How to delete all the elements from the combo box in nsis - combobox

Question

I want to delete all the elements from the combo box on click of the button in the nsis installer

Answer 1

nsDialogs does not have helper macros for every feature implemented by the Windows controls so sometimes you have to consult MSDN to find information about which message to send yourself.
!include nsDialogs.nsh
!include WinMessages.nsh
Page Custom MyPageCreate
Page InstFiles
Var MyComboHandle
Function ResetCombo
Pop $0
SendMessage $MyComboHandle ${CB_RESETCONTENT} 0 0
FunctionEnd
Function DeleteItemsButNotText
Pop $0
${NSD_GetText} $MyComboHandle $0
SendMessage $MyComboHandle ${CB_RESETCONTENT} 0 0
${NSD_SetText} $MyComboHandle $0
FunctionEnd
Function DeleteItemsButNotText_AlternateVersion
Pop $0
loop:
SendMessage $MyComboHandle ${CB_DELETESTRING} 0 0 $0 ; This will also clear the text if it matches the item
IntCmp $0 ${CB_ERR} "" loop loop
FunctionEnd
Function AddItems
Pop $0
${NSD_CB_AddString} $MyComboHandle "Foo"
${NSD_CB_AddString} $MyComboHandle "Bar"
SendMessage $MyComboHandle ${CB_SETCURSEL} 0 ""
FunctionEnd
Function MyPageCreate
nsDialogs::Create 1018
Pop $0
${NSD_CreateCombobox} 0 30u 100% 200u ""
Pop $MyComboHandle
Push ""
Call AddItems
${NSD_CreateButton} 0 50u 33% 12u "Reset"
Pop $0
${NSD_OnClick} $0 ResetCombo
${NSD_CreateButton} 33% 50u 33% 12u "Delete all items"
Pop $0
${NSD_OnClick} $0 DeleteItemsButNotText
${NSD_CreateButton} 66% 50u 33% 12u "Add items"
Pop $0
${NSD_OnClick} $0 AddItems
nsDialogs::Show
FunctionEnd