如何正确将Outlook VBA的DaysOfWeekMask转换为RRULE字符串？

你的代码核心问题出在位运算判断的逻辑错误：

1. VBA中&是字符串连接运算符，位与操作需要用And关键字
2. 未判断位与结果是否非零，导致所有If条件被错误判定为True（VBA中非零值在If判断里会被视为真）

OlDaysOfWeek关键枚举值对应：

• olSunday = 1
• olTuesday = 4
• olFriday = 32
  你创建的重复事件对应的DayMask是1+4+32=37，正确的位运算应该精准识别这三个被设置的位。

修正后的函数代码 #

Function ConvertDaysOfTheWeek(ByVal DayMask As Integer) As String
    Dim sDaysOfTheWeek As String
    sDaysOfTheWeek = ""

    If (DayMask And OlDaysOfWeek.olSunday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",SU"
    End If

    If (DayMask And OlDaysOfWeek.olMonday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",MO"
    End If
 
    If (DayMask And OlDaysOfWeek.olTuesday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",TU"
    End If

    If (DayMask And OlDaysOfWeek.olWednesday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",WE"
    End If

    If (DayMask And OlDaysOfWeek.olThursday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",TH"
    End If
 
    If (DayMask And OlDaysOfWeek.olFriday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",FR"
    End If
 
    If (DayMask And OlDaysOfWeek.olSaturday) <> 0 Then
        sDaysOfTheWeek = sDaysOfTheWeek & ",SA"
    End If

    ' 移除开头的多余逗号
    If Len(sDaysOfTheWeek) > 1 Then
        sDaysOfTheWeek = Right(sDaysOfTheWeek, Len(sDaysOfTheWeek) - 1)
    End If

    ConvertDaysOfTheWeek = sDaysOfTheWeek
End Function

关键修正说明 #

• 把所有&替换为And，执行正确的位与运算
• 每个If条件增加<> 0判断，确保仅当对应星期位被设置时才执行字符串拼接
• 统一用&做字符串连接（VBA中推荐用&而非+，避免数值与字符串混淆的潜在问题）

测试验证：传入DayMask=37时，函数会正确返回SU,TU,FR，完全匹配你每周日、周二、周五重复的需求。

内容的提问来源于stack exchange，提问作者Jonathan Small