CODEWITHSUNDEEP
c#
Control Freak
Control Freak

Reputation: 13233

'object' does not contain a definition

Why do I get this error? Here is the code:

MyClass item = new MyClass{ id=1 };
List<object> items = new List<object>();
items.Add(item);

object getitem = items[0];
int itemid = getitem.id; // <-error

In debugger the getitem object shows as having the id property, but I can't extract it without getting this error. How do I extract the id property from this object?

Upvotes: 1

Views: 2998

Answers (2)

Kyle
Kyle

Reputation: 6684

The compiler doesn't know that the actual object contained in getitem is of type MyClass, because you've told it to expect an object, which could be just about anything. Imagine you'd done this instead:

List<object> items = new List<object>();
items.Add( "Hello, World!" );

object getitem = items[0];
int itemid = getitem.id; // <-error

A string is also an object, so it's perfectly reasonable to put it in a List<object>. In fact, anything can be put into an object, so the compiler can only guarantee that whatever is in there can do what an object can do (which is have methods GetHashCode, Equals, and ToString).

Consider making your list more specific:

MyClass item = new MyClass{ id=1 };
List<MyClass> items = new List<MyClass>();
items.Add( item );

MyClass getitem = items[0];
int itemid = getitem.id;

If that's not an acceptable solution, then you'll need to cast the result from the list so the compiler knows it's actually dealing with an instance of MyClass:

MyClass getitem = (MyClass) items[0];
int itemid = getitem.id;

Upvotes: 7

Steve
Steve

Reputation: 502

The debugger is smart enough to know what type getitem really is and will display the properties. If you change it to:

MyClass getitem = (MyClass) items[0];

it will work for you. What your doing is casting the object instance to a MyClass type so the compiler knows it has an id property.

Upvotes: 4

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