将Abp移植进.NET MAUI项目

前言

写在.NET MAUI官宣正式发布之际，热烈庆祝MAUI正式发布！

去年12月份做了MAUI混合开发框架的调研，想起来文章里给自己挖了个坑，要教大家如何把Abp移植进Maui项目。

熟悉Abp的同学都知道，Abp 是一套强大的应用程序设计时框架（俗称脚手架），新版本的Abp vNext为微服务和网络优化的更多，然而本地开发经典Abp已经够用，而且官方没有停止维护，因此使用这个框架

MAUI则是跨平台的应用程序抽象层，强大的运行时框架 + 强大的设计时框架，我说这是宇宙最强大跨平台开发框架，不为过吧？😁

计划：

整个程序我们还是利用Mvvm设计模式，但是将利用Abp的Ioc容器，而不使用mvvmlight或者xamarinToolkit这些库，自行编写一个ViewModelBase
使用Abp.EntityFrameworkCore库中的EF相关功能，使用sqlite作为数据持久化方案。

目标：编写一个歌单App，对歌曲信息进行增、删、查、改。

下面来看看如何搭建

搭建MAUI项目

请注意：本文发布时，MAUI处于RC3版本，仍没有正式发布，需要安装Visual Studio 2022 17.3 (Preview)

首先按照官方教程搭建一个MAUI项目，命名为MauiBoilerplateBuild your first .NET MAUI app - .NET MAUI | Microsoft Docs

再前往Abp官网生成一个项目
Startup Templates - Create a Demo | AspNet Boilerplate

选择最新版本 v7.x 和.Net 6版本
取消勾选“Include login, register, user, role and tenant management pages”
项目名称中填入MauiBoilerplate与Maui项目保持一致

点击“Create My Project”生成abp项目文件，等待下载完成

下载，解压好后，打开src目录可以发现4个项目目录，我们仅需要Core和EntityFrameworkCore项目，将这两个目录移至项目根目录，并且添加至解决方案。

配置应用入口点

在MauiBoilerplate.Core项目中

改写默认配置文件

{"ConnectionStrings": {"Default": "Data Source=file:{0};"},"Logging": {"IncludeScopes": false,"LogLevel": {"Default": "Debug","System": "Information","Microsoft": "Information"}}
}

在MauiBoilerplate.Core.csproj中的ItemGroup节点下添加

<EmbeddedResource Include="appsettings.json"><CopyToOutputDirectory>Always</CopyToOutputDirectory></EmbeddedResource>

在MauiBoilerplate.Core项目中新建MauiBoilerplateBuilderExtensions.cs 作为程序入口

添加一个静态方法InitConfig，用于读取项目的配置文件appsettings.json，若第一次运行或者该文件不存在则读取默认的配置文件

private static void InitConfig(string logCfgName, string documentsPath){var assembly = IntrospectionExtensions.GetTypeInfo(typeof(MauiBoilerplateBuilderExtensions)).Assembly;Stream stream = assembly.GetManifestResourceStream($"MauiBoilerplate.Core.{logCfgName}");string text = "";using (var reader = new System.IO.StreamReader(stream)){text = reader.ReadToEnd();}if (DirFileHelper.IsExistFile(documentsPath)){var currentFileContent = DirFileHelper.ReadFile(documentsPath);var isSameContent = currentFileContent.ToMd5() == text.ToMd5();if (isSameContent){return;}DirFileHelper.CreateFile(documentsPath, text);}else{DirFileHelper.CreateFile(documentsPath, text);}}

添加一个静态方法InitDataBase用于初始化sqlite数据库文件"mato.db"

private static void InitDataBase(string dbName, string documentsPath){var assembly = IntrospectionExtensions.GetTypeInfo(typeof(MauiBoilerplateBuilderExtensions)).Assembly;Stream stream = assembly.GetManifestResourceStream($"MauiBoilerplate.Core.{dbName}");StreamHelper.WriteStream(stream, documentsPath);var path = Path.GetDirectoryName(documentsPath);DirFileHelper.CreateDir(path);}

