C#: Fastest way to detect change of byte in memory of program?

Question

I injected a DLL into a process with Easyhook and I can read a byte at a specific memory location with Marshal.ReadByte.

Now i want to be notified when that byte changes. What dou you think is the best way to do that when I want to detect a change as fast as possible?

Answer 1

Unfortunately, unless you are able to hook on to the function call that would modify the memory in question to tell you when the external process performed a change, your best option is to create a thread that just spins and checks the memory over and over for a new value.

I would recommend not making it "as fast as possible" as that is going to burn up a lot of CPU, you need to ask your self "what is the longest delay between a change and I get notified acceptable". If for example your answer to that was "0.1 seconds" your pooling loop would look like

private void PoolingLoop()
{
    var lastValue = Marshal.ReadByte(_location)
    while(_running)
    {
         Thread.Sleep(100);
         var newValue = Marshal.ReadByte(_location);

         if(lastValue != newValue)
             DoThisOnMemoryChanged();

         lastValue = newValue;
    }
}