Shallow copies of objects - or - Copy constructors

[Adam W Root]

So I have a Product and an extending class ProductLine. I want to create a
new ProductLine from a Product.

I wrote this in a constructor:

public Product(Product p)
{
foreach (System.Reflection.FieldInfo info in
p.GetType().GetFields(System.Reflection.BindingFla gs.Instance |
System.Reflection.BindingFlags.NonPublic))
info.SetValue(this, info.GetValue(p));
}

First, is this a huge performance hit? I've heard rumors about reflection
being the devil for performance, but as I understand it, reflection is a
central technology for the framework, and therefore there is lots of it
going on, so why would a bit more hurt anything?

Second, did I solve a problem that has already been solved? I know there is
a Memberwise clone, but this is invalid (assigning to this):

public Product(Product p)
{
this = (Product)p.MemberwiseClone();
}

Also, ICloneable's Clone method has a similar downfall.

Any feedback would be great. I've posted on this before with no response, so
I'd like to see even a "Yeah, I think that works" type of response.

Thanks everybody.

Adam

[Daniel O'Connell [C# MVP]]

"Adam W Root" <ad**@canright.com> wrote in message
news:uB*************@TK2MSFTNGP10.phx.gbl...

So I have a Product and an extending class ProductLine. I want to create a
new ProductLine from a Product.

I wrote this in a constructor:

public Product(Product p)
{
foreach (System.Reflection.FieldInfo info in
p.GetType().GetFields(System.Reflection.BindingFla gs.Instance |
System.Reflection.BindingFlags.NonPublic))
info.SetValue(this, info.GetValue(p));
}

First, is this a huge performance hit? I've heard rumors about reflection
being the devil for performance, but as I understand it, reflection is a
central technology for the framework, and therefore there is lots of it
going on, so why would a bit more hurt anything?

Second, did I solve a problem that has already been solved? I know there
is
a Memberwise clone, but this is invalid (assigning to this):
Yes, this is the point of Memberwise Clone. I would recommend *not* using
copy constructors and using ICloneable for various reasons, not the least of
which polymorphic behaviour. Copy constructors require you to know the
*exact* type of the object when you intend to clone it.
public Product(Product p)
{
this = (Product)p.MemberwiseClone();
}

Also, ICloneable's Clone method has a similar downfall.

The proper way to do things would be something like:

public object Clone()
{
MyObject x = this.MemberwiseClone();
return x;
}

while doing any particulars you need to do to x to handle other
cloning(references type fields are shallow copied(only the reference is
copied) in MemberwiseClone()). Any feedback would be great. I've posted on this before with no response,
so
I'd like to see even a "Yeah, I think that works" type of response.

Thanks everybody.

Adam

[Daniel O'Connell [C# MVP]]

"Adam W Root" <ad**@canright.com> wrote in message
news:uB*************@TK2MSFTNGP10.phx.gbl...

So I have a Product and an extending class ProductLine. I want to create a
new ProductLine from a Product.

I wrote this in a constructor:

public Product(Product p)
{
foreach (System.Reflection.FieldInfo info in
p.GetType().GetFields(System.Reflection.BindingFla gs.Instance |
System.Reflection.BindingFlags.NonPublic))
info.SetValue(this, info.GetValue(p));
}

First, is this a huge performance hit? I've heard rumors about reflection
being the devil for performance, but as I understand it, reflection is a
central technology for the framework, and therefore there is lots of it
going on, so why would a bit more hurt anything?

Second, did I solve a problem that has already been solved? I know there
is
a Memberwise clone, but this is invalid (assigning to this):
Yes, this is the point of Memberwise Clone. I would recommend *not* using
copy constructors and using ICloneable for various reasons, not the least of
which polymorphic behaviour. Copy constructors require you to know the
*exact* type of the object when you intend to clone it.
public Product(Product p)
{
this = (Product)p.MemberwiseClone();
}

Also, ICloneable's Clone method has a similar downfall.

The proper way to do things would be something like:

public object Clone()
{
MyObject x = this.MemberwiseClone();
return x;
}

while doing any particulars you need to do to x to handle other
cloning(references type fields are shallow copied(only the reference is
copied) in MemberwiseClone()). Any feedback would be great. I've posted on this before with no response,
so
I'd like to see even a "Yeah, I think that works" type of response.

Thanks everybody.

Adam