Читать книгу Excel 2019 Power Programming with VBA - Michael Alexander, Dick Kusleika - Страница 192

VBA exits a Select Case construct as soon as a True case is found. Therefore, for maximum efficiency, you should check the most likely case first.

Select Case structures can also be nested. The following procedure, for example, uses the VBA TypeName function to determine what is selected (a range, nothing, or anything else). If a range is selected, the procedure executes a nested Select Case and tests for the number of cells in the range. If one cell is selected, it displays One cell is selected. Otherwise, it displays a message with the number of selected rows.

Sub SelectionType() Select Case TypeName(Selection) Case "Range" Select Case Selection.Count Case 1 MsgBox "One cell is selected" Case Else MsgBox Selection.Rows.Count & " rows" End Select Case "Nothing" MsgBox "Nothing is selected" Case Else MsgBox "Something other than a range" End Select End Sub

This procedure also demonstrates the use of Case Else, a catchall case. You can nest Select Case constructs as deeply as you need, but make sure that each Select Case statement has a corresponding End Select statement.

This procedure demonstrates the value of using indentation in your code to clarify the structure. For example, take a look at the same procedure without the indentations:

Sub SelectionType() Select Case TypeName(Selection) Case "Range" Select Case Selection.Count Case 1 MsgBox "One cell is selected" Case Else MsgBox Selection.Rows.Count & " rows"Case "Nothing" MsgBox "Nothing is selected" Case Else MsgBox "Something other than a range" End Select End Sub

Fairly incomprehensible, eh?