Reduce allocation in TextWriter.NewLine#121508
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stephentoub merged 3 commits intodotnet:mainfrom Nov 17, 2025
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It's reasonably common for a codebase to pick a specific newline string and set it regardless of OS, but currently that ends up allocating on every OS. Two changes: 1. When setting TextWriter.NewLine to the existing value, make it a nop to avoid unnecessarily calling ToCharArray. 2. When setting TextWriter.NewLine to "\n" on Windows or to "\r\n" on Unix, use a cached array.
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Pull Request Overview
This PR optimizes TextWriter.NewLine setter to reduce allocations in common scenarios where codebases set a specific newline string regardless of OS. The changes include:
- Making the setter a no-op when setting to the same value
- Caching arrays for "\n" and "\r\n" (the non-default OS newline strings)
jozkee
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Nov 10, 2025
GerardSmit
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Nov 10, 2025
This was referenced Nov 11, 2025
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It's reasonably common for a codebase to pick a specific newline string and set it regardless of OS, but currently that ends up allocating on every OS each call to set_NewLine.
Two changes: