C# 0 The Complete Reference

Create Queries by Using the Query Methods

By using the query methods in conjunction with lambda expressions, it is possible to create 

queries that do not use the C# query syntax. Instead, the query methods are called. Let’s 

begin with a simple example. It reworks the first program in this chapter so that it uses calls 

to

Where( )

 and 

Select( )

 rather than the query keywords.

// Use the query methods to create a simple query.

// This is a reworked version of the first program in this chapter.

using System;

using System.Linq;

class SimpQuery {

  static void Main() {

    int[] nums =  { 1, -2, 3, 0, -4, 5 };

    // Use Where() and Select() to create a simple query.

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

    Console.Write("The positive values in nums: ");

    // Execute the query and display the results.

    foreach(int i in posNums) Console.Write(i + " ");

    Console.WriteLine();

  }

}

The output, shown here, is the same as the original version:

The positive values in nums: 1 3 5

In the program, pay special attention to this line:

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

This creates a query called 

posNums

 that creates a sequence of the positive values in