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Jan 9, 2026
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Document IDE0059 analyzer limitations in try/catch, lambdas, and other contexts #50897

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Copilot Jan 5, 2026
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Document IDE0059 known limitations in functions
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gewarren Jan 5, 2026
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19 changes: 18 additions & 1 deletion docs/fundamentals/code-analysis/style-rules/ide0059.md
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---
title: "IDE0059"
description: "Learn about code analysis style rule IDE0059."
ms.date: 12/13/2023
ms.date: 01/05/2026
f1_keywords:
- IDE0059
- csharp_style_unused_value_assignment_preference
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int v = Compute2();
```

## Known limitations

This rule doesn't work in certain code contexts. The analyzer fails to flag unnecessary value assignments in the following scenarios:

- Assignments inside `try` or `catch` blocks.
- Assignments inside `using` statement blocks.
- Variables assigned within lambda expressions or delegate bodies.
- Variables in the presence of expression trees (`Expression<Func<T>>`).

These limitations are tracked in the following GitHub issues:

- [IDE0059 is not always reported](https://github.com/dotnet/roslyn/issues/52292)
- [Detection of IDE0059 not working within try/catch statements](https://github.com/dotnet/roslyn/issues/65220)
- [IDE0059 not raised inside a code block with using keyword](https://github.com/dotnet/roslyn/issues/74219)
- [IDE0059 doesn't work with expression trees](https://github.com/dotnet/roslyn/issues/80033)
- [Remove unused variable/values (parent issue)](https://github.com/dotnet/roslyn/issues/75737)

## Options

The options for this specify whether to prefer the use of a discard or an unused local variable:
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