I am going to give you a class in VB.Net. I want you to add a constructor to it that can set all it's properties and I want you to implement the INotifyPropertyChanged interface. Here is the class:Public Class Person Public Property FirstName As String Public Property LastName As String Public Property Age As Integer Public Property Address As String End Class
Sure, here is the updated class with the constructor and implementation of INotifyPropertyChanged interface:
Public Class Person Implements INotifyPropertyChanged
vbnetPublic Sub New(firstName As String, lastName As String, age As Integer, address As String)
Me.FirstName = firstName
Me.LastName = lastName
Me.Age = age
Me.Address = address
End Sub
Private _firstName As String
Public Property FirstName As String
Get
Return _firstName
End Get
Set(value As String)
If Not value.Equals(_firstName) Then
_firstName = value
OnPropertyChanged("FirstName")
End If
End Set
End Property
Private _lastName As String
Public Property LastName As String
Get
Return _lastName
End Get
Set(value As String)
If Not value.Equals(_lastName) Then
_lastName = value
OnPropertyChanged("LastName")
End If
End Set
End Property
Private _age As Integer
Public Property Age As Integer
Get
Return _age
End Get
Set(value As Integer)
If Not value.Equals(_age) Then
_age = value
OnPropertyChanged("Age")
End If
End Set
End Property
Private _address As String
Public Property Address As String
Get
Return _address
End Get
Set(value As String)
If Not value.Equals(_address) Then
_address = value
OnPropertyChanged("Address")
End If
End Set
End Property
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Protected Sub OnPropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
End Class
In this updated class, I added a constructor that takes four parameters and initializes all the properties of the Person object. I also added a private field for each property and implemented the INotifyPropertyChanged interface.
The INotifyPropertyChanged interface is used to notify any subscriber of changes made to the properties of the Person object. It defines an event named PropertyChanged, which is raised whenever a property's value is changed. The OnPropertyChanged method is called whenever a property is set and raises the PropertyChanged event. The subscribers can listen to the PropertyChanged event and react accordingly to any property changes.
Instead of hard coding the properties for property changed, I want you to use the nameof operator instead.
Sure, here's the updated code for the Person
class that uses the nameof
operator to get the name of the property that has changed:
vbnetPublic Class Person
Implements INotifyPropertyChanged
Public Sub New(ByVal firstName As String, ByVal lastName As String, ByVal age As Integer, ByVal address As String)
Me.FirstName = firstName
Me.LastName = lastName
Me.Age = age
Me.Address = address
End Sub
Private _firstName As String
Public Property FirstName As String
Get
Return _firstName
End Get
Set(ByVal value As String)
If Not value.Equals(_firstName) Then
_firstName = value
OnPropertyChanged(NameOf(FirstName))
End If
End Set
End Property
Private _lastName As String
Public Property LastName As String
Get
Return _lastName
End Get
Set(ByVal value As String)
If Not value.Equals(_lastName) Then
_lastName = value
OnPropertyChanged(NameOf(LastName))
End If
End Set
End Property
Private _age As Integer
Public Property Age As Integer
Get
Return _age
End Get
Set(ByVal value As Integer)
If Not value.Equals(_age) Then
_age = value
OnPropertyChanged(NameOf(Age))
End If
End Set
End Property
Private _address As String
Public Property Address As String
Get
Return _address
End Get
Set(ByVal value As String)
If Not value.Equals(_address) Then
_address = value
OnPropertyChanged(NameOf(Address))
End If
End Set
End Property
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Protected Sub OnPropertyChanged(ByVal propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
End Class
With this update, instead of hard-coding the names of the properties in the OnPropertyChanged
method, we're using the NameOf
operator to get the property name. This ensures that if the name of the property changes, we don't have to remember to update the OnPropertyChanged
method as well.
Ok instead of passing the name of the property to OnPropertyChanged manually, I want the name of the calling property to be detected automatically instead.
