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Creating two related ComboBoxes (VB)

• • Reply

  1 year ago

  by tradnan

  Tasneem Adnan

  , Pakistan

  Joined 1 year ago

  hi ,

   

  I have two (or more) ComboBox controls and I want the options in second combo box to change based on the selected item in the first combo box. 

   When the user changes the value in the country combo box to “Canada”, you would only want to display a list of Canadian provinces/territories in the second combo box. Although if the user selected USA in the country combo box, you would only want to show the American states/regions.?

   

   

   

   

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• • Reply

  1 year ago

  by barma

  barma

  , India

  Joined 1 year ago

   

  Hello,

  To create related combo boxes, you will have to do some coding in SelectedIndexChanged() event of the Combo box. Every time you select a

  value in Combobox1, this event will fire. If I assume correctly, the values will be fetched from the database for Combobox2. Now in this event, you

  will have to loop through the database to check whether the records contains the name of the Country selected in Combobox1. Add the cities from

  the records containing the selected Country.

  For example:

  BEGIN CODE

  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

  Me.ComboBox1.Items.Add("United States")

  Me.ComboBox1.Items.Add("Canada")

  Me.ComboBox1.Items.Add("Brazil")

  Me.ComboBox1.Items.Add("Cuba")

  Me.ComboBox1.SelectedIndex = 0

  End Sub

  Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged

  Me.ComboBox2.Text = ""

  Me.ComboBox2.Items.Clear()

  If Me.ComboBox1.Text = "United States" Then

  Me.ComboBox2.Items.Add("Washington D.C.")

  ElseIf Me.ComboBox1.Text = "Canada" Then

  Me.ComboBox2.Items.Add("Ottawa")

  ElseIf Me.ComboBox1.Text = "Cuba" Then

  Me.ComboBox2.Items.Add("Havana ")

  ElseIf Me.ComboBox1.Text = "Brazil" Then

  Me.ComboBox2.Items.Add("Brasilia")

  End If

  Me.ComboBox2.SelectedIndex = 0

  End Sub

  END CODE

  I hope this will help. You can use the concept of DataReader to loop through the database records and add the items in the Combobox.

  Regards,

  Allen Smith

  ComponentOne LLC

  www.componentone.com

   

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• • Reply

  1 year ago

  by tradnan

  Tasneem Adnan

  , Pakistan

  Joined 1 year ago

  thank you  its very helpful

   

  but , if I want to get data (cities) from table in database  ?

   

  for example :

  I created table : Table1

  Country : United States,Canada,Brazil

  City : Washington D.C.,Ottawa,Brasilia

  ......

  then , I wrote this code in ComboBox1_SelectedIndexChanged:

  Dim vCon As New SqlConnection

  vCon.ConnectionString = ""........(code for open connection )

  With ComboBox1.SelectedItem

  ComboBox2.Items.Clear()

  Dim vSelectCommand As New SqlCommand

  vSelectCommand.Connection = vCon

  vSelectCommand.CommandText = " Select City From Table1 where Country ='" & ComboBox1.Text & "' "

  Dim vReader As SqlDataReader

  vCon.Open()

  vReader = vSelectCommand.ExecuteReader()

  If vReader.HasRows = True Then

  While vReader.Read

  ComboBox2.Items.Add(vReader(0))

   

  End While

  End If

  End With

  vCon.Close()

  End Sub

  ,,,,,,,,End Code,,,,,,

   

  But , it didn't work correctly !

  I don't know if its right or wrong ?!

  Could you help me and correct my code , please ?

   

  Regards,

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• • Reply

  1 year ago

  by barma

  barma

  , India

  Joined 1 year ago

   

  Hello,

  
  I think you have done everything correct.  I have created the same using OLEDB. Basic things remain the same and it works perfectly

  for me. Could you tell me what exactly happens at your end and it will be great if you can provide a small prototype of your project.

  Here is the code that I am using in SelectedIndexChange() event of ComboBox1.

  BEGIN CODE

  Dim dr As OleDbDataReader

  Dim dcs As New OleDbConnection

  Dim dc As New OleDbCommand

  dcs.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\databases\mytable.mdb;User Id=admin;Password=;"

  dc.Connection = dcs

  dc.CommandText = "Select City from Capital where Country='" & ComboBox1.Text & "'"

  dcs.Open()

  dr = dc.ExecuteReader()

  ComboBox2.Items.Clear() 

  If dr.HasRows = True Then

  While dr.Read

  ComboBox2.Items.Add(dr(0))

  End While

  End If

  dcs.Close()

  ComboBox2.SelectedIndex = 0

  END CODE

  Regards,

  Allen Smith

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• • Reply

  1 year ago

  by tradnan

  Tasneem Adnan

  , Pakistan

  Joined 1 year ago

  hi,

  In fact there is no mistake,

  But Nothing Happen

   

  When I set the country , it does not choose any city !! ( Does not show anything in combobox2) !

   

  ....

   

  why you wrote

  ComboBox2.SelectedIndex = 0  ?

  when I wrote it  , the program gives me an error that : InvalidArgument=Value of '0' is not valid for 'SelectedIndex'.
  Parameter name: SelectedIndex.

   

   

  I hope you will find solution :)

  THANK YOU

   

  Regards,

   

   
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• • Reply

  1 year ago

  by barma

  barma

  , India

  Joined 1 year ago

   

  Hello,

  By default, when we add items to combo box, it does not show any thing in its Text area till the time we select

  any option from the dropdown. To make a default selection, we use SelectedIndex and set its value to index of

  the item from the dropdown list where the indexing begins from 0.

  Now I would like to know whether the data is getting fetched using the DataReader you are using. From the error message

  you have provided, it seems that no data is being getting added into the Combo box. To verify this, put a message box to

  show the data instead of adding it to the Combo box. Let me know the results on this.

  Regards,

  Allen Smith

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• • Reply

  1 year ago

  by tradnan

  Tasneem Adnan

  , Pakistan

  Joined 1 year ago

  Hello,

  I think the data is getting fetched using the DataReader :

  I tried this :

  vSelectCommand.CommandText = " Select City From Table1 "

   when I choose any country ,  I got all the cities added  into Combobox2 .

  But ,

  When I write WHERE statment , No data is adding into Combobox2 !

   

  Regards,

   

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