Question

Suppose I have a custom object with a public sub looking something along these lines:

Public Class MyObject
   Public Function ReturnData(StartDate as Date, InputData as List(of string)) As List(Of String)
End Class

And then have another custom object that looks like this:

Public Class HoldingObject
   Public MyDate as Date
   Public MyInfo as String
End Class

Now, in a different class, I have the following:

Dim DataList as List(of HoldingObject)
Dim WorkingClass as New MyObject

Datalist looking as follows:
MyDate:         MyInfo:
1/1/2012        a
1/2/2012        b
1/2/2012        c
1/2/2012        d
1/1/2012        e
1/2/2012        f
1/2/2012        g
1/2/2012        h
1/3/2012        i
1/3/2012        j
1/3/2012        k
1/1/2012        l
1/1/2012        m

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What I would like to do, is make up some kind of a Linq statement that would:

1. Group Datalist list by date (Would be 3 grouped inputs – 1/1/2012; 1/2/2012; 1/3/2012)
2. Submit each group to WorkingClass.ReturnData as inputs and get the return value

How could I do this via Linq / Lambdas or any other way you see as being best programming practice??

Answer 1

Actually I can’t test it on my own right now, but it should work:

Dim result = (From i In DataList
             Group i By date = i.MyDate Into g
             Select WorkingClass.ReturnData(date, g.Select(Function(gi) gi.MyInfo).ToList())).ToList()