C# 2005 Programmer’s Reference - chapter 18 pptx

Convert Values to a Different Type During Data Binding Scenario/Problem:You want to convert one type to another in data binding.. Use WinForms in a WPF Application Scenario/Problem:You w

{BitmapImage image = new BitmapImage(new Uri(path));

ImageInfoViewModel model = new ImageInfoViewModel(image);

this.ImageInfo = model;

}catch (Exception ){

}}}

}

}

}

Convert Values to a Different Type During Data Binding

Here’s a part of the XAML that binds elements to the ImageInfoViewModelobject:

<Expander Header=”Image Info” IsExpanded=”True” x:Name=”imageInfoGroup”>

<Label Grid.Row=”0” Grid.Column=”0”>Filename</Label>

<TextBox IsReadOnly=”True” Grid.Row=”0” Grid.Column=”1”

Text=”{Binding Path=FileName, Mode=OneWay}”/>

<Label Grid.Row=”1” Grid.Column=”0”>Width</Label>

<TextBox IsReadOnly=”True” Grid.Row=”1” Grid.Column=”1”

Text=”{Binding Path=Width, Mode=OneWay}”/>

<Label Grid.Row=”2” Grid.Column=”0”>Height</Label>

<TextBox IsReadOnly=”True” Grid.Row=”2” Grid.Column=”1”

Text=”{Binding Path=Height, Mode=OneWay}”/>

</Grid>

</Expander>

Every time you drag an image onto the ImageViewer application, the UI will update

with information about that image automatically when the ImageInfoproperty is set.

Format Values During Data Binding

Scenario/Problem:You need to apply formatting to the bound value

Solution:Starting in NET 3.5 SP1, you can use the StringFormatproperty

<TextBox IsReadOnly=”True” Grid.Row=”1” Grid.Column=”1”

Text=”{Binding Path=Width, Mode=OneWay, StringFormat=N0}”/>

Convert Values to a Different Type During Data

Binding

Scenario/Problem:You want to convert one type to another in data binding

For example, you could bind a control’s color to some text

CHAPTER 18 WPF

Solution:Define a converter class derived from IValueConverterand implement

one or both methods:

class FilenameToColorConverter : IValueConverter

{

public object Convert(object value,

Type targetType, object parameter,System.Globalization.CultureInfo culture){

//you only need to implement this for two-way conversions

throw new NotImplementedException();

}

}

In your window XAML, define a resource and specify the converter where needed In

the following example, the background color is bound to the filename with this

converter so that it becomes red if the filename is null:

Specify How Bound Data Is Displayed

<TextBox IsReadOnly=”True” Grid.Row=”0” Grid.Column=”1”

Text=”{Binding Path=FileName, Mode=OneWay}”

Background=”{Binding Path=FileName, Mode=OneWay,

Converter={StaticResource

fileColorConverter}}”/>

</Window>

Bind to a Collection

Scenario/Problem:Some elements display a collection of items You want to

bind this to a data source

Solution:Binding to a collection of items is fairly straightforward You can declare

XAML like this:

<Expander Header=”All Properties” IsExpanded=”False”

However, because WPF doesn’t know how to display each item in the collection, it’s

just going to call ToString()on each item To customize the display, you need to

define a data template, which is covered in the next section.

Specify How Bound Data Is Displayed

Scenario/Problem:You need to control the way bound items are displayed

Solution:You can use a data template Data templates are defined as resources:

Then modify the ListBox’s ItemTemplateproperty to refer to it:

<Expander Header=”All Properties” IsExpanded=”False”

The result is an attractive display of an arbitrary number of collection items, as

previously seen in Figure 18.4.

Define the Look of Controls with Templates

Scenario/Problem:You want to set a control’s look according to one or more

templates and be able to change them at runtime

Solution:If you look closely at Figures 18.3 and 18.4, you’ll see that the latter

shows a caption under the image, whereas the former does not This is

accom-plished with control templates

The two ControlTemplates are defined, as usual, in the resources:

<Image Source=”{Binding Path=Image}” Grid.Row=”0”/>

<TextBlock Text=”{Binding Path=FileName}”

CHAPTER 18 WPF

Animate Element Properties

Scenario/Problem:You want to change UI properties over time

Solution:As far as WPF is concerned, animation is the change of an element’s

properties over time For example, you could change the x position of a button from

1 to 100 over, say, 5 seconds This would have the effect of moving the button on

the screen during that time You can animate any dependency property in WPF

The ImageViewer application uses a single animation to fade in the left-side panel over

5 seconds when the application starts Figure 18.5 shows the application with it faded

Scenario/Problem:You want to render 3D geometry.