添加一个静态方法UseMauiBoilerplate用于初始化配置文件，初始化db文件和向管道服务中注册AbpBootstrapper实例。

public static MauiAppBuilder UseMauiBoilerplate<TStartupModule>(this MauiAppBuilder builder) where TStartupModule : AbpModule{var logCfgName = "log4net.config";var appCfgName = "appsettings.json";var dbName = "mato.db";string documentsPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), MauiBoilerplateConsts.LocalizationSourceName, logCfgName);string documentsPath2 = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), MauiBoilerplateConsts.LocalizationSourceName, appCfgName);string dbPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), MauiBoilerplateConsts.LocalizationSourceName, dbName);InitConfig(logCfgName, documentsPath);InitConfig(appCfgName, documentsPath2);InitDataBase(dbName, dbPath);var _bootstrapper = AbpBootstrapper.Create<TStartupModule>(options =>{options.IocManager = new IocManager();});_bootstrapper.IocManager.IocContainer.AddFacility<LoggingFacility>(f => f.UseAbpLog4Net().WithConfig(documentsPath));builder.Services.AddSingleton(_bootstrapper);WindsorRegistrationHelper.CreateServiceProvider(_bootstrapper.IocManager.IocContainer, builder.Services);return builder;}

在MauiBoilerplate项目中

新建MauiBoilerplateModule.cs ，并编写代码如下，这是App起始模块

[DependsOn(typeof(MauiBoilerplateEntityFrameworkCoreModule))]public class MauiBoilerplateModule : AbpModule{public override void Initialize(){IocManager.RegisterAssemblyByConvention(typeof(MauiBoilerplateModule).GetAssembly());}}

打开MauiProgram.cs文件，将UseMauiBoilerplate添加到MauiAppBuilder

这里提一下, MAUI 应用跟其他.Net6应用一样采用泛型主机启动应用，在项目中有一个静态MauiProgram类，这是应用的入口点。这提供了从单个位置配置应用、服务和第三方库的功能。

更多泛型主机的信息，请参阅微软文档.NET 通用主机 | Microsoft Docs

至此，在主机管道中已经配置了MauiBoilerplate服务

配置Abp

App.xaml是应用的声明起始点，将从这里初始化Abp

打开App.xaml.cs，添加如下代码：

public partial class App : Application{private readonly AbpBootstrapper _abpBootstrapper;public App(AbpBootstrapper abpBootstrapper){_abpBootstrapper = abpBootstrapper;InitializeComponent();_abpBootstrapper.Initialize();this.MainPage = abpBootstrapper.IocManager.Resolve(typeof(MainPage)) as MainPage;}}

注意，我们还没有创建初始页面MainPage，你可以先创建这个文件，将在第三章讲UI层时介绍

至此，就完成了MAUI项目的搭建与Abp脚手架的集成，现在你可以在这个项目中使用Abp的IocManager，ConfigurationManager，工作单元特性，模组化特性，等等任何的Abp提供的功能了。

但是距离目标：制作一个具有数据访问层的App，还需要两段路要走：配置数据库，以及编写界面。

因为我们要做一个数据持久化型的小应用，所以在完成Abp功能的集成后，我们需要做数据库相关的配置工作

配置数据库

在MauiBoilerplate.Core项目中，添加两个实体类：

我们简单的写一个歌曲（song）的实体类

其中包含了歌曲标题（MusicTitle），艺术家（Artist），专辑（Album），时长（Duration）以及发售日期（ReleaseDate）

public class Song : FullAuditedEntity<long>{[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]public override long Id { get; set; }public string MusicTitle { get; set; }public string Artist { get; set; }public string Album { get; set; }public TimeSpan Duration { get; set; }public DateTime ReleaseDate { get; set; }}

在MauiBoilerplate.EntityFrameworkCore项目中：将这个类添加至MauiBoilerplateDbContext中

public class MauiBoilerplateDbContext : AbpDbContext
{//Add DbSet properties for your entities...public DbSet<Song> Song { get; set; }
}

新建WithDbContextHelper.cs

创建一个静态类WithDbContext，利用Abp的工作单元模式对dbcontext执行操作

public class WithDbContextHelper{public static void WithDbContext<TDbContext>(IIocResolver iocResolver, Action<TDbContext> contextAction)where TDbContext : DbContext{using (var uowManager = iocResolver.ResolveAsDisposable<IUnitOfWorkManager>()){using (var uow = uowManager.Object.Begin(TransactionScopeOption.Suppress)){var context = uowManager.Object.Current.GetDbContext<TDbContext>();contextAction(context);uow.Complete();}}}}

