Question

I’ve the following inputs:

collection of A: List<A>
where A is:

class A
{
    DateTime Date;
   int Value;
}

the collection represents a range of dates with values, I want to get back a Dictionary<DateTime, int>, where Key is the first day of each week, included into the range and Value is the Sum of all Value for that week. Ideally I’d like to have the felxibility of specifying the first day of the week.

I’m looking for a solution, using lamda syntax.

Answer 1

var results = yourList.GroupBy(x => GetFirstDayOfWeek(x.Date))
                      .ToDictionary(g => g.Key, g => g.Sum(x => x.Value));

// ...

private static DateTime GetFirstDayOfWeek(DateTime dt)
{
    // left as an exercise for the reader!
}