I am trying to understand what is happening with this code. I have two threads iterating over a range, and I'm trying to figure out what happens when the second thread calls GetEnumerator (). This line, in particular (T current = start;), seems to spawn a new "instance" in this method by the second thread.
Having seen that there is only one instance of the DateRange class, I try to understand why the second thread does not commit the variable "current", which is changed by the first thread.
class Program {
static void Main(string[] args) {
var daterange = new DateRange(DateTime.Now, DateTime.Now.AddDays(10), new TimeSpan(24, 0, 0));
var ts1 = new ThreadStart(delegate {
foreach (var date in daterange) {
Console.WriteLine("Thread " + Thread.CurrentThread.ManagedThreadId + " " + date);
}
});
var ts2 = new ThreadStart(delegate {
foreach (var date in daterange) {
Console.WriteLine("Thread " + Thread.CurrentThread.ManagedThreadId + " " + date);
}
});
Thread t1 = new Thread(ts1);
Thread t2 = new Thread(ts2);
t1.Start();
Thread.Sleep(4000);
t2.Start();
Console.Read();
}
}
public class DateRange : Range<DateTime> {
public DateTime Start { get; private set; }
public DateTime End { get; private set; }
public TimeSpan SkipValue { get; private set; }
public DateRange(DateTime start, DateTime end, TimeSpan skip) : base(start, end) {
SkipValue = skip;
}
public override DateTime GetNextElement(DateTime current) {
return current.Add(SkipValue);
}
}
public abstract class Range<T> : IEnumerable<T> where T : IComparable<T> {
readonly T start;
readonly T end;
public Range(T start, T end) {
if (start.CompareTo(end) > 0)
throw new ArgumentException("Start value greater than end value");
this.start = start;
this.end = end;
}
public abstract T GetNextElement(T currentElement);
public IEnumerator<T> GetEnumerator() {
T current = start;
do {
Thread.Sleep(1000);
yield return current;
current = GetNextElement(current);
} while (current.CompareTo(end) < 1);
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() {
return GetEnumerator();
}
}
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