C# 0 The Complete Reference

PART I

C h a p t e r   1 9 :  

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PART IPART I

    Console.WriteLine("Accounts in sorted order: ");

    string str = "";

    // Execute the query and display the results.

    foreach(Account acc in accInfo) {

      if(str != acc.FirstName) {

        Console.WriteLine();

        str = acc.FirstName;

      }

      Console.WriteLine("{0}, {1}\tAcc#: {2}, {3,10:C}",

                        acc.LastName, acc.FirstName,

                        acc.AccountNumber, acc.Balance);

    }

    Console.WriteLine();

  }

}

The output is shown here:

Accounts in sorted order:

Jones, Jenny       Acc#: 108CK,     $10.98

Jones, Ralph       Acc#: 434CK,  ($123.32)

Jones, Ralph       Acc#: 454MM,    $987.13

Jones, Ralph       Acc#: 436CD,  $1,923.85

Krammer, Betty     Acc#: 968MM,  $5,146.67

Krammer, Ted       Acc#: 897CD,  $3,223.19

Smith, Albert      Acc#: 445CK,  ($213.67)

Smith, Carl        Acc#: 078CD, $15,345.99

Smith, Sara        Acc#: 843CK,    $345.00

Smith, Sara        Acc#: 543MM,  $5,017.40

Smith, Sara        Acc#: 547CD, $34,955.79

Smith, Tom         Acc#: 132CK,    $100.23

Smith, Tom         Acc#: 132CD, $10,000.00

In the query, look closely at how the 

orderby

 clause is written:

var accInfo = from acc in accounts

              orderby acc.LastName, acc.FirstName, acc.Balance

              select acc;

Here is how it works. First, the results are sorted by last name, and then entries with the 

same last name are sorted by the first name. Finally, groups of entries with the same first 

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and last name are sorted by the account balance. This is why the list of accounts under the 

name Jones is shown in this order:

Jones, Jenny       Acc#: 108CK,     $10.98

Jones, Ralph       Acc#: 434CK,  ($123.32)

Jones, Ralph       Acc#: 454MM,    $987.13

Jones, Ralph       Acc#: 436CD,  $1,923.85

As the output confirms, the list is sorted by last name, then by first name, and finally by 

account balance.

When using multiple criteria, you can reverse the condition of any sort by applying 

the

descending

 option. For example, this query causes the results to be shown in order 

of decreasing balance:

var accInfo = from acc in accounts

              orderby x.LastName, x.FirstName, x.Balance descending

              select acc;

When using this version, the list of Jones entries will be displayed like this:

Jones, Jenny       Acc#: 108CK,     $10.98

Jones, Ralph       Acc#: 436CD,  $1,923.85

Jones, Ralph       Acc#: 454MM,    $987.13

Jones, Ralph       Acc#: 434CK,  ($123.32)

As you can see, now the accounts for Ralph Jones are displayed from greatest to least.