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Get Earliest and Latest Dates

Hi Experts!

Thanks for reading this.

Have this Model:

public class Model1
{
    public string PRODUCT { get; set; }
    public string STARTDATE { get; set; }
    private string _Enddate; 
    public string ENDDATE
    {
        get { return _Enddate; }
        set
        {
            if(String.IsNullOrEmpty(value))
                _Enddate = "20781231";
            else
                _Enddate = value;
        }
    }
}

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per (Model1) is populated with the following contents:
Product Listing
The following code (from FernandoSoto) should have selected the (combine of the) earliest (Start Date) and latest (End Date) for each unique Product.
var prods = (from p in per
             group p by p.PRODUCT into pGroup
             from pg in pGroup
             group pg by pg.PRODUCT into pgGroup
             select pgGroup.OrderBy( d => d.STARTDATE)
                           .ThenByDescending(d => d.ENDDATE)
                           .FirstOrDefault())
                           .ToList();

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So, for product = 0002-0800 it should have the Start Date = 19970201 and the End Date = 20781231. However, it has  Start Date = 19890201   End Date = 20340201

The results should look like this:
PRODUCT    STARTDATE   ENDDATE
0002-0800   19970201    20781231
0002-1407   19510301    20781231
0002-1975   20101201    20781231
0002-3004   20010316    20781231
0002-3227   20030110    20051123

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TIA!
Product.xlsx
0
allanau20
Asked:
allanau20
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1 Solution
 
Patrick MatthewsCommented:
So, for product = 0002-0800 it should have the Start Date = 19970201 and the End Date = 20781231. However, it has  Start Date = 19890201   End Date = 20340201

Please explain how one would get those results.  Based on your sample data, Start Date = 19890201 and End Date = 20340201 appear to both be correct.
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allanau20Author Commented:
Hi matthewspatrick.

For a unique product say 0002-0800, you would look through all the Start Dates and pick the earliest and do the same for End Date for that product.

In the example we have eight (8) products with 0002-0800, so the earliest Start Date should be 19890201 (that's correct), but the End Date should be 20781231 instead of 20340201.

Hope this makes sense.

And thanks again!
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Patrick MatthewsCommented:
Check again.  In your sample data, the earliest start for product code 0002-0800 is very clearly 19890201, and your latest end is also very clearly 20340201.
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allanau20Author Commented:
Hi matthewspatrick,

you're right if we ignore the blank values. However, in Model1 where the End Date is blank it will default to 20781231. So, it should have selected 20781231 instead of 20340201.

Thanks again for your help!
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PortletPaulCommented:
in sql for these results:
PRODUCT      MIN_START   MAX_END
0002-0800    19890201    20781231
0002-1407    19510301    20781231
0002-1975    20101201    20781231
0002-3004    20010316    20781231
0002-3227    20030110    20051123

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produced by this query:
SELECT
  product
, min(startdate) min_start
, max(CASE WHEN enddate IS NULL THEN 20781231 ELSE enddate END) max_end
FROM products
GROUP BY product

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allanau20Author Commented:
Thanks PortletPaul,

I'll see if someone can help express that into a LINQ query; in the meantime I'll continue trying... thanks again..
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Fernando SotoRetiredCommented:
Hi allanau20;

Aha I did misunderstand the requirements. I understood that we were to sort first by STARTDATE and then by ENDDATE but what you were asking was which in each product group find the earliest STARTDATE and use that value and then do the same for ENDDATE and use that value even if the two dates come from different records within the same group. Then use this query.

 var prods = (from p in per
              group p by p.PRODUCT into pGroup
              select new Model1() 
              {
                  PRODUCT = pGroup.Key,
                  STARTDATE = pGroup.OrderBy(sd => sd.STARTDATE).Select(sd => sd.STARTDATE).FirstOrDefault(),
                  ENDDATE = pGroup.OrderByDescending(ed => ed.ENDDATE).Select(ed => ed.ENDDATE).FirstOrDefault()
              }).ToList();

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allanau20Author Commented:
Yes, thank you FernandoSoto...

I shall try it out now!
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allanau20Author Commented:
Hi FernandoSoto.

Oh man; got this error when it was trying to execute prods:

{"LinqToExcel does not provide support for the Group() method"}

System.NotSupportedException was caught
  HResult=-2146233067
  Message=LinqToExcel does not provide support for the Group() method
  Source=LinqToExcel
  StackTrace:
       at LinqToExcel.Query.SqlGeneratorQueryModelVisitor.VisitQueryModel(QueryModel queryModel)
       at LinqToExcel.Query.ExcelQueryExecutor.GetSqlStatement(QueryModel queryModel)
       at LinqToExcel.Query.ExcelQueryExecutor.ExecuteCollection[T](QueryModel queryModel)
       at Remotion.Data.Linq.Clauses.StreamedData.StreamedSequenceInfo.ExecuteCollectionQueryModel[T](QueryModel queryModel, IQueryExecutor executor)
       at Remotion.Data.Linq.Clauses.StreamedData.StreamedSequenceInfo.ExecuteQueryModel(QueryModel queryModel, IQueryExecutor executor)
       at Remotion.Data.Linq.QueryModel.Execute(IQueryExecutor executor)
       at Remotion.Data.Linq.QueryProviderBase.Execute[TResult](Expression expression)
       at Remotion.Data.Linq.QueryableBase`1.GetEnumerator()
       at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
       at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
       at SomeNameSpace.Process() in C:\blah\Import.cs:line 37
  InnerException: 

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Did it work on your end?
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Fernando SotoRetiredCommented:
You should still have two queries one for LinqToExcel and the other for Linq to Objects, so the code should look like this.

            var per = (from x in excel.Worksheet<Model1>("Product")
                       select x).ToList();

            var prods = (from p in per
                         group p by p.PRODUCT into pGroup
                         select new Model1() 
                            {
                                PRODUCT = pGroup.Key,
                                STARTDATE = pGroup.OrderBy(sd => sd.STARTDATE).Select(sd => sd.STARTDATE).FirstOrDefault(),
                                ENDDATE = pGroup.OrderByDescending(ed => ed.ENDDATE).Select(ed => ed.ENDDATE).FirstOrDefault()
                            }).ToList();

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allanau20Author Commented:
my bad FernandoSoto; you're right ... earlier I was at home and now I'm at work, and between the puter the 'per' at work didn't have the 'ToList();' ... it compiled ... I'm validating now ...
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allanau20Author Commented:
Eureka! That did it!!

Thanks so much FernandoSoto; if you were in town I would've bought u lunch.
you were patient in helping me along. Thanks so much.

And thanks PortletPaul ... the absolute last resort was to dump it into a SQL table and do what I needed from there..
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allanau20Author Commented:
super answer!
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PortletPaulCommented:
happy to have assisted - not much I understood in that code though
(I'm getting too old for yet another syntax)
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Fernando SotoRetiredCommented:
Not a problem allanau20, glad I was able to help. Have a great day.
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