C# 0 The Complete Reference

PART I

C h a p t e r   1 9 :  

L I N Q  

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PART IPART I

clause returns the data by groups, with each group being able to be enumerated individually. 

As the preceding examples have shown, the 

where

 clause specifies criteria that an item 

must meet in order for it to be returned. The remaining clauses help you fine-tune a query. 

The follows sections examine each query clause.

Filter Values with where

As explained, 

where

 is used to filter the data returned by a query. The preceding examples 

have shown only its simplest form, in which a single condition is used. A key point to 

understand is that you can use 

where

 to filter data based on more than one condition. One 

way to do this is through the use of multiple 

where

 clauses. For example, consider the 

following program that displays only those values in the array that are both positive and 

less than 10:

// Use multiple where clauses.

using System;

using System.Linq;

class TwoWheres {

  static void Main() {

    int[] nums =  { 1, -2, 3, -3, 0, -8, 12, 19, 6, 9, 10 };

    // Create a query that obtains positive values less than 10.

    var posNums = from n in nums

                  where n > 0

                  where n < 10

                  select n;

    Console.Write("The positive values less than 10: ");

    // Execute the query and display the results.

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

    Console.WriteLine();

  }

}

The output is shown here:

The positive values less than 10: 1 3 6 9

As you can see, only positive values less than 10 are retrieved. This outcome is achieved by 

the use of the following two