Need help writing a UserControl

Question

I trying to create a UserControl that will be added a variable number of times to a wpf window at run-time. This is my first attempt at a UserControl. I have two requirements for this UserControl:

The content of the label is to be defined at run-time.
The StackPanel should respond to a click event at run-time.

Here is my XAML:

My specific questions are:

How to expose the Content property of the label so it can be set at run-time? This value will not change for the lifetime of the control nor will it be changeable by the user.
How to expose the MouseLeftButtonUp Event of the StackPanel.

Thanks in advance.

Answer

Hi, All controls in a user control are not visible from the outside. You have to give UserControl its own public properties. Try following demo.

XAML UserControl:

CodeBehind UserControl:

Public Class CalendarDay

  Public Event pnlDayMouseLeftButtonUp As EventHandler

  Public Property lblDay As String

  Private Sub pnlDay_Loaded(sender As Object, e As RoutedEventArgs) Handles pnlDay.Loaded
    Me.DataContext = Me
  End Sub

  Private Sub pnlDay_MouseLeftButtonUp(sender As Object, e As MouseButtonEventArgs) Handles pnlDay.MouseLeftButtonUp
    RaiseEvent pnlDayMouseLeftButtonUp(Me, New EventArgs)
  End Sub

End Class

Using in MainWindows CodeBehind:

Imports WpfControlLibrary1

Public Class MainWindow
  Private Sub Window_Loaded(sender As Object, e As RoutedEventArgs)
    Dim dv As New CalendarDay
    dv.lblDay = "Some Text"
    AddHandler dv.pnlDayMouseLeftButtonUp, AddressOf AddItem
    Me.grd.Children.Add(dv) ' Grid in XAML: x:Name="grd" '
  End Sub

  Private Sub AddItem(sender As Object, e As EventArgs)
    Debug.Print("pnlDayMouseLeftButtonUp")
  End Sub

End Class

Answer

Welcome to our Microsoft Q&A platform!

If you want to set the Content property of the label and response the MouseLeftButtonUp Event of the StackPanel,see the following code:

Thanks.

Answer

Hi Roger, it is impossible to bind trigger value. You can use a multi value binding with converter and set trigger value to result of converter. Try following demo:

XAML UserControl:

Code:

Imports System.ComponentModel
Imports System.Globalization
Imports System.Runtime.CompilerServices

Public Class Window006UC1
  Implements INotifyPropertyChanged

  Private Sub pnlDay_Loaded(sender As Object, e As RoutedEventArgs) Handles pnlDay.Loaded
    Me.DataContext = Me
  End Sub

  Public Event pnlDayMouseLeftButtonUp As EventHandler

  Private _lblDay As Date
  Public Property lblDay As Date
    Get
      Return Me._lblDay
    End Get
    Set(value As Date)
      Me._lblDay = value
      OnPropChanged()
    End Set
  End Property

  Public Property Month As Integer

  Private Sub pnlDay_MouseLeftButtonUp(sender As Object, e As MouseButtonEventArgs) Handles pnlDay.MouseLeftButtonUp
    RaiseEvent pnlDayMouseLeftButtonUp(Me, New EventArgs)
  End Sub


  Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
  Private Sub OnPropChanged( Optional propName As String = "")
    RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propName))
  End Sub

End Class

Public Class Window006UC1Converter
  Implements IMultiValueConverter

  Public Function Convert(values() As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IMultiValueConverter.Convert
    Dim p1 As Date
    If values.Count <> 2 OrElse Not Date.TryParse(values(0).ToString, p1) Then Exit Function
    Dim p2 As Integer
    If Not Integer.TryParse(values(1).ToString, p2) Then Exit Function
    Return p1.Month = p2
  End Function

  Public Function ConvertBack(value As Object, targetTypes() As Type, parameter As Object, culture As CultureInfo) As Object() Implements IMultiValueConverter.ConvertBack
    Throw New NotImplementedException()
  End Function
End Class

Answer

Hi Roger, for binding properties from ViewModel to properties in UserControl you must use DependencyProperties and the correct DataContext. Try following demo.

XAML MainWindow:


  
    
  
  
    
  
  
    
      
        
      
      
  
  
    
      
    
  


ViewModel:

Imports System.Globalization

Namespace WpfApp011
  Public Class ViewModel

    Public Property DayValue As Date = Now

    Public Property MonthValue As Integer = 5

  End Class

  Public Class TextToIntConverter
    Implements IValueConverter

    Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.Convert
      Dim n As Integer
      If Integer.TryParse(value?.ToString, n) Then Return n
      Return 0
    End Function

    Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.ConvertBack
      Return value?.ToString
    End Function
  End Class

End Namespace

XAML UserControl:


  
    
  
  
    
      
        
          
            
              
            
          
        
      
    
    
    
  


CodeBehind UserControl:

Imports System.Globalization

Public Class Window011UC1

  Public Sub New()

    ' This call is required by the designer.
    InitializeComponent()

    ' Add any initialization after the InitializeComponent() call.
    sp.DataContext = Me
  End Sub

  Public Shared ReadOnly LblDayProperty As DependencyProperty =
    DependencyProperty.RegisterAttached(
    "LblDay",
    GetType(Date),
    GetType(Window011UC1),
    New UIPropertyMetadata(Now))

  Public Shared Function GetLblDay(tvi As TreeViewItem) As Date
    Return CType(tvi.GetValue(LblDayProperty), Date)
  End Function

  Public Shared Sub SetLblDay(tvi As TreeViewItem, value As Date)
    tvi.SetValue(LblDayProperty, value)
  End Sub

  Public Shared ReadOnly LblMonthProperty As DependencyProperty =
    DependencyProperty.RegisterAttached(
    "LblMonth",
    GetType(Integer),
    GetType(Window011UC1),
    New UIPropertyMetadata(0))

  Public Shared Function GetLblMonth(tvi As TreeViewItem) As Integer
    Return CType(tvi.GetValue(LblMonthProperty), Integer)
  End Function

  Public Shared Sub SetLblMonth(tvi As TreeViewItem, value As Integer)
    tvi.SetValue(LblMonthProperty, value)
  End Sub

End Class

Public Class Window011UC1Converter
  Implements IMultiValueConverter

  Public Function Convert(values() As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IMultiValueConverter.Convert
    Dim p1 As Date
    If values.Count <> 2 OrElse Not Date.TryParse(values(0).ToString, p1) Then Exit Function
    Dim p2 As Integer
    If Not Integer.TryParse(values(1).ToString, p2) Then Exit Function
    Return p1.Month = p2
  End Function

  Public Function ConvertBack(value As Object, targetTypes() As Type, parameter As Object, culture As CultureInfo) As Object() Implements IMultiValueConverter.ConvertBack
    Throw New NotImplementedException()
  End Function
End Class

Need help writing a UserControl

4 answers