C# DLL 无法影响从 VB6 应用程序通过引用传递的数字值

发布于 2024-12-14 16:23:29 字数 806 浏览 3 评论 0原文

我有一个调用 VB6 DLL 的旧版 VB6 应用程序，并且我正在尝试将 VB6 DLL 移植到 C#，但尚未接触主 VB6 应用程序代码。旧的 VB6 DLL 有一个接口，该接口通过引用接收 VB6 long（32 位整数）并更新该值。在我编写的 C# DLL 中，主 VB6 应用程序永远看不到更新后的值。它的行为就好像真正编组到 C# DLL 的是对原始数据副本的引用，而不是对原始数据的引用。我可以成功地通过引用传递数组并更新它们，但单个值不起作用。

C# DLL 代码看起来像这样：

[ComVisible(true)]
public interface IInteropDLL
{
   void Increment(ref Int32 num);
}
[ComVisible(true)]
public class InteropDLL : IInteropDLL
{
    public void Increment(ref Int32 num) { num++; }
}

调用 VB6 代码看起来像这样：

Private dll As IInteropDLL
Private Sub Form_Load()
    Set dll = New InteropDLL
End Sub
Private Sub TestLongReference()
    Dim num As Long
    num = 1
    dll.Increment( num )
    Debug.Print num      ' prints 1, not 2.  Why?
End Sub

我做错了什么？我需要做什么来修复它？提前致谢。

原文

I have a legacy VB6 application that calls a VB6 DLL, and I am trying to port the VB6 DLL to C# without yet touching the main VB6 application code. The old VB6 DLL had one interface that received a VB6 long (32-bit integer) by reference, and updated the value. In the C# DLL I have written, the updated value is never seen by the main VB6 application. It acts as though what was really marshalled to the C# DLL was a reference to a copy of the original data, not a reference to the original data. I can successfully pass arrays by reference, and update them, but single values aren't behaving.

The C# DLL code looks something like this:

[ComVisible(true)]
public interface IInteropDLL
{
   void Increment(ref Int32 num);
}
[ComVisible(true)]
public class InteropDLL : IInteropDLL
{
    public void Increment(ref Int32 num) { num++; }
}

The calling VB6 code looks something like this:

Private dll As IInteropDLL
Private Sub Form_Load()
    Set dll = New InteropDLL
End Sub
Private Sub TestLongReference()
    Dim num As Long
    num = 1
    dll.Increment( num )
    Debug.Print num      ' prints 1, not 2.  Why?
End Sub

What am I doing wrong? What would I have to do to fix it?
Thanks in advance.

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寂寞陪衬 2024-12-21 16:23:31

dll.Increment( num )

因为您使用括号，所以该值强制按值传递，而不是按引用传递（编译器创建一个临时副本并按引用传递该）。

删除括号：

dll.Increment num

编辑：更完整的解释，作者：马克J。

dll.Increment( num )

Because you are using parentheses, the value is forcibly passed by value, not by reference (the compiler creates a temporary copy and passes that by reference).

Remove the parentheses: