c# - P/调用 const char 指针和 int 引用

Question

我尝试在 C# 中 P/Invoke C 函数，但总是收到 System.AccessViolationException。请帮助我理解我做错了什么？

C 代码:

RAYGUIDEF bool GuiListView(Rectangle bounds, const char *text, int *active, int *scrollIndex, bool editMode);

C# 代码:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct Rectangle
{
    public float x;
    public float y;
    public float width;
    public float height;

    public Rectangle(float x, float y, float width, float height)
    {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    } 
}

[DllImport(nativeLibName,CallingConvention = CallingConvention.Cdecl)]
            public static extern bool GuiListView(Rectangle bounds, [MarshalAs(UnmanagedType.LPStr)]string text,[Out] int active, [Out] int scrollIndex, bool editMode);

Answer 1

当使用 P/Invoke 传递指针时，例如使用 active 和 scrollIndex 变量，您需要在托管签名。请参阅here了解 ref 和 [out] 之间的区别。

有一些工具可以帮助生成这些签名。使用 P\Invoke Interop Assistant:

    [System.Runtime.InteropServices.DllImportAttribute("<Unknown>", EntryPoint="GuiListView")]
    [return: System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.I1)]
public static extern  bool GuiListView(Rectangle bounds, [System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string text, ref int active, ref int scrollIndex, [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.I1)] bool editMode) ;