c# - Why must write O AS INT and can't write (INT)O -


I like to use the as operator in John Skeet's book with such a type Example found, which allows the zero value. 

  using the system; Class A {static white printAUscient 32 (object o) {int? O; as nullable = int ;; Can not write // int? Nullable = (int?) O console Wrightite (nullable.HasValue? Nullable.Value.ToString (): "Zero"); } Fixed zero main () {PrintValueAsInt32 (5); PrintValueAsInt32 ("some string"); }}   
 I can not understand why I can not write  int? Nullable = (int?) O ? When I try to do this, I'm getting an exception.   
 
 
 Because checking first  cast  Types are not variable for each other, then it only gives  zero  and avoids  invalid cut exception .  
 When you are passing a string in the second call in the second call, which is not variable for  int, then try to use the  clear  artist Time Receiving an Exception

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