How do I find all variables that an exe file uses?

const int PROCESS_WM_READ = 0x0010;
const int PROCESS_ALL_ACCESS = 0x1F0FFF;
[DllImport("kernel32.dll")]
public static extern IntPtr OpenProcess(int dwDesiredAccess, bool bInheritHandle, int dwProcessId);

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

[DllImport("kernel32.dll", SetLastError = true)]
static extern bool WriteProcessMemory(int hProcess, long lpBaseAddress, byte[] lpBuffer, int dwSize, ref int lpNumberOfBytesWritten);

public Process process;
public IntPtr processHandle;

void Read()
{
    process = Process.GetProcessesByName("ProcessesName")[0];
    processHandle = OpenProcess(PROCESS_WM_READ, false, process.Id);

    IntPtr startOffset = process.MainModule.BaseAddress;
    IntPtr endOffset = IntPtr.Add(startOffset, process.MainModule.ModuleMemorySize);
    string startOffsetStr = startOffset.ToString("X");
    string endOffsetStr = endOffset.ToString("X");

    int start = int.Parse(startOffsetStr, NumberStyles.HexNumber);
    int end = int.Parse(endOffsetStr, NumberStyles.HexNumber);
    int totalBytes = end - start;
    int bytesRead = 0;
    byte[] buffer = new byte[totalBytes];

    ReadProcessMemory((int)processHandle, start, buffer, buffer.Length, ref bytesRead);
    string result = ByteArrayToHexString(buffer);
    File.WriteAllText("C:\\result.txt", result);

}
public static string ByteArrayToHexString(byte[] baytes)
{
    StringBuilder hex = new StringBuilder(baytes.Length * 2);
    for (int i = baytes.Length - 1; i >= 0; i--)
    {

        hex.AppendFormat("{0:x2}", baytes[i]);
    }

    return hex.ToString();
}