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A Sample Silverlight 4 Application Using MEF, MVVM, and WCF RIA Services - Part 1

, 7 Jul 2011
Part 1 of a series describing the creation of a Silverlight business application using MEF, MVVM Light, and WCF RIA Services.
IssueVisionforSilverlightSetup20110630.zip
IssueVision for Silverlight Setup
IssueVisionSetup.msi
setup.exe
IssueVision_for_Silverlight_setup.zip
IssueVisionSetup.msi
setup.exe
IssueVision_Silverlight20110630.zip
IssueVision.Silverlight
Assemblies
GalaSoft.MvvmLight.Extras.SL4.dll
GalaSoft.MvvmLight.SL4.dll
MenuControls.dll
System.Windows.Controls.DataVisualization.Toolkit.dll
System.Windows.Controls.Toolkit.dll
System.Windows.Controls.Toolkit.Internals.dll
System.Windows.Interactivity.dll
Database
IssueVision.Client
IssueVision.Client.csproj.user
Assets
Signin.png
Controls
Properties
Views
IssueVision.Common
IssueVision.Common.csproj.user
Controls
Helpers
Models
Properties
Resources
Themes
IssueVision.Data
IssueVision.Data.csproj.user
Properties
Web
Resources
IssueVision.Data.Web
IssueVision.edmx
Helpers
MetadataClasses
Properties
Resources
Services
IssueVision.Model
IssueVision.Model.csproj.user
Properties
IssueVision.Setup
IssueVisionSetup.vdproj
IssueVision.ViewModel
IssueVision.ViewModel.csproj.user
Properties
IssueVision.Web
IssueVision.Web.csproj.user
Properties
IssueVision_Silverlight_20110316.zip
GalaSoft.MvvmLight.Extras.SL4.dll
GalaSoft.MvvmLight.SL4.dll
MenuControls.dll
System.Windows.Controls.DataVisualization.Toolkit.dll
System.Windows.Controls.Toolkit.dll
System.Windows.Controls.Toolkit.Internals.dll
System.Windows.Interactivity.dll
IssueVision.Client.csproj.user
Signin.png
DataSources
IssueVision.Data.Web.IssueVisionContext.datasource
IssueVision.Data.Web.PasswordResetContext.datasource
IssueVision.Common.csproj.user
IssueVision.Data.csproj.user
IssueVision.edmx
DataTypes
IssueVision.Model.csproj.user
IssueVisionSetup.vdproj
IssueVision.ViewModel.csproj.user
IssueVision.Web.csproj.user
IssueVision_Silverlight_20110606.zip
GalaSoft.MvvmLight.Extras.SL4.dll
GalaSoft.MvvmLight.SL4.dll
MenuControls.dll
System.Windows.Controls.DataVisualization.Toolkit.dll
System.Windows.Controls.Toolkit.dll
System.Windows.Controls.Toolkit.Internals.dll
System.Windows.Interactivity.dll
IssueVision.Client.csproj.user
Signin.png
IssueVision.Common.csproj.user
IssueVision.Data.csproj.user
IssueVision.edmx
IssueVision.Model.csproj.user
IssueVisionSetup.vdproj
IssueVision.ViewModel.csproj.user
IssueVision.Web.csproj.user
IssueVision_Silverlight_Setup.zip
IssueVisionSetup.msi
setup.exe
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.Composition;
using System.Linq;
using System.ServiceModel.DomainServices.Client;
using System.Windows;
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using GalaSoft.MvvmLight.Messaging;
using IssueVision.Data.Web;
using IssueVision.Common;


namespace IssueVision.ViewModel
{
    [Export(ViewModelTypes.NewIssueViewModel, typeof(ViewModelBase))]
    [PartCreationPolicy(CreationPolicy.NonShared)]
    public class NewIssueViewModel : ViewModelBase
    {
        #region "Private Data Members"
        private IIssueVisionModel _issueVisionModel;
        #endregion "Private Data Members"

        #region "Constructor"
        [ImportingConstructor]
        public NewIssueViewModel(IIssueVisionModel issueVisionModel)
        {
            _issueVisionModel = issueVisionModel;

            // set up event handling
            _issueVisionModel.SaveChangesComplete += new EventHandler<SubmitOperationEventArgs>(_issueVisionModel_SaveChangesComplete);
            _issueVisionModel.PropertyChanged += new PropertyChangedEventHandler(_issueVisionModel_PropertyChanged);

            // initiate a new issue
            Issue newIssue = this._issueVisionModel.AddNewIssue();
            AppMessages.EditIssueMessage.Send(newIssue);
        }
        #endregion "Constructor"

