C#

using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace RtlSetProcessIsCriticalCSharp
{
    unsafe public partial class Form1 : Form
    {
        [DllImport("kernel32.dll")]
        static extern IntPtr LoadLibrary(string dllName);

        [DllImport("kernel32.dll")]
        static extern IntPtr GetProcAddress(IntPtr hModule, string procName);

        delegate long *ProcessIsCriticalDelegate(
        [MarshalAs(UnmanagedType.Bool)]bool bNew, bool *pbOld,
        [MarshalAs(UnmanagedType.Bool)]bool bNeedScb);

        public Form1()
        {
            InitializeComponent();
        }

        unsafe private void Form1_Load(object sender, EventArgs e)
        {
            IntPtr ntdll = LoadLibrary("ntdll.dll");
            IntPtr ProcAdd = GetProcAddress(ntdll, "RtlSetProcessIsCritical");
            ProcessIsCriticalDelegate pcd = (ProcessIsCriticalDelegate)Marshal.GetDelegateForFunctionPointer(ProcAdd, typeof(ProcessIsCriticalDelegate));
            pcd(true, null, false);
        }
    }
}

>gacutil /l SharedDemo
Microsoft (R) .NET Global Assembly Cache Utility.  Version 3.5.21022.8 Copyright (c) Microsoft Corporation.  All rights reserved.

The Global Assembly Cache contains the following assemblies:
  SharedDemo, Version=1.0.0.0, Culture=neutral, PublicKeyToken=c5bbc6da95e06b44, processorArchitecture=MSIL

  Number of items = 1

using System.Diagnostics;
using System.Net;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System;
using System.IO;
using System.Linq;

class Program
{
	static void Main()
	{
		StreamReader str = new StreamReader("C:\\Sample1.html");
		string strLings = str.ReadToEnd();
		int startIndex = strLings.IndexOf("<table>");
		int endInedx = strLings.IndexOf("</table>") + "</table>".Length - startIndex;
		string strTab = strLings.Substring(startIndex, endInedx);
		str.Close();
		StreamWriter strWr = new StreamWriter("C:\\test2.txt", true);
		strWr.Write(strTab);
		strWr.Close();
	}
}