[可选]种子数据相关类编写

编写种子数据帮助类SeedHelper.cs，与数据库初始化类InitialDbBuilder，这里将在程序启动时向数据库插入一些种子数据

public static class SeedHelper{public static void SeedHostDb(IIocResolver iocResolver){Helper.WithDbContextHelper.WithDbContext<MauiBoilerplateDbContext>(iocResolver, SeedHostDb);}public static void SeedHostDb(MauiBoilerplateDbContext context){context.SuppressAutoSetTenantId = true;// Host seednew InitialDbBuilder(context).Create();}}

编写MauiBoilerplateEntityFrameworkCoreModule.cs

[DependsOn(typeof(MauiBoilerplateCoreModule), typeof(AbpEntityFrameworkCoreModule))]public class MauiBoilerplateEntityFrameworkCoreModule : AbpModule{public bool SkipDbContextRegistration { get; set; }public bool SkipDbSeed { get; set; }public override void PreInitialize(){if (!SkipDbContextRegistration){Configuration.Modules.AbpEfCore().AddDbContext<MauiBoilerplateDbContext>(options =>{if (options.ExistingConnection != null){DbContextOptionsConfigurer.Configure(options.DbContextOptions, options.ExistingConnection);}else{DbContextOptionsConfigurer.Configure(options.DbContextOptions, options.ConnectionString);}});}}public override void Initialize(){IocManager.RegisterAssemblyByConvention(typeof(MauiBoilerplateEntityFrameworkCoreModule).GetAssembly());}public override void PostInitialize(){Helper.WithDbContextHelper.WithDbContext<MauiBoilerplateDbContext>(IocManager, RunMigrate);if (!SkipDbSeed){SeedHelper.SeedHostDb(IocManager);}}public static void RunMigrate(MauiBoilerplateDbContext dbContext){dbContext.Database.Migrate();}}

将MauiBoilerplate.EntityFrameworkCore设置为启动项目，选择框架为.net6.0

打开程序包管理器控制台，选择默认项目MauiBoilerplate.EntityFrameworkCore

编辑

运行Add-Migration命令，将生成迁移脚本

运行MauiBoilerplate.EntityFrameworkCore，将生成mato.db等三个文件，

编辑

编写基类（可选）

我们在使用相关的父类时，某某ContentPage，或者某某UserControl时，需要像使用AbpServiceBase一样使用一些常用的功能，比如字符串的本地化，配置，AutoMapper对象等，就像AbpServiceBase的注释里描述的那样：

/// <summary>
/// This class can be used as a base class for services.
/// It has some useful objects property-injected and has some basic methods
/// most of services may need to.
/// </summary>

此时，需要编写一个基类（奈何.net本身没有Mixin模式，C#语言也不支持多继承），这些基类仅是注入了一些常用的Manager，方便代码编写者使用，因此基类的创建不是必须的。

