在C# 中包含所謂的 「保留關鍵宇」 ，就是C# 本身的指令名稱，

不能用來宣告變數、常數、類別及方法名稱，下表 為C#的保留關鍵宇列表。

| C# 保留關鍵字| | | | |整理by 艾米 |
------------- | -------------
abstract| as| base| bool| break |byte
case| catch |char| checked |class |const
continue |decimal| default |delegate| do |double
else |enum| event| explicit |extern| false
finally fixed| float| for| foreach |goto|using
if |implicit| in |int| interface| internal
is |lock |long| namespace| new |null
object| operator| out| override| params |private
protected| public| readonly |ref return| sbyte|with
sealed |short| sizeof |stackalloc| static| string
struct |switch |this |throw |true |try
typeof |uint |ulong |unchecked |unsafe|ushort|
virtual |void |volatile| while| add| and
alias |ascending| async| await| by |descending
dynamic |equals |from| get |global| group
init |into| join| let| managed |nameof
nint |not |notnull |nuint| on |or
orderby |partial| record| remove |select| set
unmanaged| value| var| when| where| where
|yield| | | | | |

詳細關鍵字解釋點我到官網看更多~