Silverlight读取XML代码(非常有用^-^)

Reading XML with Silverlight

时间:2009-12-23 10:04来源:SilverlightChina.Net 作者:银光中国网 点击:369次

XML (Extensible Markup Language) is a great format for saving structured data in. In this Tip I will be showing you how to read and process XML files from Silverlight using the XmlReader object. Lets say, for example, you want to store a tree structure of

　　

XML (Extensible Markup Language) is a great format for saving structured data in. In this Tip I will be showing you how to read and process XML files from Silverlight using the XmlReader object.

Let’s say, for example, you want to store a tree structure of images grouping by them category. Your XML could look like this:

<?xml version="1.0" encoding="utf-8" ?>

<ImageTree>

  <Area name="grass">

    <Image name="Normal Grass">grass1.png</Image>

    <Image name="Dry Grass">grass2.png</Image>

    <Image name="Mixed Grass">grass3.png</Image>

    <Image name="Long Grass">grass4.png</Image>

  </Area>

  <Area name="tile">

    <Image name="Brick">brick.png</Image>

    <Image name="White Stone">stone.png</Image>

    <Image name="Cracked Stone">crackedstone.png</Image>

    <Image name="Black Brick">brick2.png</Image>

  </Area>

</ImageTree>

Few things to note about the XML above:

1. XML can only have one root node which in my case I have called <ImageTree>
2. <Area> and <Image> tags are called Elements
3. “name” is an attribute and its content is the value for the attribute.

Now, on to the code below:

1. To open an XML file I will be using the WebClient object. I have placed a file called MapImages.xml in my ClientBin folder that contains the data I will read. When the file read operation is complete (remember everything is asynchronous) the callback function client_DownloadStringCompleted will be called.
2. When reading the data I check to see what the NodeType is. I only care about nodes that are of type Element or Text and I ignore stuff like comments, whitespace, etc.
3. Once you read an Element you can get the attribute (such as name=”Brick”) for the Element by calling reader.MoveToFirstAttribute().
4. The file name for each image is stored in the Tag property of each tree view item.

public Page()

{

    InitializeComponent();           

    Uri url = new Uri("MapImages.xml", UriKind.Relative);

    WebClient client = new WebClient();

    client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);

    client.DownloadStringAsync(url);

}

void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)

{

    if (e.Error == null)

    {

        TreeViewItem areaItem = null;

        TreeView tv = new TreeView();

        TreeViewItem rootItem = new TreeViewItem();

        rootItem.Header = "Images";

        tv.Items.Add(rootItem);

        StringReader stream = new StringReader(e.Result);

        XmlReader reader = XmlReader.Create(stream);

        string imageName = String.Empty;

        string areaName = String.Empty;

        string fileName = String.Empty;

        while (reader.Read())

        {

            if (reader.NodeType == XmlNodeType.Element)

            {

                if (reader.Name == "Area")

                {

                    if (true == reader.MoveToFirstAttribute())

                    {

                        areaName = reader.Value;

                        areaItem = new TreeViewItem();

                        areaItem.Header = areaName;

                        rootItem.Items.Add(areaItem);

                    }

                }

                else if (reader.Name == "Image")

                {

                    if (true == reader.MoveToFirstAttribute())

                    {

                         imageName = reader.Value;

                    }

                }                        

            }

            else if (reader.NodeType == XmlNodeType.Text)

            {

                fileName = reader.Value;

                TreeViewItem imageItem = new TreeViewItem();

                imageItem.Header = imageName;

                imageItem.Tag = fileName;

                if (null != areaItem)

                    areaItem.Items.Add(imageItem);

            }

        }

        MainCanvas.Children.Add(tv); // Add the treeview to our main canvas.

    }

}

The result of the code above is a tree view with all the items added as seen in the image below.

On a final note, this code is hard wired to read a specifically formatted and error free file. You will want to add error checking in case the file is invalid in anyway.