Question

So often, I want the user to select a start date and a finish date. But just selecting date is not enough, we also have to alter the data.

By default, the DateTimePicker.Value are like

Value 1: 2012-01-01 10:12:09
Value 2: 2012-01-02 10:12:09

When the user selects two dates, it should be obvious that he meant

Value 1: 2012-01-01 00:00:00
Value 2: 2012-01-02 23:59:59

I often forget to do the non-intuitive

DateTime start = dateTimePicker1.Value.Date;
DateTime finish = dateTimePicker2.Value.Date.AddDays(1).AddSeconds(-1);

What more effective way of dealing with this have you found?

Answer 1

If you use DateTimePicker objects lke this a lot, you could possible create two small custom classes: a StartDateTimePicker and an EndDateTimePicker. Each class would derive from DateTimePicker, and would simply have a boolean and an EventHandler on the OnValueChanged event. The event would be used to adjust the value after it is set, and the boolean would be used to implement the Balking Pattern. Here’s an example of the StartDateTimePicker:

public class StartDateTimePicker : DateTimePicker
{
    bool handling = false;

    // Note: 
    public StartDateTimePicker()
        : base()
    {
        // This could be simplified to a lambda expression
        this.ValueChanged += new EventHandler(StartDateTimePicker_ValueChanged);
    }

    void StartDateTimePicker_ValueChanged(object sender, EventArgs e)
    {
        // If the value is being changed by this event, don't change it again
        if (handling)
        {
            return;
        }
        try
        {
            handling = true;
            // Add your DateTime adjustment logic here:
            Value = Value.Date;
        }
        finally
        {
            handling = false;
        }
    }
}

You would then simply use these in place of your normal DateTimePicker objects and you would not have to worry about making sure that the dates are appropriately adjusted anymore.

It would cost you the time to write the EndDateTimePicker class (the above is already a fully functional StartDateTimePicker), but it would make things easier down the road as you use these in more places.