Following are the 3 new Key features in .net 4.0
1) Windows work flow and WCF 4.0:- This is a major change in 4.0.
In WCF they have given following features :-

Dynamic Service and End Point discovery – The problem was faced in earlier version of WCF that if theend point has been changed at service [...]

Custom application error tracking through global.asax file. Here you can track querystrings, post data and whole exception message with url

1) Use Pascal casing for type and method names and constants:
public class YourClass
{
const int ConstantVariable = 100;
public YourMethod( )
{}
}

2) Use camel casing for local variable names and method arguments. Use p prefix for parameterized vairables:
int intNumber;
void MyMethod(int pintNumber)
{}

Here it goes

private int mstrPageSize = 1;
private int mstrTotalRecords = 1;
private int mstrCurrentPage = 1;

public int PageSize
{
get
{
return mstrPageSize;
}

Here is the few line code

try
{
int intCount = 1;
EventLog EventLog1 = new EventLog();
EventLog1.Log = “Application”

Following are the 6 differences between abstract classes and interfaces :-
1) A class can implement as many interfaces, but an subclass at most one abstract class.