Select DISTINCT on DataTable

Public Shared Function SelectDistinct(ByVal SourceTable As DataTable, ByVal ParamArray FieldNames() As String) As DataTable
Dim lastValues() As Object
Dim newTable As DataTable

If FieldNames Is Nothing OrElse FieldNames.Length = 0 Then
Throw New ArgumentNullException("FieldNames")
End If

lastValues = New Object(FieldNames.Length - 1) {}
newTable = New DataTable

For Each field As String In FieldNames
newTable.Columns.Add(field, SourceTable.Columns(field).DataType)
Next

For Each Row As DataRow In SourceTable.Select("", String.Join(", ", FieldNames))
If Not fieldValuesAreEqual(lastValues, Row, FieldNames) Then
newTable.Rows.Add(createRowClone(Row, newTable.NewRow(), FieldNames))

setLastValues(lastValues, Row, FieldNames)
End If
Next

Return newTable
End Function

Private Shared Function fieldValuesAreEqual(ByVal lastValues() As Object, ByVal currentRow As DataRow, ByVal fieldNames() As String) As Boolean
Dim areEqual As Boolean = True

For i As Integer = 0 To fieldNames.Length - 1
If lastValues(i) Is Nothing OrElse Not lastValues(i).Equals(currentRow(fieldNames(i))) Then
areEqual = False
Exit For
End If
Next

Return areEqual
End Function

Private Shared Function createRowClone(ByVal sourceRow As DataRow, ByVal newRow As DataRow, ByVal fieldNames() As String) As DataRow
For Each field As String In fieldNames
newRow(field) = sourceRow(field)
Next

Return newRow
End Function

Private Shared Sub setLastValues(ByVal lastValues() As Object, ByVal sourceRow As DataRow, ByVal fieldNames() As String)
For i As Integer = 0 To fieldNames.Length - 1
lastValues(i) = sourceRow(fieldNames(i))
Next
End Sub