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Walkthrough: Hosting a Windows Forms Composite Control in WPF

Windows Presentation Foundation (WPF) provides a rich environment for creating applications. However, when you have a substantial investment in Windows Forms code, it can be more effective to reuse at least some of that code in your WPF application rather than to rewrite it from scratch. The most common scenario is when you have existing Windows Forms controls. In some cases, you might not even have access to the source code for these controls. WPF provides a straightforward procedure for hosting such controls in a WPF application. For example, you can use WPF for most of your programming while hosting your specialized DataGridView controls.

This walkthrough steps you through an application that hosts a Windows Forms composite control to perform data entry in a WPF application. The composite control is packaged in a DLL. This general procedure can be extended to more complex applications and controls. This walkthrough is designed to be nearly identical in appearance and functionality to Walkthrough: Hosting a WPF Composite Control in Windows Forms. The primary difference is that the hosting scenario is reversed.

The walkthrough is divided into two sections. The first section briefly describes the implementation of the Windows Forms composite control. The second section discusses in detail how to host the composite control in a WPF application, receive events from the control, and access some of the control's properties.

Tasks illustrated in this walkthrough include:

  • Implementing the Windows Forms composite control.

  • Implementing the WPF host application.

For a complete code listing of the tasks illustrated in this walkthrough, see Hosting a Windows Forms Composite Control in WPF Sample.

You need the following components to complete this walkthrough:

  • Visual Studio 2010.

The Windows Forms composite control used in this example is a simple data-entry form. This form takes the user's name and address and then uses a custom event to return that information to the host. The following illustration shows the rendered control.

Windows Forms composite control

Simple Windows Forms control

To start the project:

  1. Launch Microsoft Visual Studio, and open the New Project dialog box.

  2. In the Window category, select the Windows Forms Control Library template.

  3. Name the new project MyControls.

  4. For the location, specify a conveniently named top-level folder, such as WpfHostingWindowsFormsControl. Later, you will put the host application in this folder.

  5. Click OK to create the project. The default project contains a single control named UserControl1.

  6. In Solution Explorer, rename UserControl1 to MyControl1.

Your project should have references to the following system DLLs. If any of these DLLs are not included by default, add them to the project.

  • System

  • System.Data

  • System.Drawing

  • System.Windows.Forms

  • System.Xml

To add controls to the form:

  • Open MyControl1 in the designer.

Add five Label controls and their corresponding TextBox controls, sized and arranged as they are in the preceding illustration, on the form. In the example, the TextBox controls are named:

  • txtName

  • txtAddress

  • txtCity

  • txtState

  • txtZip

Add two Button controls labeled OK and Cancel. In the example, the button names are btnOK and btnCancel, respectively.

Open the form in code view. The control returns the collected data to its host by raising the custom OnButtonClick event. The data is contained in the event argument object. The following code shows the event and delegate declaration.

Add the following code to the MyControl1 class.

Public Delegate Sub MyControlEventHandler(ByVal sender As Object, ByVal args As MyControlEventArgs)
Public Event OnButtonClick As MyControlEventHandler

The MyControlEventArgs class contains the information to be returned to the host.

Add the following class to the form.

Public Class MyControlEventArgs
    Inherits EventArgs
    Private _Name As String 
    Private _StreetAddress As String 
    Private _City As String 
    Private _State As String 
    Private _Zip As String 
    Private _IsOK As Boolean 


    Public Sub New(ByVal result As Boolean, ByVal name As String, ByVal address As String, ByVal city As String, ByVal state As String, ByVal zip As String) 
        _IsOK = result
        _Name = name
        _StreetAddress = address
        _City = city
        _State = state
        _Zip = zip

    End Sub 


    Public Property MyName() As String  
        Get 
            Return _Name
        End Get 
        Set
            _Name = value
        End Set 
    End Property 

    Public Property MyStreetAddress() As String  
        Get 
            Return _StreetAddress
        End Get 
        Set
            _StreetAddress = value
        End Set 
    End Property 

