silverlight-4.0 - MEF MVVM Silverlight 4中的导入问题

Question

我正在使用MEF，MVVM和Silverlight4，以下是我的代码

Main.cs:

using System;
using System.ComponentModel;
using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Diagnostics;
using System.ServiceModel.DomainServices.Client.ApplicationServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
 public partial class Main : UserControl
    {
        public Main()
        {
            InitializeComponent();
            // Satisfy the MEF imports for the class.
            if (!DesignerProperties.IsInDesignTool)
            {
                CompositionInitializer.SatisfyImports(this);
            }

        }


        /// <summary>
        /// Sets the datacontext to the viewmodel for this view
        /// </summary>
        [Import(ViewModelTypes.MainViewModel)]
        public object ViewModel
        {
            set
            {
                this.DataContext = value;
            }
        }
    }

View 模型:

using System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using System.Windows.Input;
    [Export(ViewModelTypes.MainViewModel)]
    [PartCreationPolicy(CreationPolicy.NonShared)]
    public class MainViewModel : ViewModelBase
    {
        [ImportingConstructor]
        public MainViewModel(IAuthenticationModel authModel, IprospectManagementModel managementModel)
        {
            this.authenticationModel = authModel;
            this.managementModel = managementModel;
        }

        /// <summary>
        /// The authentication model.
        /// </summary>
        private IAuthenticationModel authenticationModel;

        /// <summary>
        /// The Iprospect management model.
        /// </summary>
        private IprospectManagementModel managementModel;

    }

以下是我遇到的错误，请尽我所能追查。

组成保持不变。更改由于以下错误而被拒绝:合成产生单个合成错误。根本原因在下面提供。查看CompositionException.Errors属性以获取更多详细信息。

1)找不到与约束'(exportDefinition.ContractName ==“MainViewModel”)'匹配的有效导出，无效的导出可能已被拒绝。

导致:

Cannot set import 'IProspectCommonApp.Client.Main.ViewModel (ContractName="MainViewModel")' on part 'IProspectCommonApp.Client.Main'.
Element: IProspectCommonApp.Client.Main.ViewModel (ContractName="MainViewModel") -->  IProspectCommonApp.Client.Main

Answer 1

可能由于未导出IAuthenticationModel和/或IprospectManagementModel而失败。 MainViewModel通过ImportingConstructor导入了这些，因此如果尚未导出它们，则无法创建它们。

有关MEF调试的更多信息，请参见How to Debug and Diagnose MEF Failures。