Code-style rules

.NET code-style analysis provides rules that aim to maintain consistent style in your codebase. These rules have an "IDE" prefix in the rule ID.

The code-style rules are organized into the following subcategories:

• Language and unnecessary code rules

  Rules that pertain to the C# or Visual Basic language. For example, you can specify rules that regard the use of var when defining variables, or whether expression-bodied members are preferred. This category also includes rules that find unnecessary code, for example, unreachable code within methods or unused private fields, properties, or methods.

• Formatting rules

  Rules that pertain to the layout and structure of your code in order to make it easier to read. For example, you can specify a formatting option that defines whether spaces in control blocks are preferred or not.

• Naming rules

  Rules that pertain to the naming of code elements. For example, you can specify that async method names must have an "Async" suffix.

• Miscellaneous rules

  Rules that do not belong in other categories.

Index

The following table list all the code-style rules by ID and options, if any.

Rule ID	Title	Option
IDE0001	Simplify name
IDE0002	Simplify member access
IDE0003	Remove this or Me qualification	dotnet_style_qualification_for_field dotnet_style_qualification_for_property dotnet_style_qualification_for_method dotnet_style_qualification_for_event
IDE0004	Remove unnecessary cast
IDE0005	Remove unnecessary import
IDE0007	Use var instead of explicit type	csharp_style_var_for_built_in_types csharp_style_var_when_type_is_apparent csharp_style_var_elsewhere
IDE0008	Use explicit type instead of var	csharp_style_var_for_built_in_types csharp_style_var_when_type_is_apparent csharp_style_var_elsewhere
IDE0009	Add this or Me qualification	dotnet_style_qualification_for_field dotnet_style_qualification_for_property dotnet_style_qualification_for_method dotnet_style_qualification_for_event
IDE0010	Add missing cases to switch statement
IDE0011	Add braces	csharp_prefer_braces
IDE0016	Use throw expression	csharp_style_throw_expression
IDE0017	Use object initializers	dotnet_style_object_initializer
IDE0018	Inline variable declaration	csharp_style_inlined_variable_declaration
IDE0019	Use pattern matching to avoid as followed by a null check	csharp_style_pattern_matching_over_as_with_null_check
IDE0020	Use pattern matching to avoid is check followed by a cast (with variable)	csharp_style_pattern_matching_over_is_with_cast_check
IDE0021	Use expression body for constructors	csharp_style_expression_bodied_constructors
IDE0022	Use expression body for methods	csharp_style_expression_bodied_methods
IDE0023	Use expression body for conversion operators	csharp_style_expression_bodied_operators
IDE0024	Use expression body for operators	csharp_style_expression_bodied_operators
IDE0025	Use expression body for properties	csharp_style_expression_bodied_properties
IDE0026	Use expression body for indexers	csharp_style_expression_bodied_indexers
IDE0027	Use expression body for accessors	csharp_style_expression_bodied_accessors
IDE0028	Use collection initializers	dotnet_style_collection_initializer dotnet_style_prefer_collection_expression (C# only)
IDE0029	Null check can be simplified	dotnet_style_coalesce_expression
IDE0030	Null check can be simplified	dotnet_style_coalesce_expression
IDE0031	Use null propagation	dotnet_style_null_propagation
IDE0032	Use auto property	dotnet_style_prefer_auto_properties
IDE0033	Use explicitly provided tuple name	dotnet_style_explicit_tuple_names
IDE0034	Simplify default expression	csharp_prefer_simple_default_expression
IDE0035	Remove unreachable code
IDE0036	Order modifiers	csharp_preferred_modifier_order visual_basic_preferred_modifier_order
IDE0037	Use inferred member name	dotnet_style_prefer_inferred_tuple_names dotnet_style_prefer_inferred_anonymous_type_member_names
IDE0038	Use pattern matching to avoid is check followed by a cast (without variable)	csharp_style_pattern_matching_over_is_with_cast_check
IDE0039	Use local function instead of lambda	csharp_style_prefer_local_over_anonymous_function
IDE0040	Add accessibility modifiers	dotnet_style_require_accessibility_modifiers
IDE0041	Use is null check	dotnet_style_prefer_is_null_check_over_reference_equality_method
IDE0042	Deconstruct variable declaration	csharp_style_deconstructed_variable_declaration
IDE0044	Add readonly modifier	dotnet_style_readonly_field
IDE0045	Use conditional expression for assignment	dotnet_style_prefer_conditional_expression_over_assignment
IDE0046	Use conditional expression for return	dotnet_style_prefer_conditional_expression_over_return
IDE0047	Remove unnecessary parentheses	dotnet_style_parentheses_in_arithmetic_binary_operators dotnet_style_parentheses_in_relational_binary_operators dotnet_style_parentheses_in_other_binary_operators dotnet_style_parentheses_in_other_operators
IDE0048	Add parentheses for clarity	dotnet_style_parentheses_in_arithmetic_binary_operators dotnet_style_parentheses_in_relational_binary_operators dotnet_style_parentheses_in_other_binary_operators dotnet_style_parentheses_in_other_operators
IDE0049	Use language keywords instead of framework type names for type references	dotnet_style_predefined_type_for_locals_parameters_members dotnet_style_predefined_type_for_member_access
IDE0050	Convert anonymous type to tuple
IDE0051	Remove unused private member
