XmlSerializer and DefaultValue?

[Rasmus Kromann-Larsen]

Hello,

I'm currently playing around with the XmlSerializer to replace my old
handmade Xml parsing code, but am having a few small issues with
default values and derived classes.

Say we have classes A, B and C:

abstract class A
{
protected int a_value = 1;

[XmlAttribute("v alue"), DefaultValue(1)]
public int AValue
{
get { return a_value; }
set { a_value = value; }
}
}

class B : A
{
....
}

class C : A
{
....
}
Now, I want class B and C to have different default values, more
precisely, I want B to have 1 as default value and C to have
Int32.MaxValue. But I can't figure out how to actually make this work.
I tried making the property in A abstract and provide the
implementation in B and C with different default values, but it still
used the default value from A. I tried removing the default value from
A, which gave the result of having no default value, everything was
printed, always.

I then tried to remove the XmlAttribute attribute from A and only have
it and the default value in B and C, but it gave me the following
exception:

System.InvalidO perationExcepti on: There was an error reflecting
property 'AValue'. ---> System.InvalidO perationExcepti on: Member
B.AValue' hides inherited member 'A.AValue', but has different custom
attributes.
Anyone have any ideas for this? :-)

Thanks,
- Rasmus.

[Amy]

Rasmus,

Did you resolve this issue? I just encountered the same problem and
have been searching for a solution, but yours is the only posting I've
found related to the XmlSerializer and default values in derived
classes.

An interesting side note is that the PropertyGrid control recognizes
that the value assigned to the derived class is the default value
specified for the overridden property.

Thanks!
Amy

Rasmus Kromann-Larsen wrote:

Hello,

I'm currently playing around with the XmlSerializer to replace my old
handmade Xml parsing code, but am having a few small issues with
default values and derived classes.

Say we have classes A, B and C:

abstract class A
{
protected int a_value = 1;

[XmlAttribute("v alue"), DefaultValue(1)]
public int AValue
{
get { return a_value; }
set { a_value = value; }
}
}

class B : A
{
...
}

class C : A
{
...
}
Now, I want class B and C to have different default values, more
precisely, I want B to have 1 as default value and C to have
Int32.MaxValue. But I can't figure out how to actually make this work.
I tried making the property in A abstract and provide the
implementation in B and C with different default values, but it still
used the default value from A. I tried removing the default value from
A, which gave the result of having no default value, everything was
printed, always.

I then tried to remove the XmlAttribute attribute from A and only have
it and the default value in B and C, but it gave me the following
exception:

System.InvalidO perationExcepti on: There was an error reflecting
property 'AValue'. ---> System.InvalidO perationExcepti on: Member
B.AValue' hides inherited member 'A.AValue', but has different custom
attributes.
Anyone have any ideas for this? :-)

Thanks,
- Rasmus.

[Rasmus Kromann-Larsen]

No,

unfortunatly I havn't had a chance to work on that project since then,
so I havn't resolved my error yet. :-)

- Rasmus.