LINQ: Func<T> vs. Expression<Func<T>>

Continuing the previous post about differences between IEnumerable<T> and IQueryable<T> I would like to describe differences between Func<T> and Expression<Func<T>>, basic features of lambda expressions and expression trees and possible impact on Entity Framework.

What is Func<T>

Func<T> is just a predefined generic delegate which encapsulates a method that accepts no parameters and returns a value of type T. It's declared like:

public delegate T Func<out T>();

Its value can be assigned to a named method or to an anonymous method through delegate syntax or through lambda expression syntax. All the following assignments are correct and return the same result:

Entity Framework: IQueryable vs. IEnumerable

Many of us sometimes get confused of different aspects of using IEnumerable<T> and IQueryable<T> in Entity Framework. One of considered opinions is that Entity Framework and DbContext and deffered execution just do all the magic and there is no difference. But even though LINQ query result remains basically the same, it may significantly impact the query performance.

Code sample

I'm going to create a simplified database consisting of one table with million records with Entity Framework Code First.

Animated Anchor and Button with CSS3

Agenda

HTML5 and CSS3 features give us great opportunity to create rich animated user interfaces comparable with desktop versions. Here I will explain how to create rich UI button with custom HTML content and CSS3 tools only, without using javascript and images.

I am not going to explain details of an appropriate CSS3 style, but a live demo will be attached to every step, so you will be able to see how it affects different browsers.

Layout

Let's specify a general .button class, with some default styles. The class will be suitable for different kinds of tags to make them look like rich UI button.