AllowUserToOrderColumns = True

Me.DataGridView1.DataSource = found_dt

Dim sel_dt As DataTable = New DataTable()
For Each spalten As DataGridViewColumn In Me.DataGridView1.Columns
                    sel_dt.Columns.Add(spalten.Name)
Next

EALA FREYA FRESENA

 For Each dgvspalte As DataGridViewColumn In Me.DataGridView1.Columns.Cast(Of _
   DataGridViewColumn)().OrderBy(Function(dgvc) dgvc.DisplayIndex)
                        sel_dt.Columns.Add(dgvspalte.Name, dgvspalte.ValueType)
 Next

Public Class Form1
 
    Dim dt As New DataTable
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Initialize_dt()
        dgvNamen.AllowUserToOrderColumns = True
        dgvNamen.DataSource = dt
        dtFill()
 
    End Sub
 
    Private Sub dtFill()
 
        Dim newRow As DataRow = dt.NewRow
        newRow("Nachname") = "Irgendwer"
        newRow("Vorname") = "Dieter"
        newRow("Geburtsort") = "Lissabon"
        dt.Rows.Add(newRow)
 
        Dim newRow1 As DataRow = dt.NewRow
        newRow1("Nachname") = "Mustermann"
        newRow1("Vorname") = "Erika"
        newRow1("Geburtsort") = "München"
        dt.Rows.Add(newRow1)
 
        Dim newRow2 As DataRow = dt.NewRow
        newRow2("Nachname") = "Gibsnich"
        newRow2("Vorname") = "Günni"
        newRow2("Geburtsort") = "Bärlin"
        dt.Rows.Add(newRow2)
 
        Dim newRow3 As DataRow = dt.NewRow
        newRow3("Nachname") = "Wildschwein"
        newRow3("Vorname") = "Willi"
        newRow3("Geburtsort") = "Hagen"
        dt.Rows.Add(newRow3)
 
    End Sub
 
    Private Sub Initialize_dt()
        dt.TableName = "Tabelle"
 
        Dim keys(1) As DataColumn
        Dim column As New DataColumn
        column.DataType = System.Type.GetType("System.Int32")
        With column
            .ColumnName = "ID"
            .AutoIncrement = True
            .AutoIncrementStep = 1
        End With
        dt.Columns.Add(column)
        keys(0) = column
        dt.PrimaryKey = keys
 
        column = New DataColumn
        column.DataType = System.Type.GetType("System.String")
        column.ColumnName = "Nachname"
        dt.Columns.Add(column)
 
        column = New DataColumn
        column.DataType = System.Type.GetType("System.String")
        column.ColumnName = "Vorname"
        dt.Columns.Add(column)
 
        column = New DataColumn
        column.DataType = System.Type.GetType("System.String")
        column.ColumnName = "Geburtsort"
        dt.Columns.Add(column)
 
    End Sub
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles _
      Button1.Click
        Dim Spalten As Integer = dt.Columns.Count
        Dim arr(Spalten - 1) As String
        Dim i As Integer = 0
 
        For i = 0 To Spalten - 1
            arr(dgvNamen.Columns(i).DisplayIndex) = i
        Next
 
        Dim Ausgabe As String = ""
        Dim Zeile As String = ""
 
        For j = 0 To dt.Rows.Count - 1
            For i = 0 To arr.Count - 1
                Zeile = Zeile & dgvNamen.Rows(j).Cells(i).Value & ";"
            Next
            Zeile = Zeile.Substring(0, Zeile.Length - 1)
            Ausgabe = Ausgabe & Zeile & vbCrLf
            Zeile = ""
        Next
        Ausgabe = Ausgabe.Substring(0, Ausgabe.Length - 2)
 
        CSVAusgeben(Ausgabe)
 
    End Sub
 
    Private Sub CSVAusgeben(Ausgabe As String)
        Dim Ausgabedatei As String = "D:\irgendwas.csv"
        Dim sw As New System.IO.StreamWriter(Ausgabedatei)
        sw.Write(Ausgabe)
        sw.Close()
    End Sub
 
End Class

EALA FREYA FRESENA

Zeile = Zeile & dgvnamen.Rows(j).Cells(arr(i)).Value.ToString & ";"