Use null propagation (IDE0031)

  • Article
Property Value
Rule ID IDE0031
Title Use null propagation
Category Style
Subcategory Language rules (expression-level preferences)
Applicable languages C# and Visual Basic
Options dotnet_style_null_propagation

Overview

This style rule concerns the use of the null-conditional operator versus a ternary conditional expression with null check.

Options

Set the value of the associated option to specify whether null-conditional operators or ternary conditional expressions with null checks.

For more information about configuring options, see Option format.

dotnet_style_null_propagation

Property Value Description
Option name dotnet_style_null_propagation
Option values true Prefer to use null-conditional operator when possible
false Prefer to use ternary null checking where possible
Default option value true 
// dotnet_style_null_propagation = true
var v = o?.ToString();

// dotnet_style_null_propagation = false
var v = o == null ? null : o.ToString(); // or
var v = o != null ? o.ToString() : null;

' dotnet_style_null_propagation = true
Dim v = o?.ToString()

' dotnet_style_null_propagation = false
Dim v = If(o Is Nothing, Nothing, o.ToString()) ' or
Dim v = If(o IsNot Nothing, o.ToString(), Nothing)

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 IDE0031
// The code that's violating the rule is on this line.
#pragma warning restore IDE0031

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

[*.{cs,vb}]
dotnet_diagnostic.IDE0031.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