Update ZipArchive

Updated on Feb 19, 2026

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

The ZipArchive class provides three modes: Read, Create and Update. More information on creating and reading an archive is available here.

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

Example 1: Open for update

csharp

	            
	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

In order to add a new entry into the ZIP archive, you should perform the following steps:

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

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

3. Write the necessary information into the entry.

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

More information about ZipArchiveEntry you can find in ZipArchiveEntry help article.

Example 2: Add entry

csharp

	    
	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 you could obtain an entry and delete it from the ZIP archive using the Delete() method.

Example 3: Delete entry

csharp

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

Update Entry

In order to update an existing entry in the ZIP archive, you should perform the following steps:

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

2. Open entry to get a stream for reading/writing.

3. Read/Write the necessary information from/to the entry.

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

Example 4: Update entry

csharp

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

The following example demonstrates 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 will not hang indefinitely, making it a valuable addition for scenarios involving large files or limited resources.

See Also

• Getting Started