Use 'is null' check (IDE0041)

  • Article
Property Value
Rule ID IDE0041
Title Use 'is null' check
Category Style
Subcategory Language rules (expression-level preferences)
Applicable languages C# and Visual Basic
Introduced version Visual Studio 2017
Options dotnet_style_prefer_is_null_check_over_reference_equality_method

Overview

This style rule concerns the use of a null check with pattern matching versus the use of the equality operator (==) or calling Object.ReferenceEquals(Object, Object).

Options

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

dotnet_style_prefer_is_null_check_over_reference_equality_method

Property Value Description
Option name dotnet_style_prefer_is_null_check_over_reference_equality_method
Option values true Prefer is null check
false Prefer reference equality method
Default option value true 
// dotnet_style_prefer_is_null_check_over_reference_equality_method = true
if (value is null)
    return;

// dotnet_style_prefer_is_null_check_over_reference_equality_method = false
if (object.ReferenceEquals(value, null))
    return;

// dotnet_style_prefer_is_null_check_over_reference_equality_method = false
if ((object)o == null)
    return;

' dotnet_style_prefer_is_null_check_over_reference_equality_method = true
If value Is Nothing
    Return
End If

' dotnet_style_prefer_is_null_check_over_reference_equality_method = false
If Object.ReferenceEquals(value, Nothing)
    Return
End If

' dotnet_style_prefer_is_null_check_over_reference_equality_method = false
If CType(value, Object) = Nothing
    Return
End If

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 IDE0041
// The code that's violating the rule is on this line.
#pragma warning restore IDE0041

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

[*.{cs,vb}]
dotnet_diagnostic.IDE0041.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