    Public Property MyCity() As String  
        Get 
            Return _City
        End Get 
        Set
            _City = value
        End Set 
    End Property 

    Public Property MyState() As String  
        Get 
            Return _State
        End Get 
        Set
            _State = value
        End Set 
    End Property 

    Public Property MyZip() As String  
        Get 
            Return _Zip
        End Get 
        Set
            _Zip = value
        End Set 
    End Property 

    Public Property IsOK() As Boolean  
        Get 
            Return _IsOK
        End Get 
        Set
            _IsOK = value
        End Set 
    End Property 
End Class

When the user clicks the OK or Cancel button, the Click event handlers create a MyControlEventArgs object that contains the data and raises the OnButtonClick event. The only difference between the two handlers is the event argument's IsOK property. This property enables the host to determine which button was clicked. It is set to true for the OK button, and false for the Cancel button. The following code shows the two button handlers.

Add the following code to the MyControl1 class.

Private Sub btnOK_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnOK.Click

    Dim retvals As New MyControlEventArgs(True, txtName.Text, txtAddress.Text, txtCity.Text, txtState.Text, txtZip.Text)
    RaiseEvent OnButtonClick(Me, retvals)

End Sub 

Private Sub btnCancel_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnCancel.Click
    Dim retvals As New MyControlEventArgs(False, txtName.Text, txtAddress.Text, txtCity.Text, txtState.Text, txtZip.Text)
    RaiseEvent OnButtonClick(Me, retvals)

End Sub

For this assembly to be referenced by a WPF application, it must have a strong name. To create a strong name, create a key file with Sn.exe and add it to your project.

  1. Open a Visual Studio command prompt. To do so, click the Start menu, and then select All Programs/Microsoft Visual Studio 2010/Visual Studio Tools/Visual Studio Command Prompt. This launches a console window with customized environment variables.

  2. At the command prompt, use the cd command to go to your project folder.

  3. Generate a key file named MyControls.snk by running the following command.

    Sn.exe -k MyControls.snk
    

  4. To include the key file in your project, right-click the project name in Solution Explorer and then click Properties. In the Project Designer, click the Signing tab, select the Sign the assembly check box and then browse to your key file.

  5. Build the solution. The build will produce a DLL named MyControls.dll.

The WPF host application uses the WindowsFormsHost control to host MyControl1. The application handles the OnButtonClick event to receive the data from the control. It also has a collection of option buttons that enable you to change some of the control's properties from the WPF application. The following illustration shows the finished application.

The complete application, showing the control embedded in the WPF application

A control embedded in a WPF page

To start the project:

  1. Open Visual Studio, and select New Project.

  2. In the Window category, select the WPF Application template.

  3. Name the new project WpfHost.

  4. For the location, specify the same top-level folder that contains the MyControls project.

  5. Click OK to create the project.

You also need to add references to the DLL that contains MyControl1 and other assemblies.

  1. Right-click the project name in Solution Explorer and select Add Reference.

  2. Click the Browse tab, and browse to the folder that contains MyControls.dll. For this walkthrough, this folder is MyControls\bin\Debug.

  3. Select MyControls.dll, and then click OK.

  4. Add a reference to the WindowsFormsIntegration assembly, which is named WindowsFormsIntegration.dll.

The user interface (UI) of the host application is implemented in MainWindow.xaml. This file contains Extensible Application Markup Language (XAML) markup that defines the layout, and hosts the Windows Forms control. The application is divided into three regions:

  • The Control Properties panel, which contains a collection of option buttons that you can use to modify various properties of the hosted control.

  • The Data from Control panel, which contains several TextBlock elements that display the data returned from the hosted control.

  • The hosted control itself.

The basic layout is shown in the following XAML. The markup that is needed to host MyControl1 is omitted from this example, but will be discussed later.

Replace the XAML in MainWindow.xaml with the following. If you are using Visual Basic, change the class to x:Class="MainWindow".

