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Passing an Enumeration Variable by Ref

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johndoe@driver.net

I have MyEnumeratedSet { ... some values go here ... }
I have a variable that is defined as
MyEnumeratedSet MyVariable;
I have a function that needs to be able to set a variable by Ref
MyFunction(ref System.Enum Parameter)
{ ..... Parameter has to be set here }

so I have tried calling it by
MyFunction(ref (Enum) MyVariable);
unfortunately this yields compiler errors and it seems like there is no way
to pass an Enum by reference.
Am I missing something painstakingly obvious or can Enum's not be passed by
reference?

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Dennis Myrén

enum MyEnumeratedSet { Value1, Value2 }

...Main (..)
{
MyEnumeratedSet value = MyEnumeratedSet.Value1;
MyFunction(ref value);
}

... MyFunction(ref MyEnumeratedSet value)
{
value = MyEnumeratedSet.Value2;
}

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
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johndoe@driver.net

Obviously this was WAY Too simple ;) - so one should have moved onto the
obvious assumption.
That i NEEDED System.Enum in the parameters because i am going to have
multiple Enum'

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Dennis Myrén

Well, then you have to declare it as a System.Enum, because implicit type
casts
cannot be performed when passing an instance by ref.

...Main (..)
{
Enum value = MyEnumeratedSet.Value1;
MyFunction(ref value);
}

... MyFunction(ref MyEnumeratedSet value)
{
if (value is MyEnumeratedSet)
value = MyEnumeratedSet.Value2;
}

Although i would recommed using overloaded methods instead,
one for each Enum type.

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
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> Obviously this was WAY Too simple ;) - so one should have moved onto
the
[Original message clipped]

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Jon Skeet [C# MVP] (VIP)

<Click here to reveal e-mail address> wrote:
[Original message clipped]

Yes there is. For example:

using System;

enum Foo
{
Bar=1,
Baz=2
}

class Test
{
static void Main()
{
Foo z = Foo.Bar;
Change (ref z);
Console.WriteLine (z);
}

static void Change(ref Foo x)
{
x = Foo.Baz;
}
}

[Original message clipped]

Parameters passed by reference have to match in type *exactly* - you
can't pass subtypes and just cast them, as that would break type safety
(consider passing a string variable by reference to something accepting
ref object - the method could assign it a value which wasn't a
reference to a string).

If you need it to work with *any* enum, it'll involve boxing and then
unboxing afterwards:

using System;

enum Foo
{
Bar=1,
Baz=2
}

class Test
{
static void Main()
{
Foo z = Foo.Bar;
Enum tmp = z;
Change (ref tmp);
z = (Foo) tmp;
Console.WriteLine (z);
}

static void Change(ref Enum x)
{
x = Foo.Baz;
}
}

If you know the type in advance, however, it would be much better to
stick to code like the first example.

--
Jon Skeet - <Click here to reveal e-mail address>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

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johndoe@driver.net

Okay. Thanks. I was hoping there was a prettier way to do it.

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Dennis Myrén

If you ask me, it is by far the most prettiest way i can think of to do it.

--
Regards,
Dennis JD Myrén
Oslo Kodebureau
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	System.Console
	System.Enum

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