该请求基于MS Access VBA。我想知道最有效的方法是什么，看看列表框控件中是否存在某个项目。

解决方案

不幸的是，没有比线性搜索更有效的方法，除非我们知道列表框是以某种特定方式排序或者索引的。

For i = 1 To TheComboBoxControl.ListCount
  if TheComboBoxControl.ItemData(i) = "Item to search for" Then do_something()
Next i

如果我们不介意使用Windows API，则可以搜索如下所示的字符串：

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 LB_FINDSTRINGEXACT = &H1A2

Dim index as Integer
Dim searchString as String
searchString = "Target" & Chr(0)

index = SendMessage(ListBox1.hWnd, LB_FINDSTRINGEXACT , -1, searchString)

哪个应该返回包含目标字符串的行的索引。

这是一个可能适合的示例函数。

Function CheckForItem(strItem, ListB As ListBox) As Boolean
Dim rs As DAO.Recordset
Dim db As Database
Dim tdf As TableDef

    Set db = CurrentDb

    CheckForItem = False

    Select Case ListB.RowSourceType
        Case "Value List"
            CheckForItem = InStr(ListB.RowSource, strItem) > 0

        Case "Table/Query"
            Set rs = db.OpenRecordset(ListB.RowSource)

            For i = 0 To rs.Fields.Count - 1
                strList = strList & " & "","" & " & rs.Fields(i).Name
            Next

            rs.FindFirst "Instr(" & Mid(strList, 10) & ",'" & strItem & "')>0"

            If Not rs.EOF Then CheckForItem = True

        Case "Field List"

            Set tdf = db.TableDefs(ListB.RowSource)

            For Each itm In tdf.Fields
                If itm.Name = strItem Then CheckForItem = True
            Next

    End Select

End Function