Use local function instead of lambda (IDE0039)

#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

// 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

• Code style language rules
• Code style rules reference