C# 0 The Complete Reference

nums

.

It does this by use of the 

Where( ) 

method (to filter the values) and 

Select( )

 (to select the 

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values). The 

Where( )

 method can be invoked on 

nums

 because all arrays implement 

IEnumerable

, which supports the query extension methods.

Technically, the 

Select( )

 method in the preceding example is not necessary because in 

this simple case, the sequence returned by 

Where( )

 already contains the result. However, 

you can use more sophisticated selection criteria, just as you did with the query syntax. For 

example, this query returns the positive values in 

nums

 increased by an order of magnitude:

var posNums = nums.Where(n => n > 0).Select(r => r * 10);

As you might expect, you can chain together other operations. For example, this query 

selects the positive values, sorts them into descending order, and returns the resulting 

sequence:

var posNums = nums.Where(n => n > 0).OrderByDescending(j => j);

Here, the expression 

j => j

 specifies that the ordering is dependent on the input parameter, 

which is an element from the sequence obtained from 

Where( )

.

Here is an example that demonstrates the