Display the drop down list of Combo box Explicitly

[Deepak Sakpal]

When you set the DropDownStyle property of Combo box, it allows you input the text like text box control. When you type something and press down arrow key then the item from the list which starts from the text entered is selected. Imagine, how helpful it would be if we can see the drop down list while typing. Below is the code which does exactly the same.

In this code I am displaying the drop down list on GotFocus event of ComboBox.

Imports System.Runtime.InteropServices
 
Public Class Form1
 
    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
    Private Shared Function SendMessage( _
        ByVal hWnd As IntPtr, _
        ByVal Msg As UInteger, _
        ByVal wParam As IntPtr, _
        ByVal lParam As IntPtr) As IntPtr
    End Function
 
    Public Const CB_SHOWDROPDOWN As Long = &H14F
 
    Private Sub Form1_Load( _
        ByVal sender As System.Object, _
        ByVal e As System.EventArgs _
    ) Handles MyBase.Load
 
        Dim comboItems() As String
        comboItems = New String() {"the", "quick", "brown", "fox", "jumps", "over", "the", "lazy", "dog"}
 
        With ComboBox1
            .Items.Clear()
            .Items.AddRange(comboItems)
        End With
    End Sub
 
    Private Sub ComboBox1_GotFocus( _
        ByVal sender As Object, _
        ByVal e As System.EventArgs _
    ) Handles ComboBox1.GotFocus
 
        Dim iret As IntPtr
        iret = SendMessage(ComboBox1.Handle, CB_SHOWDROPDOWN, New IntPtr(CInt(True)), IntPtr.Zero)
    End Sub
 
End Class