Update ZipArchive

Updated on Jun 16, 2026

With RadZipLibrary you can update an existing ZIP archive to add new entries to it, delete entries, or update existing ones.

The ZipArchive class provides three modes: Read, Create, and Update. More information on creating and reading an archive is available in the Getting Started article.

The code snippet from Example 1 opens a ZIP archive in update mode using the ZipArchive class.

Example 1: Open for update

C#

using (Stream stream = File.Open("test.zip", FileMode.Open))
{
	using (ZipArchive archive = ZipArchive.Update(stream, null))
	{
		//Display the list of the files in the selected zip file using the ZipArchive.Entries property.
	}
}

Add Entry

To add a new entry into the ZIP archive, perform the following steps:

1. Use the CreateEntry() method of the ZipArchive object to create a new entry.

2. Open the entry to get a stream for writing.

3. Write the necessary information into the entry.

4. Dispose the entry when all necessary information is written. In the Update mode this step is optional. You can omit it if you need to add, delete, or update other entries in the archive.

More information about ZipArchiveEntry is available in the ZipArchiveEntry help article.

Example 2: Add entry

C#

using (ZipArchiveEntry entry = archive.CreateEntry("text.txt"))
			{
				StreamWriter writer = new StreamWriter(entry.Open());
				writer.WriteLine("Hello world!");
				writer.Flush();
			}

Delete Entry

The ZipArchive class provides a GetEntry() method, which allows you access to a particular entry in the archive.

Example 3 shows how to get an entry and delete it from the ZIP archive using the Delete() method.

Example 3: Delete entry

C#

ZipArchiveEntry entry = archive.GetEntry("text.txt");
			if (entry != null)
			{
				entry.Delete();
			}

Update Entry

To update an existing entry in the ZIP archive, perform the following steps:

1. Use the GetEntry() method of the ZipArchive object to get an existing entry.

2. Open the entry to get a stream for reading and writing.

3. Read or write the necessary information from or to the entry.

4. Dispose the entry when all necessary information is written. In the Update mode this step is optional. You can omit it if you need to add, delete, or update other entries in the archive.

Example 4: Update entry

C#

ZipArchiveEntry entry = archive.GetEntry("text.txt");
if (entry != null)
{
	Stream entryStream = entry.Open();
	StreamReader reader = new StreamReader(entryStream);
	string content = reader.ReadToEnd();

	entryStream.Seek(0, SeekOrigin.End);
	StreamWriter writer = new StreamWriter(entryStream);
	writer.WriteLine("Updated line.");
	writer.Flush();
}

Copy Entry

Starting with the Q2 2025 release, RadZipLibrary introduces a new extension method CopyTo for the Stream class. Use this method to copy data from one stream to another with an optional timeout parameter for more control over long-running operations. This is particularly useful when you work with large files in ZIP archives.

The following example shows how to use the CopyTo method to copy the contents of a large file from a ZIP archive to a memory stream with a specified timeout.

Example 5: Copy entry with timeout

C#

using (Stream zipStream = File.Open("input.zip", FileMode.Open))
{
    using (ZipArchive archive = ZipArchive.Read(zipStream))
    {
        ZipArchiveEntry entry = archive.Entries.ElementAt(2); // Access the third entry in the archive
        using (Stream entryStream = entry.Open())

        using (MemoryStream memoryStream = new MemoryStream())
        {
            // Copy the entry's content to the memory stream with a timeout of 5 seconds
            entryStream.CopyTo(memoryStream);
        }
    }
}

This method ensures that the operation does not hang indefinitely. It is useful for scenarios that involve large files or limited resources.

See Also

• Getting Started