Fill Several Combobox with the same values from database

Fill Several Combobox with the same values from database

• Jeff Wasliewicz

  Thanks spotty, I know this questions might sound so foolish, but I am new at vb.net

  I appreciate your help.

  George

  
  

• Thomas N. Sørensen

  This is really simple when you know why. You are binding all the controls to the same datasource and hence they all reference the same item - chnage that item and all of them will chnage. You need to create separate bindingsources and these bindingsources can all reference the same datasource but the controls use the bindingsource as the data source and each control will be independent.

  Simple example to demonstrate

  The following show in VB 2005 how to achieve what you seeing and how to achieve what you asking for. The difference in behaviour is dependent upon whether a checkbox is checked or not.

  Dont worry about the datatable - I create this just so its a self contained sample without the need to access any database.

  Youll notice the independent comboboxes have there own bindingsources, whereas the synchronized binds directly with the same dataset.

  Public Class Form1

  Dim ds As New DataTable

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  '//Create a DataTable to use for the binding
  ds.Columns.Add("col1")
  ds.Columns.Add("col2")

  ds.Rows.Add(1, 2)
  ds.Rows.Add(3, 4)
  ds.Rows.Add(5, 6)

  Me.CheckBox1.Checked = True

  End Sub

  Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
  

  If CheckBox1.Checked Then

  'INDEPENDENT COMBO BOXES

  '//Set the dataset as the datasource for two bindingsource
  Me.BindingSource1.DataSource = ds
  Me.BindingSource2.DataSource = ds

  'Bind the comboboxes to the individial BindingSources
  Me.ComboBox1.DataSource = Me.BindingSource1
  Me.ComboBox1.DisplayMember = "col1"

  Me.ComboBox2.DataSource = Me.BindingSource2
  Me.ComboBox2.DisplayMember = "col1"
  Else

  'SYNCHRONIZED COMBO BOXES

  '//This Will mean both will bind to same source and hence always
  'have the same value
  Me.ComboBox1.DataSource = ds
  Me.ComboBox2.DataSource = ds
  Me.ComboBox1.DisplayMember = "col1"
  Me.ComboBox2.DisplayMember = "col1"
  End If
  End Sub
  End Class

  
  

• eabz

  Thanks Spotty, although I'm still using a lot of code trying to fill the Combos with your solution.

  I tried to declare an array of BindingSources to reduce the code, but I get "Object reference not set to an instance of an object", and since arrays cannot be declared as "New", I had to fill them one at the time:

  Dim Bs(14) As New System.Windows.Forms.BindingSource
  Dim ColorTemp As DataTable

  Try
  
  '//Call Function that returns a datatable
  ColorTemp = ProdQueries("Select * from colors", DBConn).Tables(0)

  For i = 0 to 14
  
  Bs(i).DataSource = ColorTemp
  xcomboarray(i).ValueMember = "idcolor"
  xcomboarray(i).DisplayMember = "color"
  xcomboarray(i).DataSource = Bs(i)

  Next

  Any ideas how to do it with arrays

  
  

• Wes Payne

  Let me clarify what this is doing by chnaging the code a bit

  
  Dim controlname As String = "Combobox" & i + 1.ToString
  Dim ctrl As ComboBox = CType(Me.Controls(controlname), ComboBox)

  From this you will see I'm constructing a string which will be the name of the control I'm looking for - in this case combobox1,2 ....

  I am then using this to reference this control in the forms controls collection and specifically casting it to a type of combobox - so I get intellisense etc. The variable ctrl is a reference variable to the combobox control I'm referring to.

  You need to ensure that the controls actually exist and are named correctly so it can find them
  

  
  

• Adam Shipp

  Spotty,

  Just to conclude, your function Dim ctrl As ComboBox = CType(Me.Controls("Combobox" & i + 1.ToString), ComboBox) it returns a Nothing, why is that (I'm using it just like you said)

  Thanks in advance

  
  

• PRMARJORAM

  Simple Example

  Public Class Form1

  Dim dt As New DataTable

  Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
  dt.Columns.Add("IDcolor")
  dt.Columns.Add("Color")

  dt.Rows.Add(1, "Red")
  dt.Rows.Add(2, "Blue")
  dt.Rows.Add(3, "Green")
  End Sub

  
  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

  Dim Bs(2) As System.Windows.Forms.BindingSource
  Dim i As Integer = 0
  For i = 0 To 2
  Bs(i) = New System.Windows.Forms.BindingSource
  Bs(i).DataSource = dt
  Dim ctrl As ComboBox = CType(Me.Controls("Combobox" & i + 1.ToString), ComboBox)

  ctrl.ValueMember = "idcolor"
  ctrl.DisplayMember = "color"
  ctrl.DataSource = Bs(i)
  Next

  End Sub

  End Class
  

  
  
• Fill Several Combobox with the same values from database