This analyzer flags use of != null to test whether a value is not null.
For example this code would produce a diagnostic:
if (o != null)
{
}A code fix is offered to automate the fix, which is to use pattern syntax instead:
if (o is object)
{
}Pattern syntax is preferred because if o is typed as a struct, the compiler will report an error when testing it for null, which a struct can never be.