LowFile-scopeC# Plug & play

Use safe type casting with as operator

Use the as operator or pattern matching for safe casts and guard null results before usage.

Why this matters

Prevents InvalidCastException and makes intent explicit.

Side-by-side examples engineers can pattern-match during review.

Avoid

var d = (Derived)b; d.Run();

Prefer

if (b is Derived d) { d.Run(); }

Bad

var x = (Foo)obj;

Good

if(obj is Foo foo){ /* use foo */ }

From the same buckets as this rule.

Critical
Avoid equality operators in loop termination conditions
Check if loops use equality operators (== or !=) in termination conditions. These can lead to infinite loops if the condition is never met exactly. Instead, use relational operators like < or > for safer loop termination.
error-handlingreadability-refactor
Critical
Avoid Returning Null in Non-Async Task Methods
Returning null from a Task or Task<T> method causes a NullReferenceException if awaited. Use Task.CompletedTask or Task.FromResult<T>(null) instead.
error-handlingreadability-refactor+1
Critical
Avoid Using Boolean Expressions in `except` Statements
Detect `except` clauses that use `or` or `and` to catch multiple exceptions. This does not work as intended. Recommend using a tuple of exceptions instead.
error-handlingstack-python