Question

例如，这是IFileOpenDialog接口的完整定义，一个Windows Shell接口，取自Pinvoke站点：

[ComImport, Guid ( "d57c7288-d4ad-4768-be02-9d969532d960" ), InterfaceType ( ComInterfaceType.InterfaceIsIUnknown )]
interface IFileOpenDialog : IFileDialog
{
// Defined on IModalWindow - repeated here due to requirements of COM interop layer
// --------------------------------------------------------------------------------
[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime ), PreserveSig]
int Show ( [In] IntPtr parent );

// Defined on IFileDialog - repeated here due to requirements of COM interop layer
[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetFileTypes ( [In] uint cFileTypes, [In] COMDLG_FILTERSPEC[] rgFilterSpec );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetFileTypeIndex ( [In] uint iFileType );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetFileTypeIndex ( out uint piFileType );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void Advise ( [In, MarshalAs ( UnmanagedType.Interface )] IFileDialogEvents pfde, out uint pdwCookie );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void Unadvise ( [In] uint dwCookie );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetOptions ( [In] FOS fos );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetOptions ( out FOS pfos );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetDefaultFolder ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetFolder ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetFolder ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetCurrentSelection ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetFileName ( [In, MarshalAs ( UnmanagedType.LPWStr )] string pszName );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetFileName ( [MarshalAs ( UnmanagedType.LPWStr )] out string pszName );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetTitle ( [In, MarshalAs ( UnmanagedType.LPWStr )] string pszTitle );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetOkButtonLabel ( [In, MarshalAs ( UnmanagedType.LPWStr )] string pszText );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetFileNameLabel ( [In, MarshalAs ( UnmanagedType.LPWStr )] string pszLabel );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetResult ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void AddPlace ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi, NativeMethods.FDAP fdap );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetDefaultExtension ( [In, MarshalAs ( UnmanagedType.LPWStr )] string pszDefaultExtension );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void Close ( [MarshalAs ( UnmanagedType.Error )] int hr );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetClientGuid ( [In] ref Guid guid );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void ClearClientData ( );

// Not supported:  IShellItemFilter is not defined, converting to IntPtr
[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetFilter ( [MarshalAs ( UnmanagedType.Interface )] IntPtr pFilter );

// Defined by IFileOpenDialog
// ---------------------------------------------------------------------------------
[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetResults ( [MarshalAs ( UnmanagedType.Interface )] out IShellItemArray ppenum );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void GetSelectedItems ( [MarshalAs ( UnmanagedType.Interface )] out IShellItemArray ppsai );
}

如果我只使用此界面中的两种方法，我可以将它定义为：

[ComImport, Guid ( "d57c7288-d4ad-4768-be02-9d969532d960" ), InterfaceType ( ComInterfaceType.InterfaceIsIUnknown )]
interface IFileOpenDialog : IFileDialog
{
// Defined on IModalWindow - repeated here due to requirements of COM interop layer
// --------------------------------------------------------------------------------
[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime ), PreserveSig]
int Show ( [In] IntPtr parent );

[MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
void SetOptions ( [In] FOS fos );
}

它会起作用吗？或者我是否必须使用所有方法定义完整的界面？

Answer 1

不，这不起作用。 CLR根据声明为COM接口构建一个调度表。该表中函数指针的顺序由声明中方法定义的顺序设置。 Show（）方法将占用两种情况下的第一个插槽，没有麻烦。然而，SetOptions（）最终将调用第二个，实际上是SetFileTypes（）。它们有不同的参数，当实现获得垃圾参数并且堆栈变得不平衡时，它将以令人讨厌的方式进入kaboom。

你可以省略尾部的任何声明。另请注意，当您不调用该方法时，该方法的实际声明无关紧要。这允许你撒谎并避免必须声明他们的参数类型。确保该方法显然无法正常工作，请将其命名为 void DontCallMe2（）。

请注意，这些接口已包含在Windows API代码包以及.NET 4.0版本的Microsoft.Win32.OpenFileDialog和.NET 3.5的System.Windows.Forms.OpenFileDialog

版本中。

Answer 2

如果要定义实现接口的类型，则必须实现接口的所有元素。如果你不这样做，那么最好的情况是你的代码会出现“不稳定”的行为，最糟糕的情况是你的应用程序会在你的实现中尝试任何时崩溃界面。

请记住，这两个接口不相同：

[ComImport, Guid ( "d57c7288-d4ad-4768-be02-9d969532d960" ), InterfaceType ( ComInterfaceType.InterfaceIsIUnknown )]
interface IFileOpenDialog : IFileDialog
{
    [MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime ), PreserveSig]
    int Show ( [In] IntPtr parent );
}

[ComImport, Guid ( "d57c7288-d4ad-4768-be02-9d969532d960" ), InterfaceType ( ComInterfaceType.InterfaceIsIUnknown )]
interface IFileOpenDialog : IFileDialog
{
    [MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime ), PreserveSig]
    int Show ( [In] IntPtr parent );

    [MethodImpl ( MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime )]
    void SetOptions ( [In] FOS fos );
}

即使它们具有相同的名称，相同的Guid并且都实现Show，但只有一个实现SetOptions的事实使它们不同。

无论如何，从你未实现的接口的任何方法抛出NotImplemented异常，但是要说你实现接口ISomeInterface，你实际上必须这样做

在C＃中定义Windows API接口时，是否必须定义所有成员？我可以只定义我要使用的方法吗？

2 个答案: