example, both manually changing the value of numericUpDown1 and clicking on button1 will display "value changed". What if I only wanted to display "value changed" if it was changed through the user clicking on the up/down arrows in the control and not as a result of clicking on button1?

    private void numericUpDown1_ValueChanged(object sender, EventArgs e)
    {
        MessageBox.Show("value changed");
    }

    private void button1_Click_1(object sender, EventArgs e)
    {
        numericUpDown1.Value = 3;
    }

Answer 1

No, there is no built-in way to do what you are trying to do as the code to trigger the event is firing when the value changes.

Answer 2

There is no nice way to do it. You can find workarounds for specific cases, e.g.

• listen to MouseDown or something instead of valueChanged on the numeric drop down.

• Set a flag in button click event handler that will prohibit the message box from showing.

  In general you should try to organize your form in a way that it doesn't matter where the value got changed.

Answer 3

You could check to see if the numericUpDown is the ActiveControl. When you set the value of the numericUpDown during the button click, button1 should be the ActiveControl. When the user changes the value via the numericUpDown, then the numericUpDown should be the ActiveControl.

if(numericUpDown1 == this.ActiveControl)
{
    MessageBox.Show("value changed");
}