No duplicates in combo from datasource

Hey all,

Newbie here..

I'm having an issue wherein my combobox is populated from a datasource (access database >> http://i51.tinypic.com/2mpbvh1.jpg ) and unwanted duplicates are shown.

-Example-
http://i51.tinypic.com/x5xd2f.jpg

How can I make it so no duplicates arise?

Also on another note...I'm having difficulties linking the 2nd combo (model) to the first (make).

I would like the program to function in such a manner that

>makeCombo is populated from the database
>the user selects the Make of the vehicle from makeCombo
>modelCombo is populated from the database according to the make selected
>the user selects the Model of the vehicle from modelCombo
>user hits search
>datagrid is populated with appropriate vehicles


This has been driving me insane so any help would be GREATLY appriciated :)

You should probably redesign your database. You should not have that Make and Model information in the in that table at all. You should have a Make table, which contains one record per make. That way, you simply display the contents of that table and there will be no duplicates. You would also have a Model table, with one record per model. Each Model record would also contain a MakeID, linking it to a record in the Make table. Your Vehicle table (or whatever it will be called) can then just contain a ModelID. There's no duplication of data and, when you have a Vehicle record, you can use the ModelID to get a Model record ad the MakeID of that to get a Make record. This is how relational databases work: via relations.

Once you've got your related Make and Model tables, the two ComboBoxes are easy to configure using parent/child data-binding. For an example, follow the CodeBank link in my signature and check out my post on the subject.

That said, if you ever do have a list like that and you need to get distinct values from one column/property, the easiest way is with LINQ, e.g.

vb.net Code:

Dim makes = From row In myDataTable.AsEnumerable() Select row.Field(Of String)("Make") Distinct

Ah thank you for your help jm, I feared (but deep down probably knew) a reworking of the database was needed.

Just to confirm, would the revised relational DB look something like this

MakeTable
-make(pk)

ModelTable
-model(pk), make(fk)

SeriesTable
-series(pk), model(fk), make(fk) weight, power, blah, blah

Once again thanks for the reply

Each table probably should have an AutoNumber column as the primary key. Other than that, the Series table doesn't need a foreign key from both Make and Model. As I said before, the Series table needs only a foreign key from the Model table, which will then lead you to the Make table. If you need all the data together you execute a query that joins Series to Model and Model to Make.

Awesome thanks!

I'll rework the database tonight and get cracking on the parent/child data binding tommorow :)

I have come up with a different solution that does not involve linked combos, instead the user will just search the model through a textbox.

I'm having a different issue now however and again it is driving me insane (the worst part is, its probably something very simple).

So I would like it so after clicking an item in the datagrid, the details update automatically. Like such -
http://i51.tinypic.com/1zf3qyo.jpg

The problem is, after running a search (or hitting 'show all') the label/details no longer change when selecting a new item in the datagrid.
Like such-
http://i54.tinypic.com/opcpbr.jpg

Heres the code (there isnt much, I'm not very experienced)

Code:

---

    Private Sub Sheet1BindingNavigatorSaveItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
        Me.Validate()
        Me.Sheet1BindingSource.EndEdit()
        Me.TableAdapterManager.UpdateAll(Me.CardatabaseDataSet)

    End Sub

    Private Sub search_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'TODO: This line of code loads data into the 'CardatabaseDataSet.Sheet1' table. You can move, or remove it, as needed.
        Me.Sheet1TableAdapter.Fill(Me.CardatabaseDataSet.Sheet1)

    End Sub

    Private Sub searchButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles searchButton.Click

        If searchText.Text = "" Then
            Sheet1DataGridView.DataSource = Me.CardatabaseDataSet.Sheet1.Select("Make like '" & MakeIDComboBox.SelectedItem & "'")
        Else
            Sheet1DataGridView.DataSource = Me.CardatabaseDataSet.Sheet1.Select("Model like '" & searchText.Text & "'")
        End If
    End Sub

    Private Sub showAll_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles showAll.Click
        Sheet1DataGridView.DataSource = Me.CardatabaseDataSet.Sheet1
    End Sub

---

As always, any help would be met with massive thanks!

quick edit: just to double clarify :), the search itself filters the datagrid perfectly as intended....it just seems to stop the details from updating when new items are selected which is my problem

Read the title of this thread and then ask yourself whether your latest question belongs here or in a new thread of its own.

Noted thanks