How to find argument type (in] [out] using reflection?

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Fiz - 08 May 2008 04:00 GMT

I'm using reflection API's to find the argument types of a methods (such as
in or out etc). For example, consider this method

public int outerFoo(string str, ref double db) { return 42; }

When using reflection, I would like to know if str is [in] and db is
[in,out]. I got the code written like this

for each ( ParameterInfo^ pi in (((MethodInfo^) methInfo)->GetParameters()))
{
if(pi->IsIn)
..do something
else if(pi->IsOut)
..do something else
}

But IsIn and IsOut always return false. Are these deprecated? Any workarounds?

Any help would be appreciated
Thanks
Fiz

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Ben Voigt [C++ MVP] - 08 May 2008 15:10 GMT

> I'm using reflection API's to find the argument types of a methods
> (such as in or out etc). For example, consider this method
[quoted text clipped - 14 lines]
> But IsIn and IsOut always return false. Are these deprecated? Any
> workarounds?

Did you call GetCustomAttributes and look for InAttribute and OutAttribute?

> Any help would be appreciated
> Thanks
> Fiz

Reply to this Message

Fiz - 09 May 2008 08:40 GMT

Thanks for the response.

I tried attributes, it did not return anything.

array<Object^>^myAttributes = pi->GetCustomAttributes(false);

Length of myAttributes was 0. I also tried passing specific InAttribute and
OutAttribute typeid, that did not return either.

for each(Attribute^ attr in pi->GetCustomAttributes(InAttribute::typeid,
false))
{
do something..
}

I tried ParameterInfo->Attributes property, that returned empty

if(pi->Attributes == ParameterAttributes::In)
{
...
}

What else can I do here?

> > I'm using reflection API's to find the argument types of a methods
> > (such as in or out etc). For example, consider this method
[quoted text clipped - 20 lines]
> > Thanks
> > Fiz

Reply to this Message

Ben Voigt [C++ MVP] - 09 May 2008 19:16 GMT

> Thanks for the response.
>
[quoted text clipped - 19 lines]
>
> What else can I do here?

Note also that the ParameterType->IsByRef is closely related to out and ref
parameters. In fact, if that isn't true, I think you can safely assume the
parameter is "In". For parameters which are ByRef, you need to check for
ref vs out.

>>> I'm using reflection API's to find the argument types of a methods
>>> (such as in or out etc). For example, consider this method
[quoted text clipped - 21 lines]
>>> Thanks
>>> Fiz

Reply to this Message

Fiz - 09 May 2008 21:11 GMT

> Note also that the ParameterType->IsByRef is closely related to out and ref
> parameters. In fact, if that isn't true, I think you can safely assume the
> parameter is "In". For parameters which are ByRef, you need to check for
> ref vs out.

Thanks. However, I'm back to the same question. If it is ByRef, how do I
check for ref vs out. I checked the properties and methods of ParameterType ,
couldn't find anything. Any hint? Any URL?

It shouldn't be that difficult, I'm missing something here :(

Reply to this Message

Ben Voigt [C++ MVP] - 09 May 2008 22:50 GMT

>> Note also that the ParameterType->IsByRef is closely related to out
>> and ref parameters. In fact, if that isn't true, I think you can
[quoted text clipped - 6 lines]
>
> It shouldn't be that difficult, I'm missing something here :(

ParameterInfo.Attributes and ParameterInfo.IsOut are working for me.

code:
[TestFixture]
public class OutParameter
{
[Test]
public static void test()
{
foreach (MethodInfo mi in
typeof(double).GetMethods(BindingFlags.Public | BindingFlags.Instance |
BindingFlags.Static))
{
System.Diagnostics.Trace.WriteLine(mi.Name + " : ");
foreach (ParameterInfo pi in mi.GetParameters())
{
System.Diagnostics.Trace.WriteLine(pi.Name + " > " +
pi.Attributes);
}
}
}
}

output:
[snip]
TryParse :
s > None
result > Out
[snip]

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How to find argument type (in] [out] using reflection?

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