Installscript:

function OracleSystemChecks(sHost, sCall)
	OBJECT MyObj; 
	STRING sReturn;
	                                    	
	                                    	
	
begin
    //set the object to the migrationclass dll file
    set MyObj = DotNetCoCreateObject ( SUPPORTDIR ^ "MigrationcClass.dll", "MigrationClass.CommonFunctions", ""); 
 
   try
		sReturn = MyObj.OracleSystemChecks(sHost, sCall);  
		
		if(sReturn % "SUCCESS") then
		
			WriteLogFile("NOTE   :Oracle System Check returned " + sReturn + "");
			
		else
			WriteLogFile("");
			WriteLogFile("SEVERE   :Oracle System Check returned Failure: ");
			WriteLogFile("		    :" + sReturn + "");
			WriteLogFile("SEVERE   :The " + @IFX_PRODUCT_NAME + " installation cannot continue");
			Backout("Oracle System Check Failure"); 
		endif;
	catch
			WriteLogFile("SEVERE   :Unable to perform Oracle System Check"); 
			WriteLogFile("SEVERE   :The " + @IFX_PRODUCT_NAME + " installation cannot continue");
            Backout("Oracle System Check Failure");
	endcatch;

end;


DLL file sample

using System;
using System.Globalization;
using System.IO;
using System.Net;
using Microsoft.Win32;
using System.Windows.Forms;
using System.Security.Principal;
using System.Diagnostics;
using System.ServiceProcess;
using System.Xml;
using System.Data;
using System.Data.OleDb;
using System.Data.SqlClient;
using System.Collections;
using System.Collections.Specialized;
using System.Management;
using System.Runtime.InteropServices;

namespace MigrationClass
{
	[ComVisible(true)]
	public class CommonFunctions
	{
	
		public string OracleSystemChecks(string ipAddress, string caller)
			{
			}
	}
}