C＃：检查变量类型的昂贵

Question

How expensive is it to check the type of a variable in C#?

Eg using try / catch vs. using as vs. using typeof .

Absolute measurements are not necessary. :)

Answer 1

try / catch is definitely slower, since a thrown exception causes stack information to be gathered.

as / is are for comparing to a type known at compile time and cater for inheritance (ie. "string" is Object returns true )

typeof / GetType() can be used for types known at runtime but do not cater for inheritance (ie. "string".GetType() == typeof(Object) returns false )

Regardless, I think you probably want as (or is if you don't need the cast value)

Answer 2

Which is expensive is completely irrelevant; you should never use exception handling as a form of control flow if you can avoid it . It's called "exception handling" because it should only happen in exceptional, unavoidable circumstances . Invalid type conversion exceptions are bugs and should be fixed. Always use "is", "as", or "GetType()" to determine the type of a thing.

Answer 3

如果只想检查该类型，则应使用is运算符。