Before C# 4.0 there was no on demand initialization by default. So at the time of declaration we need to create a value or object will be null or we have to create on demand initialization via coding.. But with C# 4.0 we now have lazy class. As per MSDN it support lazy initialization so it means if we use lazy class then it will initialize the object at the time of demand. It is very useful for UI responsiveness and other scenario's. Lazy initialization delays certain initialization and it’s improve the start-up time of a application. In the earlier framework if we need this kind of functionality we have to do it manually via coding but from C# 4.0 onwards it have Lazy<T> class. With the Help of this we can improve the responsiveness of C# application. Following is a simple example.