Casting an object from a stack

Question

Why does this:

System.Collections.Stack s = new Stack();
s.Push(97);
char c = (char) s.Pop(); //throws InvalidCastException

throw an error, but this:

char c = (char) 97; //c = 'a'

work just fine?

I'm especially confused since s.Pop().GetType() returns System.Int32, so it really shouldn't matter... What's going on here? Am I missing something, or do I have to work around it?

I wonder why are you even using something from the `System.Collections` namespace instead of `System.Collections.Generic` — Camilo Terevinto, Jan 31 '19 at 13:07
@RubensFarias yeah, I could do that in this example, but not in the context of the thing I'm programming. This is massively simplified. — hensing1, Jan 31 '19 at 13:10

score 1 · Accepted Answer · answered Jan 31 '19 at 13:07

Because Stack is the non-generic variant of a stack implementation. Pop returns an object, and the cast object -> char is invalid.

This does work though:

char c = (char)(int)s.Pop();

My two cents: use a generic implementation of Stack:

`Stack<char> s = new Stack<char>();`

score 0 · Answer 2 · answered Jan 31 '19 at 13:08

0

Use a generic version of Stack<T> like

Stack<int> s = new Stack<int>();
s.Push(97);
char c = (char)s.Pop();
Console.WriteLine(c);

answered Jan 31 '19 at 13:08

Rahul

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Casting an object from a stack

2 Answers2