Extension methods syntax vs query syntax

Question

I'm trying to get a handle on if there's a good time to use standard linq keywords or linq extension methods with lambda expressions. They seems to do the same thing, just are written differently. Is it purely a matter of style?

var query = from p in Products     where p.Name.Contains("foo")     orderby c.Name     select p;  // or with extension methods: var query = Products     .Where(p => p.Name.Contains("foo"))     .OrderBy(p => p.Name); 

They're very similar with the second example being a bit more terse, but perhaps less expressive if you don't know what the => is doing.

Other than writing terse code, are there other advantages to using the extension methods as opposed to the LINQ syntax?

Answer 1

Honestly, sometimes it can be situational once you start using Funcs and Actions. Say you are using these three funcs:

  Func<DataClasses.User, String> userName = user => user.UserName;   Func<DataClasses.User, Boolean> userIDOverTen = user => user.UserID < 10;   Func<DataClasses.User, Boolean> userIDUnderTen = user => user.UserID > 10; 

As you can see the first one replaces the lamdba expression to get the user name, the second replaces a lamdba expression used to check if the ID is lower than 10, and let's face it, the third should be pretty easy to understand now.

NOTE: This is a silly example but it works.

  var userList =      from user in userList     where userIDOverTen(user)     select userName; 

Versus

  var otherList =     userList     .Where(IDIsBelowNumber)     .Select(userName) 

In this example, the second is a little less verbose since the extension method can make full use of the Func, but he Linq expression can't since it is look just for a Boolean rather than a Func that returns boolean. However, this is where it might be better to use the expression language. Say you already had a method that takes in more than just a user:

  private Boolean IDIsBelowNumber(DataClasses.User user,            Int32 someNumber, Boolean doSomething)   {     return user.UserID < someNumber;   } 

Note: doSomething is just there because of the where extension method being ok with a method that takes in a user and integer and returns boolean. Kind of annoying for this example.

Now if you look at the Linq query:

  var completeList =      from user in userList      where IDIsBelowNumber(user, 10, true)      select userName; 

You're good for it. Now the Extension Method:

  var otherList =     userList     .Where(IDIsBelowNumber????)     .Select(userName) 

Without a lambda expression, I really can't call that method. So now what I have to do is create a method that creates a Func based off the original method call.

   private Func<DataClasses.User, Boolean> IDIsBelowNumberFunc(Int32 number)    {       return user => IDIsBelowNumber(user, number, true);    } 

And then plug it in:

  var otherList =      userList      .Where(IDIsBelowNumberFunc(10))      .Select(userName) 

So you can see, sometimes it may just be easier to use the query approach at times.