Simplify LINQ expression (IDE0120)

#Overview

This rule flags overly complex LINQ expressions, specifically expressions that call [System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable{},System.Func{`,System.Int32,System.Boolean})](https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.where--1) followed by one of the following methods:

• System.Linq.Enumerable.Any(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.Count(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.First(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.FirstOrDefault(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.Last(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.LastOrDefault(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.Single(System.Collections.Generic.IEnumerable{})
• System.Linq.Enumerable.SingleOrDefault(System.Collections.Generic.IEnumerable{})

Such expressions can be simplified by removing the call to [System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable{},System.Func{,System.Int32,System.Boolean})](https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.where--1) 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