Solution:Starting in this section, you’ll see that WPF provides the unprecedented

ability to merge 3D graphics with standard user interface elements and multimedia

Effectively using 3D graphics requires learning a little about cameras, lighting,

materi-als, and coordinate systems Thankfully, WPF makes a lot of this very easy.

This simple demonstration creates a cube, complete with color and lighting, as seen in

Figure 18.6

FIGURE 18.6This cube demonstrates simple lighting andtexture usage

CHAPTER 18 WPF

First, the geometry needs to be defined For our simple examples, the shapes will be

defined in the Window.Resourcessections Here is the definition for the six faces of

Put Video on a 3D Surface

Scenario/Problem:You want to put some media onto a 3D surface

Solution:A plain-old cube is great, but what about one of those cube faces playing

a movie (or showing an image, or any other WPF element)? Now, that is pretty cool

WPF makes this almost too easy

<Window x:Class=”MovieIn3D.Window1”

xmlns=”http://schemas.microsoft.com/winfx/2006/xaml/presentation”

xmlns:x=”http://schemas.microsoft.com/winfx/2006/xaml”

xmlns:interactive3D=”clr-namespace:_3DTools;assembly=3DTools”

Title=”Movie and Controls in 3D”

Height=”480” Width=”640” Loaded=”Window_Loaded”>

<Window.Resources>

The movie can be loaded into the MediaElementwith code like this:

mediaPlayer.Source = new Uri(filename);

mediaPlayer.Play();

In the next section, we’ll hook it up to some controls, also in 3D.

Yes, the ability to do this kind of stuff is pretty neat, but don’t go overboard

A movie pasted on to a 3D surface might make sense as part of a presentation, in a

store kiosk, or perhaps as supporting material or as an animation to bring the movie

to the foreground, but it’s probably not the best scenario for watching a whole movie

Just because you can do something doesn’t always mean you should.

NOTE

Put Interactive Controls onto a 3D Surface

Put Interactive Controls onto a 3D Surface

Scenario/Problem:You can easily put any WPF element onto a 3D surface

using the VisualBrush demonstrated earlier, but you won’t have interaction that

way

Solution:For that, Microsoft has released 3D Tools for Windows Presentation

Foundation, available at http://3dtools.codeplex.com/ This package includes

objects that wrap around WPF elements and translate the 3D environment into

something the elements can understand

In this example, let’s add some file selection and playback controls to our crazy video

player (see Figure 18.7) You will also need to add a reference to the 3DTools.dll

assembly in your project.

Title=”Movie and Controls in 3D”

Height=”480” Width=”640” Loaded=”Window_Loaded”>

<Window.Resources>

<MeshGeometry3D

The code-behind provides the button functionality:

public partial class Window1 : Window

mediaPlayer.Source = new Uri(ofd.FileName);

//force the first frame to appear so we see a change

Use WPF in a WinForms App

Scenario/Problem:You want to take advantage of WPF, but can’t afford to

convert all your existing applications

Use WPF in a WinForms App

Solution:You can easily interoperate between Windows Forms and WPF with the

//create our WPF Control and add it to a hosting control

//we can declare a WPF control

directly //after all, it’s just Net code

MyWpfControl wpfControl = new MyWpfControl();

//the WPF control declares this custom event

Figure 18.8 shows a Windows Forms application with a standard WinForms control

and a WPF control (It’s a button with a Label and TextBox in it just to prove it’s

really WPF.)

FIGURE 18.8

A provably WPF control inside a Windows Formsapplication

<! Yes, you can declare WinForms UI in XAML! >

<WindowsFormsHost Margin=”12,41,66,12” Name=”windowsFormsHost1”>

Use WinForms in a WPF Application

Scenario/Problem:You want to start using WPF for new development but can’t

afford to reimplement all your existing controls and forms

FIGURE 18.9

No NumericUpDown control in WPF (Yet, we hope.)

