`ZipArchive` should document limitation on concurrent entry creation

[DL444]

Type of issue

Missing information

Description

ZipArchive currently does not allow concurrent entry creation, and doing so results in IOException being thrown at run time. For example:

using System.IO.Compression;

using MemoryStream memoryStream = new();
using ZipArchive archive = new(memoryStream, ZipArchiveMode.Create);
Task[] tasks = new Task[32];
for (int i = 0; i < tasks.Length; i++)
{
    tasks[i] = CreateEntryAsync(archive);
}
await Task.WhenAll(tasks).ConfigureAwait(false);

static async Task CreateEntryAsync(ZipArchive zipArchive)
{
    ZipArchiveEntry entry = zipArchive.CreateEntry(Path.GetRandomFileName());
    using Stream stream = entry.Open();
    await Task.Delay(100); // Simulate asynchronous write
}

throws:

Unhandled exception. System.IO.IOException: Entries cannot be created while previously created entries are still open.
   at System.IO.Compression.ZipArchive.AcquireArchiveStream(ZipArchiveEntry entry)
   at System.IO.Compression.ZipArchive.DoCreateEntry(String entryName, Nullable`1 compressionLevel)
   at System.IO.Compression.ZipArchive.CreateEntry(String entryName)
   at Program.<<Main>$>g__CreateEntryAsync|0_0(ZipArchive zipArchive) in Program.cs:line 14
   at Program.<Main>$(String[] args) in Program.cs:line 10
   at Program.<Main>(String[] args)

While the limitation itself is understandable, I think it should be pointed out by the documentation. Right now neither the Exceptions section nor the Remarks section mentions this behavior.

Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.io.compression.ziparchive.createentry?view=net-9.0

Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.IO.Compression/ZipArchive.xml

Document Version Independent Id

6edb630b-4e65-bdf8-8efd-cb5974682887

Platform Id

5bc53832-8985-3cc1-93b6-79225f7fb140

Article author

@dotnet-bot

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