比如可以增加一个ContentPageBase类作为ContentPage实例控件的基类

新建ContentPageBase.cs文件，创建类ContentPageBase继承于ContentPage

public class ContentPageBase : ContentPage{public IObjectMapper ObjectMapper { get; set; }/// <summary>/// Reference to the setting manager./// </summary>public ISettingManager SettingManager { get; set; }/// <summary>/// Reference to the localization manager./// </summary>public ILocalizationManager LocalizationManager { get; set; }/// <summary>/// Gets/sets name of the localization source that is used in this application service./// It must be set in order to use <see cref="L(string)"/> and <see cref="L(string,CultureInfo)"/> methods./// </summary>protected string LocalizationSourceName { get; set; }/// <summary>/// Gets localization source./// It's valid if <see cref="LocalizationSourceName"/> is set./// </summary>protected ILocalizationSource LocalizationSource{get{if (LocalizationSourceName == null){throw new AbpException("Must set LocalizationSourceName before, in order to get LocalizationSource");}if (_localizationSource == null || _localizationSource.Name != LocalizationSourceName){_localizationSource = LocalizationManager.GetSource(LocalizationSourceName);}return _localizationSource;}}private ILocalizationSource _localizationSource;/// <summary>/// Constructor./// </summary>protected ContentPageBase(){LocalizationSourceName = MauiBoilerplateConsts.LocalizationSourceName;ObjectMapper = NullObjectMapper.Instance;LocalizationManager = NullLocalizationManager.Instance;}/// <summary>/// Gets localized string for given key name and current language./// </summary>/// <param name="name">Key name</param>/// <returns>Localized string</returns>protected virtual string L(string name){return LocalizationSource.GetString(name);}/// <summary>/// Gets localized string for given key name and current language with formatting strings./// </summary>/// <param name="name">Key name</param>/// <param name="args">Format arguments</param>/// <returns>Localized string</returns>protected virtual string L(string name, params object[] args){return LocalizationSource.GetString(name, args);}/// <summary>/// Gets localized string for given key name and specified culture information./// </summary>/// <param name="name">Key name</param>/// <param name="culture">culture information</param>/// <returns>Localized string</returns>protected virtual string L(string name, CultureInfo culture){return LocalizationSource.GetString(name, culture);}/// <summary>/// Gets localized string for given key name and current language with formatting strings./// </summary>/// <param name="name">Key name</param>/// <param name="culture">culture information</param>/// <param name="args">Format arguments</param>/// <returns>Localized string</returns>protected virtual string L(string name, CultureInfo culture, params object[] args){return LocalizationSource.GetString(name, culture, args);}}

同理，若我们使用了其他控件类时，可以增加一个Base类作为实例控件的基类的

比如Popup控件，就编写一个PopupBase基类。

在这里我们编写了两个基类

编辑

本地化配置

新建一个TranslateExtension.cs作为Xaml标签的本地化处理类

[ContentProperty("Text")]public class TranslateExtension : DomainService, IMarkupExtension{public TranslateExtension(){LocalizationSourceName = MauiBoilerplateConsts.LocalizationSourceName;}public string Text { get; set; }public object ProvideValue(IServiceProvider serviceProvider){if (Text == null)return "";var translation = L(Text);          return translation;}}

在MauiBoilerplateLocalization.cs配置好SourceFiles

public static void Configure(ILocalizationConfiguration localizationConfiguration){localizationConfiguration.Sources.Add(new DictionaryBasedLocalizationSource(MauiBoilerplateConsts.LocalizationSourceName,new XmlEmbeddedFileLocalizationDictionaryProvider(typeof(LocalizationConfigurer).GetAssembly(),"MauiBoilerplate.Core.Localization.SourceFiles")));}

编写ViewModelBase

为实现Mvvm设计模式，页面需要绑定一个继承于ViewModelBase的类型

在ViewModelBase中，需要实现INotifyPropertyChanged以处理绑定成员变化时候的通知消息；

ViewModelBase集成于AbpServiceBase以方便ViewModel代码编写者使用常用的功能，比如字符串的本地化，配置，AutoMapper对象等。

public abstract class ViewModelBase : AbpServiceBase, ISingletonDependency, INotifyPropertyChanged{public ViewModelBase(){LocalizationSourceName = MauiBoilerplateConsts.LocalizationSourceName;}public event PropertyChangedEventHandler PropertyChanged;protected PropertyChangedEventHandler PropertyChangedHandler { get; }public void VerifyPropertyName(string propertyName){Type type = GetType();if (!string.IsNullOrEmpty(propertyName) && type.GetTypeInfo().GetDeclaredProperty(propertyName) == null)throw new ArgumentException("找不到属性", propertyName);}public virtual void RaisePropertyChanged([CallerMemberName] string propertyName = null){PropertyChangedEventHandler propertyChanged = PropertyChanged;if (propertyChanged == null)return;propertyChanged(this, new PropertyChangedEventArgs(propertyName));}public virtual void RaisePropertyChanged<T>(Expression<Func<T>> propertyExpression){if (PropertyChanged == null)return;string propertyName = GetPropertyName(propertyExpression);if (string.IsNullOrEmpty(propertyName))return;RaisePropertyChanged(propertyName);}protected static string GetPropertyName<T>(Expression<Func<T>> propertyExpression){if (propertyExpression == null)throw new ArgumentNullException(nameof(propertyExpression));MemberExpression body = propertyExpression.Body as MemberExpression;if (body == null)throw new ArgumentException("参数不合法", nameof(propertyExpression));PropertyInfo member = body.Member as PropertyInfo;if (member == null)throw new ArgumentException("找不到属性", nameof(propertyExpression));return member.Name;}}

