Use collection expression for fluent (IDE0305)
| Property | Value |
|---|---|
| Rule ID | IDE0305 |
| Title | Use collection expression for fluent |
| Category | Style |
| Subcategory | Language rules (expression-level preferences) |
| Applicable languages | C# 12+ |
| Options | dotnet_style_prefer_collection_expression |
Overview
This rule flags places where a collection is built in a fluent manner, that is, where methods like Add(), AddRange(), AsSpan(), ToList(), and ToArray() are chained. Instead, a collection expression could be used to initialize the collection. For example, x.AddRange(y).Add(z).AsSpan() is converted to [x, ..y, z].
Options
Options specify the behavior that you want the rule to enforce. For information about configuring options, see Option format.
dotnet_style_prefer_collection_expression
| Property | Value | Description |
|---|---|---|
| Option name | dotnet_style_prefer_collection_expression | |
| Option values | true | when_types_exactly_match |
Prefer to use collection expressions only when types match exactly, for example, List<int> list = new[] { 1, 2, 3 }.ToList();. |
when_types_loosely_match(.NET 9 and later versions)* |
Prefer to use collection expressions even when types match loosely, for example, IEnumerable<int> list = new[] { 1, 2, 3 }.ToList();. The targeted type must match the type on the right-hand side or be one of the following types: IEnumerable<T>, ICollection<T>, IList<T>, IReadOnlyCollection<T>, IReadOnlyList<T>. |
|
false | never |
Disables the rule. | |
| Default option value | true in .NET 8when_types_loosely_match in .NET 9 and later versions |
*The code fix when this option is used might change the semantics of your code.
Example
// Code with violation.
List<int> i = new[] { 1, 2, 3 }.ToList();
IEnumerable<int> j = new[] { 1, 2, 3 }.ToList();
// Fixed code.
List<int> i = [1, 2, 3];
IEnumerable<int> j = [1, 2, 3];
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 IDE0305
// The code that's violating the rule is on this line.
#pragma warning restore IDE0305
To disable the rule for a file, folder, or project, set its severity to none in the configuration file.
[*.{cs,vb}]
dotnet_diagnostic.IDE0305.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.
