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Make method synchronous (IDE0390 and IDE0391)

Property Value
Rule ID IDE0390, IDE0391
Title Make method synchronous
Category Style
Subcategory Unnecessary code rules (modifier preferences)
Applicable languages C#
Options None

Overview

These rules flag async methods that don't contain any await expressions. For better performance, remove the async modifier and adjust the return type, because an async method that never awaits anything runs synchronously but with the overhead of the async state machine.

The two rules target different scenarios:

  • IDE0390: Reports async methods, local functions, and lambda expressions that aren't interface implementations or overrides.
  • IDE0391: Reports async methods that implement an interface member or override a base class method.

To avoid breaking the ability of callers to await the method through the interface, use caution when applying the fix to interface implementations or overrides. Removing async can have different behavioral implications in those cases.

Example

// Code with violations.

// IDE0390: Regular method with no 'await'.
public async Task<int> GetValueAsync()
{
    return 42;
}

// IDE0391: Override method with no 'await'.
public override async Task<string> GetNameAsync()
{
    return "example";
}

// Fixed code.

// Remove 'async' and return the value directly.
public Task<int> GetValueAsync()
{
    return Task.FromResult(42);
}

// Remove 'async' and return the value directly.
public override Task<string> GetNameAsync()
{
    return Task.FromResult("example");
}

Suppress a warning

If you want to suppress only a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable IDE0390
// The code that's violating the rule is on this line.
#pragma warning restore IDE0390

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.cs]
dotnet_diagnostic.IDE0390.severity = none
dotnet_diagnostic.IDE0391.severity = none

To disable all of the code-style rules, set the severity for the category Style to none in the configuration file.

[*.cs]
dotnet_analyzer_diagnostic.category-Style.severity = none

For more information, see How to suppress code analysis warnings.

See also

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