Extract XHTML Files from ZIP Archives in C#

Extract XHTML Content from ZIP in .NET

Use Aspose.ZIP for .NET to inspect a ZIP archive and restore only the XHTML files required by a C# application. XHTML is an XML-conformant HTML document used for structured web content. On this page, extraction means selecting that file from a ZIP container and writing it to a controlled destination; Aspose.ZIP does not interpret or convert the file’s internal content.

Selective extraction fits web-content migration, static-site imports, template processing, documentation builds, and packaged application resources. The application can skip unrelated entries, enforce output and resource policies, and pass approved files to the next service without expanding the complete archive.

How to Extract XHTML Files from ZIP Using C#

Install the Aspose.ZIP package for .NET and import the Aspose.Zip namespace. Archive metadata is available before anything is written, allowing the application to evaluate ArchiveEntry.Name, ArchiveEntry.IsDirectory, and ArchiveEntry.UncompressedSize as part of its acceptance policy.

PM> Install-Package Aspose.Zip

C# Example: Select XHTML Files in a ZIP Archive

The code opens a ZIP package, filters non-directory entries by the approved extension, and writes matching files to one output directory. Flattening archived paths keeps this example compact and prevents parent-directory segments from controlling the destination. Production code should also define a deterministic policy for duplicate output names.

using Aspose.Zip;
using System;
using System.IO;

string archivePath = Path.GetFullPath("package.zip");
string outputDirectory = Path.GetFullPath("extracted-xhtml");
string[] allowedExtensions = { ".xhtml", ".xht" };
const ulong MaxEntrySize = 100UL * 1024 * 1024;

Directory.CreateDirectory(outputDirectory);

using (var archive = new Archive(archivePath))
{
    foreach (ArchiveEntry entry in archive.Entries)
    {
        if (entry.IsDirectory) continue;

        string fileName = Path.GetFileName(entry.Name);
        if (string.IsNullOrWhiteSpace(fileName)) continue;

        string extension = Path.GetExtension(fileName);
        if (!Array.Exists(
            allowedExtensions,
            value => string.Equals(value, extension, StringComparison.OrdinalIgnoreCase)))
        {
            continue;
        }

        if (entry.UncompressedSize > MaxEntrySize)
        {
            throw new InvalidDataException(
                $"Entry '{fileName}' exceeds the 100 MB extraction limit.");
        }

        string destinationPath = Path.Combine(outputDirectory, fileName);
        entry.Extract(destinationPath);
    }
}

Implementation Notes for XHTML Packages

XHTML content may rely on style sheets, scripts, fonts, and images stored elsewhere in the archive. Decide whether the workflow needs only the document or a complete resource set, and never render extracted active content in a trusted browser context without sanitization.

Restored markup and scripts remain untrusted input. Parse or render them in a restricted environment, and apply the application’s rules for active content, external references, and encoding.

The example flattens archived paths for ordinary files. If two accepted entries have the same final name, ArchiveEntry.Extract can overwrite an existing output, so choose an explicit collision policy: reject the duplicate, generate a unique name, or preserve a validated relative directory tree. Use a separate destination for each job so concurrent requests cannot mix results.

Security and Privacy Considerations

Treat archive names and payloads as untrusted. Never append ArchiveEntry.Name directly to the destination path because absolute paths and parent-directory segments can write outside the intended folder. The standard example uses Path.GetFileName; workflows that retain directories must resolve the full path and verify that it remains below the approved root.

Set limits for compressed input size, per-entry and total expanded size, entry count, processing time, and concurrent jobs. Extract into restricted temporary storage, clean up partial output after failures, scan files when the application requires it, and avoid logging private filenames or document contents.

XHTML Extraction FAQ

How do I extract only XHTML files from a ZIP archive in C#?

Open the ZIP with Archive, enumerate Archive.Entries, match the .xhtml or .xht extensions, and call Extract for each accepted destination path.

Does Aspose.ZIP validate the content of an extracted XHTML file?

No. The extension is only a first-pass filter. Validate the restored file with a component that understands XHTML content.

Can the same selection pattern be used with 7Z, RAR, or TAR containers?

Yes, but open each container with its corresponding Aspose.ZIP archive class. Entry types and available extraction methods can differ by archive format.

How should duplicate XHTML filenames be handled?

Choose the rule before extraction: reject duplicates, generate unique names, or preserve a validated relative directory structure.