how do get arrays from head of group and subgroup with Linq?

Question

hi

Waiting for output

array1=(a1,a2,a3)

array2=(1-2,3-4,5)

Note: head group is [key] .thank

      Dim dt As New DataTable
        dt.Columns.Add("a")
        dt.Columns.Add("b")
        dt.Rows.Add("a1", "1")
        dt.Rows.Add("a1", "2")
        dt.Rows.Add("a2", "3")
        dt.Rows.Add("a2", "4")
        dt.Rows.Add("a3", "5")
        Dim dr() As DataRow
        dr = dt.Select()
        Dim drGroup = dr.GroupBy(Function(row) row("a"))
        'need array1=(a1,a2,a3)
        'need array2=(1-2,3-4,5)

Answer 1

Hi @Mansour_Dalir , You can refer to the following code, using Linq.

        Dim query = From row In dt.AsEnumerable()
                    Group row("b") By key = row("a") Into Group
                    Select New With {
                .Key = key,
                .Values = String.Join("-", Group.Select(Function(r) r.ToString()))
            }

        Dim array1 = query.Select(Function(item) item.Key).ToArray()
        Dim array2 = query.Select(Function(item) item.Values).ToArray()

Answer 2

Hi @Mansour_Dalir ,

You can refer to the following code.

Use dictionary key-value pairs to implement categorical storage data.

        Dim dt As New DataTable
        dt.Columns.Add("a")
        dt.Columns.Add("b")
        dt.Rows.Add("a1", "1")
        dt.Rows.Add("a1", "2")
        dt.Rows.Add("a2", "3")
        dt.Rows.Add("a2", "4")
        dt.Rows.Add("a3", "5")
        dt.Rows.Add("a3", "6")

        Dim dict As New Dictionary(Of String, List(Of String))()
        Dim array1 As New List(Of String)()
        Dim array2 As New List(Of String)()

        For i As Integer = 0 To dt.Rows.Count - 1
            Dim key As String = dt.Rows(i)("a").ToString()
            Dim value As String = dt.Rows(i)("b").ToString()

            If dict.ContainsKey(key) Then
                dict(key).Add(value)
            Else
                dict(key) = New List(Of String) From {value}
                array1.Add(key)
            End If
        Next

        For Each pair As KeyValuePair(Of String, List(Of String)) In dict
            array2.Add(String.Join("-", pair.Value))
        Next

Best Regards.

Jiachen Li

---

If the answer is helpful, please click "Accept Answer" and upvote it.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.