MSDN Magazine - July 2008 - (Page 41)

you only need to supply the value you’re seeking. If you’re attempting to determine whether a more complex object exists within a sequence, you must supply an instance of a class that implements IEqualityComparer(Of T). The sample code in Figure 6 demonstrates both calls to Enumerable.Contains. The first example simply determines whether the number 5 appears within a list; the second determines whether an element corresponding to Chai appears within the list of products (this example uses the same ProductComparer class you saw earlier in the column). To determine whether two sequences are equal, call the Enumerable.SequenceEqual method. Just like the Enumerable.Contains method, you can either compare two sequences of simple values using the default comparer or two sequences of more complex objects using a custom comparer. If the two sequences don’t contain the same types or are of different lengths, the comparison fails immediately. If they contain the same type and are of the same length, the Enumerable.SequenceEqual method compares each item using the specified comparer. Figure 7 demonstrates both ways of calling the Enumerable.SequenceEqual method. In both cases, the return value is False. In my next column, I’m going to focus on the remaining methods of the Enumerable class, including some fun methods that perform useful set-based operations. Until then, you can download the sample application and give the Enumerable class’s methods a Figure 7 Comparing Sequences ' From SequenceEqualDemo in sample: Dim rnd As New Random Dim start = rnd.Next Dim count = 10 Dim s1 = Enumerable.Range(start, count) ' Choose a different random starting point: start = rnd.Next Dim s2 = Enumerable.Range(start, count) Dim sequencesEqual = s1.SequenceEqual(s2) sw.WriteLine("sequencesEqual = {0}", sequencesEqual) ' What if there's no default comparer? Must use your own: Dim products1 = _ From prod In db.Products _ Where prod.CategoryID = 1 Dim products2 = _ From prod In products1 _ Where prod.UnitPrice > 5 sequencesEqual = _ products1.SequenceEqual(products2, New ProductComparer()) sw.WriteLine("sequencesEqual = {0}", sequencesEqual) try. They’ll certainly enrich your work with data structures in Visual Studio® 2008. KEN GETZ is a Senior Consultant with MCW Technologies and a courseware author for AppDev (www.appdev.com). He is coauthor of ASP .NET Developers Jumpstart, Access Developer’s Handbook, and VBA Developer’s Handbook, 2nd Edition. Reach him at keng@mcwtech.com. NCache TM Clustered Object Cache for .NET Boost your .NET application performance! If your .NET application runs in a server-farm and has large number of users, then use NCache to boost its performance and scalability. NCache is an extremely fast distributed object cache for .NET. Enterprise Distributed Object Cache Cache data, reduce database trips, and boost performance Scale up thru Replicated, Partitioned, and Client Cache topologies Distributed ASP.NET Session Cache Faster & more scalable session storage Integrate without any code change Distributed ASP.NET Output Cache Cache rendered pages and serve content without re-rendering Integrate without any code change msdnmagazine.com Ph: +1-925-236-3830 Download FREE Trial www.alachisoft.com July 2008 41 http://www.appdev.com http://www.alachisoft.com http://www.alachisoft.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - July 2008

MSDN Magazine - July 2008 Contents Toolbox CLR Inside Out Flex Your Data Data Points Advanced Basics Office Space Cutting Edge Data Services ADO.NET Data and WPF Transactions WCF P2P Test Run Security Briefs Foundations .NET Matters {End Bracket}

MSDN Magazine - July 2008

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