c# - Ways to cast objects to a generic type -

in relation casting generic type "as t" whilst enforcing type of t

and following example

private static t deserialize<t>(string streng) t : class {     xmlserializer ser = new xmlserializer(typeof(t));     stringreader reader = new stringreader(streng);     return ser.deserialize(reader) t; } 

and

private static t deserialize<t>(string streng) {     xmlserializer ser = new xmlserializer(typeof(t));     stringreader reader = new stringreader(streng);     return (t)ser.deserialize(reader); } 

i'm used doing object type casting, little confused when found couldn't t. found question above , in solution as t compiler error.

but why where t : class necessary when using object t , not when using (t)object? actual difference between 2 ways of casting object?

because as implies cast fail and return null. without : class, t int etc - can't null. (t)obj explode in shower of sparks; no need handle null.

as aside (re struct), note can use as if known casting nullable<> - example:

static t? cast<t>(object obj) t : struct {     return obj t?; }