Getting Started with LINQ – Part 2

In this section, we’ll proceed further and look at different projection strategies. So, the first case which I am using here is the Object Initializers. With C# Object Initializers, we can project the same into more complex types. For example, suppose, as a first step in a query, we want to strip vowels from a list of names while still keeping the original versions alongside, for the benefit of subsequent queries. Therefore, we can write as shown below:

void Main()
{
	var names = new[] { "Rahul", "Sahay", "Tom", "Dave", "Hari" }.AsQueryable();
	
	IEnumerable<TempProjectionItem> temp =
		from n in names
		select new TempProjectionItem
		{
			Original  = n,
			Vowelless = n.Replace ("a", "").Replace ("e", "").Replace ("i", "").Replace 
                         ("o", "").Replace ("u", "")
		};
		
	temp.Dump();
	  
	}
	class TempProjectionItem
	{
		public string Original;      // Original name
		public string Vowelless;   // Vowel-stripped name
		
}

// Define other methods and classes here

However, Anonymous Types allow you to structure your intermediate results without writing special classes. So, here we can remove TempProjectionItem as shown below in the example.

void Main()
{
	var names = new[] { "Rahul", "Sahay", "Tom", "Dave", "Hari" }.AsQueryable();
	
	var intermediate = from n in names
	select new
	{
		Original = n,
		Vowelless = n.Replace ("a", "").Replace ("e", "").Replace ("i", "").Replace 
                    ("o", "").Replace ("u", "")
	};
	
	(
		from    item in intermediate
		where   item.Vowelless.Length > 2
		select  item.Original
	)
	.Dump();
	
	// With the into keyword we can do this in one step:
	
	(
		from n in names
		select new
		{
			Original = n,
			Vowelless = n.Replace ("a", "").Replace ("e", "").Replace ("i", "").Replace 
                        ("o", "").Replace ("u", "")
		}
		into   temp
		where  temp.Vowelless.Length > 2
		select temp.Original
	)
	.Dump ("With the 'into' keyword");
}

// Define other methods and classes here

The let keyword introduces a new variable alongside the range variable. With let, we can write a query extracting strings whose length, excluding vowels, exceeds two characters, as follows:

void Main()
{
	var names = new[] { "Rahul", "Sahay", "Tom", "Dave", "Hari" }.AsQueryable();
	(
		from n in names
		let vowelless = n.Replace ("a", "").Replace ("e", "").Replace ("i", "").Replace 
                         ("o", "").Replace ("u", "")
		where vowelless.Length > 2
		orderby vowelless
		select n		       // Thanks to let, n is still in scope.
	)
	.Dump();
}

// Define other methods and classes here

The compiler resolves a let clause by projecting into a temporary anonymous type that contains both the range variable and the new expression variable. Thanks for joining me. In the next section, we’ll delve further and check other pieces as well. Till then, stay tuned and happy coding!