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      x:Class="WpfHost.MainWindow"
      xmlns:mcl="clr-namespace:MyControls;assembly=MyControls"
      Loaded="Init">
  <DockPanel>
    <DockPanel.Resources>
      <Style x:Key="inlineText" TargetType="{x:Type Inline}">
        <Setter Property="FontWeight" Value="Normal"/>
      </Style>
      <Style x:Key="titleText" TargetType="{x:Type TextBlock}">
        <Setter Property="DockPanel.Dock" Value="Top"/>
        <Setter Property="FontWeight" Value="Bold"/>
        <Setter Property="Margin" Value="10,5,10,0"/>
      </Style>
    </DockPanel.Resources>

    <StackPanel Orientation="Vertical"
                DockPanel.Dock="Left"
                Background="Bisque"
                Width="250">

      <TextBlock  Margin="10,10,10,10"
                  FontWeight="Bold"
                  FontSize="12">Control Properties</TextBlock>
      <TextBlock Style="{StaticResource titleText}">Background Color</TextBlock>
      <StackPanel Margin="10,10,10,10">
        <RadioButton Name="rdbtnOriginalBackColor"
                    IsChecked="True"
                    Click="BackColorChanged">Original</RadioButton>
        <RadioButton Name="rdbtnBackGreen"
                    Click="BackColorChanged">LightGreen</RadioButton>
        <RadioButton Name="rdbtnBackSalmon"
                    Click="BackColorChanged">LightSalmon</RadioButton>
      </StackPanel>

      <TextBlock Style="{StaticResource titleText}">Foreground Color</TextBlock>
      <StackPanel Margin="10,10,10,10">
        <RadioButton Name="rdbtnOriginalForeColor"
                    IsChecked="True"
                    Click="ForeColorChanged">Original</RadioButton>
        <RadioButton Name="rdbtnForeRed"
                    Click="ForeColorChanged">Red</RadioButton>
        <RadioButton Name="rdbtnForeYellow"
                    Click="ForeColorChanged">Yellow</RadioButton>
      </StackPanel>

      <TextBlock Style="{StaticResource titleText}">Font Family</TextBlock>
      <StackPanel Margin="10,10,10,10">
        <RadioButton Name="rdbtnOriginalFamily"
                     IsChecked="True"
                    Click="FontChanged">Original</RadioButton>
        <RadioButton Name="rdbtnTimes"
                    Click="FontChanged">Times New Roman</RadioButton>
        <RadioButton Name="rdbtnWingdings"
                    Click="FontChanged">Wingdings</RadioButton>
      </StackPanel>

      <TextBlock Style="{StaticResource titleText}">Font Size</TextBlock>
      <StackPanel Margin="10,10,10,10">
        <RadioButton Name="rdbtnOriginalSize"
                    IsChecked="True"
                    Click="FontSizeChanged">Original</RadioButton>
        <RadioButton Name="rdbtnTen"
                    Click="FontSizeChanged">10</RadioButton>
        <RadioButton Name="rdbtnTwelve"
                    Click="FontSizeChanged">12</RadioButton>
      </StackPanel>

      <TextBlock Style="{StaticResource titleText}">Font Style</TextBlock>
      <StackPanel Margin="10,10,10,10">
        <RadioButton Name="rdbtnNormalStyle"
                     IsChecked="True"
                     Click="StyleChanged">Original</RadioButton>
        <RadioButton Name="rdbtnItalic"
                     Click="StyleChanged">Italic</RadioButton>
      </StackPanel>

      <TextBlock Style="{StaticResource titleText}">Font Weight</TextBlock>
      <StackPanel Margin="10,10,10,10">
        <RadioButton Name="rdbtnOriginalWeight"
                     IsChecked="True"
                   Click="WeightChanged">
          Original
        </RadioButton>
        <RadioButton Name="rdbtnBold"
                   Click="WeightChanged">Bold</RadioButton>
      </StackPanel>
    </StackPanel>

    <WindowsFormsHost Name="wfh"
                     DockPanel.Dock="Top"
                     Height="300">
      <mcl:MyControl1 Name="mc"/>
    </WindowsFormsHost>

