'TestString' is not declared. It may be inaccessible due to its protection level. (BC30451) [closed]

问题

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.

Closed 6 years ago.

I am trying out some on the fly code compilation using the VBCodeProvider class. What I want to be able to do is modify a public variable in my assembly in the code.

I have a Public TestString As String = "" in my application.

This is the code I am using to compile:

    Dim codeProvider As New VBCodeProvider()
    Dim optParams As New CompilerParameters
    optParams.ReferencedAssemblies.Add("MyAssembly.exe")
    optParams.ReferencedAssemblies.Add("system.windows.forms.dll")
    optParams.CompilerOptions = "/t:library"
    optParams.GenerateInMemory = True
    Dim results As CompilerResults = codeProvider.CompileAssemblyFromSource(optParams, RichTextBox1.Text)

    If results.Errors.Count > 0 Then
        Dim sb As New StringBuilder("Compilation Failed with the following error(s)" + CR_LF + CR_LF)
        For Each CompErr As CompilerError In results.Errors
            sb.Append(String.Format("Line {0} - {1} ({2}){3}", CompErr.Line, CompErr.ErrorText, CompErr.ErrorNumber, CR_LF))
        Next
        MessageBox.Show(sb.ToString, "Compile Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
    Else
        Dim assy As System.Reflection.Assembly = results.CompiledAssembly
        Dim exeinstance As Object = assy.CreateInstance("Script")
        Dim typ As Type = exeinstance.GetType
        Dim method As MethodInfo = typ.GetMethod("Main")
        method.Invoke(exeinstance, Nothing)
    End If

This is the code in my textbox:

Imports System
Imports MyAssembly

Class Script
    Sub Main()
       TestString="foo"' <-- This line fails compilation
    End Sub
End Class

The error I get is 'TestString' is not declared. It may be inaccessible due to its protection level. (BC30451)

回答1:

Just like normal VB.NET, as well as adding a reference, you have to Imports the relevant namespace, or specify it fully. (You've edited the question to now include this.)

After inserting your code into a new Console project in VS2008 (because that's what I had open) and adjusting for my assembly names, I saw the same as you.

I fixed it by adding Public to the default Module Module1.

来源：https://stackoverflow.com/questions/11860742/teststring-is-not-declared-it-may-be-inaccessible-due-to-its-protection-level