Code Inspection: Arrange null checking pattern

When checking an expression for null with the type-testing 'is' operator, you can choose between two null-checking patterns:

Use the 'not null' pattern that makes the expression more readable.
Use the object pattern syntax `{ }` that makes the expression more flexible, allowing you to declare a local variable after it.

                
public static void Test(object? obj)
{
  if (obj is not null)
    Console.WriteLine("not null");
}

                
public static void Test(object? obj)
{
  if (obj is { })
    Console.WriteLine("not null");
}

By default, ReSharper highlights object pattern syntax { } in null-checking expressions and suggests replace them with the not null pattern:

ReSharper syntax style inspection: Use 'not null' pattern

If you prefer to use the { } pattern, you can change the corresponding preferences and ReSharper will help you replace not null patterns accordingly:

ReSharper syntax style inspection: Use '{ }' pattern

For more information, see Code Syntax Style: Null checking pattern.

Last modified: 30 March 2023