Как получить функцию GetData IDataObject, не зная тип?

Question

Я разработал функциональность, с помощью которой пользователь может перетаскивать вложенные вложения электронной почты в мое приложение. Я извлекаю удаленные имена вложений, передавая формат "FileGroupDescriptor" и используя формат "FileContents" для извлечения потока вложений. Это нормально работает в моей системе, но на некоторых другие парни системы эта функция не может извлечь данные вложения. Итак, я думал о реализации функции, где я не жестко кодировать формат типа и извлекать его из самого IDataObject. Есть ли способ сделать это? Пожалуйста, найдите ниже код, который я использую:

public object GetData(string format, bool autoConvert)
{
        try
        {
            //handle the "FileGroupDescriptor" and "FileContents" format request in this class otherwise pass through to underlying IDataObject 
            switch (format)
            {
                case "FileGroupDescriptor":
                    //override the default handling of FileGroupDescriptor which returns a
                    //MemoryStream and instead return a string array of file names
                    IntPtr fileGroupDescriptorAPointer = IntPtr.Zero;
                    try
                    {
                        //use the underlying IDataObject to get the FileGroupDescriptor as a MemoryStream
                        Object o = underlyingDataObject.GetData(typeof(Object));
                        MemoryStream fileGroupDescriptorStream = (MemoryStream)this.underlyingDataObject.GetData("FileGroupDescriptor", autoConvert);
                        byte[] fileGroupDescriptorBytes = new byte[fileGroupDescriptorStream.Length];
                        fileGroupDescriptorStream.Read(fileGroupDescriptorBytes, 0, fileGroupDescriptorBytes.Length);
                        fileGroupDescriptorStream.Close();

                        //copy the file group descriptor into unmanaged memory 
                        fileGroupDescriptorAPointer = Marshal.AllocHGlobal(fileGroupDescriptorBytes.Length);
                        Marshal.Copy(fileGroupDescriptorBytes, 0, fileGroupDescriptorAPointer, fileGroupDescriptorBytes.Length);

                        //marshal the unmanaged memory to to FILEGROUPDESCRIPTORA struct
                        object fileGroupDescriptorObject = Marshal.PtrToStructure(fileGroupDescriptorAPointer, typeof(NativeMethods.FILEGROUPDESCRIPTORA));
                        NativeMethods.FILEGROUPDESCRIPTORA fileGroupDescriptor = (NativeMethods.FILEGROUPDESCRIPTORA)fileGroupDescriptorObject;

                        //create a new array to store file names in of the number of items in the file group descriptor
                        string[] fileNames = new string[fileGroupDescriptor.cItems];

                        //get the pointer to the first file descriptor
                        IntPtr fileDescriptorPointer = (IntPtr)((long)fileGroupDescriptorAPointer + Marshal.SizeOf(fileGroupDescriptorAPointer));

                        //loop for the number of files acording to the file group descriptor
                        for (int fileDescriptorIndex = 0; fileDescriptorIndex < fileGroupDescriptor.cItems; fileDescriptorIndex++)
                        {
                            //marshal the pointer top the file descriptor as a FILEDESCRIPTORA struct and get the file name
                            NativeMethods.FILEDESCRIPTORA fileDescriptor = (NativeMethods.FILEDESCRIPTORA)Marshal.PtrToStructure(fileDescriptorPointer, typeof(NativeMethods.FILEDESCRIPTORA));
                            fileNames[fileDescriptorIndex] = fileDescriptor.cFileName;

                            //move the file descriptor pointer to the next file descriptor
                            fileDescriptorPointer = (IntPtr)((long)fileDescriptorPointer + Marshal.SizeOf(fileDescriptor));
                        }

                        //return the array of filenames
                        return fileNames;
                    }
                    finally
                    {
                        //free unmanaged memory pointer
                        Marshal.FreeHGlobal(fileGroupDescriptorAPointer);
                    }

                case "FileGroupDescriptorW":
                    //override the default handling of FileGroupDescriptorW which returns a
                    //MemoryStream and instead return a string array of file names
                    IntPtr fileGroupDescriptorWPointer = IntPtr.Zero;
                    try
                    {
                        //use the underlying IDataObject to get the FileGroupDescriptorW as a MemoryStream
                        MemoryStream fileGroupDescriptorStream = (MemoryStream)this.underlyingDataObject.GetData("FileGroupDescriptorW");
                        byte[] fileGroupDescriptorBytes = new byte[fileGroupDescriptorStream.Length];
                        fileGroupDescriptorStream.Read(fileGroupDescriptorBytes, 0, fileGroupDescriptorBytes.Length);
                        fileGroupDescriptorStream.Close();

