Hi Tony,
Based on my understanding, you have two DataTables in a master-detail
relationship and two ComboBoxes. What you want is to have one ComboBox show
the data in the master table and the other ComboBox show the corresponding
records in the detail table. If I'm off base, please feel free to let me
know.
If you're using VS05, you can add a DataRelation between the master and
detail tables and use BindingSource as the data source of the ComboBoxes.
I will illustrate this with an example. Create a WinForm application
project and add two ComboBoxes on the form. In the Form Load event hanlder,
add the following code:
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Dim ds As New DataSet
Dim parent As New DataTable("ParentTable")
Dim col As New DataColumn("ID", GetType(Integer))
parent.Columns.Add(col)
col = New DataColumn("Text", GetType(String))
parent.Columns.Add(col)
Dim child As New DataTable("ChildTable")
col = New DataColumn("ID", GetType(Integer))
child.Columns.Add(col)
col = New DataColumn("PID", GetType(Integer))
child.Columns.Add(col)
col = New DataColumn("Text", GetType(String))
child.Columns.Add(col)
Dim row As DataRow = parent.NewRow
row(0) = 1
row(1) = "parent text 1"
parent.Rows.Add(row)
row = parent.NewRow
row(0) = 2
row(1) = "parent text 2"
parent.Rows.Add(row)
row = parent.NewRow
row(0) = 3
row(1) = "parent text 3"
parent.Rows.Add(row)
row = child.NewRow()
row(0) = 1
row(1) = 1
row(2) = "child text 1"
child.Rows.Add(row)
row = child.NewRow()
row(0) = 2
row(1) = 1
row(2) = "child text 2"
child.Rows.Add(row)
row = child.NewRow()
row(0) = 3
row(1) = 2
row(2) = "child text 3"
child.Rows.Add(row)
row = child.NewRow()
row(0) = 4
row(1) = 2
row(2) = "child text 4"
child.Rows.Add(row)
row = child.NewRow()
row(0) = 5
row(1) = 3
row(2) = "child text 5"
child.Rows.Add(row)
row = child.NewRow()
row(0) = 6
row(1) = 3
row(2) = "child text 6"
child.Rows.Add(row)
ds.Tables.Add(parent)
ds.Tables.Add(child)
Dim relation As New DataRelation("parent_child",
parent.Columns("ID"), child.Columns("PID"))
ds.Relations.Add(relation)
Dim parentBS As New BindingSource()
parentBS.DataSource = ds
parentBS.DataMember = "ParentTable"
Dim childBS As New BindingSource
' Set the DataSource property of the childBS to the parentBS and
the DataMember property to the data relation. This is the key point.
childBS.DataSource = parentBS
childBS.DataMember = "parent_child"
Me.comboBox1.DataSource = parentBS
Me.comboBox1.DisplayMember = "Text"
Me.comboBox1.ValueMember = "ID"
Me.comboBox2.DataSource = childBS
Me.comboBox2.DisplayMember = "Text"
Me.comboBox2.ValueMember = "ID"
End Sub
Build the project and run the application. You should see the text
displayed in the comboBox1 is "parent text 1" and its drop down list
contains three items "parent text 1", "parent text 2" and "parent text 3".
The drop down list of the comBox2 contains two items "child text 1" and
"child text 2". If you select "parent text 2" in the comboBox1, the drop
down list of the comboBox2 contains "child text 3" and "child text 4".
Hope this helps.
If you have any question, please feel free to let me know.
Sincerely,
Linda Liu
Microsoft Online Community Support
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