Simplify LINQ expression (IDE0120)
| Property | Value |
|---|---|
| Rule ID | IDE0120 |
| Title | Simplify LINQ expression |
| Category | Style |
| Subcategory | Unnecessary code rules (expression-level preferences) |
| Applicable languages | C# and Visual Basic |
Overview
This rule flags overly complex LINQ expressions, specifically expressions that call Enumerable.Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) followed by one of the following methods:
- Any<TSource>(IEnumerable<TSource>)
- Count<TSource>(IEnumerable<TSource>)
- First<TSource>(IEnumerable<TSource>)
- FirstOrDefault<TSource>(IEnumerable<TSource>)
- Last<TSource>(IEnumerable<TSource>)
- LastOrDefault<TSource>(IEnumerable<TSource>)
- Single<TSource>(IEnumerable<TSource>)
- SingleOrDefault<TSource>(IEnumerable<TSource>)
Such expressions can be simplified by removing the call to Where<TSource>(IEnumerable<TSource>, 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.
