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Dependency Properties
If data binding is required to certain properties, then these need to be implemented as Dependency Properties.
Here is a good example (from: C# is Easy: Dependency Property):
public class Button : ButtonBase { // The dependency property public static readonly DependencyProperty IsCancelProperty; // Constructor static Button() { // Register the property Button.IsCancelProperty = DependencyProperty.Register(“IsCancel”, typeof(bool), typeof(Button), new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnIsCancelPropertyChanged))); … } // A .NET property wrapper (not must) public bool IsCancel { get { return (bool)GetValue(Button.IsCancelProperty ); } set { SetValue(Button.IsCancelProperty , value); } } // A property changed callback (not must) private static void OnIsCancelPropertyChanged( DependencyObject o, DependencyPropertyChangedEventArgs e) { … } … }
Alternatively:
public class Button : ButtonBase { // The dependency property declaration, and registration public static readonly DependencyProperty IsCancelProperty = DependencyProperty.Register(“IsCancel”, typeof(bool), typeof(Button), new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnIsCancelPropertyChanged))); // A .NET property wrapper (not must) public bool IsCancel { get { return (bool)GetValue(Button.IsCancelProperty ); } set { SetValue(Button.IsCancelProperty , value); } } // A property changed callback (not must) private static void OnIsCancelPropertyChanged( DependencyObject source, DependencyPropertyChangedEventArgs e) { bool control = source as bool; // Put some update logic here... control = (bool)e.NewValue; if (control == true) { // do something } } // Constructor static Button() { } … }
IMPORTANT: The accessor property is fine to use, but the XAML code will only call the SetValue() and GetValue() methods directly, so make sure that no other code gets added to the accessor property, to make sure both work the same.
Example
public class Employee : DependencyObject { private static readonly DependencyProperty EmpIdProperty = DependencyProperty.Register("EmpId", typeof(int), typeof(Employee), new PropertyMetadata(0, new PropertyChangedCallback(EmpIdCallBack), new CoerceValueCallback(CoerceEmpId))); private static readonly DependencyProperty NameProperty = DependencyProperty.Register("Name", typeof(string), typeof(Employee)); private static readonly DependencyProperty DepartmentProperty = DependencyProperty.Register("Department", typeof(string), typeof(Employee)); private static readonly DependencyProperty CompanyProperty = DependencyProperty.Register("Company", typeof(string), typeof(Employee), new PropertyMetadata("WPF In Corp")); // If employee id is greater than 1000 then make it 1000 static void EmpIdCallBack(DependencyObject d, DependencyPropertyChangedEventArgs args) { Employee emp = (Employee)d; if (emp.EmpId >= 1000) { emp.EmpId = 1000; } } // If the employee Id is negative then make it positive static Object CoerceEmpId(DependencyObject d, Object baseValue) { int value = (int)baseValue; if (value < 0) return value * -1; else return value; } public int EmpId { get { return (int)GetValue(EmpIdProperty); } set { SetValue(EmpIdProperty, value); } } public string Name { get { return (string)GetValue(NameProperty); } set { SetValue(NameProperty, value); } } public string Department { get { return (string)GetValue(DepartmentProperty); } set { SetValue(DepartmentProperty, value); } } public string Company { get { return (string)GetValue(CompanyProperty); } set { SetValue(CompanyProperty, value); } } }