Create DLL with fasm

Hello Community,

I am relatively new to fasm and I like to make a little project.
My vision is to create a DLL file with fasm which has two basic functions.
And addition function and a multiplication function.
Both function should accept two integer values and return the result, something like this :

Code:

static int Addition(int a, int b)
{ 
return a+b; 
}

static int Multiplication(int a, int b)
{ 
return a*b; 
}

Later on I want to call the DLL from C# by using PInvoke/DLLImport.
Furthermore I want the DLL to work on both, x86 and x64 systems, - so I guess it needs to be built using x86 commands/registers, right (?)

Can someone give me some resources (not the finals solution please otherwise I won't learn anything) to get started to build a small DLL only with the stuff I need.

I hope to hear from you Smile

-yq8dev