如何将结构封送为指向结构的指针? [英] How do I marshal a structure as a pointer to a structure?

问题描述

我试图将结构从C#传递到C ++库.我将结构作为对象传递，C ++函数期望它作为指针(void *).

I am trying to pass a structure from C# into C++ library. I pass structure as an object, and C++ function expects it as a pointer (void *).

我在传递结构时遇到问题.

I am having problem passing the structure.

[DllImport("MockVadavLib.dll", CharSet = CharSet.Ansi)]
public static extern IntPtr TheFunction([MarshalAs(UnmanagedType.LPStruct)] UserRec userRec);

这是我得到的运行时异常文本:

Here is the run-time exception text I get:

无法编组参数#1":无效的托管/非托管类型组合(此值类型必须与Struct配对)."

"Cannot marshal 'parameter #1': Invalid managed/unmanaged type combination (this value type must be paired with Struct)."

尽管我找到了在这种情况下使用LPStruct的MSDN文章.

Though I found an MSDN article that uses LPStruct in exactly this context.

这是我要封送的结构:

[StructLayout(LayoutKind.Sequential)]
public struct UserRec {
    [MarshalAs(UnmanagedType.I4)]
    public int userParam1;
}

这是C ++函数:

MOCKVADAVLIB_API tVDACQ_CallBackRec * TheFunction(void * userParams) {...

推荐答案

尝试将结构作为ref参数传递.

Try passing the structure as a ref parameter.

[DllImport("MockVadavLib.dll", CharSet = CharSet.Ansi)]
public static extern IntPtr TheFunction(ref UserRec userRec);

当您将ref与结构结合使用时，它在概念上会传递地址.

When you use a ref combined with a structure, it conceptually passes the address.

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