Question

I have update function that I’d like to overload according to the input parameter (whether it is value type or reference type)

public void Update<T>(T item) where T : ValueType

the compiler has error and it insist I cannot use valuetype (and couple more as a constraint).
should I give up or is there a neat way to overload method according to my desired types?

Answer 1

You can use where T : struct to enforce that T is a non-nullable value type (this doesn’t work with Nullable<T>, despite that being a value type).

However, this won’t help your bigger goal, as you can’t overload by type constraints – so this is invalid:

// Invalid overloading
void Foo<T>(T item) where T : class
void Foo<T>(T item) where T : struct

Basically although the number of type parameters is part of the signature of the method (in terms of overloading), the names and constraints aren’t.

There are horrible ways round this, but I’d recommend using different method names instead.