help with combo box

[syntax101]

VB 2005
im using two combo box and i bind the two

(cb_dailyplanter and cb_dailyhacienda)
-cb_dailyplanter-contains the list planter name
-cb_dailyhacienda-contains the list of hacienda name

whenever i change the cb_dailyplanter the data of the cb_dailyhacienda changes, it depends which planter owns the hacienda

ex.

planter ------------hacienda
henry--------------Ahacienda
-----------------Bhacienda
my problem is i want to get the primary key of hacienda not the hacienda_name (Ahacienda,Bhacienda)

this is the table

hac_num -------hac_name
1-----------------Ahacienda
2------------------Bhacienda

how to get the primary key of the table if the hac_name(hacienda name is displayed on the combo box)

[Lord Orwell]

i dont think you can read it from the combo box. you will probably have to open a connection and iterate through the items.

[syntax101]

i dont think you can read it from the combo box. you will probably have to open a connection and iterate through the items.

how do iterate it. can you give me a hint how to do it?

[jmcilhinney]

If you've bound the data correctly then it should be simple.

1. Get your data into two DataTables in the same DataSet.
2. Create a DataRelation between them.
3. Bind one BindingSource to the DataSet with the parent table name as the DataMember.
4. Bind a second BindingSource to the first BindingSource with the relation name as the DataMember.
5. Bind the parent ComboBox to the first BindingSource, setting the ValueMember to the name of the primary key column.
6. Bind the child ComboBox to the second BindingSource, setting the ValueMember to the name of the primary key column.

Now the filtering of the child data will occur automatically. When the user selects a child record its primary key value is available via the SelectedValue property of the second ComboBox, e.g.

If haciendaCombo.SelectedItem IsNot Nothing
    Dim haciendaID As Integer = CInt(haciendaCombo.SelectedValue)
End If

[syntax101]

how do i create a data relation i dont know how to do it, can u please help.

[jmcilhinney]

Funny you should ask that. I've been considering for some time submitting some code to the CodeBank to demonstrate this type of thing. Prompted by this thread I just did it. You can find it here. See the GetDataSet method in the posted code for the addition of a DataRelation to the DataSet. There are various ways to do it. They are all very similar and that is probably the easiest.

[syntax101]

i already got it. thanx for your help.

[syntax101]

sorry, it still wont work, the data that i retrieve is the selectedindex of the datacombo. im using the designer mode im not coding it .

[jmcilhinney]

Then don't retrieve the SelectedIndex. Retrieve the SelectedValue. It makes no difference whether you set up your data-binding in the designer or you write the code yourself. All the designer does is generate the code for you, so it's all done with code in the end either way. If you have set the ValueMember property of the ComboBox to the name of the column containing the bound table's primary key, when the user selects an item the primary key value of the corresponding row will be returned by the ComboBox's SelectedValue property. That's what I said in post #4 and it hasn't changed.