Sure! To automatically detect the name of the calling property, we can use the CallerMemberName
attribute, which is part of the System.Runtime.CompilerServices
namespace.
Here's the updated code for the Person
class that uses the CallerMemberName
attribute to automatically detect the name of the calling property:
vbnetImports System.ComponentModel
Imports System.Runtime.CompilerServices
Public Class Person
Implements INotifyPropertyChanged
Public Sub New(ByVal firstName As String, ByVal lastName As String, ByVal age As Integer, ByVal address As String)
Me.FirstName = firstName
Me.LastName = lastName
Me.Age = age
Me.Address = address
End Sub
Private _firstName As String
Public Property FirstName As String
Get
Return _firstName
End Get
Set(ByVal value As String)
If Not value.Equals(_firstName) Then
_firstName = value
OnPropertyChanged()
End If
End Set
End Property
Private _lastName As String
Public Property LastName As String
Get
Return _lastName
End Get
Set(ByVal value As String)
If Not value.Equals(_lastName) Then
_lastName = value
OnPropertyChanged()
End If
End Set
End Property
Private _age As Integer
Public Property Age As Integer
Get
Return _age
End Get
Set(ByVal value As Integer)
If Not value.Equals(_age) Then
_age = value
OnPropertyChanged()
End If
End Set
End Property
Private _address As String
Public Property Address As String
Get
Return _address
End Get
Set(ByVal value As String)
If Not value.Equals(_address) Then
_address = value
OnPropertyChanged()
End If
End Set
End Property
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Protected Sub OnPropertyChanged(<CallerMemberName> Optional ByVal propertyName As String = Nothing)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
End Class
In this updated code, we've added the <CallerMemberName>
attribute to the propertyName
parameter in the OnPropertyChanged
method. This attribute allows the name of the calling property to be automatically detected and passed to the PropertyChanged
event.
Now, when any of the properties are changed, the OnPropertyChanged
method is called without passing any arguments. The propertyName
parameter is automatically set to the name of the calling property, which is then passed to the PropertyChanged
event. This way, we don't have to pass the name of the property manually every time.
That is good. Now I just want to move the private fields that backs the properties to one place at the top of the class. I also want to move the PropertyChanged event declaration to the top of the class but under the fields.
Sure, here's the updated Person
class with the private fields and PropertyChanged
event declaration moved to the top of the class as per your request:
vbnetImports System.ComponentModel
Imports System.Runtime.CompilerServices
Public Class Person
Implements INotifyPropertyChanged
Private _firstName As String
Private _lastName As String
Private _age As Integer
Private _address As String
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Public Sub New(ByVal firstName As String, ByVal lastName As String, ByVal age As Integer, ByVal address As String)
Me.FirstName = firstName
Me.LastName = lastName
Me.Age = age
Me.Address = address
End Sub
Public Property FirstName As String
Get
Return _firstName
End Get
Set(ByVal value As String)
If Not value.Equals(_firstName) Then
_firstName = value
OnPropertyChanged()
End If
End Set
End Property
Public Property LastName As String
Get
Return _lastName
End Get
Set(ByVal value As String)
If Not value.Equals(_lastName) Then
_lastName = value
OnPropertyChanged()
End If
End Set
End Property
Public Property Age As Integer
Get
Return _age
End Get
Set(ByVal value As Integer)
If Not value.Equals(_age) Then
_age = value
OnPropertyChanged()
End If
End Set
End Property
Public Property Address As String
Get
Return _address
End Get
Set(ByVal value As String)
If Not value.Equals(_address) Then
_address = value
OnPropertyChanged()
End If
End Set
End Property
Protected Sub OnPropertyChanged(<CallerMemberName> Optional ByVal propertyName As String = Nothing)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
End Class
In this updated code, the private fields that back the properties are moved to the top of the class, and the PropertyChanged
event declaration is moved below them. This way, all the fields are grouped together in one place, and the PropertyChanged
event declaration is easily accessible for reference.