public object MethodName(ref float y)
{
// elided
}
How do I define a Func delegate for this method?
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2 Answers
It cannot be done by Func but you can define a custom delegate for it:
public delegate object MethodNameDelegate(ref float y);
Usage example:
public object MethodWithRefFloat(ref float y)
{
return null;
}
public void MethodCallThroughDelegate()
{
MethodNameDelegate myDelegate = MethodWithRefFloat;
float y = 0;
myDelegate(ref y);
}
3 Comments
Eric Lippert
The reason being: all generic type arguments must be things that are convertible to object. "ref float" is not convertible to object, so you cannot use it as a generic type argument.
chugh97
Thanks for that, I was struggling to use Func so I know why I cant use it when type is not convertible to object
Kyle Baran
Does that mean that the delegate typing will require boxing/unboxing in this case?
In .NET 4+ you can also support ref types this way...
public delegate bool MyFuncExtension<in string, MyRefType, out Boolean>(string input, ref MyRefType refType);
2 Comments
NoOps
Not to resurrect a dead thread but it should definitely be noted for anyone that comes across this that while you can support a ref param with generics this way, the generic type parameter will be invariant. Generic type parameters don't support variance (covariance or contravariance) for ref or out parameters in c#. Still fine if you don't need to worry about implicit type conversions though.
Glenn Slayden
Sorry, this answer is a bit off-track. The
in and out you're showing for paramerizing the delegate pertain to co- versus "contra-variance", and are not related to what the OP is asking about. The question was about delegates which can accept parameters by reference, not the agility of a (generic) delegate with regard to its type parameteriization.