如何：创建返回 UI 的外接程序

此示例演示如何创建将 Windows Presentation Foundation （WPF） 返回到主机 WPF 独立应用程序的外接程序。

外接程序返回一个 UI，该 UI 是 WPF 用户控件。 用户控件的内容是单击后显示消息框的单个按钮。 WPF 独立应用程序托管附加模块，并将附加模块返回的用户控件显示为主应用程序窗口的内容。

先决条件

此示例重点介绍 .NET Framework 外接程序模型中的 WPF 扩展如何实现这个场景，并假设以下条件成立：

• 了解 .NET Framework 加载项模型，包括管道、加载项（外接程序）和主机开发。 如果不熟悉这些概念，请参阅加载项和扩展性。 有关演示管道、加载项和主机应用程序的实现的教程，请参阅 演练：创建可扩展应用程序。

• .NET Framework 加载项模型 WPF 扩展的知识可以在此处找到：WPF 加载项概述。

示例：

若要创建返回 WPF UI 的外接程序，需要每个管道段、加载项和主机应用程序的特定代码。

实现协定管道段

方法必须由返回 UI 的协定定义，并且其返回值的类型必须为 INativeHandleContract。 这由以下代码中的 GetAddInUI 协定的 IWPFAddInContract 方法演示。

using System.AddIn.Contract;
using System.AddIn.Pipeline;

namespace Contracts
{
    /// <summary>
    /// Defines the services that an add-in will provide to a host application
    /// </summary>
    [AddInContract]
    public interface IWPFAddInContract : IContract
    {
        // Return a UI to the host application
        INativeHandleContract GetAddInUI();
    }
}

Imports System.AddIn.Contract
Imports System.AddIn.Pipeline

Namespace Contracts
    ''' <summary>
    ''' Defines the services that an add-in will provide to a host application
    ''' </summary>
    <AddInContract>
    Public Interface IWPFAddInContract
        Inherits IContract
        ' Return a UI to the host application
        Function GetAddInUI() As INativeHandleContract
    End Interface
End Namespace

实现外接程序视图管道段

由于外接程序将其提供的 UI 实现为 FrameworkElement的子类，与 IWPFAddInView.GetAddInUI 相关联的外接程序视图方法必须返回类型为 FrameworkElement的值。 以下代码显示作为接口实现的协定的外接程序视图。

using System.AddIn.Pipeline;
using System.Windows;

namespace AddInViews
{
    /// <summary>
    /// Defines the add-in's view of the contract
    /// </summary>
    [AddInBase]
    public interface IWPFAddInView
    {
        // The add-in's implementation of this method will return
        // a UI type that directly or indirectly derives from
        // FrameworkElement.
        FrameworkElement GetAddInUI();
    }
}

Imports System.AddIn.Pipeline
Imports System.Windows

Namespace AddInViews
    ''' <summary>
    ''' Defines the add-in's view of the contract
    ''' </summary>
    <AddInBase>
    Public Interface IWPFAddInView
        ' The add-in's implementation of this method will return
        ' a UI type that directly or indirectly derives from 
        ' FrameworkElement.
        Function GetAddInUI() As FrameworkElement
    End Interface
End Namespace

实现外接程序端适配器管道段

协定方法返回 INativeHandleContract，但加载项返回 FrameworkElement（如加载项视图所指定）。 因此，在跨越隔离边界之前，必须将 FrameworkElement 转换为 INativeHandleContract。 这一工作由加载项方适配器通过调用 ViewToContractAdapter 来执行，如以下代码中所示。

using System.AddIn.Contract;
using System.AddIn.Pipeline;
using System.Windows;

using AddInViews;
using Contracts;

namespace AddInSideAdapters
{
    /// <summary>
    /// Adapts the add-in's view of the contract to the add-in contract
    /// </summary>
    [AddInAdapter]
    public class WPFAddIn_ViewToContractAddInSideAdapter : ContractBase, IWPFAddInContract
    {
        IWPFAddInView wpfAddInView;

        public WPFAddIn_ViewToContractAddInSideAdapter(IWPFAddInView wpfAddInView)
        {
            // Adapt the add-in view of the contract (IWPFAddInView)
            // to the contract (IWPFAddInContract)
            this.wpfAddInView = wpfAddInView;
        }

        public INativeHandleContract GetAddInUI()
        {
            // Convert the FrameworkElement from the add-in to an INativeHandleContract
            // that will be passed across the isolation boundary to the host application.
            FrameworkElement fe = this.wpfAddInView.GetAddInUI();
            INativeHandleContract inhc = FrameworkElementAdapters.ViewToContractAdapter(fe);
            return inhc;
        }
    }
}

Imports System.AddIn.Contract
Imports System.AddIn.Pipeline
Imports System.Windows