    <StackPanel Orientation="Vertical"
                Height="Auto"
                Background="LightBlue">
      <TextBlock Margin="10,10,10,10"
            FontWeight="Bold"
            FontSize="12">Data From Control</TextBlock>
      <TextBlock Style="{StaticResource titleText}">
        Name: <Span Name="txtName" Style="{StaticResource inlineText}"/>
      </TextBlock>
      <TextBlock Style="{StaticResource titleText}">
        Street Address: <Span Name="txtAddress" Style="{StaticResource inlineText}"/>
      </TextBlock>
      <TextBlock Style="{StaticResource titleText}">
        City: <Span Name="txtCity" Style="{StaticResource inlineText}"/>
      </TextBlock>
      <TextBlock Style="{StaticResource titleText}">
        State: <Span Name="txtState" Style="{StaticResource inlineText}"/>
      </TextBlock>
      <TextBlock Style="{StaticResource titleText}">
        Zip: <Span Name="txtZip" Style="{StaticResource inlineText}"/>
      </TextBlock>
    </StackPanel>
  </DockPanel>
</Window>

The first StackPanel element contains several sets of RadioButton controls that enable you to modify various default properties of the hosted control. That is followed by a WindowsFormsHost element, which hosts MyControl1. The final StackPanel element contains several TextBlock elements that display the data that is returned by the hosted control. The ordering of the elements and the Dock and Height attribute settings embed the hosted control into the window with no gaps or distortion.

The following edited version of the previous XAML focuses on the elements that are needed to host MyControl1.

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      x:Class="WpfHost.MainWindow"
      xmlns:mcl="clr-namespace:MyControls;assembly=MyControls"
      Loaded="Init">


...


<WindowsFormsHost Name="wfh"
                 DockPanel.Dock="Top"
                 Height="300">
  <mcl:MyControl1 Name="mc"/>
</WindowsFormsHost>

The xmlns namespace mapping attribute creates a reference to the MyControls namespace that contains the hosted control. This mapping enables you to represent MyControl1 in XAML as <mcl:MyControl1>.

Two elements in the XAML handle the hosting:

  • WindowsFormsHost represents the WindowsFormsHost element that enables you to host a Windows Forms control in a WPF application.

  • mcl:MyControl1, which represents MyControl1, is added to the WindowsFormsHost element's child collection. As a result, this Windows Forms control is rendered as part of the WPF window, and you can communicate with the control from the application.

The code-behind file, MainWindow.xaml.vb or MainWindow.xaml.cs, contains the procedural code that implements the functionality of the UI discussed in the preceding section. The primary tasks are:

  • Attaching an event handler to MyControl1's OnButtonClick event.

  • Modifying various properties of MyControl1, based on how the collection of option buttons are set.

  • Displaying the data collected by the control.

The initialization code is contained in an event handler for the window's Loaded event and attaches an event handler to the control's OnButtonClick event.

In MainWindow.xaml.vb or MainWindow.xaml.cs, add the following code to the MainWindow class.

Private app As Application
Private myWindow As Window
Private initFontWeight As FontWeight
Private initFontSize As [Double]
Private initFontStyle As FontStyle
Private initBackBrush As SolidColorBrush
Private initForeBrush As SolidColorBrush
Private initFontFamily As FontFamily
Private UIIsReady As Boolean = False 


Private Sub Init(ByVal sender As Object, ByVal e As RoutedEventArgs)
    app = System.Windows.Application.Current
    myWindow = CType(app.MainWindow, Window)
    myWindow.SizeToContent = SizeToContent.WidthAndHeight
    wfh.TabIndex = 10
    initFontSize = wfh.FontSize
    initFontWeight = wfh.FontWeight
    initFontFamily = wfh.FontFamily
    initFontStyle = wfh.FontStyle
    initBackBrush = CType(wfh.Background, SolidColorBrush)
    initForeBrush = CType(wfh.Foreground, SolidColorBrush)

    Dim mc As MyControl1 = wfh.Child

    AddHandler mc.OnButtonClick, AddressOf Pane1_OnButtonClick
    UIIsReady = True 

End Sub

Because the XAML discussed previously added MyControl1 to the WindowsFormsHost element's child element collection, you can cast the WindowsFormsHost element's Child to get the reference to MyControl1. You can then use that reference to attach an event handler to OnButtonClick.

