Question

在以下代码段中，由于调试器说在Strings.InStr（）函数的以下行正常工作时未分配变量Test1，因此正在跳过Strings.Len（）函数或不返回值：

   sOPCTagItem = opcTagItem.Cells.Value --> assigns "DO1001_Inp_IOFault"    
   sBaseTagItemName = Left(sOPCTagItem, InStr(sOPCTagItem, "_") - 1) --> assigns "DO1001"

   iTest1 = Len(sOPCTagItem)  --> = nothing assigned
   iTest2 = InStr(sOPCTagItem, "_") --> = 7
   iTest1 = iTest1 - iTest2   --> = nothing assigned
   sBaseTagItemExtension = Right(sOPCTagItem, Len(sOPCTagItem) - InStr    (sOPCTagItem, "_"))   --> = nothing assigned

Answer 1

这两种方法均适用于您的方案。它们将取决于您的输入数据以及数据中下划线定界符的一致性。

您可能只是想念Option Explicit On

Private Sub Button18_Click(sender As Object, e As EventArgs) Handles Button18.Click
    Debug.Print(getBaseTagItem("DO1001_Inp_IOFault"))
    Debug.Print(getBaseTagItemOldSchool("DO1001_Inp_IOFault"))
End Sub

Private Function getBaseTagItem(tagItem As String)

    Dim vals() As String = tagItem.Split("_"c)
    Return String.Concat(vals(1), "_", vals(2))

End Function

Private Function getBaseTagItemOldSchool(tagItem As String)

    Dim sOPCTagItem As String = tagItem
    Dim sBaseTagItemName As String = Strings.Left(sOPCTagItem, InStr(sOPCTagItem, "_") - 1)

    Dim iTest1 As Integer = Len(sOPCTagItem)
    Dim iTest2 As Integer = InStr(sOPCTagItem, "_")
    iTest1 = iTest1 - iTest2
    Dim sBaseTagItemExtension As String = Strings.Right(sOPCTagItem, Len(sOPCTagItem) - InStr(sOPCTagItem, "_"))
    Return sBaseTagItemExtension

End Function

Answer 2

奇怪的是，它们的返回值是整数，因此什么也不返回。我会尝试使用适当的String方法。

    iTest1 = sOPCTagItem.Length
    iTest2 = sOPCTagItem.IndexOf("_")
    iTest1 = iTest1 - iTest2
    sBaseTagItemExtension = sOPCTagItem.Substring(sOPCTagItem.Length - sOPCTagItem.IndexOf("_"))

LEN函数未在VB.NET中返回值

2 个答案: