vb.net bindingSource to navigate two tables - combobox

Question

I am using VB.Net to load data from SQL server, institute and country and fill each table in a dataset. Country table has countryId, countryName where countryId as the primary key. Institute has instId, name, countryId columns where countryId as a foreign key taken from country table. I am using bindingSource to navigate through data in table institute and display data in text boxes. In other hand I have a combobox that also has a bindingSource which is the country table. I want now when I navigate the institute table I also get data in my combobx get changed based on the value in institute countryId.
Have a look to the following code:
Private Sub frmSystemOptions_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Try
dsOptions = New DataSet
loadOptions()
bsInstitute = New BindingSource(dsOptions, "institute")
InstIdTextBox.DataBindings.Add("Text", bsInstitute, "instId")
NameTextBox.DataBindings.Add("Text", bsInstitute, "name")
CountryIdTextBox.DataBindings.Add("Text", bsInstitute, "countryId")
bsCountry = New BindingSource(dsOptions, "country")
cmbCountry.DataSource = bsCountry
cmbCountry.DisplayMember = "countryName"
cmbCountry.ValueMember = "countryId"
Catch ex As Exception
MsgBox(Err.Description)
End Try
End Sub
Sub loadOptions()
Dim sql As String
Try
sqlConn = New SqlConnection(connString)
sqlConn.Open()
sql = "select instId, name, countryId from institute"
daInstitute = New SqlDataAdapter(sql, sqlConn)
daInstitute.Fill(dsOptions, "institute")
'----------------------------------------------------------------------
sql = "select countryId, countryName from country"
daAdapter = New SqlDataAdapter(sql, sqlConn)
daAdapter.Fill(dsOptions, "country")
'----------------------------------------------------------------------
sqlConn.Close()
Catch ex As Exception
sqlConn.Close()
MsgBox(Err.Description)
End Try
End Sub
Also for navigation I use the following code:
Private Sub btnNext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNext.Click
If bsInstitute.Position + 1 < bsInstitute.Count Then
bsInstitute.MoveNext()
Else
bsInstitute.MoveFirst()
End If
Me.Invalidate()
End Sub
Now how can I make the countryName in the combobx changes based on the value of the countryId in the institute table?

Answer 1

You need to bind the combobox as following:
Private Sub frmSystemOptions_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Try
dsOptions = New DataSet
loadOptions()
bsInstitute = New BindingSource(dsOptions, "institute")
bsCountry = New BindingSource(dsOptions, "country")
InstIdTextBox.DataBindings.Add("Text", bsInstitute, "instId")
NameTextBox.DataBindings.Add("Text", bsInstitute, "name")
CountryIdTextBox.DataBindings.Add("Text", bsInstitute, "countryId")
cmbCountry.DataSource = bsCountry
cmbCountry.DisplayMember = "countryName"
cmbCountry.ValueMember = "countryId"
cmbCountry.DataBindings.Add(New Binding("SelectedValue", _
Me.bsInstitute, "countryId", True))
Catch ex As Exception
MsgBox(Err.Description)
End Try
End Sub
Sub loadOptions()
Dim sql As String
Try
sqlConn = New SqlConnection(connString)
sqlConn.Open()
sql = "select instId, name, countryId from institute"
daInstitute = New SqlDataAdapter(sql, sqlConn)
daInstitute.Fill(dsOptions, "institute")
'----------------------------------------------------------------------
sql = "select countryId, countryName from country"
daAdapter = New SqlDataAdapter(sql, sqlConn)
daAdapter.Fill(dsOptions, "country")
'----------------------------------------------------------------------
sqlConn.Close()
Catch ex As Exception
sqlConn.Close()
MsgBox(Err.Description)
End Try
End Sub