[RESOLVED] vb.net improve programs

[eurostar_italia]

ok i guess this is too much difficult for me..
stations it's correctly filled but combobox1 is empty.
i keep on matrix.
it takes longer,very hard to inquiry but it works
many thanks to all of you

[ChrisE]

you can create a Access .mdb and Access doesn't have to be Installed
on your Company PC

 Private Sub Button4_Click(sender As System.Object, e As System.EventArgs) Handles Button4.Click
        'Add the COM Reference, "Microsoft ADO Ext. 6.0 for DLL and Security"
        ' create the empty DB file
        Dim cat As New ADOX.Catalog()
        cat.Create("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\Berichte\Backup.mdb")
        cat = Nothing
    End Sub

as easy as that

[eurostar_italia]

It's not going to be a SQL query because you're not querying a database. Let's say that you have a DataTable with the names of stations in Partenza and Arrivo columns and you want to list distinct values in alphabetical order. One option is to use a LINQ query:

Dim partenzaStations = table.AsEnumerable().Select(Function(row) row.Field(Of String)("Partenza"))
Dim arrivoStations = table.AsEnumerable().Select(Function(row) row.Field(Of String)("Arrivo"))
Dim stations = partenzaStations.Concat(arrivoStations).Distinct().OrderBy(Function(s) s).ToArray()
 
stationComboBox.DataSource = stations

it works only if i don't order the list,otherwise the combobox it wont' be loaded !!
i guess it's due the first value is nothing.
but the where condition can not be applyied in the query.so strange

[eurostar_italia]

at the end i solved in this way :

Dim partenzaStations = From n In treno1.AsEnumerable()
				   Where n.Field(Of String)("Partenza") IsNot Nothing
				   Select n.Field(Of String)("Partenza")

				   Dim arrivoStations = From n In treno1.AsEnumerable()
				   Where n.Field(Of String)("Arrivo") IsNot Nothing
             			 Select n.Field(Of String)("Arrivo")

				Dim stations = partenzaStations.Concat(arrivoStations).Distinct().OrderBy(Function(s) s).ToArray()

			       ComboBox1.DataSource = stations.ToArray
				ComboBox1.SelectedIndex = -1

maybe it will help somebody else