Use primary constructor (IDE0290)

Property	Value
Rule ID	IDE0290
Title	Use primary constructor
Category	Style
Subcategory	Language rules (code block preferences)
Applicable languages	C# 12+
Options	csharp_style_prefer_primary_constructors

Overview

This rule flags classes that can use a primary constructor instead of a separate constructor definition. You define a primary constructor by placing any constructor parameters in parentheses following the type name. A primary constructor indicates that these parameters are necessary for any instance of the type.

Options

Options specify the behavior that you want the rule to enforce. For information about configuring options, see Option format.

csharp_style_prefer_primary_constructors

Property	Value	Description
Option name	csharp_style_prefer_primary_constructors
Option values	true	Prefer to use primary constructors.
	false	Disables the rule.
Default option value	true

Example

// Code with violations.
class C
{
    public C(int i) { }
}

// Fixed code.
class C(int i)
{
}

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 IDE0290
// The code that's violating the rule is on this line.
#pragma warning restore IDE0290

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

[*.{cs,vb}]
dotnet_diagnostic.IDE0290.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.