Replace byte in a int

A int is composed of 4 bytes. How could I replace one of those 4 bytes with a new byte. In other words I am looking for a method: ``` int ReplaceByte(int index, int value, byte replaceByte) { // implementation } ``` for example if I have the value `FFFFFFFF` (-1) and I will like to replace the byte `0` with `0A` (10) then I will call the method as: `ReplaceByte(0,-1,10)` and I will like that method to return me `FFFFFF0A` Do I have to convert the int to a byte array then replace the byte I want then convert back to an int? I am looking for an efficient way of doing this. We are creating a debugger like program that connects to a target (board) and we update these values very frequently. Edit (results) Thanks to your answers I compared the methods: here are the results: Note my implementation was the slowest! Here is the code: ``` static void Main ( string[ ] args ) { byte[ ] randomBytes = new byte[ 1024 * 1024 * 512 ]; Random r = new Random( ); r.NextBytes( randomBytes ); Int64 sum; var now = DateTime.Now; Console.WriteLine( "Test 1" ); sum = 0; now = DateTime.Now; foreach ( var bt in randomBytes ) { sum += ReplaceByte1( 1 , -1 , bt ); } Console.WriteLine( "Test 1 finished in {0} seconds \t hash = {1} \n" , ( DateTime.Now - now ).TotalSeconds, sum ); Console.WriteLine( "Test 2" ); sum = 0; now = DateTime.Now; foreach ( var bt in randomBytes ) { sum += ReplaceByte2( 1 , -1 , bt ); } Console.WriteLine( "Test 2 finished in {0} seconds \t hash = {1} \n" , ( DateTime.Now - now ).TotalSeconds, sum ); Console.WriteLine( "Test 3" ); sum = 0; now = DateTime.Now; foreach ( var bt in randomBytes ) { sum += ReplaceByte3( 1 , -1 , bt ); } Console.WriteLine( "Test 3 finished in {0} seconds \t hash = {1} \n" , ( DateTime.Now - now ).TotalSeconds , sum ); Console.Read( ); } // test 1 static int ReplaceByte1 ( int index , int value , byte replaceByte ) { return ( value & ~( 0xFF << ( index * 8 ) ) ) | ( replaceByte << ( index * 8 ) ); } // test 2 static int ReplaceByte2 ( int index , int value , byte replaceByte ) { // how many bits you should shift replaceByte to bring it "in position" var shiftBits = 8 * index; // bitwise AND this with value to clear the bits that should become replaceByte var mask = ~( 0xff << shiftBits ); // clear those bits and then set them to whatever replaceByte is return value & mask | ( replaceByte << shiftBits ); } // test 3 static int ReplaceByte3 ( int index , int value , byte replaceByte ) { var bytes = BitConverter.GetBytes( value ); bytes[ index ] = replaceByte; return BitConverter.ToInt32( bytes , 0 ); } ```