In the middle of translating some code from C++ to C#, I found this,
unsigned char *p = m_pRecvBuffer + 5;
unsigned int noncelen1 = *p * 256 + p[1];
How do I translate this into C#? m_pRecvBuffer is a char-array, however I store it as a byte-array.
Hmm I wonder if some refactoring would be in order for this piece of code. Yes you can use pointers in C#. However, based on that snippet there may be better options. It looks like you're trying to read parts of an incoming stream. Maybe C#'s stream library would work better for this piece of your code?
You analyse what the code actually does and translate behaviour, not code. While you could use unsafe methods and pointer arithmetic in c#, this will probably create more problems than it will solve.
Something akin to
byte[] p = new byte[m_pRecvBuffer.Length - 5];
Array.Copy(m_precvBuffer, p, m_pRecvBuffer.Length - 5);
uint noncelen1 = p[0] * 256 + p[1];
But in that case I don't think you actually need to use an array copy. Just using
uint noncelen1 = p[5] * 256 + p[6];
should be enough, I guess.
Assuming RecvBuffer is declared as byte[], you would do something like this:
int noncelen1 = RecvBuffer[5] * 256 + RecvBuffer[6];