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DevExpress WPF入门指南 - 运行时生成的POCO视图模型(一)

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POCO(Plain Old CLR Objects)视图模型简化并加快了开发过程。

POCO 视图模型允许您:

这允许您创建干净、简单、可维护和可测试的 MVVM 代码,POCO 视图模型与任何 WPF 控件完全兼容。

您可以使用在编译时生成的视图模型在编译时为您的视图模型生成样板代码。

DevExpress WPF v21.2正式版下载

生成 POCO 视图模型的基础知识

POCO 类不实现接口,也不需要继承自基类,例如 ViewModelBase 或 BindableBase。要将 POCO 类转换为功能齐全的 ViewModel,请使用 DevExpress.Mvvm.POCO.ViewModelSource.Create 方法创建一个类实例,请参见下面的示例。

C#

public class LoginViewModel {
//This property will be converted to a bindable one
public virtual string UserName { get; set; }

//SaveAccountSettingsCommand will be created for the SaveAccountSettings and CanSaveAccountSettings methods:
//SaveAccountSettingsCommand = new DelegateCommand<string>(SaveAccountSettings, CanSaveAccountSettings);
public void SaveAccountSettings(string fileName) {
//...
}
public bool CanSaveAccountSettings(string fileName) {
return !string.IsNullOrEmpty(fileName);
}

//We recommend that you not use public constructors to prevent creating the View Model without the ViewModelSource
protected LoginViewModel() { }
//This is a helper method that uses the ViewModelSource class for creating a LoginViewModel instance
public static LoginViewModel Create() {
return ViewModelSource.Create(() => new LoginViewModel());
}
}

您可以使用 ViewModelSource 类在 XAML 中创建视图模型实例。

XAML

<UserControl x:Class="DXPOCO.Views.LoginView"
xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm"
xmlns:ViewModels="clr-namespace:DXPOCO.ViewModels"
DataContext="{dxmvvm:ViewModelSource Type=ViewModels:LoginViewModel}"
...>
<Grid>
<!--...-->
</Grid>
</UserControl>

ViewModelSource.Create 方法使用Reflection Emit 创建指定 ViewModel 类的后代,并在运行时返回后代类实例。 下面的代码类似于 ViewModelSource 基于 LoginViewModel 类生成的代码。

C#

public class LoginViewModel_EXTENSION : LoginViewModel, INotifyPropertyChanged {
public override string UserName {
get { return base.UserName; }
set {
if(base.UserName == value) return;
base.UserName = value;
RaisePropertyChanged("UserName");
}
}
DelegateCommand<string> saveAccountSettingsCommand;
public DelegateCommand<string> SaveAccountSettingsCommand {
get {
return saveAccountSettingsCommand ??
(saveAccountSettingsCommand =
new DelegateCommand<string>(SaveAccountSettings, CanSaveAccountSettings));
}
}

//INotifyPropertyChanged Implementation
}
将参数传递给 ViewModel 构造函数

您可以使用以下任何方法将参数传递给 ViewModel 的构造函数。

C#

ViewModelSource.Create(() => new LoginViewModel(caption: "Login") {
UserName = "John Smith"
});

C#

var factory = ViewModelSource.Factory((string caption) => new LoginViewModel(caption));
factory("Login");

这个例子演示了如何使用 POCO 机制来创建视图模型。

LoginView.xaml

<UserControl x:Class="Example.View.LoginView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:ViewModel="clr-namespace:Example.ViewModel"
xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm"
xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" d:DesignHeight="500" d:DesignWidth="600"
DataContext="{dxmvvm:ViewModelSource Type=ViewModel:LoginViewModel}">

<dxmvvm:Interaction.Behaviors>
<dx:DXMessageBoxService/>
</dxmvvm:Interaction.Behaviors>

<Grid x:Name="LayoutRoot" Background="White">
<StackPanel Orientation="Vertical">
<StackPanel Orientation="Horizontal" Margin="10">
<TextBlock Text="UserName: " Margin="3" VerticalAlignment="Center"/>
<TextBox Text="{Binding UserName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Margin="3" Width="80"/>
</StackPanel>
<Button Content="Login" Command="{Binding LoginCommand}" Margin="5"
HorizontalAlignment="Left"/>
</StackPanel>
</Grid>
</UserControl>

LoginViewModel.cs

using DevExpress.Mvvm;
using DevExpress.Mvvm.DataAnnotations;
using DevExpress.Mvvm.POCO;

namespace Example.ViewModel {
[POCOViewModel]
public class LoginViewModel {
public static LoginViewModel Create() {
return ViewModelSource.Create(() => new LoginViewModel());
}
protected LoginViewModel() { }

public virtual string UserName { get; set; }
public void Login() {
this.GetService<IMessageBoxService>().Show("Login succeeded", "Login", MessageButton.OK, MessageIcon.Information, MessageResult.OK);
}
public bool CanLogin() {
return !string.IsNullOrEmpty(UserName);
}
}
}

LoginViewModel.vb

Imports DevExpress.Mvvm
Imports DevExpress.Mvvm.DataAnnotations
Imports DevExpress.Mvvm.POCO

Namespace Example.ViewModel
<POCOViewModel> _
Public Class LoginViewModel
Public Shared Function Create() As LoginViewModel
Return ViewModelSource.Create(Function() New LoginViewModel())
End Function
Protected Sub New()
End Sub

Public Overridable Property UserName() As String
Public Sub Login()
Me.GetService(Of IMessageBoxService)().Show("Login succeeded", "Login", MessageButton.OK, MessageIcon.Information, MessageResult.OK)
End Sub
Public Function CanLogin() As Boolean
Return Not String.IsNullOrEmpty(UserName)
End Function
End Class
End Namespace

DevExpress WPF | 下载试用

DevExpress WPF拥有120+个控件和库,将帮助您交付满足甚至超出企业需求的高性能业务应用程序。通过DevExpress WPF能创建有着强大互动功能的XAML基础应用程序,这些应用程序专注于当代客户的需求和构建未来新一代支持触摸的解决方案。 无论是Office办公软件的衍伸产品,还是以数据为中心的商业智能产品,都能通过DevExpress WPF控件来实现。


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标签:UserName,POCO,DevExpress,视图,LoginViewModel,ViewModelSource,public
来源: https://www.cnblogs.com/AABBbaby/p/16177446.html