Check for Null with comboboxes

[Hardik Patel]

hi guys,
I have form that contain three textbox,combobox and button.
I want that user must have to choose value from combobox or if combobox is empty and you clicked on button you should get message that you must have to choose value from combo box.
so what i should have to do.

i tried this on button click event .but it did,'t work

If (Forms!Form_Name![Combobox_Name].value = null) then
msgbox "You must have to choose value"
End If

----------------And------- this also-----------

If (Forms!Form_Name![Combobox_Name].value = " ") then
msgbox "You must have to choose value"
End If

And this works but not perfecyly when i choose value then it said type mismatch error

if nz(me.combobox_name,"" = "") then
msgbox "you must have to choose value"
End if

Thanks a Lot

[Marc Brown]

Try using..

If IsNull(me.combobox_name) then
msgbox "You must have to choose value"
End If

The nz() function creates a replacement value if the object is null so the reason it is working is that me.combobox is null so it replaces the value with "" = "" which returns true. Anouther way of doing is this is

If nz(me.combobox_name,"") = "" then

[Hardik Patel]

Thanks dear,
Great!its work nicely that i want