how to convert int value to byte value

Use Convert.ToByte(intValue) which will convert your integer value to byte. If the entered value is too big or too small, it will through OverFlowException.

Better to use the Byte.TryParse(...) method.

int intValue = 2;

byte byteValue = Convert.ToByte(intValue);

This is what you're looking for?

As indeed pointed out below a byte goes until the number 255 and then stops because a byte can holds 8 bits

binary: 11111111 = 255

As already pointed out, generally speaking, an integer will not fit in a byte. Please post some context info (why do you need to perform such a conversion?) to get better help.
:)

Maybe what you need is converting an integer to its byte representation? i.e. 4 bytes for 32 bits integers.

In order to do that, the framework provides the BitConverter class.

http://msdn.microsoft.com/en-us/library/system.bitconverter.aspx[^]