dotnet clr: InvalidCastException -- dotnet clr

Re: InvalidCastException

Mrinal Kamboj
7/20/2005 12:00:00 AM

Way it goes is :

InvalidCastException is thrown only when tried between types which are
possible to typecast for e.g:

string s = "1" ;
int i = (int) s ; // Compiler Error

Object s = "1" ;
int i = (int) s ; // Invalid Cast Exception

so even if you do something like :

int j = 1 ;
object s = j.toString() ;
int i = (int) s ; // Invalid Cast Exception

so , invariably at runtime what is inside an object type is unknown ,
till the point it applies the typecasting logic and try to map it to
given data type , when it leads to exception .

I think this makes it clear , that why info is limited in exception
block , but i think if u try deriving a new class from it , then you may
be able to get something that u need .

Mrinal

[quoted text, click to view]

Re: InvalidCastException

cody
7/20/2005 10:55:03 AM

Iam not interested in the stacktrace but in the value which was tried to
cast, and the type which it was tryied to cast to. It would be great if the
InvalidCastException would have these properties.

"Scott M." <s-mar@nospam.nospam> schrieb im Newsbeitrag
news:u42YzzLjFHA.1412@TK2MSFTNGP09.phx.gbl...
[quoted text, click to view]

Re: InvalidCastException

Jon Skeet [C# MVP]
7/20/2005 5:35:40 PM

[quoted text, click to view]

Yes, but I believe what the OP is trying to say is that the exception
could say what the actual type was, like it does in Java. Consider the
following two programs:

Java:
public class Test
{
public static void main (String[] args)
{
try
{
Object o = new Object();
String s = (String)o;
}
catch (Exception e)
{
System.out.println(e);
}
}
}

C#:
using System;

public class Test
{
public static void Main (String[] args)
{
try
{
Object o = new Object();
String s = (String)o;
}
catch (Exception e)
{
Console.WriteLine(e);
}
}
}

Results (with stack traces removed):

Java:
java.lang.ClassCastException: java.lang.Object

C# (with .NET 1.1):
System.InvalidCastException: Specified cast is not valid.

C# (with .NET 2.0 beta):
System.InvalidCastException: Unable to cast object of type
'System.Object' to type 'System.String'.

So it seems that .NET 1.1 is the worst offender, giving you no
information at all about the types involved. Java is somewhat better
telling you what you were trying to cast, but not what you were trying
to cast it to. .NET 2.0 is the best of the bunch, telling you both
types involved.

--
Jon Skeet - <skeet@pobox.com>
http://www.pobox.com/~skeet

Re: InvalidCastException

cody
7/21/2005 9:30:42 AM

[quoted text, click to view]

that's great :)

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