Παραθέτω ένα παράδειγμα για να περιγράψω το προβλημά μου....
Dim table As DataTable = New DataTable("table")
Dim colItem As DataColumn = New DataColumn("item1", GetType(Integer))
table.Columns.Add(colItem)
colItem = New DataColumn("item2", GetType(String))
table.Columns.Add(colItem)
Dim PrimaryKey(0) As DataColumn
PrimaryKey(0) = table.Columns("item1")
table.PrimaryKey = PrimaryKey
Dim newRow(table.Columns.Count - 1) As Object
' Set the values of the array.
Dim row As DataRow = Nothing
For i As Integer = 1 To 5
Try
newRow(0) = 1
newRow(1) = "dddddd" & i
row = table.LoadDataRow(newRow, False)
Dim es As System.Enum = row.RowState
Select Case es.ToString
Case "Added"
Console.WriteLine(es.ToString)
Case "Modified"
Console.WriteLine(es.ToString)
Case "Unchanged"
Console.WriteLine(es.ToString)
Case Else
MsgBox("Uknown System.Enum=" & es.ToString)
End Select
Catch ex As Exception
Console.WriteLine(ex.ToString)
End Try
NextΔιαβάζω για την μέθοδο ...
The LoadDataRow method takes an array of values and finds the matching
value(s) in the primary key column(s).
If a column has a default value, pass a null value in the array to set the
default value for that column. Similarly, if a column has its AutoIncrement property set
to true, pass a null value in the array to set the automatically generated value
for the row.
If the fAcceptChanges parameter is true
or not specified, the new data is added and then AcceptChanges is called to
accept all changes in the DataTable;
if the argument is false, newly added rows are marked as insertions, and
changes to existing rows are marked as modifications.
Exceptions can also occur during either a ColumnChanging or RowChanging event. If an
exception occurs, the row is not added to the table.
Use LoadDataRow in conjunction with BeginLoadData and EndLoadData
........................................
Στο δεύτερο Loop πέρνω Exception
System.Data.ConstraintException: Column 'item1' is constrained to be unique. Value '1' is already present.
ενώ νομίζω θά έπρεπε να πάρω row.RowState="Modified"
Τι μου ξεφεύγει ? 
George Matzouranis