[VBA]应用 Select Case 语句代替 If 语句

在程序中进行逻辑判断是不可避免的场景，IF语句非常方便地满足了我们的需求，但往往被滥用，过度的IF嵌套使代码的可读性大大降低，尤其是在多次更新而懒于重构代码的情况下。

适当地使用 Select Case 语句代替 IF 语句，可以说是程序员脱离普通的第一步，假设一份代码打开充斥着 IF 语句，那第一反应肯定是“菜鸡”。

Select Case 的结构很简单，如下所示：

Select Case Value
       Case Value1
               Code1
       Case Value2
               Code2
       Case Value3
               Code3
       ……   ……
       Case Else
               Code Else

End Select

这里提供两个示例：

' Example 1

Worksheets("Sheet1").Activate
Select Case ActiveCell.LocationInTable
Case Is = xlRowHeader
    MsgBox "Active cell is part of a row header"
Case Is = xlColumnHeader
    MsgBox "Active cell is part of a column header"
Case Is = xlPageHeader
    MsgBox "Active cell is part of a page header"
Case Is = xlDataHeader
    MsgBox "Active cell is part of a data header"
Case Is = xlRowItem
    MsgBox "Active cell is part of a row item"
Case Is = xlColumnItem
    MsgBox "Active cell is part of a column item"
Case Is = xlPageItem
    MsgBox "Active cell is part of a page item"
Case Is = xlDataItem
    MsgBox "Active cell is part of a data item"
Case Is = xlTableBody
    MsgBox "Active cell is part of the table body"
End Select

' Example 2

Worksheets("Sheet1").Activate
If IsError(ActiveCell.Value) Then
    errval = ActiveCell.Value
    Select Case errval
        Case CVErr(xlErrDiv0)
            MsgBox "#DIV/0! error"
        Case CVErr(xlErrNA)
            MsgBox "#N/A error"
        Case CVErr(xlErrName)
            MsgBox "#NAME? error"
        Case CVErr(xlErrNull)
            MsgBox "#NULL! error"
        Case CVErr(xlErrNum)
            MsgBox "#NUM! error"
        Case CVErr(xlErrRef)
            MsgBox "#REF! error"
        Case CVErr(xlErrValue)
            MsgBox "#VALUE! error"
        Case Else
            MsgBox "This should never happen!!"
    End Select
End If