Question

private void dateTimePicker1_ValueChanged(object sender, Series myseries, int multiplier, EventArgs e)
{
  if (datelimitsset == 1) {
    var dt1 = dateTimePicker1.Value;
    chart1.Series.Clear();

    for (int i = 0; i < multiplier; i++)
    {
      config();
      myseries.Points.AddXY(Convert.ToString(date[i]), Convert.ToDouble(array[i]));
      string[] rowi = { Convert.ToString(date[i]), Convert.ToString(array[i]) };
      dataGridView1.Rows.Add(rowi);
    }
  }
}

This is giving me the error:

No overload for ‘dateTimePicker1_ValueChanged’ matches delegate ‘System.EventHandler’

I do not fully understand event handlers, can anyone give me advice?

Answer 1

It’s because your handler must have the same signature specified by the EventHandler delegate.

That is, you’ll have to remove your two middle parameters:

private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
{
}

In terms of a workaround for passing these parameters into the function, you have a few options…

1. Generate the event handler as an anonymous function (as per James’ answer)
2. Store and retrieve them from instance variables
3. Store them on the DateTimePicker control’s Tag property and resolve them in the handler

The second option should be obvious enough…

The third option might look like:

// In control initialization somewhere
dateTimePicker1.Tag = new DateTimePickerParams() { Series = myseries, Multiplier = multiplier }; // Where DateTimePickerParams is your own private class/struct defined explicitly for this purpose...

private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
{
    var ctl = sender as DateTimePicker;
    var parameters = ctl.Tag as DateTimePickerParams;

    var mySeries = parameters.Series;
    var multiplier = parameters.Multiplier;

    // Execute...
}