至此，我们完成了数据库的配置，内容页基类与 ViewModel基类的编写，接下来可以制作我们的页面了。

很开心，终于到了创建页面的时候了！

我们需要两个页面

MainPage 主页面
MusicItemPage 条目编辑页面

编写主页面

新建一个MainPageViewModel.cs，作为MainPage的ViewModel层

public class MainPageViewModel : ViewModelBase{private readonly IRepository<Song, long> songRepository;public MainPageViewModel(IRepository<Song, long> songRepository){this.RefreshCommand=new Command(Refresh, (o) => true);this.DeleteCommand=new Command(Delete, (o) => true);this.songRepository=songRepository;}private void Delete(object obj){songRepository.Delete(obj as Song);}private async void Refresh(object obj){this.IsRefreshing=true;var getSongs = this.songRepository.GetAllListAsync();await getSongs.ContinueWith(r => IsRefreshing=false);var songs = await getSongs;this.Songs=new ObservableCollection<Song>(songs);}private ObservableCollection<Song> songs;public ObservableCollection<Song> Songs{get { return songs; }set{songs = value;RaisePropertyChanged();}}private Song currentSong;public Song CurrentSong{get { return currentSong; }set{currentSong = value;RaisePropertyChanged();}}private bool _isRefreshing;public bool IsRefreshing{get { return _isRefreshing; }set{_isRefreshing = value;RaisePropertyChanged();}}public Command RefreshCommand { get; set; }public Command DeleteCommand { get; private set; }}

新建一个MainPage页面

编写Xaml为：

注意这个页面将继承MauiBoilerplate.ContentPageBase

<?xml version="1.0" encoding="utf-8" ?>
<mato:ContentPageBase xmlns="http://schemas.microsoft.com/dotnet/2021/maui"xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"xmlns:mato="clr-namespace:MauiBoilerplate;assembly=MauiBoilerplate.Core"x:Class="MauiBoilerplate.MainPage"><Grid><Grid.RowDefinitions><RowDefinition Height="155"></RowDefinition><RowDefinition></RowDefinition></Grid.RowDefinitions><Label Text="My Music" FontSize="65"></Label><ListView Grid.Row="1"ItemsSource="{Binding Songs,Mode=TwoWay}"x:Name="MainListView"RowHeight="74" IsPullToRefreshEnabled="True"IsRefreshing="{Binding IsRefreshing}"RefreshCommand="{Binding RefreshCommand}"SelectedItem="{Binding CurrentSong,Mode=TwoWay}"><ListView.Header><Grid HeightRequest="96"><Grid.RowDefinitions><RowDefinition></RowDefinition><RowDefinition></RowDefinition></Grid.RowDefinitions><Button Clicked="AddButton_Clicked"CornerRadius="100"Text=""HeightRequest="44"WidthRequest="200"FontFamily="FontAwesome"></Button><StackLayout VerticalOptions="End"Margin="0,0,0,8"Grid.Row="1"HorizontalOptions="Center"Orientation="Horizontal"><Label HorizontalTextAlignment="Center"FontSize="Small" Text="{Binding Songs.Count}"></Label><Label  HorizontalTextAlignment="Center"FontSize="Small" Text="首歌"></Label></StackLayout></Grid></ListView.Header><ListView.ItemTemplate><DataTemplate><ViewCell><Grid x:Name="ModeControlLayout" VerticalOptions="CenterAndExpand"><Grid.ColumnDefinitions><ColumnDefinition Width="*" /><ColumnDefinition Width="Auto" /></Grid.ColumnDefinitions><StackLayout Grid.Column="0" HorizontalOptions="Center" VerticalOptions="CenterAndExpand"><Label Text="{Binding MusicTitle}"                                    HorizontalOptions="FillAndExpand" HorizontalTextAlignment="Center" FontSize="Body" /><LabelText="{Binding Artist}" HorizontalOptions="FillAndExpand" HorizontalTextAlignment="Center" FontSize="Body" /></StackLayout><Button x:Name="MoreButton"HeightRequest="44" WidthRequest="44" Margin="10"Text=""Clicked="SongMoreButton_OnClicked"FontFamily="FontAwesome"Grid.Column="1" CornerRadius="100"HorizontalOptions="Center" /></Grid></ViewCell></DataTemplate></ListView.ItemTemplate></ListView></Grid>
</mato:ContentPageBase>

