类型不能作为非托管结构封送

Question

我正在尝试更改核心项目中的分辨率。

var devmode = default(Devmode);
devmode.DmDeviceName = new string(new char[32]);
devmode.DmFormName = new string(new char[32]);
devmode.Dmsize = (short)Marshal.SizeOf(devmode);

在上述代码的第 3 行，它失败并产生 "cannot be marshaled as an unmanaged structure; no meaningful size or offset can be computed" 错误。

任何人都可以提供一些关于我应该如何解决这个问题的见解吗？奇怪的是，在我提取一些不应该影响此代码的其他代码之前，它工作正常。

结构：

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct Devmode
{
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    public string DmFormName;
    public string DmDeviceName;

    public short Dmsize;

    public int DmPelsWidth;
    public int DmPelsHeight;

    private readonly short dmlogPixels;
    private readonly short dmbitsPerPel;
    private readonly int dmdisplayFlags;
    private readonly int dmdisplayFrequency;
    private readonly int dmiCMMethod;
    private readonly int dmiCMIntent;
    private readonly int dmmediaType;
    private readonly int dmditherType;
    private readonly int dmreserved1;
    private readonly int dmreserved2;
    private readonly int dmpanningWidth;
    private readonly int dmpanningHeight;

    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    private readonly short dmspecVersion;
    private readonly short dmdriverVersion;
    private readonly short dmdriverExtra;
    private readonly int dmfields;
    private readonly int dmpositionX;
    private readonly int dmpositionY;
    private readonly int dmdisplayOrientation;
    private readonly int dmdisplayFixedOutput;
    private readonly short dmcolor;
    private readonly short dmduplex;
    private readonly short dmyResolution;
    private readonly short dmtTOption;
    private readonly short dmcollate;
}

编辑：我现在将代码更改为：

        [StructLayout(LayoutKind.Sequential)]
    public struct Devmode
    {
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 0x20)]

        private readonly string dmdeviceName;

        private readonly short dmspecVersion;
        private readonly short dmdriverVersion;

        public short Dmsize;

        private readonly short dmdriverExtra;
        private readonly int dmfields;
        private readonly int dmpositionX;
        private readonly int dmpositionY;
        private readonly int dmdisplayOrientation;
        private readonly int dmdisplayFixedOutput;
        private readonly short dmcolor;
        private readonly short dmduplex;
        private readonly short dmyResolution;
        private readonly short dmtTOption;
        private readonly short dmcollate;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 0x20)]
        private readonly string dmformName;
        private readonly short dmlogPixels;
        private readonly short dmbitsPerPel;

        public int dmpelsWidth;
        public int dmpelsHeight;

        private readonly int dmdisplayFlags;
        private readonly int dmdisplayFrequency;
        private readonly int dmiCMMethod;
        private readonly int dmiCMIntent;
        private readonly int dmmediaType;
        private readonly int dmditherType;
        private readonly int dmreserved1;
        private readonly int dmreserved2;
        private readonly int dmpanningWidth;
        private readonly int dmpanningHeight;
    }

但是我收到 dmpelsWidth、dmpelsHeight 和 Dmsize 的错误。 'Public' 位会员必须在 'private' 位会员之前...

有什么想法吗？

Answer 1

DmDeviceName 字段缺少 MarshalAs 属性。

它应该看起来像：

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string DmFormName;

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
public string DmDeviceName;

顺便说一句，这段代码毫无意义：

devmode.DmDeviceName = new string(new char[32]);
devmode.DmFormName = new string(new char[32]);

只需删除这些行。这些值将由调用的 WinAPI 函数填充（如果可能）。

而最大的问题是：你的结构定义无效！字段顺序重要！您不能重新排序字段。请像我一样使用结构定义 .

类型不能作为非托管结构封送

Type cannot be marshaled as an unmanaged structure

c#

pinvoke

winapi

struct

marshalling