Question

LINQ - How to make a distinct on multiple datarow field?

Asked by: Dnx_7

Hi experts

i have this LINQ

Dim searchTrigger As IEnumerable(Of DataRow) = From r As DataRow In Me._dtTrigger.AsEnumerable _
                                                               Where r.Field(Of String)("BCEID").ToUpper Like searchBuilder.ToString _
                                                               Select r _
                                                               Distinct


what i have is a datatable with 2 columns, i have to select the whole datarow but i have to filter (distinct) result on one specific field...

can you help me to achieve this?

Kind regards

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Asked On
2008-07-19 at 17:28:20ID23579572
Tags

.NET 3

Topics

Language Integrated Query - LINQ

,

Microsoft Visual Basic.Net

,

.NET Framework 3.x versions

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Answers

 

by: naspinskiPosted on 2008-07-19 at 19:22:59ID: 22044264

Dim searchTrigger  = (From r As DataRow In Me._dtTrigger.AsEnumerable _ Where r.Field(Of String)("BCEID").ToUpper Like searchBuilder.ToString Select r).Distinct()

                                              
1:

Select allOpen in new window

 

by: naspinskiPosted on 2008-07-19 at 19:24:11ID: 22044269

woops

Dim searchTrigger  = (From r As DataRow In Me._dtTrigger.AsEnumerable Where r("BCEID").ToUpper.contains(searchBuilder.ToString) Select r).Distinct()

                                              
1:

Select allOpen in new window

 

by: Dnx_7Posted on 2008-07-20 at 02:19:25ID: 22045066

doesn't work, your query is the same as mine... even the contains doesn't work like the "Like" Operator...

regards

 

by: naspinskiPosted on 2008-07-20 at 02:29:34ID: 22045085

sorry, you are correct

Dim searchTrigger  = (From r As DataRow In Me._dtTrigger.AsEnumerable Where r("BCEID").ToUpper.Equals(searchBuilder.ToString.ToUpper) Select r).Distinct()

                                              
1:

Select allOpen in new window

 

by: Dnx_7Posted on 2008-07-20 at 02:34:02ID: 22045096

Hi,

the problem is not on the Like operator...
the like works perfectly but i have to distinct result on field

because this linq is on "textChanged" event
suppose the user type "B"

i have to search all the "BCEID" like "B" but the result has to be filtered(distinct) because i have some duplicate rows and i only want to show ONE instance.

regards

 

by: naspinskiPosted on 2008-07-20 at 02:40:36ID: 22045103

ok, then all you need to do is put the query inside parentheses and add .Distinct()  and it will only return distinct rows

 

by: Dnx_7Posted on 2008-07-20 at 02:48:34ID: 22045116

that is my query as shown in my previous post


Dim searchTrigger As IEnumerable(Of DataRow) = From r As DataRow In Me._dtTrigger.AsEnumerable _
                                                               Where r.Field(Of String)("BCEID").ToUpper Like searchBuilder.ToString _
                                                               Select r _
                                                               Distinct

and i also tried this :

searchBuilder.Append("*").Append(searchPattern).Append("*")

                Dim searchTrigger As IEnumerable(Of DataRow) = (From r As DataRow In Me._dtTrigger.AsEnumerable _
                                                               Where r.Field(Of String)("BCEID").ToUpper Like searchBuilder.ToString _
                                                               Select r).Distinct


as you can see, i put a distinct at the end of query but the result isn't distincted...

Regards

 

by: naspinskiPosted on 2008-07-20 at 03:33:44ID: 22045184

I understand that, but have you tried putting it inside parentheses then distincting it, or just using distinct on the next line.  You are putting it at the end, but not actually calling distinct properly.

Dim distinctQuery = searchTrigger.Distinct()

                                              
1:

Select allOpen in new window

 

by: Dnx_7Posted on 2008-07-20 at 03:56:29ID: 22045238

that is the same...

i tried your solution to be sure... but didn't work.

 

by: Dnx_7Posted on 2008-07-20 at 09:43:06ID: 22046196

hi, i found the solution :

 Dim searchTrigger As IEnumerable(Of DataRow) = (From r As DataRow In Me._dtTrigger.AsEnumerable _
                                                               Where r.Field(Of String)("BCEID").ToUpper Like searchBuilder.ToString _
                                                               Select r).Distinct(New StringComparer("BCEID"))


and i added this custom iequalityComparer :


Public Class StringComparer
    Implements IEqualityComparer(Of DataRow)
    Private _fieldToCompare As String

    Public Sub New(ByVal FieldToCompare As String)
        Me._fieldToCompare = FieldToCompare
    End Sub

    Public Function Equals1(ByVal x As System.Data.DataRow, ByVal y As System.Data.DataRow) As Boolean Implements System.Collections.Generic.IEqualityComparer(Of System.Data.DataRow).Equals
        Return String.Compare(x.Field(Of String)(Me._fieldToCompare), y.Field(Of String)(Me._fieldToCompare), True) = 0
    End Function

    Public Function GetHashCode1(ByVal obj As System.Data.DataRow) As Integer Implements System.Collections.Generic.IEqualityComparer(Of System.Data.DataRow).GetHashCode
        Return obj.ToString.GetHashCode()
    End Function
End Class


Thank you anyway ;)

Regards

20120131-EE-VQP-002

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