About conversion

Hello everybody,
I just went through a code clash where I had to convert a binary to an hexadecimal.
So, I first wanted to convert the input string to Int32 :
(The T string contains a binary expression of an integer)
System.Convert.ToInt32(T, 2)
and I got very ugly messages in red about an exception on this line.
Well, this is in the System library, I presume it should be available.
Any idea what happened ?
The other people successed, but not with the same language. But I did conversions this afternoon, so I do not realize what the problem is.
I did a copy/paste from Visual Studio, in case there is a typo …

What did the ugly red message say?

Well, I have to admit that in the stress I did not have the reflex of depressing the print screen key.

But that looks like a missing reference. Is there a way to find a test on the same topic ? Maybe we find that exception -except if it was a temporary deficiency.

sure, take any puzzle and add that line and play it.