Can't reset ComboBox default text.

Question

I have a ComboBox on my form. Default text is "Select Type".

One of my options is not yet supported. So if the user selects it, I display a MsgBox and then attempt to reset it. But for some reason, no matter what I do, I can't reset it to display the default text again. I've tried all variations of the following:

Properties:
ComboBox.Text = "Select Type"
ComboBox.Items are "Option #1" & "Option #2".

Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
If ComboBox1.SelectedIndex = 1 Then
MsgBox("Contents: '" & ComboBox1.Text & "'")
ComboBox1.SelectedIndex = -1
ComboBox1.SelectedItem = -1
ComboBox1.ResetText()
ComboBox1.Text = "Select Type"
End If
End Sub

Setting "SelectedIndex = -1" simply erases the text.
The other three setting ("SelectedItem", "ResetText()" and "Text = "Reset"") all simply re-highlights the selected item.

No combination of those options work. Nothing I try resets the default text to appear.

Is this a bug in VS2019? Any work-around? TIA

Answer 1

You can use a Banner

For example :

    Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged  
        If ComboBox1.SelectedIndex = 1 Then  
            MsgBox("Contents: '" & ComboBox1.Text & "'")  
            ComboBox1.SelectedIndex = -1  
            Dim pMessage As IntPtr = Marshal.StringToHGlobalUni("Select Type")  
            If ComboBox1.DropDownStyle = ComboBoxStyle.DropDownList Then  
                SendMessage(ComboBox1.Handle, CB_SETCUEBANNER, 0, pMessage)  
            Else  
                Dim hEdit As IntPtr = GetWindow(ComboBox1.Handle, GW_CHILD)  
                SendMessage(hEdit, EM_SETCUEBANNER, 0, pMessage)  
                ActiveControl = Nothing  
            End If  
        End If  
    End Sub  

with :

Public Const ECM_FIRST = &H1500  
Public Const EM_SETCUEBANNER = (ECM_FIRST + 1)  
Public Const CB_SETCUEBANNER As Integer = &H1703  
  
<DllImport("User32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)>  
Public Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As Integer, ByVal wParam As Integer, ByVal lParam As IntPtr) As Integer  
End Function  
  
<DllImport("User32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)>  
Public Shared Function GetWindow(hWnd As IntPtr, uCmd As UInteger) As IntPtr  
End Function  

Public Const GW_HWNDFIRST = 0  
Public Const GW_HWNDLAST = 1  
Public Const GW_HWNDNEXT = 2  
Public Const GW_HWNDPREV = 3  
Public Const GW_OWNER = 4  
Public Const GW_CHILD = 5  

Answer 2

Here is a path to consider, its not exactly what you want but shows an alternate path to take.

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        ComboBox1.DropDownStyle = ComboBoxStyle.DropDownList

        ComboBox1.DataSource = New List(Of Item) From {
            New Item() With {.Text = "Select Type", .Identifier = -1},
            New Item() With {.Text = "Option 1", .Identifier = 1},
            New Item() With {.Text = "Option 2", .Identifier = 2},
            New Item() With {.Text = "Option 3", .Identifier = 3}
        }

        ComboBox1.SelectedIndex = -1

        AddHandler ComboBox1.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged

    End Sub

    Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs)
        Dim item = CType(ComboBox1.SelectedItem, Item)
        If item.Identifier = -1 OrElse item.Identifier = 3 Then
            RemoveHandler ComboBox1.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged
            ComboBox1.SelectedIndex = -1
            MessageBox.Show("Please make a selection")
            AddHandler ComboBox1.SelectedIndexChanged, AddressOf ComboBox1_SelectedIndexChanged
        Else
            MessageBox.Show($"{item.Identifier} - {item.Text}")
        End If
    End Sub
End Class
Public Class Item
    Public Property Text() As String
    Public Property Identifier() As Integer

    Public Overrides Function ToString() As String
        Return Text
    End Function
End Class