编写CodeBehind为：

注意将它继承ITransientDependency接口

这个页面之前提到过，已经通过IocManager.Resolve(typeof(MainPage))解析出实例并赋值给App.MainPage了。

public partial class MainPage : ContentPageBase, ITransientDependency
{private readonly MainPageViewModel mainPageViewModel;private readonly MusicItemPageViewModel musicItemPageViewModel;private readonly MusicItemPage musicItemPage;public MainPage(MainPageViewModel mainPageViewModel, MusicItemPageViewModel musicItemPageViewModel, MusicItemPage musicItemPage){InitializeComponent();this.mainPageViewModel=mainPageViewModel;this.musicItemPageViewModel=musicItemPageViewModel;this.musicItemPage=musicItemPage;BindingContext=this.mainPageViewModel;}protected override void OnAppearing(){base.OnAppearing();mainPageViewModel.RefreshCommand.Execute(null);}private async void SongMoreButton_OnClicked(object sender, EventArgs e){var currentsong = (sender as BindableObject).BindingContext as Song;string action = await DisplayActionSheet(currentsong.MusicTitle, "取消", null, "修改", "删除");if (action=="修改"){musicItemPageViewModel.CurrentSong  = currentsong;await Navigation.PushModalAsync(musicItemPage);}else if (action=="删除"){mainPageViewModel.DeleteCommand.Execute(currentsong);mainPageViewModel.RefreshCommand.Execute(null);}}private async void AddButton_Clicked(object sender, EventArgs e){musicItemPageViewModel.CurrentSong  = new Song();await Navigation.PushModalAsync(musicItemPage);}
}

此页面将显示一个列表，并在列表条目下可以弹出一个菜单

编写条目编辑页面

新建一个MusicItemPageViewModel.cs，作为MusicItemPage的ViewModel层

public class MusicItemPageViewModel : ViewModelBase{private readonly IIocResolver iocResolver;private readonly IRepository<Song, long> songRepository;public event EventHandler OnFinished;public MusicItemPageViewModel(IIocResolver iocResolver,IRepository<Song, long> songRepository){this.CommitCommand=new Command(Commit, (o) => CurrentSong!=null);this.iocResolver=iocResolver;this.songRepository=songRepository;this.PropertyChanged+=MusicItemPageViewModel_PropertyChanged;}private void MusicItemPageViewModel_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e){if (e.PropertyName==nameof(CurrentSong)){CommitCommand.ChangeCanExecute();}}private void Commit(object obj){songRepository.InsertOrUpdate(currentSong);       }private Song currentSong;public Song CurrentSong{get { return currentSong; }set{currentSong = value;RaisePropertyChanged();}}}

新建一个MusicItemPage 页面

编写Xaml为：

注意这个页面将继承MauiBoilerplate.ContentPageBase

<?xml version="1.0" encoding="utf-8" ?>
<mato:ContentPageBase xmlns="http://schemas.microsoft.com/dotnet/2021/maui"xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"xmlns:mato="clr-namespace:MauiBoilerplate;assembly=MauiBoilerplate.Core"x:Class="MauiBoilerplate.MusicItemPage"><Grid><Grid.RowDefinitions><RowDefinition></RowDefinition><RowDefinition Height="155"></RowDefinition></Grid.RowDefinitions><TableView Intent="Form"><TableRoot><TableSection Title="基础"><EntryCell Label="标题"   Text="{Binding CurrentSong.MusicTitle, Mode=TwoWay}"/><EntryCell  Label="艺术家"  Text="{Binding CurrentSong.Artist, Mode=TwoWay}"/><EntryCell  Label="专辑"  Text="{Binding CurrentSong.Album, Mode=TwoWay}"/></TableSection><TableSection Title="其他"><EntryCell  Label="时长"  Text="{Binding CurrentSong.Duration}"/><EntryCell  Label="发布日期"  Text="{Binding CurrentSong.ReleaseDate}"/></TableSection></TableRoot></TableView><Button x:Name="CommitButton"Grid.Row="1"CornerRadius="100"HeightRequest="44"WidthRequest="200"Text=""Command="{Binding CommitCommand}"FontFamily="FontAwesome"             HorizontalOptions="Center" /></Grid>
</mato:ContentPageBase>

