WPF Data Binding Explained

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WPF Data BindingExplained

• Peter Himschoot
• Trainer _at_ U2U
• Microsoft Regional Director Belux
• www.u2u.info/Blogs/Peter

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Data Binding

• The need for data binding
• Using simple data binding
• Converting and validating data
• Using complex data binding
• Customizing data binding with templates
• Master-detail data binding
• Filtering, sorting and grouping data
• Xml, LINQ, ADO.NET data binding
• Debugging Data Binding

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The need for Data Binding

• Imagine showing data retrieved from DB
• Move data from a column to a control
• Allow user to edit the data
• Validate the data
• Then move data from control to column
• Update the column
• Data Binding automates this!

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What is Data Binding
Object
Property
One Way
Two Way
Control
Property
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Simple Data Binding

• Bind one controls property to one objects data
• Control to control
• Control to (data) object

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Data Conversion

• Bind to another type by converting it
• Add Converter class as a resource
• Use Converter

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Building a Converter

• Implement the IValueConverter interface

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UpdateSourceTrigger

• TextBox doesnt change value immediately
• To do so, set UpdateSourceTrigger
• UpdateSourceTrigger values
• Default
• LostFocus ( Default for TextBox)
• PropertyChanged
• Explicit

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Data Validation

• Users will always make mistakes
• Validation helps users determine these
• Default DataBinding doesnt support this
• You need more verbose Binding

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Exception Validation

• Data Source can throw Exception
• ExceptionValidationRule catches this

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Custom Validation Rules

• Derive from ValidationRule

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Using the ValidationRule

• Add it to the ltValidationRulesgt element

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Custom Error Feedback

• Define a ControlTemplate resource

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Using the ControlTemplate

• Set Validation.ErrorTemplate attached prop
• Validation will use this for feedback

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Using Styles

• Even better, use a style for all textboxes

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Using Tooltips

• User cannot see what is wrong
• Use a tooltip to show the actual error

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Data Binding Multiple Properties

• Avoid repeating the same source
• Use DataContext!

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Provide Data from Code

• May be easier to load data in codebehind
• Can set DataContext in code

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Using Complex Data Binding

• Bind a controls items to list of objects
• Objects are displayed using ToString()

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Using Data Templates

• Display object with a DataTemplate
• Set controls ItemTemplate
• DataTemplate DataSource object

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Selecting the DataTemplate

• By Name
• By Type

Type selects DataTemplate
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Dynamically Selecting a Template

• Use a DataTemplateSelector

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PersonDataTemplateSelector
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Binding with DataProviders

• Use DataProvider in XAML
• Then set ItemsSource in XAML

Your class or Service Proxy
(Optional) Method to call
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Asynchronous Data Binding

• Data Provider allows async binding
• Call method in background

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Master Detail Binding

• Use ItemsControl (e.g. ListBox) as master
• Set IsSynchronizedWithCurrentItem"True"
• Other bindings on same source will follow master

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Master Detail
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DisplayMemberPath

• Replaces single-field template

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Filtering with Views

• Use a CollectionView
• CollectionViewSource in XAML
• Implement the Filter event

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Sorting and Grouping

• Again use a CollectionView

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Sorting and Grouping

• Use a CollectionViewSource
• Define a GroupStyle

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Binding to XML
ltXmlDataProvider xKey"cars"
XPath"/Cars/Car" Source"cars.xml" /gt
ltTextBlock TextContent"Binding XPath_at_Make,
SourceStaticResource
cars" /gt
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Provide XML from Code

• Can load XML data in codebehind
• Just like any other data

XmlDocument doc new XmlDocument() doc.LoadXml("
ltFoogtltBargtHello, worldlt/Bargtlt/Foogt") myGrid.Data
Context doc
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Binding To DataSets

• Fill the DataSet as usual
• Then use it as the DataContext
• Controls use Path to reference
• Tables
• Columns

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Dude, wheres the DataGrid?

• DataGrid like controls not provided
• Provided 3d party controls
• Infragistics
• Xceed

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Debugging Data Binding

• Binding failures generate debug messages
• Check the Output window in Visual Studio

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