如何从.dll导入和使用功能到VB.NET？ 我在VBA中对此有解决方案，但对于VB.NET没有？

Question

我是VB.NET的新手。 我有一些用VBA编写的应用程序，现在想转移到VB.NET。 有一个示例我如何声明这些.dll函数：

Public Declare Function loadsession Lib "vpmsdl32" (ByVal vpmname As String) As Long
Public Declare Function setvar Lib "vpmsdl32.dll" (ByVal session As Long, ByVal fieldname As String, ByVal value As String) As Long
Public Declare Function compute Lib "vpmsdl32.dll" (ByVal session As Long, ByVal what As String, ByVal result As String, ByVal result_buffer_size As Long, ByVal message As String, ByVal message_buffer_size As Long, ByVal fieldref As String, ByVal fieldref_buffer_size As Long) As Long
Public Declare Function closesession Lib "vpmsdl32.dll" (ByVal session As Long) As Long
Public Declare Function unloadall Lib "vpmsdl32" () As Long

我在VBA代码中使用这种方式，例如，当我使用函数loadsession打开会话时：

session = loadsession("absolute-path-to-the-file")

设置输入参数：

ret = setvar(session, "Input name", "Input value")

（提示：我不必声明变量ret ）之后，我可以使用以下命令执行计算：

retcomp = compute(session, "Output name", result, 4000, msg, 1000, fieldref, 250)

（提示：我也不必声明变量retcomp ）之后，我得到变量结果中的计算result （对于某些情况，我不清楚如何使用变量将函数作为输出变量调用）为什么此函数将计算result分配给可变result ，但是它起作用了！）

现在，我正在尝试在VB.NET应用程序中实现类似的方法。 首先，我执行DLLImport of these functions ：

Public Class PInvoke
<DllImport("vpmsdl32.dll", SetLastError:=True, CharSet:=CharSet.Unicode, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function loadsession(ByVal vpmname As String) As Long
End Function

<DllImport("vpmsdl32.dll", SetLastError:=True, CharSet:=CharSet.Unicode, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function setvar(ByVal session As Long, ByVal fieldname As String, ByVal value As String) As Long
End Function

<DllImport("vpmsdl32.dll", SetLastError:=True, CharSet:=CharSet.Unicode, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function compute(ByVal session As Long, ByVal what As String, ByVal result As String, ByVal result_buffer_size As Long, ByVal message As String, ByVal message_buffer_size As Long, ByVal fieldref As String, ByVal fieldref_buffer_size As Long) As Long
End Function

<DllImport("vpmsdl32.dll", SetLastError:=True, CharSet:=CharSet.Unicode, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function closesession(ByVal session As Long) As Long
End Function

<DllImport("vpmsdl32.dll", SetLastError:=True, CharSet:=CharSet.Unicode, CallingConvention:=CallingConvention.StdCall)> _
Public Shared Function unloadall() As Long
End Function
End Class

然后我调用这些函数，它可以用于打开会话，例如PInvoke.loadsession 。 但是我不知道如何通过我在VBA中使用的类似原理来访问PInvoke.compute函数的结果？

非常感谢您的答复！