Screenshot with 0 bytes breaks preview about sentry-xamarin

[Mahdibenamor]

facing the same error here, with release mode (working on the debug mode), seems to be critical and breaking the feature, cause we can't use it in production @benvinegar

[bruno-garcia]

This is happening when running the SDK on .NET 6 app (https://github.com/getsentry/symbol-collector) before that, it was working with the exception of a few cases.

Two things:

1. Why does it fail? Can we list the cases where it works and where it fails so we can properly document this? Perhaps we must make sure the event is captured in the UI thread?
2. Or instead of streaming the screenshot, we should try to buffer it, and avoid adding the 0 byte attachment altogether. Alternatively we change the .NET SDK to have 2 attachment processing mode: Buffer vs Stream. The current way is Stream but buffer is introduced and made default: It will first read the stream into a memory stream, make sure it has more than 0 bytes, and only in that case, add the EnvelopeItem.

Here we add attachments (but don't read the data of it yet): https://github.com/getsentry/sentry-dotnet/blob/3d007fd512520421f3813d3d2b01b179ef09003e/src/Sentry/Envelopes/Envelope.cs#L131

Here we read the envelope item data into a stream we receive: https://github.com/getsentry/sentry-dotnet/blob/3d007fd512520421f3813d3d2b01b179ef09003e/src/Sentry/Envelopes/EnvelopeItem.cs#L69-L71
This new mode would go here. We first buffer it into a memory stream before writing into the stream passed as an argument (often a file stream or a network stream).

[lucas-zimerman]

Waiting for the next release of the Sentry .NET to be able to fix this issue.