Imports AddInViews
Imports Contracts

Namespace AddInSideAdapters
    ''' <summary>
    ''' Adapts the add-in's view of the contract to the add-in contract
    ''' </summary>
    <AddInAdapter>
    Public Class WPFAddIn_ViewToContractAddInSideAdapter
        Inherits ContractBase
        Implements IWPFAddInContract
        Private wpfAddInView As IWPFAddInView

        Public Sub New(ByVal wpfAddInView As IWPFAddInView)
            ' Adapt the add-in view of the contract (IWPFAddInView) 
            ' to the contract (IWPFAddInContract)
            Me.wpfAddInView = wpfAddInView
        End Sub

        Public Function GetAddInUI() As INativeHandleContract Implements IWPFAddInContract.GetAddInUI
            ' Convert the FrameworkElement from the add-in to an INativeHandleContract 
            ' that will be passed across the isolation boundary to the host application.
            Dim fe As FrameworkElement = Me.wpfAddInView.GetAddInUI()
            Dim inhc As INativeHandleContract = FrameworkElementAdapters.ViewToContractAdapter(fe)
            Return inhc
        End Function
    End Class
End Namespace

实现主机视图管道段

由于主机应用程序将显示 FrameworkElement，因此与 IWPFAddInHostView.GetAddInUI 相关的主机视图中的方法必须返回类型 FrameworkElement的值。 以下代码显示了以接口方式实现的协定的主机视图。

using System.Windows;

namespace HostViews
{
    /// <summary>
    /// Defines the host's view of the add-in
    /// </summary>
    public interface IWPFAddInHostView
    {
        // The view returns as a class that directly or indirectly derives from
        // FrameworkElement and can subsequently be displayed by the host
        // application by embedding it as content or sub-content of a UI that is
        // implemented by the host application.
        FrameworkElement GetAddInUI();
    }
}

Imports System.Windows

Namespace HostViews
    ''' <summary>
    ''' Defines the host's view of the add-in
    ''' </summary>
    Public Interface IWPFAddInHostView
        ' The view returns as a class that directly or indirectly derives from 
        ' FrameworkElement and can subsequently be displayed by the host 
        ' application by embedding it as content or sub-content of a UI that is 
        ' implemented by the host application.
        Function GetAddInUI() As FrameworkElement
    End Interface
End Namespace

实现主机端适配器管道段

协定方法返回 INativeHandleContract，但主机应用程序预期 FrameworkElement（如主机视图所指定）。 因此，在越过隔离边界后，必须将 INativeHandleContract 转换为 FrameworkElement。 此工作由主机端适配器通过调用 ContractToViewAdapter来执行，如以下代码所示。

using System.AddIn.Contract;
using System.AddIn.Pipeline;
using System.Windows;

using Contracts;
using HostViews;

namespace HostSideAdapters
{
    /// <summary>
    /// Adapts the add-in contract to the host's view of the add-in
    /// </summary>
    [HostAdapter]
    public class WPFAddIn_ContractToViewHostSideAdapter : IWPFAddInHostView
    {
        IWPFAddInContract wpfAddInContract;
        ContractHandle wpfAddInContractHandle;

        public WPFAddIn_ContractToViewHostSideAdapter(IWPFAddInContract wpfAddInContract)
        {
            // Adapt the contract (IWPFAddInContract) to the host application's
            // view of the contract (IWPFAddInHostView)
            this.wpfAddInContract = wpfAddInContract;

            // Prevent the reference to the contract from being released while the
            // host application uses the add-in
            this.wpfAddInContractHandle = new ContractHandle(wpfAddInContract);
        }

        public FrameworkElement GetAddInUI()
        {
            // Convert the INativeHandleContract that was passed from the add-in side
            // of the isolation boundary to a FrameworkElement
            INativeHandleContract inhc = this.wpfAddInContract.GetAddInUI();
            FrameworkElement fe = FrameworkElementAdapters.ContractToViewAdapter(inhc);
            return fe;
        }
    }
}

Imports System.AddIn.Contract
Imports System.AddIn.Pipeline
Imports System.Windows

Imports Contracts
Imports HostViews

Namespace HostSideAdapters
    ''' <summary>
    ''' Adapts the add-in contract to the host's view of the add-in
    ''' </summary>
    <HostAdapter>
    Public Class WPFAddIn_ContractToViewHostSideAdapter
        Implements IWPFAddInHostView
        Private wpfAddInContract As IWPFAddInContract
        Private wpfAddInContractHandle As ContractHandle

        Public Sub New(ByVal wpfAddInContract As IWPFAddInContract)
            ' Adapt the contract (IWPFAddInContract) to the host application's
            ' view of the contract (IWPFAddInHostView)
            Me.wpfAddInContract = wpfAddInContract

            ' Prevent the reference to the contract from being released while the
            ' host application uses the add-in
            Me.wpfAddInContractHandle = New ContractHandle(wpfAddInContract)
        End Sub

