Deviding dates into periods by linq c# - linq

Question

I have a datatable contains three columns (Names and Dates)
Names Dates amount
----------------------------------
John 01/01/2019 5
John 02/01/2019 10
John 04/01/2019 5
John 05/01/2019 4
Adam 01/01/2019 5
Adam 03/01/2019 5
Adam 04/01/2019 5
I need to check missed days and make periods
I expect output like
Names Fr To amount
John 01/01/2019 02/01/2019 15
John 04/01/2019 05/01/2019 9
Adam 01/01/2019 01/01/2019 5
Adam 03/01/2019 04/01/2019 10

Answer 1

If you divide the problem into sub-parts then it becomes a lot simpler.
Make pairs from the entries of the datatable.
Now make groups based on Name.
On this groups check which group has the time difference of 1 month.
Project this groups using a foreach loop.
Now the code,
public static class Program
{
static int CountNumberOfMonths(DateTime date1, DateTime date2) => (date2.Month - date1.Month) + 12 * (date2.Year - date1.Year);
static void Main(string[] args)
{
DataTable table = new DataTable();
table.Columns.Add("Name", typeof(string));
table.Columns.Add("Dates", typeof(DateTime));
table.Columns.Add("Amount", typeof(int));
table.Rows.Add("John", new DateTime(2019, 1, 1), 5);
table.Rows.Add("John", new DateTime(2019, 2, 1), 10);
table.Rows.Add("John", new DateTime(2019, 4, 1), 5);
table.Rows.Add("John", new DateTime(2019, 5, 1), 4);
table.Rows.Add("Adam", new DateTime(2019, 1, 1), 5);
table.Rows.Add("Adam", new DateTime(2019, 3, 1), 5);
table.Rows.Add("Adam", new DateTime(2019, 4, 1), 5);
var enumeratedDatatable = table.AsEnumerable();
var filteredData = enumeratedDatatable
.Zip(enumeratedDatatable.Skip(1), Tuple.Create)
.GroupBy(x => x.Item1.Field<string>("Name"))
.Select(x => x.Where(y =>
{
int numMonths = CountNumberOfMonths(y.Item1.Field<DateTime>("Dates"), y.Item2.Field<DateTime>("Dates"));
return numMonths > 0 && numMonths == 1;
}));
DataTable result = new DataTable();
result.Columns.Add("Name", typeof(string));
result.Columns.Add("From", typeof(DateTime));
result.Columns.Add("Sum", typeof(DateTime));
result.Columns.Add("Amount", typeof(int));
foreach (var item in filteredData)
{
string name = item.ElementAt(0).Item1.Field<string>("Name");
foreach (var innerItem in item)
{
int sumAmount = innerItem.Item1.Field<int>("Amount") + innerItem.Item2.Field<int>("Amount");
DateTime from = innerItem.Item1.Field<DateTime>("Dates");
DateTime to = innerItem.Item2.Field<DateTime>("Dates");
result.Rows.Add(name, from, to, sumAmount);
}
}
// Printing the results to standard output
foreach (DataRow row in result.Rows)
{
string rowItem = string.Join("\t", row.ItemArray);
Console.WriteLine(rowItem);
}
}
}
Outputting:
John 01/01/2019 00:00:00 02/01/2019 00:00:00 15
John 04/01/2019 00:00:00 05/01/2019 00:00:00 9
Adam 03/01/2019 00:00:00 04/01/2019 00:00:00 10