Change WeakReference to WeakReference<T>

[Wraith2]

Reading #1121 I remembered that we're using WeakReference and not WeakReference<T>, the generic version has a different api shape using bool isAlive = TryGetTarget(out T target) to prevent the possibility of a GC between IsAlive and Target property accesses. Note that TryGetTarget returns false for null which is why some null checks are no longer needed.

[Dzoge]

Is this issue also fixed in System.Data.SqlClient package?

[Wraith2]

Unlikely. The System.Data.SqlClient package is deprecated in favour of this library and the only things that get back ported are security and high impact stability changes. This is simply a modernization.