ide-warnings

name	ide-warnings
description	.NET IDE code style warning meanings and examples

.NET code-style warnings

Use this skill when the build reports enabled IDE* diagnostics.

.NET code-style diagnostics (IDE)

IDE0001 - Simplify name

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: fully qualified name is used when an import makes it unnecessary.
• Fix: simplify the name.

IDE0002 - Simplify member access

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: this.member or type qualification is unnecessary for access.
• Fix: simplify member access.

IDE0003 - Remove this or Me qualification

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: this._value where qualification is not required by style.
• Fix: remove this..

IDE0004 - Remove unnecessary cast

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: (string)name where name is already string.
• Fix: remove the unnecessary cast.

IDE0005 - Remove unnecessary using directive

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: unused using System.Text;.
• Fix: remove the unused using.

IDE0007 - Use var instead of explicit type

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: Customer customer = GetCustomer(); where style prefers var.
• Fix: use var customer = GetCustomer();.

IDE0009 - Add this or Me qualification

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: _value where style requires this._value.
• Fix: add the configured qualification.

IDE0010 - Add missing cases to switch statement

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: switch statement omits enum cases.
• Fix: add missing cases or a default case.

IDE0011 - Add braces

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: if (ready) Run();.
• Fix: add braces.

IDE0016 - Use throw expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: if (x is null) throw ...; return x;.
• Fix: use a throw expression when it improves clarity.

IDE0017 - Use object initializer

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: create object then assign simple properties one by one.
• Fix: use an object initializer.

IDE0018 - Inline variable declaration

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: declare an out variable before the call.
• Fix: inline the declaration in the out argument.

IDE0019 - Use pattern matching

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: var c = o as Control; if (c != null).
• Fix: use if (o is Control c).

IDE0021 - Use expression body for constructors

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: constructor body only delegates one expression where expression body is preferred.
• Fix: use an expression-bodied constructor if style allows.

IDE0022 - Use expression body for methods

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: method body only returns one expression.
• Fix: use expression body if style requires.

IDE0023 - Use expression body for conversion operators

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: conversion operator uses a trivial block body.
• Fix: use expression body if style requires.

IDE0024 - Use expression body for operators

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: operator uses a trivial block body.
• Fix: use expression body if style requires.

IDE0025 - Use expression body for properties

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: property getter only returns one expression.
• Fix: use expression-bodied property if style requires.

IDE0026 - Use expression body for indexers

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: indexer getter only returns one expression.
• Fix: use expression-bodied indexer if style requires.

IDE0027 - Use expression body for accessors

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: accessor only returns or assigns one expression.
• Fix: use expression-bodied accessor if style requires.

IDE0028 - Use collection initializer

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: create collection then call Add repeatedly.
• Fix: use collection initializer.

IDE0029 - Use coalesce expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: x == null ? fallback : x.
• Fix: use x ?? fallback.

IDE0030 - Use coalesce expression for nullable

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: nullable value manually checked before fallback.
• Fix: use a coalesce expression.

IDE0031 - Use null propagation

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: x == null ? null : x.Name.
• Fix: use x?.Name.

IDE0032 - Use auto property

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: property only wraps a backing field with no logic.
• Fix: use an auto-property.

IDE0033 - Use explicitly provided tuple name

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: tuple field name is repeated unnecessarily.
• Fix: rely on the explicitly provided tuple name.

IDE0034 - Simplify default expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: default(string).
• Fix: use default where target type is clear.

IDE0035 - Remove unreachable code

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: code remains after an unconditional return/throw.
• Fix: remove unreachable code.

IDE0036 - Order modifiers

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: static public.
• Fix: order modifiers consistently, e.g. public static.

IDE0037 - Use inferred member name

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: anonymous object repeats obvious member name.
• Fix: use inferred member name.

IDE0039 - Use local function

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: lambda assigned only for local reuse.
• Fix: use a local function where clearer.

IDE0041 - Use is null check

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: object.ReferenceEquals(value, null).
• Fix: use value is null.

IDE0042 - Deconstruct variable declaration

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: assign tuple fields manually after tuple-returning call.
• Fix: use deconstruction.

IDE0045 - Use conditional expression for assignment

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: if assigns one of two values to the same variable.
• Fix: use a conditional expression when readable.

IDE0046 - Use conditional expression for return

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: if returns one of two values.
• Fix: use a conditional expression when readable.

IDE0049 - Use language keywords instead of framework type names

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: System.String.
• Fix: use string.

IDE0050 - Convert anonymous type to tuple

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: anonymous type is used like a tuple.
• Fix: use a tuple when names/types fit.

IDE0051 - Remove unused private member

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: private method is never used.
• Fix: remove it or call it intentionally.

IDE0052 - Remove unread private member

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: private field is written but never read.
• Fix: remove it or read it intentionally.

IDE0053 - Use expression body for lambdas

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: lambda block only returns one expression.
• Fix: use expression-bodied lambda.

