Question

I am trying to understand LINQ and become confident at using it. What I am struggling with are the parameters asked for. Example:

var sortedWords = words.OrderBy(a=>a.Length) 

words is an array collection. OrderBy‘s intellisense says:

Func<string, TKey> keyselector 

A func executes a method, and a string is the value, TKey a key.

In the example http://msdn.microsoft.com/en-us/vcsharp/aa336756.aspx#thenBySimple (ThenBy – Comparer), we compare length by saying a => a.Length. I understand that syntax, but how is that related to what the intellisense is asking for?

I tend to find the method signature and intellisense unreadable because of all the generics.

Thanks.

Answer 1

a => a.Length 

I understand that syntax, but how is that related to what the intellisense is asking for?

This chunk of code is a lambda expression. A lambda expression is a handy way of generating an Anonymous method (in this case), or a System.Linq.Expressions.Expression . Let’s break it down by parts.

• The most noticeable feature is the =>, which seperates parameters from a method body.
• On the left side of the =>, there is a symbol: a. This is the declaration of a parameter for our anonymous method. The compiler is aware that we are calling OrderBy(), and that OrderBy requires a Func<string, object>. The parameter for such a function is a string, so the compiler determines that a must be a string. The only thing the programmer needed to provide is a name.
• On the right side of the =>, there is method body. Since this is a one-liner, the return keyword is implied. The IDE provides intellisense against a as a string, which allows you to use the Length property.

Now, consider this C# 2.0 …

IEnumerable<string> sortedWords =    Enumerable.OrderBy(words, delegate(string a) {return a.Length;}); 

With the C# 3.0

IEnumerable<string> sortedWords = words   .OrderBy(a => a.Length);