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Conversion from base classes

Posted on 2004-08-26
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Last Modified: 2010-04-15
I have written a class, ObjectBase, that is the base for two other classes, OrganizationalPerson and OrganizationalUnit.  OrganizationalUnit is an Enumerable class that can either contain a list of OrganizationalPersons or other OrganizationalUnits.   The following is my implementation of Current:

public object Current
{
      get { return new ObjectBase(_searchResult[_index].GetDirectoryEntry()); }
}

Everything works until I try the following:

foreach(OrganizationalUnit o in ou)
      Response.Write(String.Format("{0}<br>", o.name));

I get a "Specified Cast is not valid" error when trying to run the above code.  When I try to write an implicit or an explicit conversion, the code will not compile.  How can I accomplish this?
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Question by:dirtdart
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6 Comments
 
LVL 3

Assisted Solution

by:GrumbleBot
GrumbleBot earned 750 total points
ID: 11909087
You want variable o to be Object?

if so you would want

foreach(Object o in ou)
    Response.Write(String.Format("{0}<br>", o.Name.ToString()));

Hope this helps
Good luck
0
 
LVL 10

Accepted Solution

by:
eternal_21 earned 750 total points
ID: 11909302
** NOT FOR POINTS ***

  foreach(ObjectBase o in ou)
    Response.Write(String.Format("{0}<br>", o.Name.ToString()));

* Note that it is ObjectBase, not object (assuming that ObjectBase.Name is a valid method).
0
 
LVL 1

Expert Comment

by:johanjohansson
ID: 11910518
Why do you use the 'new' keyword when getting an item from the list? Why not

public object Current
{
     get { return _searchResult[_index].GetDirectoryEntry(); }
}

or

public ObjectBase Current
{
     get { return (ObjectBase)_searchResult[_index].GetDirectoryEntry(); }
}
0
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LVL 5

Author Comment

by:dirtdart
ID: 11911184
johanjohansson:  That is done because _searchResult[_index].GetDirectoryEntry() does not cast directy to ObjectBase.  It is passed as a parameter to the constructor, and all information loaded into the ObjectBase through it.
0
 
LVL 5

Author Comment

by:dirtdart
ID: 11911206
GrumbleBot:  No, I want o to be type OrganizationalUnit.

eternal_21:  That would work for the name property.  Unfortunately, there are some other properties that are not present in ObjectBase that I have to access. However....
0
 
LVL 5

Author Comment

by:dirtdart
ID: 11911324
Well, the two of you got me close.  I created a new constructor for OrganizationalUnit that acccepts an ObjectBase as an argument.  Then did this:

foreach(ObjectBase o in ou)
{
      OrganizationalUnit u = new OrganizationalUnit(o);

I still can't data bind it, but I can work around that.
0

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