Common .NET runtime exceptions, C# compiler errors (CS0103, CS1061), nullability issues, and async deadlocks.
Attempting to access a member or invoke a method on a variable that is null.
Accessing an array or list element using an index smaller than 0 or greater than or equal to its length.
Explicit reference or unboxing casting fails due to incompatible runtime types.
Referencing a variable, method, or class name that compiler cannot find in scope.
Calling a property or method that does not exist on the specified type.
Passing null to a method argument that does not accept null values.
An asynchronous task was cancelled before completion via CancellationToken.
Calling LINQ First() or Single() on an empty collection.
Attempting to access or read a file at a path that does not exist on disk.
Parsing a string into a numeric or other type fails because the format is invalid.