Reflection question (for <= .NET 3.5)

[MarkB777]

Hey guys, Long story short: I have a number of classes that are structured like this:

class ClassA
{
[WantToCopy]
public Property1 { get; set; }
public Property2 { get; set; } // ...
}

class ClassB : ClassA
{
public Property1 { get; set; }
public Property2 { get; set; } // ...
}

class ClassC
{
public ClassB { get; set; }
public Property1 { get; set; }
public Property2 { get; set; } // ...
}

I am trying copy the ClassA values (marked with a specific attribute) from an instance of ClassB to a new instance of ClassA. This is what I am doing:

T resp = GetClassC(); // get a pretend instance of ClassC

var types = resp.GetType().GetProperties();
foreach (var type in types)
{
// I use this to figure out if the field in ClassC == ClassB
if(type.PropertyType.IsSubclassOf(this.GetType()))
{
// I use this custom method to get the properties in ClassA that have the
// attribute mentioned above
List fields = GetFields(type.PropertyType);
foreach (var field in fields)
{
// here is the problem!
var value = field.GetValue(resp , null); // resp is ClassC
field.SetValue(this, value , null); // 'this' is ClassA
}
}
}

The problem is I get a TargetException when I try and get a ClassA value from a ClassC instance (which makes sense). ClassC is a generic type. I don't know anything about the ClassB member. Does anyone have any tricks that could help me out here? Or will I have to use an interface? P.S I am keen to keep this code to <= .NET 3.5 if possible. Thank you, Mark

Mark Brock "We're definitely not going to make a G or a PG version of this. It's not PillowfightCraft." -- Chris Metzen

[Richard Deeming]

You're trying to read the value of a property defined in ClassA from an instance of ClassC, which doesn't inherit from ClassA. Try something like this instead:

// This is an expensive call; cache the result:
Type myType = this.GetType();

// No need to examine sub-classes; if a property isn't
// defined on this class, you won't be able to copy it:
List propertiesToCopy = GetFields(myType);

foreach (PropertyInfo property in resp.GetType().GetProperties())
{
// IsSubclassOf returns false if the types are the same:
if (property.PropertyType.IsSubclassOf(myType) || property.PropertyType == myType)
{
// Get the instance of ClassB:
var propertyValue = property.GetValue(resp, null);

    // Can't copy properties from a null instance:
    if (propertyValue == null) continue;
    
    foreach (PropertyInfo propertyToCopy in propertiesToCopy)
    {
        var value = propertyToCopy.GetValue(propertyValue, null);
        propertyToCopy.SetValue(this, value, null);
    }
}

}

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[PIEBALDconsult]

As you seem to have access to the code, why not add a copy constructor or Clone method to ClassA?

[MarkB777]

Thanks Richard that looks like it will do what I am trying to achieve, cheers mate!

Mark Brock I'm pretty sure there's a lot more to life than being really, really, ridiculously good looking

[MarkB777]

Thanks for your response. That is a good suggestion, but in this particular case I am trying to avoid using that approach. Much appreciated anyway

Mark Brock I'm pretty sure there's a lot more to life than being really, really, ridiculously good looking