wpf lable text binding not working, where i am going wrong - wpf

Question

I am new to WPF and trying something like this to update a label text in the WPF form from the class.
The onchange event is getting triggered, but not getting displayed on the form
Here is my class
Public Class ExtractDetails
Inherits UserControl
Implements INotifyPropertyChanged
Private _prdFrstName as string
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Public Property PrdFrstName() As String
Get
Return _prdFrstName
End Get
Set(ByVal value As String)
If _prdFrstName <> value Then
_prdFrstName = value
Me.OnPropertyChanged("PrdFrstName")
End If
End Set
End Property
Public Sub suMainStrt()
PrdFrstName = strComurl ''contyains teh URL to nagigate to
webBrwFrst = New WebBrowser
webBrwFrst.Navigate(New Uri(strComurl))
Call extract(webBrwFrst, strComurl)
end sub
end class
the url keeps on changing as i ma getting the values from an excel file and looping for each URL.
i wanted to display the URL currently working now
this is my XAML
<Window x:Class="Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Avenet Prduct Description Extractor" Height="396.627" Width="588.123" Background="AliceBlue" Icon="LGIcon.ico">
<Grid Height="341.077" Width="567.721" Background="AliceBlue">
<StackPanel Margin="170.225,226.418,3.143,0" Name="StackPanel1" Height="97.994" VerticalAlignment="Top">
<Label Height="30.906" Name="lblCrntSt1" Content="{Binding Path=PrdFrstName, UpdateSourceTrigger=PropertyChanged}" Width="161" BorderThickness="2" BorderBrush="AliceBlue" Background="Red" Foreground="White" FontSize="13"></Label>
</StackPanel>
</Grid>
and this is my windows class.
Class Window1
Dim clsIniti As New ExtractDetails
Public Sub New()
' This call is required by the Windows Form Designer.
InitializeComponent()
'clsIniti = New ExtractDetails
Me.DataContext = clsIniti
End Sub
end class
without updating the text labels the entire function is working good. but i wish to display few things. where i am going wrong
I tried data binding by removing few parts to new created project. it works there. so some thing wrong in this code??? :`(

Answer 1

I see two possible causes that this doesn't work for you.
A. How does your OnPropertyChanged method look like?
' Correct implementation:
Private Sub OnPropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
B. Make sure the ExtractDetails instance you call suMainStrt on, is the same as your DataContext instance. Test this by calling suMainStrt directly from the constructor of Window1:
Class Window1
Dim clsIniti As New ExtractDetails
Public Sub New()
' This call is required by the Windows Form Designer.
InitializeComponent()
'clsIniti = New ExtractDetails
Me.DataContext = clsIniti
' test (if this works, your problem is B.)
clsIniti.suMainStrt()
End Sub
End Class
As a side note: Unless you have good reasons to do this, I suggest you create a dedicated viewmodel (class, not usercontrol) that contains the properties you want to bind to.