vb.net How to overwrite the text in a combobox after the dropdownclosed event - vb.net

Question

I created this piece of code to illustrate the idea, it uses a combobox and a textbox
Private Sub ComboBox2_DropDown(sender As Object, e As EventArgs) Handles ComboBox2.DropDown
ComboBox2.Items.Clear()
ComboBox2.Items.Add("0001 | Apple")
ComboBox2.Items.Add("0002 | Pear")
ComboBox2.Items.Add("0003 | Banana")
ComboBox2.Items.Add("0004 | Pineapple")
ComboBox2.Items.Add("0005 | Cherry")
End Sub
Private Sub ComboBox2_DropDownClosed(sender As Object, e As EventArgs) Handles ComboBox2.DropDownClosed
Dim selecteditem As String = ComboBox2.Items(ComboBox2.SelectedIndex)
ComboBox2.Text = Strings.Left(selecteditem,4)
TextBox2.Text = Strings.Left(selecteditem,4)
End Sub
When I select an item from the combobox what happens is that the combobox keeps showing the whole string while the textbox only shows the first 4 characters.
How can I overwrite the combobox text after I close the combobox?
* edit *
I tried a combo of the solutions but ran into a problem because the data was bound to a datasource so it's not possible to change the item.
This is the new code:
Private Sub ComboBox2_DropDown(sender As Object, e As EventArgs) Handles ComboBox2.DropDown
SQL.ExecQuery($"select ID, Name, RTRIM(ID + ' | ' + Name) as SingleColumn from GCCTEST.dbo.tblFruit")
ComboBox2.DataSource = SQL.DBDT
ComboBox2.DisplayMember = "SingleColumn"
End Sub
Private Sub ComboBox2_DropDownClosed(sender As Object, e As EventArgs) Handles ComboBox2.DropDownClosed
ComboBox2.DisplayMember = "ID"
ComboBox2.SelectedIndex = 0
End Sub
Now I only need to have the 0 be the index I chose...

Answer 1

The following should work.
If not necessary, don't populate the combobox on every drop-down, instead call the FillComboBox-method when loading the Form.
Private Sub FillComboBox()
SQL.ExecQuery($"select ID, Name, RTRIM(ID + ' | ' + Name) as SingleColumn from GCCTEST.dbo.tblFruit")
ComboBox2.DataSource = SQL.DBDT
ComboBox2.DisplayMember = "ID"
ComboBox2.ValueMember = "ID"
End Sub
Private Sub ComboBox2_DropDown(sender As Object, e As EventArgs) Handles ComboBox2.DropDown
Me.ComboBox2.DisplayMember = "SingleColumn"
End Sub
Private Sub ComboBox2_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox2.SelectionChangeCommitted
Dim selV As Object = Me.ComboBox2.SelectedValue
Me.TextBox2.Text = CStr(selV)
Me.ComboBox2.DisplayMember = "ID"
'Set the current value again, otherwise the combobox will always display the first item
Me.ComboBox2.SelectedValue = selV
End Sub

Answer 2

I used a few properties and .net String.SubString method instead of the old vb6 Strings.Left.
Private Sub ComboBox1_DropDownClosed(sender As Object, e As EventArgs) Handles ComboBox1.DropDownClosed
Dim SelectedString As String = ComboBox1.SelectedItem.ToString
Dim ChangedString As String = SelectedString.Substring(0, 4)
Dim index As Integer = ComboBox1.SelectedIndex
ComboBox1.Items(index) = ChangedString
End Sub
You can fill your combo box one by one to avoid binding problems as follows...
Private Sub ComboBox1_DropDown(sender As Object, e As EventArgs) Handles ComboBox1.DropDown
Using cn As New SqlConnection("Your connection string")
Using cmd As New SqlCommand("Select ID, Name From tblFruit;", cn)
cn.Open()
Using dr As SqlDataReader = cmd.ExecuteReader
ComboBox1.BeginUpdate()
While dr.Read
ComboBox1.Items.Add(dr(0).ToString & " | " & dr(1).ToString)
End While
ComboBox1.EndUpdate()
End Using
End Using
End Using

Answer 3

You can solve this graphical problem putting a Label in your Form and moving it over your ComboBox.
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
Me.Label1.AutoSize = False
Me.Label1.BackColor = Me.ComboBox1.BackColor
Me.Label1.Location = New Point(Me.ComboBox1.Location.X + 1, Me.ComboBox1.Location.Y + 1)
Me.Label1.Size = New Size(Me.ComboBox1.Width - 18, Me.ComboBox1.Height - 2)
Me.ComboBox1.Items.Add("0001 | Apple")
Me.ComboBox1.Items.Add("0002 | Pear")
Me.ComboBox1.Items.Add("0003 | Banana")
Me.ComboBox1.Items.Add("0004 | Pineapple")
Me.ComboBox1.Items.Add("0005 | Cherry")
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
Me.Label1.Text = Trim(Me.ComboBox1.SelectedItem.Split("|")(0))
End Sub
Please note that:
you can populate your ComboBox a single time during Form load event
you can use SelectedIndexChanged instead of DropDown and DropDownClosed event
if this is not a graphical problem please give a look at DisplayMember and ValueMember properties