C H A P T E R 1 9

ASP.NET

IN THIS CHAPTER

View Debug and Trace Information

Determine Web Browser Capabilities

Redirect to Another Page

Use Forms Authentication for User Login

Use Master Pages for a Consistent Look

Add a Menu

Bind Data to a GridView

Create a User Control

Create a Flexible UI with Web Parts

Create a Simple AJAX Page

Do Data Validation

Maintain Application State

Maintain UI State

Maintain User Data in a Session

Store Session State

Use Cookies to Restore Session State

Use ASP.NET Model-View-Controller (MVC)

CHAPTER 19 ASP.NET

Software is increasingly a web-based proposition, and ASP.NET is a wonderful

plat-form for building advanced applications With ASP.NET, you have access to the rich

functionality of the entire NET Framework Although the topic of ASP.NET is large,

this chapter gives you a jumpstart into the important topics.

View Debug and Trace Information

Scenario/Problem:You need to debug an ASP.NET application that is behaving

badly, or you just want to add your own trace information to output

Debugging ASP.NET applications can be a very different process from debugging

native client applications During development, Visual Studio’s integrated debugger

gives you a lot of power, but once an application is deployed, it’s not always feasible

to attach a debugger to a web app Debug and trace information becomes vitally

important.

Solution:ASP.NET has built-in support for dumping a lot of data to logs or even

appending it to the bottom of the page you’re looking at so you can easily view it

The following sections demonstrate a few different techniques you can use

Enable Tracing for a Specific Page

To enable tracing for a specific page, add Trace=”true”to the @Pageelement in the

Enable Tracing for All Pages

If you cannot modify the pages themselves, or want to see trace info on every page,

you can modify web.config to enable tracing on all pages:

<system.web>

<trace enabled=”true” localOnly=”true” pageOutput=”true”/>

View Debug and Trace Information

Log Your Own Trace Messages

You can use the Traceclass to write your own messages to the trace log:

protected void Page_Load(object sender, EventArgs e)

CHAPTER 19 ASP.NET

Determine Web Browser Capabilities

Scenario/Problem:You need to change your application’s behavior based on

the browser the user is using

Given how many platforms websites must display on these days, including different

browsers, operating systems, and mobile devices, it can seem amazing that the Web

works at all Each web browser has many differences in rendering, the ability to load

add-ons such as ActiveX controls, JavaScript engines, and more.

Solution:.NET provides an easy way to discover many of these capabilities

auto-matically, using the Request.Browserstructure, which contains Boolean or string

values for many important properties

CreateCapabilityRowis just a helper method to create a table row to insert the

results, as shown in Figure 19.2.

Redirect to Another Page

Redirect to Another Page

Scenario/Problem:You need to redirect the user to another page for further

This tells the user’s browser to actually navigate to the target page.

If instead you want to actually transfer the processing of the current request to another

page in the same directory without notifying the user (that is, the user’s browser does

not actually go to the other page), you can do the following:

protected void buttonSubmit_Click(object sender, EventArgs e)

From the user’s perspective, the URL has not changed.

To see exactly how this works, look at the FormSubmitAndRedirect project in the

included sample code.

Figure 19.3 shows the application running with a form allowing the user to select

forms of transfer that should be done Figure 19.4 shows the results if the second

option is chosen.

CHAPTER 19 ASP.NET

FIGURE 19.3

This simple app demonstrates how to process a form on the same page, redirect to another

page, or transfer control to another page without notifying the user

FIGURE 19.4

Notice how the output comes from the target page, but the URL still says default.aspx

Use Forms Authentication for User Login

Scenario/Problem:You want to authenticate the user before allowing him to

use part of the application

Use Forms Authentication for User Login

Solution:A common workflow for user authentication on websites is to wait for a

user to access a protected area, redirect him to a login form, then send him on to

where he wanted to go This is very easy to accomplish in ASP.NET

First, you need to create your login page (see Listings 19.1 and 19.2).

<asp:Label ID=”LabelStatus” runat=”server”

Text=”Enter your login info” />

//want to keep user logged in? pass true insteadFormsAuthentication.RedirectFromLoginPage(

//you could authenticate against a database or a file here

return username == “user” && password == “pass”;

The only other page in this example is the default page, shown in Listing 19.3, which

will automatically be protected by login.