IDE0054 - Use compound assignment

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: x = x + 1.
• Fix: use x += 1.

IDE0056 - Use index operator

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: items[items.Length - 1].
• Fix: use items[^1].

IDE0057 - Use range operator

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: text.Substring(1, text.Length - 2).
• Fix: use range syntax when readable.

IDE0058 - Remove unnecessary expression value

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: Compute(); where the returned value is intentionally ignored but analyzer expects discard.
• Fix: assign to discard or remove the call if unnecessary.

IDE0059 - Remove unnecessary assignment

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: assigned value is overwritten before being read.
• Fix: remove the assignment.

IDE0061 - Use expression body for local functions

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: local function block only returns one expression.
• Fix: use expression body if style requires.

IDE0063 - Use simple using statement

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: using (...) { ... } where simple using is preferred.
• Fix: use using var.

IDE0070 - Use System.HashCode

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: hand-written hash code combination.
• Fix: use HashCode.Combine.

IDE0071 - Simplify interpolation

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: interpolation contains unnecessary .ToString().
• Fix: simplify the interpolation.

IDE0072 - Add missing cases to switch expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: switch expression omits enum values.
• Fix: add arms for missing values.

IDE0074 - Use compound assignment

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: x = x && y.
• Fix: use compound assignment where valid.

IDE0075 - Simplify conditional expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: condition ? true : false.
• Fix: use condition.

IDE0080 - Remove unnecessary suppression operator

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: value! where nullability analysis already proves non-null.
• Fix: remove !.

IDE0082 - Convert typeof to nameof

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: typeof(Customer).Name for a symbol name.
• Fix: use nameof(Customer).

IDE0090 - Use new expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: new Customer() when target type is clear.
• Fix: use target-typed new() if project style allows.

IDE0100 - Remove unnecessary equality operator

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: unnecessary == true or == false.
• Fix: simplify the boolean expression.

IDE0110 - Remove unnecessary discard

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: _ = value; discard is unnecessary.
• Fix: remove the discard.

IDE0120 - Simplify LINQ expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: verbose LINQ chain can be simplified.
• Fix: apply the simpler LINQ form suggested by the analyzer.

IDE0130 - Namespace does not match folder structure

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: namespace does not match the folder path.
• Fix: move the file or change the namespace.

IDE0150 - Prefer null check over type check

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: x is string ? x != null : false style checks.
• Fix: prefer direct null checks over type checks when appropriate.

IDE0160 - Use block-scoped namespace

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: file-scoped namespace is used where block-scoped is configured.
• Fix: use block-scoped namespace.

IDE0161 - Use file-scoped namespace

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: block-scoped namespace is used where file-scoped is configured.
• Fix: use file-scoped namespace.

IDE0180 - Use tuple swap

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: swap uses a temporary variable.
• Fix: use tuple swap (a, b) = (b, a).

IDE0200 - Remove unnecessary lambda expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: lambda only calls another method with same arguments.
• Fix: use method group conversion.

IDE0210 - Convert to top-level statements

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: Program class boilerplate where top-level statements are preferred.
• Fix: convert to top-level statements if appropriate.

IDE0211 - Convert from top-level statements

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: top-level statements where explicit Program is preferred.
• Fix: convert to Program.Main if configured.

IDE0220 - Add explicit cast in foreach loop

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: foreach conversion is implicit and unclear.
• Fix: add an explicit cast in the foreach source.

IDE0230 - Use UTF-8 string literal

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: UTF-8 byte array literal built from string at runtime.
• Fix: use UTF-8 string literal when available.

IDE0240 - Nullable directive is unnecessary

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: nullable directive repeats the project default.
• Fix: remove unnecessary directive.

IDE0241 - Nullable directive is unnecessary

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: nullable directive is redundant for the current context.
• Fix: remove unnecessary directive.

IDE0270 - Use coalesce throw expression

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: null guard throws in a separate statement.
• Fix: use value ?? throw ... when readable.

IDE0290 - Use primary constructor

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: constructor only assigns parameters to members.
• Fix: use a primary constructor if project style allows.

IDE0300 - Use collection expression for array

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: new int[] { 1, 2 } where collection expression is preferred.
• Fix: use [1, 2].

IDE0301 - Use collection expression for empty collection

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: Array.Empty<int>() where collection expression is preferred.
• Fix: use [] where target type is clear.

IDE0302 - Use collection expression for stackalloc

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: stackalloc initializer can use collection expression.
• Fix: use collection expression syntax.

IDE0303 - Use collection expression for Create method

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: collection factory call can use collection expression.
• Fix: use collection expression syntax.

IDE0304 - Use collection expression for builder

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: builder pattern collection creation can use collection expression.
• Fix: use collection expression syntax.

IDE0305 - Use collection expression for fluent calls

What it flags: The .NET code-style analyzer found code that differs from the configured style or can be simplified.

Example:

• Bad: fluent collection creation can use collection expression.
• Fix: use collection expression syntax.