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…ble string formatting/allocations
zivkan
approved these changes
Jan 8, 2026
martinrrm
approved these changes
Jan 9, 2026
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@zivkan, @martinrrm thanks for reviewing. Would you be able to merge it as I don't seem to have permissions. |
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@nareshjo Thanks for the contribution, I queued the CI, should be automatically merged if it succeeds. |
This was referenced Jan 23, 2026
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Issue: The
ReadAsyncmethod inDownloadTimeoutStream.csallocates a timeout error message string viastring.Format()on every single call (line withvar timeoutMessage = string.Format(...)), even though this message is only used when aTimeoutExceptionis caught. This can lead to unnecessary allocations. Evidence: The stack trace showsString.FormatHelperbeing called fromDownloadTimeoutStream+<ReadAsync>d__.MoveNext, and the source code confirmsstring.Formatis called unconditionally at the start of everyReadAsyncinvocation.Allocation path:
DownloadTimeoutStream.ReadAsync→String.FormatHelper→StringBuilder.ToString→TypeAllocated!System.StringIssue type: Reduce string allocations
Proposed fix: Move the
string.Formatcall from the beginning of theReadAsyncmethod into thecatch (TimeoutException)block. This defers the string allocation to only occur when a timeout exception is actually caught, eliminating allocations on the hot path (normal successful reads).Best practices wiki
See related failure in PRISM
ADO work item