// REQUIRED CONSTS

const int PROCESS_QUERY_INFORMATION = 0x0400;
const int MEM_COMMIT = 0x00001000;
const int PAGE_READWRITE = 0x04;
const int PROCESS_WM_READ = 0x0010;


// REQUIRED METHODS

[DllImport("kernel32.dll")]
public static extern IntPtr OpenProcess(int dwDesiredAccess, bool bInheritHandle, int dwProcessId);

[DllImport("kernel32.dll")]
public static extern bool ReadProcessMemory(int hProcess, int lpBaseAddress, byte[] lpBuffer, int dwSize, ref int lpNumberOfBytesRead);

[DllImport("kernel32.dll")]
static extern void GetSystemInfo(out SYSTEM_INFO lpSystemInfo);

[DllImport("kernel32.dll", SetLastError = true)]
static extern int VirtualQueryEx(IntPtr hProcess, IntPtr lpAddress, out MEMORY_BASIC_INFORMATION lpBuffer, uint dwLength);


// REQUIRED STRUCTS

public struct MEMORY_BASIC_INFORMATION {
  public int BaseAddress;
  public int AllocationBase;
  public int AllocationProtect;
  public int RegionSize;
  public int State;
  public int Protect;
  public int lType;
}


public struct SYSTEM_INFO {
  public ushort processorArchitecture;
  ushort reserved;
  public uint pageSize;
  public IntPtr minimumApplicationAddress;
  public IntPtr maximumApplicationAddress;
  public IntPtr activeProcessorMask;
  public uint numberOfProcessors;
  public uint processorType;
  public uint allocationGranularity;
  public ushort processorLevel;
  public ushort processorRevision;
}

public static void locateMemoryForProcess(Process process) {

    long addrCount = 0;

    SYSTEM_INFO sys_info = new SYSTEM_INFO();
    GetSystemInfo(out sys_info);

    IntPtr proc_min_address = sys_info.minimumApplicationAddress;
    IntPtr proc_max_address = sys_info.maximumApplicationAddress;

    long proc_min_address_l = (long)proc_min_address;
    long proc_max_address_l = (long)proc_max_address;

    IntPtr processHandle = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_WM_READ, false, process.Id);

    MEMORY_BASIC_INFORMATION mem_basic_info = new MEMORY_BASIC_INFORMATION();

    int bytesRead = 0;  // number of bytes read with ReadProcessMemory

    uint infoSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(mem_basic_info);
    VirtualQueryEx(processHandle, proc_min_address, out mem_basic_info, infoSize);

    var err = Marshal.GetLastWin32Error();
    Console.WriteLine("Error : " + err);

    ...