Question

Let’s have a byte array

byte[] Test = { 0, 0, 0, 0 };

I want to do this:

UInt32* p = &Test[0];
p* = 0xAABBCCDD;

or shortly:

(int*)(&Test[0])* = 0xAABBCCDD;

In Delphi I’d do:

PUInt32(@Test[0])^ := $AABBCCDD;

where PUInt32 = ^Uint32 or typdef PUInt32 = *UInt32 in C#.

But don’t know how it works in C#.

Answer 1

This kind of code is fundamentally unsafe, it defeats the compiler’s type system. And won’t be accepted by the verifier. If you accidentally declare the array wrong, 3 elements for example, then you’ll corrupt memory and produce a very hard to diagnose bug.

This can however also be done safely:

byte[] test = BitConverter.GetBytes(0xaabbccdd);

Which the slight disadvantage that it creates the array for you. Bypassing that requires the unsafe version:

fixed (byte* ptr = test)
{
    *((uint*)ptr) = 0xaabbccdd;
}

Which requires you to use the unsafe keyword in the method declaration and tick the Project + Properties, Build, “Allow unsafe code” option.