WindowBuilder Pro уже установлен в Eclipse?

Да. Измените использование FastZip на new ZipFile(stream), но это работает только в том случае, если ваш поток может искать. (Просто используйте свой MemoryStream в new ZipFile(fs); вместо чтения потока файлов, как в примере.)

C#
using ICSharpCode.SharpZipLib.Core;
using ICSharpCode.SharpZipLib.Zip;

public void ExtractZipFile(string archiveFilenameIn, string password, string outFolder) {
    ZipFile zf = null;
    try {
        FileStream fs = File.OpenRead(archiveFilenameIn);
        zf = new ZipFile(fs);
        if (!String.IsNullOrEmpty(password)) {
            zf.Password = password;     // AES encrypted entries are handled automatically
        }
        foreach (ZipEntry zipEntry in zf) {
            if (!zipEntry.IsFile) {
                continue;           // Ignore directories
            }
            String entryFileName = zipEntry.Name;
            // to remove the folder from the entry:- entryFileName = Path.GetFileName(entryFileName);
            // Optionally match entrynames against a selection list here to skip as desired.
            // The unpacked length is available in the zipEntry.Size property.

            byte[] buffer = new byte[4096];     // 4K is optimum
            Stream zipStream = zf.GetInputStream(zipEntry);

            // Manipulate the output filename here as desired.
            String fullZipToPath = Path.Combine(outFolder, entryFileName);
            string directoryName = Path.GetDirectoryName(fullZipToPath);
            if (directoryName.Length > 0)
                Directory.CreateDirectory(directoryName);

            // Unzip file in buffered chunks. This is just as fast as unpacking to a buffer the full size
            // of the file, but does not waste memory.
            // The "using" will close the stream even if an exception occurs.
            using (FileStream streamWriter = File.Create(fullZipToPath)) {
                StreamUtils.Copy(zipStream, streamWriter, buffer);
            }
        }
    } finally {
        if (zf != null) {
            zf.IsStreamOwner = true; // Makes close also shut the underlying stream
            zf.Close(); // Ensure we release resources
        }
    }
}

Если вы используете поток без поиска, используйте ZipInputStream.

// Calling example:
    WebClient webClient = new WebClient();
    Stream data = webClient.OpenRead("http://www.example.com/test.zip");
    // This stream cannot be opened with the ZipFile class because CanSeek is false.
    UnzipFromStream(data, @"c:\temp");

public void UnzipFromStream(Stream zipStream, string outFolder) {

    ZipInputStream zipInputStream = new ZipInputStream(zipStream);
    ZipEntry zipEntry = zipInputStream.GetNextEntry();
    while (zipEntry != null) {
        String entryFileName = zipEntry.Name;
        // to remove the folder from the entry:- entryFileName = Path.GetFileName(entryFileName);
        // Optionally match entrynames against a selection list here to skip as desired.
        // The unpacked length is available in the zipEntry.Size property.

        byte[] buffer = new byte[4096];     // 4K is optimum

        // Manipulate the output filename here as desired.
        String fullZipToPath = Path.Combine(outFolder, entryFileName);
        string directoryName = Path.GetDirectoryName(fullZipToPath);
        if (directoryName.Length > 0)
            Directory.CreateDirectory(directoryName);

        // Unzip file in buffered chunks. This is just as fast as unpacking to a buffer the full size
        // of the file, but does not waste memory.
        // The "using" will close the stream even if an exception occurs.
        using (FileStream streamWriter = File.Create(fullZipToPath)) {
            StreamUtils.Copy(zipInputStream, streamWriter, buffer);
        }
        zipEntry = zipInputStream.GetNextEntry();
    }
}

Примеры, взятые из ICSharpCode Wiki