Saving Files Locally in Silverlight - Page 3
       by kirupa  |  31 January 2010

In the previous page, you added references and copied some code to make your application work. That's pretty cool, but this page is much cooler. In this page, we'll look at the code in greater detail.

The Code Explained
Getting the application to work is only one part of this tutorial. The last and most important part is learning why the code works the way it does. At a very high level, there are several things that our code actually does:

1. Displays the Save As dialog.
2. Opens a pathway to the file that gets created.
3. Begins the process of writing the XML data.
4. Closes the pathway to the file once all of the data has been written.

Let's start zooming in on the various layers starting with the Save As dialog.

The Save As Dialog
The code that deals with the Save As dialog is covered in the following four lines plus another line that I will show later:

SaveFileDialog saveFileDialog = new SaveFileDialog();

 

saveFileDialog.DefaultExt = "xml";

saveFileDialog.Filter = "XML Files (*.xml)|*.xml|All Files (*.*)|*.*";

saveFileDialog.FilterIndex = 1;

The first thing I do is declare and initialize my saveFileDialog object whose type is SaveFileDialog. Through my saveFileDialog object, I can set the properties that allow me to customize the dialog that appears. The main customizations I made are ones that define what extension to save my file as by default:

[ the supported file extensions list ]

As you can tell, the two file extensions that you can pick for your file are .xml or anything that you specify *.*. The supported list of the extensions is controlled by the following lines of code:

saveFileDialog.DefaultExt = "xml";

saveFileDialog.Filter = "XML Files (*.xml)|*.xml|All Files (*.*)|*.*";

saveFileDialog.FilterIndex = 1;

In the first line, I specify the default extension to be xml. As you will see shortly, the first line isn't really all that important. The second line is one of the more interesting ones you'll see ever in your life.

The Filter property takes a vertical pipe delimited string that alternates between describing the extension and defining the extension itself:

saveFileDialog.Filter = "XML Files (*.xml)|*.xml|All Files (*.*)|*.*";

In our case, the description is XML Files (*.xml), and the associated extension is *.xml. I repeat that format for All Files (*.*) whose extension is *.*.

All of this is well and good, but none of the lines of code you saw actually launch the dialog. The display of the dialog is made when you call the ShowDialog() method on your saveFileDialog object as:

saveFileDialog.ShowDialog();

The ShowDialog() method returns true if the Save button has been clicked and false if the window was closed or Canceled. Since all we care about is really the Save case, I am combining the ShowDialog() and checking for true in the same line in our code:

if (saveFileDialog.ShowDialog() == true)

{

using (Stream stream = saveFileDialog.OpenFile())

{

StreamWriter sw = new StreamWriter(stream,
                        System.Text.Encoding.UTF8);

sw.Write(GetGeneratedXML().ToString());

sw.Close();

 

stream.Close();

}

}

If you stop right after you call ShowDialog, an empty file will be created for you with the name you specified. What you need to do is now open the file and write the XML data that you want into it.

Onwards to the next page!

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