Use collection expression for builder (IDE0304)
Property | Value |
---|---|
Rule ID | IDE0304 |
Title | Use collection expression for builder |
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 CreateBuilder()
or similar method is called to create a builder type that adds elements and finally constructs a collection type that has the CollectionBuilderAttribute attribute (for example, by calling ImmutableArray<T>.Builder.ToImmutable()). Instead, a collection expression ([...]
) could be used to initialize the collection.
Note
This rule requires more recent versions of the immutable APIs (for example, System.Collections.Immutable), which opt into the collection-expression pattern.
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. |
when_types_loosely_match (.NET 9 and later versions)* |
Prefer to use collection expressions even when types match loosely. 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.
var builder = ImmutableArray.CreateBuilder<int>();
builder.Add(1);
builder.AddRange(new int[] { 5, 6, 7 });
ImmutableArray<int> i = builder.ToImmutable();
// Fixed code.
ImmutableArray<int> i = [1, .. new int[] { 5, 6, 7 }];
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 IDE0304
// The code that's violating the rule is on this line.
#pragma warning restore IDE0304
To disable the rule for a file, folder, or project, set its severity to none
in the configuration file.
[*.{cs,vb}]
dotnet_diagnostic.IDE0304.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
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