IDE0120: Simplify LINQ expression - .NET (original) (raw)

Overview

This rule flags overly complex LINQ expressions, specifically expressions that call Enumerable.Where(IEnumerable, Func<TSource,Int32,Boolean>) followed by one of the following methods:

• Any(IEnumerable)
• Count(IEnumerable)
• First(IEnumerable)
• FirstOrDefault(IEnumerable)
• Last(IEnumerable)
• LastOrDefault(IEnumerable)
• Single(IEnumerable)
• SingleOrDefault(IEnumerable)

Such expressions can be simplified by removing the call to Where(IEnumerable, Func<TSource,Int32,Boolean>) and instead calling an overload of Any(), Count(), First(), FirstOrDefault(), Last(), LastOrDefault(), Single, or SingleOrDefault() that accepts a predicate function to filter the elements.

Options

This rule has no associated code-style options.

Example

// Code with violations.
IEnumerable<string> words = new List<string> { "hello", "world", "!" };
var result = words.Where(x => x.Equals("hello")).Any();

// Fixed code.
IEnumerable<string> words = new List<string> { "hello", "world", "!" };
var result = words.Any(x => x.Equals("hello"));

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 IDE0120
// The code that's violating the rule is on this line.
#pragma warning restore IDE0120

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

[*.{cs,vb}]
dotnet_diagnostic.IDE0120.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

• Language rules
• Code style rules reference