/// <summary>
/// Create a CronExpression object from a Cron string.
/// Cron strings are in the format of "MINUTE HOUR DAY MONTH".
/// Each segment of the Cron string can be either an asterisk (*), a number (ex. "30") or multiple numbers (ex. "0,30")
/// Example: The Cron string "0,30 * * *" will execute, when the minute mark hits either 0 or 30. The rest of the segments are redundant.
/// <param name="cronString">The input Cron string.</param>
/// </summary>
public CronExpression(string cronString)
{
if (!CronUtilities.IsExpressionStringValid(cronString))
{
throw new System.Exception("Cron expression string is invalid.");
}
string[] expressionSegments = cronString.Split(' ');
this.minute = expressionSegments[0];
this.hour = expressionSegments[1];
this.day = expressionSegments[2];
this.month = expressionSegments[3];
}
/// <summary>
/// Returns a DateTime object, with the next time the Cron is expected to execute.
/// </summary>
public DateTime GetNextRunTime()
{
string expressionString = GetCronExpressionString();
DateTime now = DateTime.Now;
if (!CronUtilities.IsExpressionStringValid(expressionString))
{
throw new System.Exception("Cron expression string is invalid.");
}
// Set the Seconds-value to 0, so the Cron will execute when the minute mark gets reached.
now = now.AddSeconds(-now.Second);
// If the Cron expression is set to run every minute,
// return the current time, plus a minute.
if (expressionString == "* * * *")
{
return(now.AddMinutes(1));
}
if (minute != "*")
{
while (now.Minute != Convert.ToInt32(minute))
{
now = now.AddMinutes(1);
}
}
if (hour != "*")
{
while (now.Hour != Convert.ToInt32(hour))
{
now = now.AddHours(1);
}
}
if (day != "*")
{
while (now.Day != Convert.ToInt32(day))
{
now = now.AddDays(1);
}
}
if (month != "*")
{
while (now.Month != Convert.ToInt32(month))
{
now = now.AddMonths(1);
}
}
return(now);
}
