Writeprocessmemory

[DllImport("Kernel32.dll", SetLastError = true)][return: MarshalAs(UnmanagedType.Bool)]
public static extern bool WriteProcessMemory(IntPtr hProcess,
   IntPtr lpBaseAddress,
   [MarshalAs(UnmanagedType.LPArray)] byte[] lpBuffer,
   uint nSize,
   out uint lpNumberOfBytesWritten
);

Microsoft documentation: Link