编写CodeBehind为：

注意将它继承ITransientDependency接口

public partial class MusicItemPage : ContentPageBase, ITransientDependency
{private readonly MusicItemPageViewModel musicItemPageViewModel;public MusicItemPage(MusicItemPageViewModel musicItemPageViewModel){InitializeComponent();this.musicItemPageViewModel=musicItemPageViewModel;this.musicItemPageViewModel.OnValidateErrors+=MusicItemPageViewModel_OnValidateErrors;this.musicItemPageViewModel.OnFinished+=MusicItemPageViewModel_OnFinished;BindingContext=this.musicItemPageViewModel;Unloaded+=MusicItemPage_Unloaded;}private async void MusicItemPageViewModel_OnFinished(object sender, EventArgs e){await this.Navigation.PopModalAsync();}private void MusicItemPage_Unloaded(object sender, EventArgs e){musicItemPageViewModel.CurrentSong = null;}private async void MusicItemPageViewModel_OnValidateErrors(object sender, List<System.ComponentModel.DataAnnotations.ValidationResult> e){var content = string.Join(',', e);await DisplayAlert("请注意", content, "好的");}
}

这个页面提供歌曲条目新增和编辑的交互功能

[可选]使用Abp校验数据功能

这个部分使用Abp的ValidationConfiguration功能校验表单数据，以展示Abp功能的使用

首先在MusicItemPageViewModel 构造函数中添加对IValidationConfiguration对象的注入

编辑

添加OnValidateErrors事件，并且在Page中订阅这个事件。此事件将在校验未通过时触发

MusicItemPageViewModel.cs中：

public event EventHandler<List<ValidationResult>> OnValidateErrors;

MusicItemPage.xaml.cs中：

this.musicItemPageViewModel.OnValidateErrors+=MusicItemPageViewModel_OnValidateErrors;

private async void MusicItemPageViewModel_OnValidateErrors(object sender, List<System.ComponentModel.DataAnnotations.ValidationResult> e){var content = string.Join(',', e);await DisplayAlert("请注意", content, "好的");}

编写校验逻辑代码

MusicItemPageViewModel.cs中：

protected List<ValidationResult> GetValidationErrors(Song validatingObject){List<ValidationResult> validationErrors = new List<ValidationResult>();foreach (var validatorType in _configuration.Validators){using (var validator = iocResolver.ResolveAsDisposable<IMethodParameterValidator>(validatorType)){var validationResults = validator.Object.Validate(validatingObject);validationErrors.AddRange(validationResults);}}return validationErrors;}

Commit提交方法，改造如下：

当GetValidationErrors返回的校验错误列表中有内容时，将OnValidateErrors事件Invoke

private void Commit(object obj){var validateErrors = GetValidationErrors(this.CurrentSong);if (validateErrors.Count==0){songRepository.InsertOrUpdate(currentSong);this.OnFinished?.Invoke(this, EventArgs.Empty);}else{OnValidateErrors?.Invoke(this, validateErrors);}}

接下来在实体中定义校验规则，校验器将按照这些规则返回校验结果

public class Song : FullAuditedEntity<long>, IValidatableObject{[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]public override long Id { get; set; }[Required][StringLength(6, ErrorMessage = "歌曲名称要在6个字以内")]public string MusicTitle { get; set; }[Required][StringLength(10, ErrorMessage = "歌曲名称要在10个字以内")]public string Artist { get; set; }[Required][StringLength(10, ErrorMessage = "歌曲名称要在10个字以内")]public string Album { get; set; }public TimeSpan Duration { get; set; }public DateTime ReleaseDate { get; set; }public IEnumerable<ValidationResult> Validate(ValidationContext validationContext){if (ReleaseDate != default && ReleaseDate>DateTime.Now){yield return new ValidationResult("ReleaseDate不能大于当天",new[] { nameof(ReleaseDate) });}}}