CSIsNull002

Property	Value
Title	Use an is expression for non-null checks
Category	Usage
Default severity	Info

This analyzer reports a diagnostic when C# code uses the built-in != operator to compare a reference or nullable value with null.

Pattern syntax cannot invoke an overloaded inequality operator. It also lets the compiler reject null checks against non-nullable value types.

Example

For example, this code produces a diagnostic:

if (value != null)
{
}

The code fixes replace the inequality check with pattern matching (is) syntax and support Fix All.

For C# 9 or later, is not null is listed first:

if (value is not null)
{
}

The is object form is also available:

if (value is object)
{
}

For earlier C# language versions, and within expression trees where is not null is unsupported, only is object is offered. Both forms let the compiler reject null checks against non-nullable value types.

Configuration and suppression

The rule has no custom options. Configure its severity with the standard .editorconfig key dotnet_diagnostic.CSIsNull002.severity, or suppress a specific occurrence with standard pragma or SuppressMessage mechanisms.