In my c# app, I pass a string variable that is of format yyyymmdd-yyyymmdd that represents a from and to date. I want to get the start and end times for these dates respectively. Currently I have the below code but was wondering if there was more of an elegant solution?

So for pdr = 20090521-20090523 would get "20090521 00:00:00" and "20090523 23:59:59"

private void ValidateDatePeriod(string pdr, out DateTime startDate,
                                out DateTime endDate)
{
    string[] dates = pdr.Split('-');

    if (dates.Length != 2)
    {
        throw new Exception("Date period is of incorrect format");
    }

    if (dates[0].Length != 8 || dates[1].Length != 8)
    {
        throw new Exception("Split date periods are of incorrect format");
    }

    startDate = DateTime.ParseExact(dates[0] + " 00:00:00",
        "yyyyMMdd HH:mm:ss", null);
    endDate = DateTime.ParseExact(dates[1] + "23:59:59",
        "yyyyMMdd HH::mm:ss", null);
}

If you are only worried about .Net precision...

startDate = DateTime.ParseExact(dates[0], "yyyyMMdd");
endDate = DateTime.ParseExact(dates[1], "yyyyMMdd").AddTicks(-1).AddDays(1);

You really don't need to concatenate extra values onto the string for the time portion.

As an addendum, if you are using this for a query against, for example, a database...

startDate = DateTime.ParseExact(dates[0], "yyyyMMdd");
endDate = DateTime.ParseExact(dates[1], "yyyyMMdd").AddDays(1);

With a query of...

WHERE "startDate" >= @startDate AND "endDate" < @endDate

Then the precision issues noted in the comments won't really matter. The endDate in this case would not be part of the range, but the outside boundary.