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Use local function instead of lambda (IDE0039)

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Property Value
Rule ID IDE0039
Title Use local function instead of lambda
Category Style
Subcategory Language rules (expression-level preferences)
Applicable languages C#
Options csharp_style_prefer_local_over_anonymous_function

Overview

This style rule concerns the use of local functions versus lambda expressions (anonymous functions).

Options

Options specify the behavior that you want the rule to enforce. For information about configuring options, see Option format.

csharp_style_prefer_local_over_anonymous_function

Property Value Description
Option name csharp_style_prefer_local_over_anonymous_function
Option values true Prefer local functions over anonymous functions
false Prefer anonymous functions over local functions
Default option value true 
// csharp_style_prefer_local_over_anonymous_function = true
int fibonacci(int n)
{
    return n <= 1 ? 1 : fibonacci(n-1) + fibonacci(n-2);
}

// csharp_style_prefer_local_over_anonymous_function = false
Func<int, int> fibonacci = (int n) =>
{
    return n <= 1 ? 1 : fibonacci(n - 1) + fibonacci(n - 2);
};

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 IDE0039
// The code that's violating the rule is on this line.
#pragma warning restore IDE0039

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

[*.{cs,vb}]
dotnet_diagnostic.IDE0039.severity = none

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

[*.{cs,vb}]
dotnet_analyzer_diagnostic.category-Style.severity = none

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

See also