I have a variable of type sbyte and would like to copy the content to a byte. The conversion wouldn't be a value conversion, rather a bit per bit copy.
For example,
if mySbyte in bits is: '10101100', after conversion, the corresponding byte variable will also contain the bits '10101100'.
Answer
Let me clarify the unchecked business. The MSDN page states that unchecked is used to prevent overflow checking, which would otherwise, when inside a checked context, give a compile error or throw an exception.
...IF inside a checked context.
The context is checked either explicitly:
checked { ... }
or implicitly*, when dealing with compile-time constants:
byte b = (byte)-6; //compile error
byte b2 = (byte)(200 + 200); //compile error
int i = int.MaxValue + 10; //compiler error
But when dealing with runtime variables, the context is unchecked by default**:
sbyte sb = -6;
byte b = (byte)sb; //no problem, sb is a variable
int i = int.MaxValue;
int j = i + 10; //no problem, i is a variable
To summarize and answer the original question:
Need byte<->sbyte conversion on constants? Use unchecked and cast:
byte b = unchecked( (byte) -6 );
Need byte<->sbyte conversion on variables? Just cast:
sbyte sb = -6;
byte b = (byte) sb;
* There is a third way to get a checked context by default: by tweaking the compiler settings. E.g. Visual Studio -> Project properties -> Build -> Advanced... -> [X] Check for arithmetic overflow/underflow
** The runtime context is unchecked by default in C#. In VB.NET for example, the default runtime context is CHECKED.