C# (.NET) Design Flaws [closed]

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  • the Reset() method on IEnumerator<T> was a mistake (for iterator blocks, the language spec even demands that this throws an exception)
  • the reflection methods that return arrays were, in Eric’s view, a mistake
  • array covariance was and remains an oddity
    • Update: C# 4.0 with .NET 4.0 added covariant/contravariance support to generic interfaces (like IEnumerable<out T> and Func<in T, out TResult>, but not concrete types (like List<T>).
  • ApplicationException rather fell out of favor – was that a mistake?
  • synchronized collections – a nice idea, but not necessarily useful in reality: you usually need to synchronize multiple operations (Contains, then Add), so a collection that synchronizes distinct operations isn’t all that useful
    • Update: The System.Collections.Concurrent types, with TryAdd, GetOrAdd, TryRemove, etc were added in .NET Framework 4.0 – though methods that accept a factory delegate do not guarantee the factory will only be invoked once per key.
  • more use could have been made of the using/lock pattern – perhaps allowing them to share a re-usable (extensible?) syntax; you can simulate this by returning IDisposable and using using, but it could have been clearer
  • iterator blocks : no simple way of checking arguments ahead-of-time (rather than lazily). Sure, you can write two chained methods, but that is ugly
  • simpler immutability would be nice; C# 4.0 helps a bit, but not quite enough
  • no “this ref-type parameter cannot be null” support – although contracts (in 4.0) help with this somewhat. But syntax like Foo(SqlConnection! connection) (that injects a null-check / throw) would be nice (contrast to int? etc)
    • Update: This is fixed in C# 8.0.
  • lack of support of operators and non-default constructors with generics; C# 4.0 solves this a bit with dynamic, or you can enable it like this
  • the iterator variable being declared outside the while in the foreach expansion, meaning that anon-methods/lambdas capture the single variable, rather than one per iteration (painful with threading/async/etc)
    • Update: This was fixed in C# 5.0.

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