C# has a special syntax for simultaneously testing and "destructuring" a nullable value type. It is something like "if (Value b is not null = c) {", and if "c" is non-null its value is assigned to b. I've used this a dozen times but I can't remember the syntax and also I cannot search for it because Google returns nothing but stack overflow questions from 2012, which predate whatever this syntax is. Does anyone remember this?

For example, here I am trying to access field "x" from a struct "B3":