In addition to providing a reference to the control itself, WindowsFormsHost exposes a number of the control's properties, which you can manipulate from the application. The initialization code assigns those values to private global variables for later use in the application.

So that you can easily access the types in the MyControls DLL, add the following Imports or using statement to the top of the file.

Imports MyControls

MyControl1 raises the OnButtonClick event when the user clicks either of the control's buttons.

Add the following code to the MainWindow class.

'Handle button clicks on the Windows Form control 
Private Sub Pane1_OnButtonClick(ByVal sender As Object, ByVal args As MyControlEventArgs)
    txtName.Inlines.Clear()
    txtAddress.Inlines.Clear()
    txtCity.Inlines.Clear()
    txtState.Inlines.Clear()
    txtZip.Inlines.Clear()

    If args.IsOK Then
        txtName.Inlines.Add(" " + args.MyName)
        txtAddress.Inlines.Add(" " + args.MyStreetAddress)
        txtCity.Inlines.Add(" " + args.MyCity)
        txtState.Inlines.Add(" " + args.MyState)
        txtZip.Inlines.Add(" " + args.MyZip)
    End If 

End Sub

The data in the text boxes is packed into the MyControlEventArgs object. If the user clicks the OK button, the event handler extracts the data and displays it in the panel below MyControl1.

The WindowsFormsHost element exposes several of the hosted control's default properties. As a result, you can change the appearance of the control to match the style of your application more closely. The sets of option buttons in the left panel enable the user to modify several color and font properties. Each set of buttons has a handler for the Click event, which detects the user's option button selections and changes the corresponding property on the control.

Add the following code to the MainWindow class.

Private Sub BackColorChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)

    If sender.Equals(rdbtnBackGreen) Then
        wfh.Background = New SolidColorBrush(Colors.LightGreen)
    ElseIf sender.Equals(rdbtnBackSalmon) Then
        wfh.Background = New SolidColorBrush(Colors.LightSalmon)
    ElseIf UIIsReady = True Then
        wfh.Background = initBackBrush
    End If 

End Sub 

Private Sub ForeColorChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)
    If sender.Equals(rdbtnForeRed) Then
        wfh.Foreground = New SolidColorBrush(Colors.Red)
    ElseIf sender.Equals(rdbtnForeYellow) Then
        wfh.Foreground = New SolidColorBrush(Colors.Yellow)
    ElseIf UIIsReady = True Then
        wfh.Foreground = initForeBrush
    End If 

End Sub 

Private Sub FontChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)
    If sender.Equals(rdbtnTimes) Then
        wfh.FontFamily = New FontFamily("Times New Roman")
    ElseIf sender.Equals(rdbtnWingdings) Then
        wfh.FontFamily = New FontFamily("Wingdings")
    ElseIf UIIsReady = True Then
        wfh.FontFamily = initFontFamily
    End If 

End Sub 

Private Sub FontSizeChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)
    If sender.Equals(rdbtnTen) Then
        wfh.FontSize = 10
    ElseIf sender.Equals(rdbtnTwelve) Then
        wfh.FontSize = 12
    ElseIf UIIsReady = True Then
        wfh.FontSize = initFontSize
    End If 

End Sub 

Private Sub StyleChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)
    If sender.Equals(rdbtnItalic) Then
        wfh.FontStyle = FontStyles.Italic
    ElseIf UIIsReady = True Then
        wfh.FontStyle = initFontStyle
    End If 

End Sub 

Private Sub WeightChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)
    If sender.Equals(rdbtnBold) Then
        wfh.FontWeight = FontWeights.Bold
    ElseIf UIIsReady = True Then
        wfh.FontWeight = initFontWeight
    End If 

End Sub

Build and run the application. Add some text in the Windows Forms composite control and then click OK. The text appears in the labels. Click the different radio buttons to see the effect on the control.

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