Skip to content

Update CA1806 with Pure methods #49544

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
Oct 30, 2025
Merged

Update CA1806 with Pure methods #49544

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
d7676bd
Update CA1806 with Pure methods
gewarren Oct 30, 2025
6c1cc86
Apply suggestions from code review
gewarren Oct 30, 2025
10331f5
Update docs/fundamentals/code-analysis/quality-rules/ca1806.md
gewarren Oct 30, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 5 additions & 4 deletions docs/fundamentals/code-analysis/quality-rules/ca1806.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
---
title: "CA1806: Do not ignore method results (code analysis)"
description: "Learn about code analysis rule CA1806: Do not ignore method results"
ms.date: 06/08/2022
ms.date: 10/30/2025
f1_keywords:
- CA1806
- DoNotIgnoreMethodResults
Expand Down Expand Up @@ -32,6 +32,7 @@ There are several possible reasons for this warning:
- A method that creates and returns a new string is called and the new string is never used.
- A COM or P/Invoke method returns a `HRESULT` or error code that's never used.
- A language-integrated query (LINQ) method returns a result that's never used.
- A `[Pure]` method is called and the return value is never used.

## Rule description

Expand All @@ -41,7 +42,7 @@ Strings are immutable and methods such as <xref:System.String.ToUpper%2A?display

Ignoring `HRESULT` or an error code can lead to low-resource conditions or unexpected behavior in error conditions.

LINQ methods are known to not have side effects, and the result should not be ignored.
LINQ methods and methods annotated with <xref:System.Diagnostics.Contracts.PureAttribute> are known to not have side effects, and the result should not be ignored.

## How to fix violations

Expand All @@ -57,7 +58,7 @@ If method A calls method B but does not use the `HRESULT` or error code that the

-or-

If a LINQ method A calls method B but does not use the result, use the result in a conditional statement, assign the result to a variable, or pass it as an argument to another method.
If method A calls a LINQ or pure method B but does not use the result, use the result in a conditional statement, assign the result to a variable, or pass it as an argument to another method.

## When to suppress warnings

Expand Down Expand Up @@ -122,7 +123,7 @@ The following example fixes the violation by assigning the result of <xref:Syste
The following example shows a method that doesn't use an object that it creates.

> [!NOTE]
> This violation cannot be reproduced in Visual Basic.
> This violation can't be reproduced in Visual Basic.

:::code language="csharp" source="snippets/csharp/all-rules/ca1806.cs" id="snippet3":::

Expand Down