                        //copy the file group descriptor into unmanaged memory
                        fileGroupDescriptorWPointer = Marshal.AllocHGlobal(fileGroupDescriptorBytes.Length);
                        Marshal.Copy(fileGroupDescriptorBytes, 0, fileGroupDescriptorWPointer, fileGroupDescriptorBytes.Length);

                        //marshal the unmanaged memory to to FILEGROUPDESCRIPTORW struct
                        object fileGroupDescriptorObject = Marshal.PtrToStructure(fileGroupDescriptorWPointer, typeof(NativeMethods.FILEGROUPDESCRIPTORW));
                        NativeMethods.FILEGROUPDESCRIPTORW fileGroupDescriptor = (NativeMethods.FILEGROUPDESCRIPTORW)fileGroupDescriptorObject;

                        //create a new array to store file names in of the number of items in the file group descriptor
                        string[] fileNames = new string[fileGroupDescriptor.cItems];

                        //get the pointer to the first file descriptor
                        IntPtr fileDescriptorPointer = (IntPtr)((int)fileGroupDescriptorWPointer + Marshal.SizeOf(fileGroupDescriptorWPointer));

                        //loop for the number of files acording to the file group descriptor
                        for (int fileDescriptorIndex = 0; fileDescriptorIndex < fileGroupDescriptor.cItems; fileDescriptorIndex++)
                        {
                            //marshal the pointer top the file descriptor as a FILEDESCRIPTORW struct and get the file name
                            NativeMethods.FILEDESCRIPTORW fileDescriptor = (NativeMethods.FILEDESCRIPTORW)Marshal.PtrToStructure(fileDescriptorPointer, typeof(NativeMethods.FILEDESCRIPTORW));
                            fileNames[fileDescriptorIndex] = fileDescriptor.cFileName;

                            //move the file descriptor pointer to the next file descriptor
                            fileDescriptorPointer = (IntPtr)((int)fileDescriptorPointer + Marshal.SizeOf(fileDescriptor));
                        }

                        //return the array of filenames
                        return fileNames;
                    }
                    finally
                    {
                        //free unmanaged memory pointer
                        Marshal.FreeHGlobal(fileGroupDescriptorWPointer);
                    }

                case "FileContents":
                    //override the default handling of FileContents which returns the
                    //contents of the first file as a memory stream and instead return
                    //a array of MemoryStreams containing the data to each file dropped

                    //get the array of filenames which lets us know how many file contents exist
                    string[] fileContentNames = (string[])this.GetData("FileGroupDescriptor");

                    //create a MemoryStream array to store the file contents
                    MemoryStream[] fileContents = new MemoryStream[fileContentNames.Length];

                    //loop for the number of files acording to the file names
                    for (int fileIndex = 0; fileIndex < fileContentNames.Length; fileIndex++)
                    {
                        //get the data at the file index and store in array
                        fileContents[fileIndex] = this.GetData(format, fileIndex);
                    }

                    //return array of MemoryStreams containing file contents
                    return fileContents;
            }

            //use underlying IDataObject to handle getting of data
            return this.underlyingDataObject.GetData(format, autoConvert);
        }
        catch (Exception ex)
        {

        }
}

Я вызываю вышеуказанную функцию, используя следующий код:

if (e.Data.GetDataPresent(DataFormats.FileDrop))  
// drag drop from explorer to outlook DM Repository
      filenames = (string[])(e.Data.GetData(DataFormats.FileDrop));
else
{
      OutlookDataObject dataObject = new OutlookDataObject(e.Data);
      filenames = (string[])dataObject.GetData("FileGroupDescriptor");
      filestreams = (MemoryStream[])dataObject.GetData("FileContents");
}

Answer 1

Используйте метод IDataObject::EnumFormatEtc - см. https://msdn.microsoft.com/en-us/library/windows/desktop/ms683979(v=vs.85).aspx