Modifying a DataBound Collection - Page 7
       by kirupa  |  9 December 2007

In the previous page, you wrapped up work on the PeopleData class. In this page, you will learn how to use this class by modifying the AddButton_Click event handler to get everything working...again.

Modifying the AddButton_Click Event Handler
One of the earlier gripes was that the AddButton_Click event handler simply contains too much important code. It would be better to offload some of that code to a dedicated part of your project where the data-related tasks are handled. So far, we have done that by creating our PeopleData class.

Let's finish up our last task by modifying our AddButton_Click event handler to use the new methods created in the PeopleData class. Make sure you have Window1.xaml.cs open in Visual Studio. Your AddButton_Click event handler currently contains the following code:

private void AddButton_Click(object sender, RoutedEventArgs e)

{

ObjectDataProvider odp = this.FindResource("PeopleListDS") as ObjectDataProvider;

PeopleList people = odp.Data as PeopleList;

 

Person newPerson = new Person();

newPerson.PersonName = NameInput.Text;

 

people.Add(newPerson);

 

NameInput.Text = String.Empty;

}

Delete everything except for the last line where you have NameInput.Text = String.Empty. Copy and paste the following one line of code to the top of your AddButton_Click event handler:

PeopleData.AddPerson(NameInput.Text);

Your AddButton_Click event handler will now look like the following:

private void AddButton_Click(object sender, RoutedEventArgs e)

{

PeopleData.AddPerson(NameInput.Text);

 

NameInput.Text = String.Empty;

}

Go ahead and test out your application. Notice that everything still works just like before, and best of all, we greatly improved how our application is structured. Now, let's go back a few steps and look at why the code you added works.

Revisiting the Code
In the past few pages, you copied and pasted some code. I haven't fully explained what each line of code you added does, so let's go back and look at it in greater detail:

public static ObjectDataProvider PeopleDataSource

{

get;

set;

}

In your PeopleData class you have a static property of type ObjectDataProvider called PeopleDataSource. This property is fairly simple and contains just your standard get and set statements that allow you to store or retrieve a value.

public static void AddPerson(string name)

{

Person newPerson = new Person();

newPerson.PersonName = name;

 

(PeopleData.PeopleDataSource.Data as PeopleList).Add(newPerson);

}

The only other thing in your PeopleData class that needs revisiting is our static AddPerson method. This method takes an argument for a person's name as a string and assigns it to the PersonName field of a new Person object.

In the final line, I call the earlier PeopleData source property. Because it returns data in the form of an ObjectDataProvider, I am able to use the Data property to get at the PeopleList that I am interested in. Notice that I am typecasting the returned values as a PeopleList. Once I have access to the PeopleList data, I can use the Add method to add the new Person object I created. This ensures that our listbox gets the new value.

We are almost done with this tutorial! In the next page, let's look at the Initialized code we added and review everything you've done by running through our application to see how everything works together.

Onwards to the next page!

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