Question

您好我有以下代码：

Dim ColMap As Integer = Val(Microsoft.VisualBasic.Left(dr("MappedTo").ToString(), 3))  
Dim ValorLeido As String  

ValorLeido = temp(dr("NoColumn").ToString())  

Select Case ColMap  
      Case 101  
         _101 = ValorLeido  
      Case 102  
         _102 = ValorLeido  
      Case 103  
         _103 = ValorLeido  
End Select

有没有办法可以使用像我这样的东西（“_”和ColMap）= ValorLeido ??

Answer 1

以下是显示 CallByName（）的简化示例。请注意，目标变量为公开：

Public Class Form1

    Public _101 As String
    Public _102 As String = "{Default Value}"
    Public _103 As String

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Debug.Print("Before: _102 = " & _102)

        Dim ColMap As Integer = 102
        Dim ValorLeido As String = "Hello World!"

        Dim varName As String = "_" & ColMap
        CallByName(Me, varName, CallType.Let, ValorLeido)

        Debug.Print("After: _102 = " & _102)
    End Sub

End Class

通过反射来实现同样的目的，它允许目标变量私有：

Imports System.Reflection
Public Class Form1

    Private _101 As String
    Private _102 As String = "{Default Value}"
    Private _103 As String

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Debug.Print("Before: _102 = " & _102)

        Dim ColMap As Integer = 102
        Dim ValorLeido As String = "Hello World!"

        Dim varName As String = "_" & ColMap
        Dim fi As FieldInfo = Me.GetType.GetField(varName, Reflection.BindingFlags.Public Or Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
        fi.SetValue(Me, ValorLeido)

        Debug.Print("After: _102 = " & _102)
    End Sub

End Class

Answer 2

尝试使用存储介质来保存一系列ID到一系列值，例如词典

Dim ColMap As Integer = Val(Microsoft.VisualBasic.Left(dr("MappedTo").ToString(), 3))  
Dim ValorLeido As String = temp(dr("NoColumn").ToString())  
Dim Lookup as New Generic.Dictionary(of Integer,String)
Lookup(ColMap) = ValorLeido

' 1 way of Reading values out of a dictionary safely
Dim Value as string
Value=""

if lookup.trygetvalue("101",value) then
    msgbox("Value for 101 is """ & value & """")
else
    msgbox("Value for 101 is not found)
end if

如果此结构已存在，您还可以通过单个索引属性进行访问

public property Value(Index as integer) as string
    get
         select case index
             case 101
                  return _101
             case 102
                  return _102
             case 103
                  return _103
             case else
                  Throw new exception("Index not present " & index)
    end get
    set (value as string)
        ' populate with reverse process ...
    end set
end property

vb.net如何引用局部变量

2 个答案: