在 Do Until 循环中未触发退出条件

Question

我正在尝试编写一个应用程序，它需要一个报告（Excel 工作表），操作一行，然后转到下一行，然后是下一行，等等，然后在前两个单元格中退出 Do Until 循环下一行是空的（表示没有更多行要处理），如下所示：

Imports Excel = Microsoft.Office.Interop.Excel

Dim MSExcel As New Excel.Application
MSExcel.Visible = True

Dim WorkbookA As Excel.Workbook
Dim WorksheetA As Excel.Worksheet

Dim i As Integer = 2 'Skipping header row
Dim Split() As String
Dim SomeStrings() As String = {"StringA", "StringB"} 'etc... an array of strings

WorkbookA = MSExcel.Workbooks.Open(TextBox1.Text)
WorksheetA = WorkbookA.Sheets.Item(1)

Do Until WorksheetA.Cells(i, 1).Value = "" And WorksheetA.Cells(i, 2).Value = ""

'~~If Column A cell does not contain 'valueA' or Column E cell does not contain 'valueB', delete the row
        Do Until InStr(WorksheetDisplay.Cells(i, 1).Value, "ValueA") <> 0 And InStr(WorksheetDisplay.Cells(i, 5).Value, "ValueB") <> 0 _
            And InStr("somenumbershere", Strings.Left((WorksheetDisplay.Cells(i, 3).Value), 1)) <> 0 'Only keeps entries that begin with a certain number
            WorksheetDisplay.Rows(i).Delete() 'Otherwise we delete the row
        Loop

        For Each Str As String In SomeStrings
            If Str = WorksheetDisplay.Cells(i, 3).Value Then
                Split = Strings.Split(WorksheetDisplay.Cells(i, 3).Value, " ")
                WorksheetDisplay.Cells(i, 3).Value = Split(0) & " some text here"
            End If
        Next

        i = i + 1

Loop

但是程序永远不会停止运行。

知道为什么吗？

Answer 1

在您的内部执行 until..loop 中，您正在检查三个不同的条件，如果不满足所有 3 个条件，您的代码将继续删除工作表的第一行。这会导致 Excel 不断向工作表底部添加行。

因此，这个内部 do 循环有可能永远运行，从而防止外部 do 循环评估空白单元格的存在。更好的逻辑安排可能是：

Do Until WorksheetA.Cells(i, 1).Value = "" And WorksheetA.Cells(i, 2).Value = ""
  If InStr(WorksheetDisplay.Cells(i, 1).Value, "ValueA") <> 0 And InStr(WorksheetDisplay.Cells(i, 5).Value, "ValueB") <> 0 _
            And InStr("somenumbershere", Strings.Left((WorksheetDisplay.Cells(i, 3).Value), 1)) <> 0 'Only keeps entries that begin with a certain number
    WorksheetDisplay.Rows(i).Delete() 'Otherwise we delete the row
    'Decrement i so that the row that used to be beneath the row just deleted is not skipped.
    i = i - 1
  Else
    For Each Str As String In SomeStrings
      If Str = WorksheetDisplay.Cells(i, 3).Value Then
        Split = Strings.Split(WorksheetDisplay.Cells(i, 3).Value, " ")
        WorksheetDisplay.Cells(i, 3).Value = Split(0) & " some text here"
      End If
    Next
  End If
  i = i + 1
Loop

我没有运行这段代码，因为我不知道你需要测试什么样的数据集；但基本上，如果你删除了一行，你需要回到外部的do循环来检查你是否已经用完了数据，如果有就停止执行。