Casting to inhering type from inherited type

livez

Hey! I got a problem with a class of mine inheriting from xmldocument. When I have an actual xmldocument I can´t cast it to my class, I get System.InvalidCastException. Why is this? I have done the same with for instance another class inheriting from UriBuilder.

leppie

livez wrote:

When I have an actual xmldocument I can´t cast it to my class, I get System.InvalidCastException. Why is this?

Because the instance you are trying to cast is obviously not of your inherited type!

xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)

livez

This is what I tried:

class test : XmlDocument
{
public test()
{

    }

    public void testing ()
    {
        test t = new test();
        XmlDocument doc = new XmlDocument();
        t = (test)doc;
    }
}

Jan Scamba

[Message Deleted]

leppie

livez wrote:

XmlDocument doc = new XmlDocument(); t = (test)doc;

XmlDocument doc = new test();
test t = (test) doc;

I am not saying any more.

xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)

livez

Didnt work :(

Jan Scamba

try leppies solution bellow

livez

So I can´t cast to a more advanced type, but casting to a less advanced is okay.

leppie

I think you need to study inheritance and polymorphism a bit more. It takes a while to get to understand it, but once you do, it all seems natural.

xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)

livez

Thanks for your help, though u could work on your manners a bit.

leppie

My manners are irrelevant. I do not like to spoon-feed people.

xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)

Colin Angus Mackay

leppie wrote:

My manners are irrelevant.

Well said, Seven! :-D

Recent blog posts: * Introduction to LINQ to XML (Part 1) - (Part 2) - (part 3) My website | Blog

Colin Angus Mackay

livez wrote:

work on your manners a bit

His responses appeared to be quite polite. Curt, for sure, but polite.

Recent blog posts: * Introduction to LINQ to XML (Part 1) - (Part 2) - (part 3) My website | Blog

Scott Dorman

Why was the message deleted? Because the OP said the proposed solution didn't work? That's not a very good reason as now no one else who runs into the same (or similar) problem will know not to try that approach.

Scott. —In just two days, tomorrow will be yesterday. —Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai

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leppie

:)

xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)

livez

Yes you´re quite right. My apologies Leppie.

Russell Jones

in general these kinds of casts will only work towards the base class. ie a test is an XmlDocument but an XmlDocument is Not necessarily a test. you could use the "as" operator t = doc as test; this will return t == null if doc is not of type test. If you know how to convert an XmlDocument into a test then you could create a cast for it public static explicit operator Test(XmlDocument doc) { //your conversion algorithm here } HTH Russ