Question

我正在寻找有关更改返回/传递到p / invoke函数的对象的结构/类布局的最佳实践指南。我已经找到了答案，但也许我太累了，而且我没有有效地搜索。

我能提出的最简单的例子（真正的一个在这里有点过于复杂）与GetWindowRect类似。

如果我想为RECT结构添加一些额外的属性，我应该将它添加到结构本身的定义中，还是应该切换到子类化以添加额外的属性？

是否有来自Microsoft或其他可靠来源的最佳做法围绕以下方法？这些都是最佳做法吗？

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetWindowRect(HandleRef hWnd, out RECT lpRect);

[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
    public int Left;        // x position of upper-left corner
    public int Top;         // y position of upper-left corner
    public int Right;       // x position of lower-right corner
    public int Bottom;      // y position of lower-right corner

    public string Extra;    // ADDED
}

对战

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetWindowRect(HandleRef hWnd, out RECT lpRect);

[StructLayout(LayoutKind.Sequential)]
public class RECT
{
    public int Left;        // x position of upper-left corner
    public int Top;         // y position of upper-left corner
    public int Right;       // x position of lower-right corner
    public int Bottom;      // y position of lower-right corner
}

public class RectEx : RECT
{
    public string Extra;    // Added

    public RectEx(RECT r)
    {
        Left = r.Left;
        Top = r.Top;
        Right = r.Right;
        Bottom = r.Bottom;
        Extra = "test";
    }
}

Answer 1

这是另一个选项：这允许您维护本机功能并为您正在使用的对象提供一些安全性。

// used internally in native method
[StructLayout(LayoutKind.Sequential)]
internal struct RECT
{
    public int Left;        // x position of upper-left corner
    public int Top;         // y position of upper-left corner
    public int Right;       // x position of lower-right corner
    public int Bottom;      // y position of lower-right corner
}


// public accessible struct with extra fields 
public struct RectEx
{
    public int Left;        // x position of upper-left corner
    public int Top;         // y position of upper-left corner
    public int Right;       // x position of lower-right corner
    public int Bottom;      // y position of lower-right corner

    public dynamic Extra = "Extra";
}


public static class UnsafeNativeMethods
{
    //used internally to populate RECT struct
    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool GetWindowRect(HandleRef hWnd, out RECT lpRect);

    //public safe method with exception handling and returns a RectEx
    public static RectEx GetWindowRectangle(HandleRef hWnd)
    {
        RECT r = new RECT();
        RectEx result = new RectEx();

        try
        {
            GetWindowRect(hWnd, r);
            result.Left = r.Left;
            result.Top = r.Top;
            result.Right = r.Right;
            result.Bottom = r.Bottom;
            // assign extra fields
        }
        catch(Exception ex)
        {
            // handle ex
        }

    return result;
    }
}

Answer 2

您还可以使用：的 StructLayout（LayoutKind.Explicit）

[StructLayout(LayoutKind.Sequential)] public struct Point { public int x; public int y; } [StructLayout(LayoutKind.Explicit)] public struct Rect { [FieldOffset(0)] public int left; [FieldOffset(4)] public int top; [FieldOffset(8)] public int right; [FieldOffset(12)] public int bottom; }

（来自http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.layoutkind.aspx）

从p / invoke修改struct布局

2 个答案: