NE.15 Data Binding In Windows Presentation Foundation

Transcription

1 NE.15 Data Binding In Windows Presentation Foundation Brian Noyes Chief Architect IDesign Inc ( 1 About Brian Chief Architect, IDesignInc. ( Microsoft Regional Director/MVP Writing Developing Applications with Windows Workflow Foundation, LiveLessons, June 2007 Smart Client Deployment with ClickOnce, Addison-Wesley, Jan 2007 Data Binding in Windows Forms 2.0, Addison-Wesley, January 2006 MSDN Magazine, MSDN Online, CoDe Magazine, TheServerSide.NET, asp.netpro, Visual Studio Magazine Speaking Microsoft TechEd, Visual Studio Connections, DevTeach, DevReach, INETA Speakers Bureau, MSDN Webcasts Participates in Microsoft Design Reviews brian.noyes@idesign.net Blog: 2 Copyright 2008 IDesign, Brian Noyes 1

2 Agenda Data Sources for Data Binding DataContext and Bindings Collection Views and Data Providers Data Templates Value Conversion and Data Validation 3 Data Sources Data binding data sources are always objects in memory Single objects Collections of objects DataSets Populating in memory data objects is not data binding Data access WPF changes nothing about how to do data access in.net LINQ might 4 Copyright 2008 IDesign, Brian Noyes 2

3 Data Binding Interfaces Data binding in WPF (and Windows Forms) is based on interfaces IEnumerable Basic iteration pattern of.net IList Indexed, ordered collection INotifyPropertyChanged Allows objects to notify when property values are changed INotifyCollectionChanged Allows collections to notify when contained items change ICollectionView Navigation, sorting, filtering, and grouping of items in a collection 5 Dependency Properties New kind of property Adds many semantics on top of simple.net properties Value inheritance, animations, styling, data binding, etc. Defined on objects derived from DependencyObject Have built in change notifications Work seamlessly with WPF data binding Consider exposing DependencyProperties for all data bound properties 6 Copyright 2008 IDesign, Brian Noyes 3

4 ObservableCollection<T> The collection of choice for data bound custom objects (entities) Implements INotifyPropertyChanged and INotifyCollectionChanged Participates with 100% fidelity in WPF data binding 7 Agenda Data Sources for Data Binding DataContext and Bindings Collection Views and Data Providers Data Templates Value Conversion and Data Validation 8 Copyright 2008 IDesign, Brian Noyes 4

5 Data Binding Overview One-way data binding Taking data from an in-memory object and automatically presenting it through control properties on the screen Taking data from control and pushing it into an object Two-way data-binding Both of the above 9 Data Binding In WPF Rich infrastructure for binding control properties to objects and collections Loosely coupled model Control does not need to know anything about the type it is being bound to Can generate UI based on bound collections Like ASP.NET 10 Copyright 2008 IDesign, Brian Noyes 5

6 DataContext Dependency property defined on FrameworkElement Provides ambient data source for an element and its children May be set to a collection or an individual object Flows down the element hierarchy to child elements Picked up by bindings on child elements 11 Bindings Tie a property on an object to a value source for that property Example Text property on TextBox Pick up DataContext on element or parent if set DataContext knows current item if collection 12 Copyright 2008 IDesign, Brian Noyes 6

7 Binding Properties Path property path on source object Source can set source object specifically by reference RelativeSource can set source object through relative path reference ElementName set to specific element in the element hierarchy by name IsAsync does the data binding asychronously from main UI rendering Mode allows you to specify one or two way data binding Converter specify a converter type that will be called to coerce values 13 Agenda Data Sources for Data Binding DataContext and Bindings Collection Views and Data Providers Data Templates Value Conversion and Data Validation 14 Copyright 2008 IDesign, Brian Noyes 7

8 Managing Bound Data ICollectionView Defines API for managing data collection Navigation Sorting/Searching/Filtering/Grouping Similar to IBindingList in Windows Forms CollectionViewSource Obtain a collection view from a collection Can wrap any IList or IListSource Ex: DataSet/DataTable 15 ObjectDataProvider Data Providers Creates source object (with parameterized constructor) Point to a source method on object ObjectType, MethodName properties XmlDataProvider Bind to a chunk of XML Source, XPath properties 16 Copyright 2008 IDesign, Brian Noyes 8

9 Agenda Data Sources for Data Binding DataContext and Bindings Collection Views and Data Providers Data Templates Value Conversion and Data Validation 17 Data Templates Reusable chunks of XAML that can be emitted during data binding Can be defined through resources or on control itself Copy of template gets spit out by ItemsControl derived class for each item in a data bound collection Much like Repeater and DataList in ASP.NET 18 Copyright 2008 IDesign, Brian Noyes 9

10 Agenda Data Sources for Data Binding DataContext and Bindings Collection Views and Data Providers Data Templates Value Conversion and Data Validation 19 Value Conversion Converter property on Binding, parameter optional Class that implements IValueConverter Should put ValueConversion attribute on class [ValueConversion(typeof(Binary),typeof(byte[]))] public class BinaryToArrayConverter : IValueConverter { public object Convert(object value, Type targettype, object parameter, CultureInfo culture) { Binary bits = value as Binary; return (bits!= null)? bits.toarray() : null; } public object ConvertBack(object value, Type targettype, object parameter, CultureInfo culture) { throw new NotImplementedException(); } } 20 Copyright 2008 IDesign, Brian Noyes 10

11 Two options Validation rules Data Validation IDataErrorInfo implementation on entity (.NET 3.5 only) 21 Validation Rules Derive from ValidationRule class Override Validate Method public class AgeRule : ValidationRule { public override ValidationResult Validate(object value, CultureInfo cultureinfo) { if ((int)value < 18) return new ValidationResult(false, "Must be older than 18"); else return new ValidationResult(true, null); } } 22 Copyright 2008 IDesign, Brian Noyes 11

12 Add to Binding Validation Rules <TextBox Name="ageTextBox"> <TextBox.Text> <Binding Path="Age"> <Binding.ValidationRules> <local:agerule /> </Binding.ValidationRules> </Binding> </TextBox.Text> </TextBox> 23 IDataErrorInfo Implement IDataErrorInfo on entity class Set error properties when validation fails in property setters Add DataErrorValidationRule to Binding.ValidationRules or set ValidatesOnDataErrors property on Binding public class SomeEntity : IDataErrorInfo { public string Error {get;set;} public string this[string columnname] {get;set;} } // Data members with validation in set blocks 24 Copyright 2008 IDesign, Brian Noyes 12

13 Resources WPF Unleashed, Adam Nathan, Sams Publishing, Programming WPF 2nd Edition, Chris Sells and Ian Griffiths, O Reilly Sells/dp/ Essential WPF, Chris Anderson, Addison Wesley, Rocks! TV: (episodes 56,59, 101) Data Binding with Windows Forms 2.0, Brian Noyes, Addison Wesley brian.noyes@idesign.net Blog: 25 Copyright 2008 IDesign, Brian Noyes 13