如何使用VB.NET为字符串赋值？

Question

考虑以下代码:

    Dim S1 As String = "a"

    'this is the string in a file
    Dim StringFromFile As String = "S1=hello"

    Dim temp() As String = Split(StringFromFile, "=", -1, CompareMethod.Binary)
    'temp(0) = variable name
    'temp(1) = variable value

    'my question is: how to assign value to S1?

我已经声明了一个名为S1的字符串.现在我想为S1分配新值.新字符串值使用以下格式存储在文件中:[变量名称] [=作为分隔符] [字符串值].在检索存储在文件中的字符串变量名称和值后,如何将值分配给S1？

注意:

temp(0) = "S1"
temp(1) = "hello"

应该注意的是,带有数据的字符串来自一个可能会不时变化的文件!当文件发生变化时,我也希望变量也能改变.

进一步澄清

我需要一段代码,当处理像"S1 = hello"这样的字符串时,代码将首先找到一个声明的变量(即S1),然后为S1变量分配"hello"字符串."="仅作为变量名和变量值的分隔符.

更新:

我尝试使用Mathias Lykkegaard Lorenzen的EDIT 2示例,但在这一行上失败了"NullReferenceException" "Field.SetValue(Me, VariableValue)".请帮我解决问题.以下是基于Mathias Lykkegaard Lorenzen的EDIT 2示例的代码:

Public Sub Ask()
    Try
        Dim S1 As String = "a"

        Dim StringFromFile As String = "S1=hello"

        Dim temp() As String = Split(StringFromFile, "=", -1, CompareMethod.Binary)
        'temp(0) = variable name
        'temp(1) = variable value

        'my question is: how to assign value to S1?
        Dim TypeOfMe As Type = Me.GetType()

        'did this for readability.
        Dim VariableName As String = temp(0)
        Dim VariableValue As String = temp(1)

        'get the field in the class which is private, given the specific name (VariableName).
        Dim Field As FieldInfo = TypeOfMe.GetField(VariableName, BindingFlags.NonPublic Or BindingFlags.Instance)

        'set the value of that field, on the object "Me".
        Field.SetValue(Me, VariableValue) '<-- this line caused NullReferenceException
        MessageBox.Show(S1)
    Catch ex As Exception
        MessageBox.Show(ex.ToString)
    End Try

End Sub

Answer 1

您可以使用反射来设置S1值:

Imports System.Reflection

Public Class Form1
    Public S1 As String = "a"

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Dim StringFromFile As String = "S1=hello"

        Dim temp() As String = Split(StringFromFile, "=", -1, CompareMethod.Binary)
        'temp(0) = variable name
        'temp(1) = variable value

        SetS1(Me, "S1", temp(1))
        MessageBox.Show(S1)
    End Sub

    ''' <summary>
    ''' 
    ''' </summary>
    ''' <param name="obj">the class that stores your S1 public field</param>
    ''' <param name="fieldName">that is your S1 field</param>
    ''' <param name="Value">S1 new value, that is hello</param>
    ''' <remarks></remarks>
    Public Sub SetS1(ByVal obj As Object, ByVal fieldName As String, ByVal Value As Object)
        Try
            Dim fi As FieldInfo = obj.GetType().GetField(fieldName, BindingFlags.Instance Or BindingFlags.Public Or BindingFlags.NonPublic)
            If Not fi Is Nothing Then
                fi.SetValue(obj, Value)
            End If

        Catch ex As Exception

        End Try
    End Sub
End Class

额外资源

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