IDE0052	Remove unread private member
IDE0053	Use expression body for lambdas	csharp_style_expression_bodied_lambdas
IDE0054	Use compound assignment	dotnet_style_prefer_compound_assignment
IDE0055	Fix formatting	(Too many to list here. See .NET formatting options and C# formatting options.)
IDE0056	Use index operator	csharp_style_prefer_index_operator
IDE0057	Use range operator	csharp_style_prefer_range_operator
IDE0058	Remove unused expression value	csharp_style_unused_value_expression_statement_preference visual_basic_style_unused_value_expression_statement_preference
IDE0059	Remove unnecessary value assignment	csharp_style_unused_value_assignment_preference visual_basic_style_unused_value_assignment_preference
IDE0060	Remove unused parameter	dotnet_code_quality_unused_parameters
IDE0061	Use expression body for local functions	csharp_style_expression_bodied_local_functions
IDE0062	Make local function static	csharp_prefer_static_local_function
IDE0063	Use simple using statement	csharp_prefer_simple_using_statement
IDE0064	Make struct fields writable
IDE0065	using directive placement	csharp_using_directive_placement
IDE0066	Use switch expression	csharp_style_prefer_switch_expression
IDE0070	Use System.HashCode.Combine
IDE0071	Simplify interpolation	dotnet_style_prefer_simplified_interpolation
IDE0072	Add missing cases to switch expression
IDE0073	Use file header	file_header_template
IDE0074	Use coalesce compound assignment	dotnet_style_prefer_compound_assignment
IDE0075	Simplify conditional expression	dotnet_style_prefer_simplified_boolean_expressions
IDE0076	Remove invalid global SuppressMessageAttribute
IDE0077	Avoid legacy format target in global SuppressMessageAttribute
IDE0078	Use pattern matching	csharp_style_prefer_pattern_matching
IDE0079	Remove unnecessary suppression	dotnet_remove_unnecessary_suppression_exclusions
IDE0080	Remove unnecessary suppression operator
IDE0081	Remove ByVal
IDE0082	Convert typeof to nameof
IDE0083	Use pattern matching (not operator)	csharp_style_prefer_not_pattern
IDE0084	Use pattern matching (IsNot operator)	visual_basic_style_prefer_isnot_expression
IDE0090	Simplify new expression	csharp_style_implicit_object_creation_when_type_is_apparent
IDE0100	Remove unnecessary equality operator
IDE0110	Remove unnecessary discard
IDE0120	Simplify LINQ expression
IDE0130	Namespace does not match folder structure	dotnet_style_namespace_match_folder
IDE0140	Simplify object creation	visual_basic_style_prefer_simplified_object_creation
IDE0150	Prefer null check over type check	csharp_style_prefer_null_check_over_type_check
IDE0160	Use block-scoped namespace	csharp_style_namespace_declarations
IDE0161	Use file-scoped namespace	csharp_style_namespace_declarations
IDE0170	Simplify property pattern	csharp_style_prefer_extended_property_pattern
IDE0180	Use tuple to swap values	csharp_style_prefer_tuple_swap
IDE0200	Remove unnecessary lambda expression	csharp_style_prefer_method_group_conversion
IDE0210	Convert to top-level statements	csharp_style_prefer_top_level_statements
IDE0211	Convert to 'Program.Main' style program	csharp_style_prefer_top_level_statements
IDE0220	Add explicit cast in foreach loop	dotnet_style_prefer_foreach_explicit_cast_in_source
IDE0230	Use UTF-8 string literal	csharp_style_prefer_utf8_string_literals
IDE0240	Nullable directive is redundant
IDE0241	Nullable directive is unnecessary
IDE0250	Struct can be made 'readonly'	csharp_style_prefer_readonly_struct
IDE0251	Member can be made 'readonly'	csharp_style_prefer_readonly_struct_member
IDE0260	Use pattern matching	csharp_style_pattern_matching_over_as_with_null_check
IDE0270	Null check can be simplified	dotnet_style_coalesce_expression
IDE0280	Use nameof
IDE0290	Use primary constructor	csharp_style_prefer_primary_constructors
IDE0300	Use collection expression for array	dotnet_style_prefer_collection_expression
IDE0301	Use collection expression for empty	dotnet_style_prefer_collection_expression
IDE0302	Use collection expression for stackalloc	dotnet_style_prefer_collection_expression
IDE0303	Use collection expression for Create()	dotnet_style_prefer_collection_expression
IDE0304	Use collection expression for builder	dotnet_style_prefer_collection_expression
IDE0305	Use collection expression for fluent	dotnet_style_prefer_collection_expression
IDE1005	Use conditional delegate call	csharp_style_conditional_delegate_call
IDE1006	Naming styles

Note

There are some rules that only surface in the Visual Studio IDE, and these regard JSON and regular expression pattern strings. For more information, see JSON001, JSON002, and RE0001.

Legend

The following table shows the type of information that's provided for each rule in the reference documentation.

Item	Description
Rule ID	The unique identifier for the rule. Used for configuring rule severity and suppressing warnings in the code file.
Title	The title for the rule.
Category	The category for the rule.
Subcategory	The subcategory for the rule, such as Language rules, Formatting rules, or Naming rules.
Applicable languages	Applicable .NET languages (C# or Visual Basic), along with the minimum language version, if applicable.
Introduced version	Version of the .NET SDK or Visual Studio when the rule was first introduced.
Options	Any available options for the rule.

See also

• Enforce code style on build
• Quick Actions in Visual Studio
• Create portable custom editor options in Visual Studio