c# - Check for 'null' on value and reference types -

i'm little confused checking 'null' (empty, not available, without value) on value , or reference types. there seem lot of possible ways , of them used.

let's i've got following extension method can used somehow similar maybe monad:

public static tresult usewith<t, tresult>(this t value, func<t, tresult> action) {     // if value not null     //     execute action     // else return default value of 'tresult' } 

so? how check null?

if(value != null) 

or (which checks null on reference types, default on value types)

if(!equals(value, default(t)) 

or

if(!equalitycomparer<t>.default.equals(value, default(t)) 

or (with precheck)

 if (!typeof(t).isvaluetype)  {      if (equals(source, default(t)))            return tresult;   } 

or better create 2 methods restrictions?

 public static tresult usewith<t, tresult>(this t value, func<t, tresult> action)     t : class  {     if(value == null)    public static tresult usewith<t, tresult>(this t value, func<t, tresult> action)     t : struct  {     if(value.hasvalue) 

the pseudocode in first snippet work want to. variable typed unbounded generic argument can compared null using == operator. code compile, , evaluate false whenever t non-nullable value type.

you don't want compare t default value, because default value may not null.

there no need explicitly check if t value type, or have separate overloads reference/value types, == operator handles when it's jitted.