是否可以为XAttribute AND XElement编写方法？

Question

XAttribute and XElement both derive from the XObject type.

Both have a Value property.

So far, this is what I've come up with to do what I want :

string FooMyXObject( XObject bar ){
    if ( bar.NodeType == NodeType.Element )
        return ( bar as XElement ).Value;
    else if ( bar.NodeType == NodeType.XAttribute )
        return ( bar as XAttribute ).Value;
    else
        throw new Exception( "Generic Fail Message" );
}

This feels clunky. I'm hoping there is some way to make this less clunky. Some way of accessing the Value property from the XObject , since they both have a string property names Value .

Is this possible, or am I just forced to doing it in thus clunky fashion?

Answer 1

If the .Value property is defined on the XObject, Then you can write this pretty simply using generics.

ie

string FooMyXObject<T>(T bar) where T : XObject
{
    return bar.Value;
}

If that is not the case then you should consider moving it to the base class if it is common functionality of the derived classes.

Edit: Your code is pretty much right if it is the case the Value property is not on the base class. Maybe you could refactor it like so using a case for easier extension:

string FooMyXObject(XObject bar)
{
   switch(bar.NodeType)
   {
      case NodeType.Element:
          return ( bar as XElement ).Value;
      case NodeType.XAttribute:
          return ( bar as XAttribute ).Value;
      default:
          throw new Exception( "Generic Fail Message" );
   }
}

or just for fun

string FooMyXObject(XObject bar)
    {
       try
       {
           dynamic temp = bar;
           return temp.Value;
       } 
       catch ()
       {
           throw new Exception( "Generic Fail Message" );
       }
    }

Answer 2

You can cast bar to dynamic to avoid separate branches:

string FooMyXObject( XObject bar ){
    if (bar.NodeType == NodeType.Element || bar.NodeType == NodeType.XAttribute)
        return ((dynamic)bar).Value;
    else
        throw new Exception( "Generic Fail Message" );
}

Answer 3

The answers given by @meganaut and @dasblinkenlight are both correct, but there is more to be said.

In the System.Linq.Xml namespace, XElement and XAttribute both extend XObject , but they each define their Value property separately, so this kind of branching or the use of the dynamic type is required.

In other object models, generics might be usable in a similar scenario as suggested by @meganaut.