Constants and literals explicit conversion

Question

When i try the following :

const int x = 1000;
byte b1 = (byte)x;

//Or

byte b2 = (byte)1000;

The compiler claims that it didn't convert constant 1000 to b1 or b2.

But when i tried the following :

const int x = 1000;
byte b1 = unchecked((byte)x);

//Or

byte b2 = unchecked((byte)1000);

This code worked fine.Why?

Do you know what `unchecked` means in c#? You have to to understand why it works. — MarcinJuraszek, Nov 24 '13 at 16:57
I can't believe you couldn't make the effort to look that up on MSDN. — James World, Nov 24 '13 at 16:58

score 3 · Answer 1 · answered Nov 24 '13 at 16:58

The compiler claims that it didn't convert constant 1000 to b1 or b2.

Yes because In .NET Framework, byte represents 8-bit unsigned integer and it can hold the values from 0 to 255.

But when i tried the following... This code worked fine.Why?

When you use unchecked keyword, you are allowing the overflow is not flagged.

If the unchecked environment is removed, a compilation error occurs. The overflow can be detected at compile time because all the terms of the expression are constants.

score 3 · Answer 2 · answered Nov 24 '13 at 16:58

3

It is obvious.

byte has range 0-255. You are trying to put there 1000 which leads to overflow. unchecked allows it because

The unchecked keyword is used to suppress overflow-checking for integral-type arithmetic operations and conversions.

answered Nov 24 '13 at 16:58

Ondrej Janacek

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Constants and literals explicit conversion

2 Answers2