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.NET Tip: Take Advantage of Interfaces

  • July 19, 2007
  • By Jay Miller
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Take advantage of interfaces to make your code cleaner and more reusable. A simple example of where interfaces can be applied is in populating UI controls. How many ListBox controls do you have to populate in your web application? One solution is to write the code to populate each ListBox individually in the Page_Load method. Another method could be to create a helper method that takes an array of data items and a ListBox as parameters, populating the ListBox from the array of data. Here is an example of such a method.

private void LoadListBox(object[] data, ListBox ListBoxControl)
{
   for (int i = 0; i < data.Length; i++)
      ListBoxControl.Items.Add(data[i].ToString());
}

With the LoadListBox method in place, the code to populate the ListBox in the Page_Load method is simplified.

string[] TestItems = { "Sunday", "Monday", "Tuesday", "Wednesday",
                       "Thursday", "Friday", "Saturday" };
LoadListBox(TestItems, ListBox1); 

Although this is better than doing all the work in the Page_Load method, you can do much better. This works fine for a ListBox, but what about other list type controls? If you apply interfaces, you can enhance the helper method to support a variety of data sources and list type controls. Instead of the helper method taking an array of data items and a ListBox control, it now takes an ICollection and a ListControl.

private void LoadListControlFromCollection(ICollection data,
   ListControl ListControlControl)
{
   foreach (object item in data)
      ListControlControl.Items.Add(item.ToString());
}

Usage of the new LoadListControlFromCollection method to load a ListBox with data items remains the same.

string[] TestItems = { "Sunday", "Monday", "Tuesday", "Wednesday",
                       "Thursday", "Friday", "Saturday" };
LoadListControlFromCollection(TestItems, ListBox1);

The advantage of the new method, however, is that you also can apply it to other list type controls. The flexibility is evident when you use the same method to populate a CheckListBox, DropDownList, RadioButtonList, or BulletList.

LoadListControlFromCollection(TestItems, CheckBoxList1);
LoadListControlFromCollection(TestItems, DropDownList1);
LoadListControlFromCollection(TestItems, RadioButtonList1);
LoadListControlFromCollection(TestItems, BulletedList1);

Applying the use of interfaces can make your applications simpler and more flexible. If you take a look through your code, I bet you can find several places where your application would benefit from using interfaces. Start thinking about interfaces today; the person who comes behind you and has to maintain your code will thank you.

About the Author

Jay Miller is a Software Engineer with Electronic Tracking Systems, a company dedicated to robbery prevention, apprehension, and recovery based in Carrollton, Texas. Jay has been working with .NET since the first beta's release and is co-author of Learn Microsoft Visual Basic.Net In a Weekend. Jay can be reached via email at jmiller@sm-ets.com.






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