Exploring Silverlight 4 - Part I (The Printing API)

One of the major peeves that Silverlight developers had in its earlier versions was the lack of printing support. Printing is an essential feature of many applications and more so in the case of LOB applications. Hence, when Silverlight 4 was released with a full featured Printing API, developers welcomed it with open arms.

What’s Included in the Printing API

The System.Windows.Printing namespace

This namespace provides printing services for a Silverlight application through its various classes.

Class Name	What It Does
PrintDocument	Provides printing capabilities for a Silverlight application
PrintPageEventArgs	Provides data for the PrintPage event
BeginPrintEventArgs	Provides data for the BeginPrint event
EndPrintEventArgs	Provides data for the EndPrint event

PrintDocument Class

The commonly used methods, properties, and events of this class are as follows:

Method	Description
Print	Starts the printing process for the specified document by opening the print dialog box

Property	Description
PrintedPageCount	Gets the number of pages that have printed

Event	Description
BeginPrint	Occurs after the Print() method is called and the print dialog box successfully returns, but before the PrintPage event is raised
EndPrint	Occurs when the printing operation is complete or when the print operation is canceled by the application author
PrintPage	Occurs when each page is printing

PrintPageEventArgs Class

The commonly used properties of this class are:

Name	Description
HasMorePages	Retrieves or specifies whether there are more pages to print
PageMargins	Retrieves the margins of the page that are currently printing
PageVisual	Retrieves or specifies the visual element to print
PrintableArea	Retrieves the size of the printable area

Basic Steps for Adding Printing Functionality in a Silverlight Application

1. Add a Print button or a Print menu option through which user can initiate a print operation.
2. Create an instance of PrintDocument in the application
3. Call the Print() method to open a print dialog box
4. Write code for the PrintPage event handler for PrintDocument to perform the print operation

You have several options for printing: print the entire Silverlight control, print part of a control, and so forth.

If you set the PageVisual property to the layout root of the Silverlight content, such as a Grid, you can print the entire control. If you set PageVisual to a particular control or UIElement, you can print only that Silverlight control.

The HasMorePages property can be used to print multiple pages.

Enough said about the theory, let’s now move on to some examples.

Example

Assume that you have created a TreeView application and want to print the entire content of the grid. A button, Print, is added to the page. The markup for MainPage.xaml is as follows:

Listing 1

<UserControl x:Class="TreeViewPrint.MainPage"
xmlns="http://schemas.microsoft.com/winfx/
2006/xaml/presentation"
xmlns:x=
Technorati Tags: silverlight, silverlight 4, printing
"http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression
/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400"
xmlns:
sdk="http://schemas.microsoft.com/winfx/
2006/xaml/presentation/sdk">
<Grid x:Name="LayoutRoot" Background="LightSeaGreen">
<sdk:TreeView Width="150" Height="150" 
Background="Beige" Name="techTree">
<sdk:TreeViewItem Header="Microsoft Technology" 
IsExpanded="True" >
<sdk:TreeViewItem Header=".NET" IsExpanded="True">
<sdk:TreeViewItem Header="C#" >
<sdk:TreeViewItem Header="3.0">
<sdk:TreeViewItem Header="4.0">
</sdk:TreeViewItem>
</sdk:TreeViewItem>
</sdk:TreeViewItem>
</sdk:TreeViewItem>
</sdk:TreeViewItem>
</sdk:TreeView>
<Button Content="Print" Height="23" 
HorizontalAlignment="Left" Name="btnPrint" 
    Width="75" Click="btnPrint_Click" />
</Grid>
</UserControl>

The markup creates a TreeView control, adds TreeViewItems to it, and creates a button with caption, Print.

In the code-behind, write the following code:

Listing 2

private void btnPrint_Click(object sender, RoutedEventArgs e)
{
PrintDocument prnt = new PrintDocument();
prnt.PrintPage += new
EventHandler<PrintPageEventArgs>(prnt_PrintPage);
prnt.Print("TreeView Application");
}
void prnt_PrintPage(object sender, PrintPageEventArgs e)
{
e.PageVisual = LayoutRoot;
}

The above code is simple and self-explanatory. To print only the tree and not the whole grid, you can fine tune the above code as follows.

Listing 3

void prnt_PrintPage(object sender, PrintPageEventArgs e)
{
e.PageVisual = techTree;
}

Tip: To print a Silverlight 4 RichTextBox without a surrounding border, set BorderBrush="{x:Null}".

You can add headers and footers to the page by using TextBlock controls. The PrintableArea property of PrintPageEventArgs enables you to set the print area.

There is a lot more to explore in the printing API but this is it from me for now. With time, there will be more to come.