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How to add items to combo box control using API

Using API is one of way of adding items to combo box control. Using API is much faster comparing with regular add item method.

Instructions:

• Create a new Project
• Add a new Form to it and name it as Form1
• Add a combo box control to it and name it as combo1
• Add a command button control to it and name it as command1

Now, copy the following code to Form1:

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Option Explicit
 
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const CB_ADDSTRING = &H143
 
Private Sub Command1_Click()
    Dim sItem As String
    Dim I As Integer
    combo1.Clear
    For I = 1 To 5000
        sItem = "Item number " & CStr(I)
        SendMessage combo1.hWnd, CB_ADDSTRING, 0, ByVal sItem
    Next
End Sub

This function uses SendMessage API function.

If you have any questions, please post as a comment. Thanks