        #region "ICleanup interface implementation"
        public override void Cleanup()
        {
            if (_issueVisionModel != null)
            {
                // unregister all events
                _issueVisionModel.SaveChangesComplete -= new EventHandler<SubmitOperationEventArgs>(_issueVisionModel_SaveChangesComplete);
                _issueVisionModel.PropertyChanged -= new PropertyChangedEventHandler(_issueVisionModel_PropertyChanged);
                _issueVisionModel = null;
            }
            // unregister any messages for this ViewModel
            base.Cleanup();
        }
        #endregion "ICleanup interface implementation"

        #region "Public Commands"

        private RelayCommand _submitChangeCommand = null;

        public RelayCommand SubmitChangeCommand
        {
            get
            {
                if (_submitChangeCommand == null)
                {
                    _submitChangeCommand = new RelayCommand(
                        () => this.OnSubmitChangeCommand(),
                        () => (this._issueVisionModel != null) && (this._issueVisionModel.HasChanges));
                }
                return _submitChangeCommand;
            }
        }

        private void OnSubmitChangeCommand()
        {
            try
            {
                if (!_issueVisionModel.IsBusy)
                {
                    AppMessages.SubmitChangesMessage.Send();
                }
            }
            catch (Exception ex)
            {
                // notify user if there is any error
                AppMessages.RaiseErrorMessage.Send(ex);
            }
        }

        private RelayCommand _cancelChangeCommand = null;

        public RelayCommand CancelChangeCommand
        {
            get
            {
                if (_cancelChangeCommand == null)
                {
                    _cancelChangeCommand = new RelayCommand(
                        () => this.OnCancelChangeCommand(),
                        () => (this._issueVisionModel != null) && (this._issueVisionModel.HasChanges));
                }
                return _cancelChangeCommand;
            }
        }

        private void OnCancelChangeCommand()
        {
            try
            {
                MessageBoxResult theResult = MessageBoxResult.Cancel;

                if (!_issueVisionModel.IsBusy)
                {
                    // ask to confirm canceling this new issue first
                    DialogMessage dialogMessage = new DialogMessage(
                        this,
                        CommonResources.CancelCurrentIssueMessageBoxText,
                        s => theResult = s)
                    {
                        Button = MessageBoxButton.OKCancel,
                        Caption = CommonResources.ConfirmMessageBoxCaption
                    };

                    AppMessages.PleaseConfirmMessage.Send(dialogMessage);

                    if (theResult == MessageBoxResult.OK)
                    {
                        // if confirmed, cancel this issue
                        AppMessages.CancelChangesMessage.Send();
                        // initiate a new issue again
                        Issue newIssue = this._issueVisionModel.AddNewIssue();
                        AppMessages.EditIssueMessage.Send(newIssue);
                    }
                }
            }
            catch (Exception ex)
            {
                // notify user if there is any error
                AppMessages.RaiseErrorMessage.Send(ex);
            }
        }

        #endregion "Public Commands"

        #region "Private Methods"

        private void _issueVisionModel_SaveChangesComplete(object sender, SubmitOperationEventArgs e)
        {
            if (!e.HasError)
            {
                // notify user of the new issue ID
                foreach (Entity entity in e.SubmitOp.ChangeSet.AddedEntities)
                {
                    Issue addedIssue = entity as Issue;
                    if (addedIssue != null)
                    {
                        // notify user of the new issue ID
                        DialogMessage dialogMessage = new DialogMessage(
                                    this,
                                    CommonResources.NewIssueCreatedText + addedIssue.IssueID,
                                    null)
                        {
                            Button = MessageBoxButton.OK,
                            Caption = CommonResources.NewIssueCreatedCaption
                        };

                        AppMessages.StatusUpdateMessage.Send(dialogMessage);
                    }
                }
                // save is successful, start another new issue
                Issue newIssue = this._issueVisionModel.AddNewIssue();
                AppMessages.EditIssueMessage.Send(newIssue);
            }
            else
            {
                // notify user if there is any error
                AppMessages.RaiseErrorMessage.Send(e.Error);
            }
        }

        private void _issueVisionModel_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (e.PropertyName.Equals("HasChanges"))
            {
                SubmitChangeCommand.RaiseCanExecuteChanged();
                CancelChangeCommand.RaiseCanExecuteChanged();
            }
        }
        
        #endregion "Private Methods"
    }
}

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About the Author

Weidong Shen
Software Developer (Senior)
United States United States
Weidong has been an information system professional since 1990. He has a Master's degree in Computer Science, and is currently a MCSD .NET

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Web01 | 2.8.140814.1 | Last Updated 7 Jul 2011
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