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The Baker's Dozen Doubleheader: 26 Productivity Tips for Managing Data (Part 2 of 2) : Page 3

The conclusion of a two-part article on managing data with Visual Studio 2005 and SQL Server focuses on .NET generics, provides an introduction to the new ObjectDataSource class, and demonstrates some additional new capabilities in T-SQL 2005.


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Tip 4: Searching with .NET Generics and (Optionally) Anonymous Methods
The .NET generics List class exposes methods to perform a Find, FindAll, and FindLast. I can write an anonymous method to implement my own search logic in-line as shown below, or I can build a class that serves as a Predicate (a Boolean-valued function) for the Find methods (see Listing 1 and Listing 2).

private void TestFindBaseballClass() { List<BaseballClass> oBaseball = new List<BaseballClass>(); oBaseball = this.PopulateBaseballClass(); string cSearch = "Astros"; BaseballClass oSingleFind = oBaseball.Find( delegate(BaseballClass f1) { return f1.Team == cSearch; }); MessageBox.Show("Single find is " + oSingleFind); string cResults = ""; foreach (BaseballClass oRecord in oBaseball.FindAll( (delegate(BaseballClass f1) { return f1.Team == cSearch; }))) cResults += oRecord + "\r\n"; MessageBox.Show("Multiple find is " + oSingleFind); }

The preceding code uses the same technique as the previous example: An in-line method sets up a delegate to search the populated Baseball class for the first instance of a match. Note that I could use different string functions inside the anonymous method if I wanted to implement a partial string search instead of an exact match.

I can also use the FindAll method of the List class in the same manner. I've specified an in-line delegate and an anonymous method to return a Boolean for each incoming BaseballClass object that equals the search string. The FindAll method allows me to implement filtering capabilities that ADO.NET provides with the DataTable object.

string cSearch = "Astros"; // Perform a single search on the first hit BaseballClass oSingleFind = oBaseball.Find( delegate(BaseballClass f1) { return f1.Team == cSearch; }); // Perform a find all (almost like a filter) string cResults = ""; foreach (BaseballClass oRecord in oBaseball.FindAll((delegate(BaseballClass f1) { return f1.Team == cSearch; }))) cResults += oRecord + "\r\n";

For those who prefer to write a separate class (or are using VB.NET, which does not support anonymous methods in Visual Studio 2005), Listing 1 and Listing 2 demonstrate a separate Find class and a code sample for using the Find class.

Tip 5: Using the List Class to Store Other Objects
As stated earlier, I can use the new List class to store any .NET type that I wish. Listing 3 contains an example that stores classes that implement an interface. Suppose I have report classes that all contain a method called GenerateDocument. I can set up a master controlling loop structure that does the following:

  • Define an interface called IDocument that contains one method, GenerateDocument
  • Build multiple report document classes (SimpleClass1, SimpleClass2, etc.) that implement IDocument
  • Instantiate a List object that stores classes that implement the IDocument interface


List<SimpleInterface.IDocument> oList = new List<SimpleInterface.IDocument>();

  • Create instances of the report document classes (SimpleClass1, etc.) and add the instances to the list
  • Loop through the list and call the GenerateDocument method

foreach(SimpleInterface.IDocument oClass in oList) oClass.GenerateDocument();

Special thanks to Rob Hale from GE Healthcare for this one. Rob attended my C# 2.0 session at Boston CodeCamp and came up with the idea for this one. Two thumbs up, Rob!

Tip 6: Other Classes in the Generics Namespace
I've focused on the new List class in Visual Studio 2005. Now I want to talk about three other classes in the System.Collections.Generics namespace to be aware of. Let's take a moment and look at the new Dictionary, SortedDictionary, and Collection classes.

Visual Studio 2005 introduces the new Dictionary class. This abstract class allows developers to map keys and elements in a collection. Some functions in the .NET 2.0 Framework use the Dictionary class: One example is one of the new overloads for creating a new TCP channel. In the example below, I create a new dictionary object and specify that both the key and value will contain a string.

// Create a new dictionary object with two strings Dictionary<string, string> oDict = new Dictionary<string, string>(); oDict.Add("secure", "true"); oDict.Add("password", "kevin"); TcpChannel oChannel = new TcpChannel(oDict, null, null);

If you need to sort the dictionary entries by key, you'll be better off using the new SortedDictionary class, which maintains a sort order on key.

Next, while I've used the new List class, Visual Studio 2005 also offers a lightweight Collection class for simple lists that don't require sorting and filtering capabilities.

Collection<int> oCol = new Collection<int>(); oCol.Add(2); oCol.Add(3); oCol.Insert(0,1);

I can also store custom classes into the Collection object.

Collection<BaseballClass> oBaseballCollection = new Collection<BaseballClass>(); oBaseballCollection.Add( new BaseballClass("Tom Glavine","Mets")); oBaseballCollection.Add( new BaseballClass("Derek Jeter","Yankees")); foreach (BaseballClass oBaseball in oBaseballCollection) MessageBox.Show(oBaseball.ToString());

Finally, .NET generics offers other classes, such as a LinkedList and LinkedListNote, for working with linked list data, as well as a Queue and Stack class.



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