compile time error or runtime error?

Question

Hello everyone,

Could anyone let me know why compiler can not make runtime error report in the following code, other than throw cast exception during runtime?

[Code]
    static void Main()
    {
        int i = 100;
        object b = i;
        long l = (long)b; // why compiler can not make type check here?

return;
}
[/Code]

thanks in advance,
George

George George · Answer

Thanks Bechir, 1. "You can also check the cast using 'checked' and trap the error in a try catch block." How to "trap the error" in a try catch block? Could you show me please? 2. "You can also check the cast using 'checked' and trap the error in a try catch block." What means 'checked'? A language feature of C# or a feature of VS? 3. How to use generics to solve the unbox to wrong type issue? regards, George

Bechir Bejaoui · Answer

I can't trap "catch the error" because at the compile time the b variable is supposed as object and not as long and this is one of the weakness of the C# 2.0 that is after ajusted by introducing generics within C# 3.0

George George · Answer

What means "'checked' and trap the error"? Any documents? regards, George

Scott Lysle · Answer

It happens at runtime. Variable b in an object; in your code, you are trying to unbox it into the wrong type (long) after setting it to an int value; unbox it first into the right type (int) and then cast it over as long: long l = (long)((int)b); You can also check the cast using 'checked' and trap the error in a try catch block.

compile time error or runtime error?

Answers (4)