Header enumeration issues

It works most of the time, but when we have many requests at the same time for the same resource, we sometimes end up with this (and other exceptions, that doesn’t make any sense)

Version of SDK: 4.0.5 Using .NET 6.0

Exception:

System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at System.Net.Http.Headers.HttpHeaders.ReadStoreValues[T](Span`1 values, Object storeValue, HttpHeaderParser parser, Int32& currentIndex)
   at System.Net.Http.Headers.HttpHeaders.GetStoreValuesAsStringOrStringArray(HeaderDescriptor descriptor, Object sourceValues, String& singleValue, String[]& multiValue)
   at System.Net.Http.Headers.HttpHeaders.GetEnumeratorCore()+MoveNext()
   at Minio.ResponseResult.get_Headers() in /root/.q/sources/minio-dotnet/Minio/ResponseResult.cs:line 113
   at Minio.MinioClient.StatObjectAsync(StatObjectArgs args, CancellationToken cancellationToken) in /root/.q/sources/minio-dotnet/Minio/ApiEndpoints/ObjectOperations.cs:line 1095
   at Minio.MinioClient.getObjectHelper(GetObjectArgs args, CancellationToken cancellationToken) in /root/.q/sources/minio-dotnet/Minio/Helper/OperationsHelper.cs:line 50

Code (snippet) used to get the file:

var outFile = new MemoryStream();

var getObjectArgs = new GetObjectArgs()
.WithBucket(bucketName)
.WithObject(minioObjectName)
.WithCallbackStream((s) =>
	s.CopyTo(outFile)
);

await _minioClient.GetObjectAsync(getObjectArgs, cancellationToken: cancellationToken);

outFile.Seek(0, SeekOrigin.Begin);

return File(outFile, dbfr.MimeType, null, true);

[ebozduman]

One more thing: It is almost always suggested to add/call ConfigureAwait(false) after an awaited async method, like: await _minioClient.GetObjectAsync(getObjectArgs, cancellationToken: cancellationToken).ConfigureAwait(false);

It means that you do not care if the code after the await, runs on the captured context or not, unless otherwise is true in your scenario. This will also help performance.

Could you apply this change, if it is ok, and then try to reproduce the issue?

[ebozduman]

ok @itssimple. Thank you for confirming it. The issue is closed.