When the user tries to access Default.aspx, he is redirected to LoginForm.aspx first,

shown in Figure 19.5, and then back to Default.aspx upon a successful authentication.

FIGURE 19.5

The login form LoginForm.aspx

Use Master Pages for a Consistent Look

Scenario/Problem:You want your pages to have a consistent, templated look

and feel

CHAPTER 19 ASP.NET

Solution:Master pages are essentially templates that define the overall structure

of a page They contain all the common elements for a set of pages as well as

content placeholder objects that are filled in by content pages

Listing 19.4 shows the master page for a book inventory application, which is the

BooksApp sample application in the accompanying source code

As you can see, a master page is very similar to a normal aspx page Master pages can

also have code-behind This master page contains three ContentPlaceHolderobjects

for the <head>element, the body’s header, and content sections Notice that the

<head>placeholder contains a default <title>tag This will be used if the content

page does not put its own content there.

Scenario/Problem:You want to provide a menu for site navigation.

Solution:Start by adding a Sitemap file called web.sitemap to your project Give it

this content:

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

<siteMap xmlns=”http://schemas.microsoft.com/AspNet/SiteMap-File-1.0” >

<! there can only be one siteMapNode under siteMap,

so we’ll ignore it when we create the menu,

and just use its children >

<siteMapNode url=”” title=”” description=””>

<siteMapNode url=”~/Default.aspx” title=”Home”

description=”Site default page” />

<siteMapNode url=”~/BookList.aspx” title=”Book List”

description=”List of all books”/>

<siteMapNode url=”~/BookDetail.aspx” title=”Book Details”

description=”Details of one book” />

</siteMapNode>

</siteMap>

CHAPTER 19 ASP.NET

In the master page where you want the menu, add the following:

<div style=”position:absolute; top:100px;

This attaches the menu to a SiteMapDataSourceobject that automatically reads the

web.sitemap file Our simple menu is visible in Figure 19.6.

FIGURE 19.6

By adding to the web.sitemap file, you can immediately adjust the menu items

Bind Data to a GridView

Scenario/Problem:You need to bind table data (such as from a database

table) to a view on a web page

Solution:Use the flexible GridView control Listing 19.6 shows the BookList page

that shows a grid of books

LISTING 19.6 BookList.aspx

<%@ Page Title=”” Language=”C#” MasterPageFile=”~/MasterPage.Master”

➥AutoEventWireup=”true” CodeBehind=”BookList.aspx.cs”

➥Inherits=”BooksApp.WebForm2” %>

Bind Data to a GridView

LISTING 19.6 BookList.aspx(continued)

<asp:Content ID=”Content1” ContentPlaceHolderID=”head” runat=”server”>

<% disable column generation since we’re

specifying them below %>

<asp:GridView ID=”BookListGrid” runat=”server”

AutoGenerateColumns=”False”>

<Columns>

<% Make the title into a link that

goes to a detail page %>

To set up the databinding, the code-behind file for this page has the following:

public partial class WebForm2 : System.Web.UI.Page

CHAPTER 19 ASP.NET

FIGURE 19.7

Binding a GridView to a data set automatically inserts rows of contents You can configure it

to sort and paginate the table as well

Create a User Control

Scenario/Problem:You want to combine the basic ASP.NET controls into a

coherent component that can be easily reused in multiple places (either on the

same site or in different projects)

Solution:User controls in ASP.NET are similar to user controls in Windows Forms

and WPF They provide an easy way to encapsulate multiple controls into a unified

interface

Listing 19.7 shows the code for a control that binds a number of text fields together

into a single book entry view Listing 19.8 shows the code behind for this control.

LISTING 19.7 BookEntrycontrol.ascx

<%@ Control Language=”C#” AutoEventWireup=”true”

CodeBehind=”BookEntryControl.ascx.cs”

Inherits=”BooksApp.BookEntryControl” %>

<asp:Panel ID=”Panel1” runat=”server” BorderWidth=”1px” Width=”265px”>

<asp:Label ID=”Label5” runat=”server”

Text=”Book Entry” Font-Bold=”True” />

<asp:Table ID=”Table1” runat=”server”>

<asp:TableRow>

<asp:TableCell>