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IDE0030Language rules (expression-level preferences)

Null check can be simplified (if null check)

Null check can be simplified (if null check)

Microsoft docs
Documented together with IDE0270Null check can be simplified (if null check)

Description

Rules IDE0029 and IDE0030 concern the use of null-coalescing expressions, for example, x ?? y, versus ternary conditional expressions with null checks, for example, x != null ? x : y. The rules differ with respect to the nullability of the expressions:

  • IDE0029: Used when non-nullable expressions are involved. For example, this rule could recommend x ?? y instead of x != null ? x : y when x and y are non-nullable reference types.
  • IDE0030: Used when nullable expressions are involved. For example, this rule could recommend x ?? y instead of x != null ? x : y when x and y are nullable value types or nullable reference types.

Rule IDE0270 flags the use of a null check (== null or is null) instead of the null-coalescing operator (??).

Example

// Code with violation.
var v = x != null ? x : y; // or
var v = x == null ? y : x;

// Fixed code.
var v = x ?? y;

// Code with violation.
class C
{
    void M()
    {
        var item = FindItem() as C;
        if (item == null)
            throw new System.InvalidOperationException();
    }

    object? FindItem() => null;
}

// Fixed code (dotnet_style_coalesce_expression = true).
class C
{
    void M()
    {
        var item = FindItem() as C ?? throw new System.InvalidOperationException();
    }

    object? FindItem() => null;
}

Configurable options

Vote for the value each option should take in the generated .editorconfig.

dotnet_style_coalesce_expression
default: true
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