        Public Function GetAddInUI() As FrameworkElement Implements IWPFAddInHostView.GetAddInUI
            ' Convert the INativeHandleContract that was passed from the add-in side
            ' of the isolation boundary to a FrameworkElement
            Dim inhc As INativeHandleContract = Me.wpfAddInContract.GetAddInUI()
            Dim fe As FrameworkElement = FrameworkElementAdapters.ContractToViewAdapter(inhc)
            Return fe
        End Function
    End Class
End Namespace

实现外接程序

创建外接程序适配器和外接程序视图后，外接程序（WPFAddIn1.AddIn）必须实现 IWPFAddInView.GetAddInUI 方法，以便返回一个 FrameworkElement 对象（在此示例中为 UserControl）。 UserControl、AddInUI的实现由以下代码展示。

    <UserControl
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="WPFAddIn1.AddInUI">
    
    <StackPanel>
        <Button Click="clickMeButton_Click" Content="Click Me!" />
    </StackPanel>
    
</UserControl>

using System.Windows;
using System.Windows.Controls;

namespace WPFAddIn1
{
    public partial class AddInUI : UserControl
    {
        public AddInUI()
        {
            InitializeComponent();
        }

        void clickMeButton_Click(object sender, RoutedEventArgs e)
        {
            MessageBox.Show("Hello from WPFAddIn1");
        }
    }
}

Imports System.Windows
Imports System.Windows.Controls

Namespace WPFAddIn1
    Partial Public Class AddInUI
        Inherits UserControl
        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub clickMeButton_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
            MessageBox.Show("Hello from WPFAddIn1")
        End Sub
    End Class
End Namespace

通过加载项实现 IWPFAddInView.GetAddInUI 仅需返回 AddInUI 的新实例，如以下代码所示。

using System.AddIn;
using System.Windows;

using AddInViews;

namespace WPFAddIn1
{
    /// <summary>
    /// Add-In implementation
    /// </summary>
    [AddIn("WPF Add-In 1")]
    public class WPFAddIn : IWPFAddInView
    {
        public FrameworkElement GetAddInUI()
        {
            // Return add-in UI
            return new AddInUI();
        }
    }
}

Imports System.AddIn
Imports System.Windows

Imports AddInViews

Namespace WPFAddIn1
    ''' <summary>
    ''' Add-In implementation
    ''' </summary>
    <AddIn("WPF Add-In 1")>
    Public Class WPFAddIn
        Implements IWPFAddInView
        Public Function GetAddInUI() As FrameworkElement Implements IWPFAddInView.GetAddInUI
            ' Return add-in UI
            Return New AddInUI()
        End Function
    End Class
End Namespace

实现宿主应用程序

创建主机端适配器和主机视图后，主机应用程序可以使用 .NET Framework 外接程序模型打开管道，获取外接程序的主机视图，并调用 IWPFAddInHostView.GetAddInUI 方法。 以下步骤显示在以下代码中。

// Get add-in pipeline folder (the folder in which this application was launched from)
string appPath = Environment.CurrentDirectory;

// Rebuild visual add-in pipeline
string[] warnings = AddInStore.Rebuild(appPath);
if (warnings.Length > 0)
{
    string msg = "Could not rebuild pipeline:";
    foreach (string warning in warnings) msg += "\n" + warning;
    MessageBox.Show(msg);
    return;
}

// Activate add-in with Internet zone security isolation
Collection<AddInToken> addInTokens = AddInStore.FindAddIns(typeof(IWPFAddInHostView), appPath);
AddInToken wpfAddInToken = addInTokens[0];
this.wpfAddInHostView = wpfAddInToken.Activate<IWPFAddInHostView>(AddInSecurityLevel.Internet);

// Get and display add-in UI
FrameworkElement addInUI = this.wpfAddInHostView.GetAddInUI();
this.addInUIHostGrid.Children.Add(addInUI);

' Get add-in pipeline folder (the folder in which this application was launched from)
Dim appPath As String = Environment.CurrentDirectory

' Rebuild visual add-in pipeline
Dim warnings() As String = AddInStore.Rebuild(appPath)
If warnings.Length > 0 Then
    Dim msg As String = "Could not rebuild pipeline:"
    For Each warning As String In warnings
        msg &= vbLf & warning
    Next warning
    MessageBox.Show(msg)
    Return
End If

' Activate add-in with Internet zone security isolation
Dim addInTokens As Collection(Of AddInToken) = AddInStore.FindAddIns(GetType(IWPFAddInHostView), appPath)
Dim wpfAddInToken As AddInToken = addInTokens(0)
Me.wpfAddInHostView = wpfAddInToken.Activate(Of IWPFAddInHostView)(AddInSecurityLevel.Internet)

' Get and display add-in UI
Dim addInUI As FrameworkElement = Me.wpfAddInHostView.GetAddInUI()
Me.addInUIHostGrid.Children.Add(addInUI)

另请参阅

• 外接程序和扩展性
• WPF 外接程序概述