[C#] ReadWritingMemory Error [NEED HELP]

public class ReadWritingMemory
    {

        [Flags()]
        public enum ProcessAccessType
        {

            PROCESS_TERMINATE = 1,

            PROCESS_CREATE_THREAD = 2,

            PROCESS_SET_SESSIONID = 4,

            PROCESS_VM_OPERATION = 8,

            PROCESS_VM_READ = 16,

            PROCESS_VM_WRITE = 32,

            PROCESS_DUP_HANDLE = 64,

            PROCESS_CREATE_PROCESS = 128,

            PROCESS_SET_QUOTA = 256,

            PROCESS_SET_INFORMATION = 512,

            PROCESS_QUERY_INFORMATION = 1024,
        }

        [DllImport("kernel32.dll")]
        public static extern IntPtr OpenProcess(UInt32 dwDesiredAccess, Int32 bInheritHandle, Int32 dwProcessId);

        [DllImport("kernel32.dll")]
        public static extern Int32 CloseHandle(IntPtr hObject);

        [DllImport("kernel32.dll")]
        public static extern Int32 ReadProcessMemory(IntPtr hProcess, IntPtr lpBaseAddress, byte[] buffer, UInt32 size, ref IntPtr lpNumberOfBytesRead);

        [DllImport("kernel32.dll")]
        public static extern Int32 WriteProcessMemory(IntPtr hProcess, IntPtr lpBaseAddress, byte[] buffer, UInt32 size, ref IntPtr lpNumberOfBytesWritten);

        public static void WriteLong(string ProcessName, int Address, long Value, int nsize)
        {
            if (ProcessName.EndsWith(".exe"))
            {
                ProcessName = ProcessName.Replace(".exe", "");
            }
            Process[] processesByName = Process.GetProcessesByName(ProcessName);
            if ((processesByName.Length == 0))
            {
                MessageBox.Show((ProcessName + " is not running"));
            }
            else
            {
                IntPtr ptr = ((IntPtr)(OpenProcess(127231, 0, processesByName[0].Id)));
                if ((ptr == IntPtr.Zero))
                {
                    MessageBox.Show(("Failed to open: "
                                    + (ProcessName + "!")));
                }
                else
                {
                    int lpBaseAddress = Address;
                    long lpBuffer = Value;
                    int lpNumberOfBytesWritten = 0;
                    WriteProcessMemory3(((int)(ptr)), lpBaseAddress, ref lpBuffer, nsize, ref lpNumberOfBytesWritten);
                }
            }
        }

        [DllImport("kernel32.dll", EntryPoint = "WriteProcessMemory")]
        private static extern int WriteProcessMemory1(int hProcess, int lpBaseAddress, ref int lpBuffer, int nSize, ref int lpNumberOfBytesWritten);

        [DllImport("kernel32.dll", EntryPoint = "WriteProcessMemory")]
        private static extern float WriteProcessMemory2(int hProcess, int lpBaseAddress, ref float lpBuffer, int nSize, ref int lpNumberOfBytesWritten);

        [DllImport("kernel32.dll", EntryPoint = "WriteProcessMemory")]
        private static extern long WriteProcessMemory3(int hProcess, int lpBaseAddress, ref long lpBuffer, int nSize, ref int lpNumberOfBytesWritten);

        private const int PROCESS_ALL_ACCESS = 127231;
    }

if (checkBoxZ1.Checked == true)
            {
                ReadWritingMemory.WriteLong("S4Client.exe" + 0x5A40D6, 267620496);
            }