如何调用带有可接受多种不同类型参数的函数?

本文关键字：类型参数函数可接受何调用调用 | 更新日期: 2023-09-27 18:10:13

看一下:

[DllImport("User32.dll")]
public static extern StatusCode DisplayConfigGetDeviceInfo(
    ref IDisplayConfigInfo a
);

现在我的结构继承自IDisplayConfigInfo:

var displayConfigTargetDeviceName = new DisplayConfigTargetDeviceName
{
    header = new DisplayConfigDeviceInfoHeader
    {
        adapterId = targetModeInfo.adapterId,
        id = targetModeInfo.id,
        size = Marshal.SizeOf(typeof(DisplayConfigTargetDeviceName)),
        type = DisplayConfigDeviceInfoType.GetTargetName,
    }
};
var configTargetDeviceName = (IDisplayConfigInfo) displayConfigTargetDeviceName;
var retval = CCDWrapper.DisplayConfigGetDeviceInfo(ref configTargetDeviceName);

现在有一个问题。检索将返回"InvalidParameter"值。为什么呢?这是因为我试图使用界面，但我不明白为什么。

当我明确地说DisplayConfigGetDeviceInfo()接受DisplayConfigTargetDeviceName而不是interface，并将DisplayConfigTargetDeviceName直接传递给它时，它就工作了。

问题是，我不想为每个结构创建8-9个重载。注意，c++版本只有一个重载。它会从我传递的指针中计算出剩余的值。

//结构:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct DisplayConfigTargetDeviceName : IDisplayConfigInfo
{
    public DisplayConfigDeviceInfoHeader header;
    public DisplayConfigTargetDeviceNameFlags flags;
    public DisplayConfigVideoOutputTechnology outputTechnology;
    public ushort edidManufactureId;
    public ushort edidProductCodeId;
    public uint connectorInstance;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)] 
    public string monitorFriendlyDeviceName;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)] 
    public string monitorDevicePath;
}
[StructLayout(LayoutKind.Sequential)]
public struct DisplayConfigDeviceInfoHeader
{
    public DisplayConfigDeviceInfoType type;
    public int size;
    public LUID adapterId;
    public uint id;
}

和IDisplayConfig接口为空。

如何调用带有可接受多种不同类型参数的函数?

感谢David，我能够想出一个聪明的解决方案(在我看来)，它似乎工作得很好。

[DllImport("User32.dll")]
private static extern StatusCode DisplayConfigSetDeviceInfo(IntPtr requestPacket);
public static StatusCode DisplayConfigSetDeviceInfo<T>(ref T displayConfig) 
   where T : IDisplayConfigInfo
{
    return WrapStructureAndCall(ref displayConfig, DisplayConfigSetDeviceInfo);
}

[DllImport("User32.dll")]
private static extern StatusCode DisplayConfigGetDeviceInfo(IntPtr targetDeviceName);
public static StatusCode DisplayConfigGetDeviceInfo<T>(ref T displayConfig) 
  where T : IDisplayConfigInfo
{
    return WrapStructureAndCall(ref displayConfig, DisplayConfigGetDeviceInfo);
}
public static StatusCode WrapStructureAndCall<T>(ref T displayConfig,
    Func<IntPtr, StatusCode> func) where T : IDisplayConfigInfo
{
    var ptr = Marshal.AllocHGlobal(Marshal.SizeOf(displayConfig));
    Marshal.StructureToPtr(displayConfig, ptr, false);
    var retval = func(ptr);
    displayConfig = (T)Marshal.PtrToStructure(ptr, displayConfig.GetType());
    Marshal.FreeHGlobal(ptr);
    return retval;
}

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