Prism 6 DelegateCommand ObservesProperty code

本文关键字：code ObservesProperty DelegateCommand Prism | 更新日期: 2023-09-27 18:21:28

大家好，我对WPF和MVVM设计模式很陌生，我从PRISM的布莱恩·拉古纳斯爵士的博客和视频中学到了很多。。但我只是想问一个小问题。。我的代码出了什么问题，对我来说不起作用…任何帮助都非常感谢。这是我的代码：

我的视图模型

public class Person : BindableBase
{
    private myPErson _MyPerson;
    public myPErson MyPerson
    {
        get { return _MyPerson; }
        set
        {
            SetProperty(ref _MyPerson, value);
        }
    }
    public Person()
    {
        _MyPerson = new myPErson();
        updateCommand = new DelegateCommand(Execute, CanExecute).ObservesProperty(() => MyPerson.FirstName).ObservesProperty(() => MyPerson.Lastname);
    //    updateCommand = new DelegateCommand(Execute).ObservesCanExecute((p) => CanExecute); /// JUST WANNA TRY THIS BUT DUNNO HOW
    }
    private bool CanExecute()
    {
        return !String.IsNullOrWhiteSpace(MyPerson.FirstName) && !String.IsNullOrWhiteSpace(MyPerson.Lastname);
    }
    private void Execute()
    {
        MessageBox.Show("HOLA");
    }
    public DelegateCommand updateCommand { get; set; }
}

myModel

声明给另一个类文件

public class myPErson : BindableBase
{
    private string _firstName;
    public string FirstName
    {
        get { return _firstName; }
        set
        {
            SetProperty(ref _firstName, value);
        }
    }
    private string _lastname;
    public string Lastname
    {
        get { return _lastname; }
        set
        {
            SetProperty(ref _lastname, value);
        }
    }
}

查看Xaml代码

<Window x:Class="Prism6Test.Views.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:myVM="clr-namespace:Prism6Test.ViewModel"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <myVM:Person x:Key="mainVM"/>
    </Window.Resources>
<Grid DataContext="{StaticResource mainVM}">
        <TextBox HorizontalAlignment="Left" Height="23" Margin="217,103,0,0" TextWrapping="Wrap" Text="{Binding MyPerson.FirstName,UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top" Width="120"/>
        <TextBox HorizontalAlignment="Left" Height="23" Margin="217,131,0,0" TextWrapping="Wrap" Text="{Binding MyPerson.Lastname,UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Top" Width="120"/>
        <Button Content="Button" Command="{Binding updateCommand}" HorizontalAlignment="Left" Margin="242,159,0,0" VerticalAlignment="Top" Width="75"/>
    </Grid>
</Window>

我已经读过了，但它对我不起作用。我不明白如何正确地编码它。请帮我解决这个问题。。希望尽快得到答复。。thx

ObservesProperty方法不是'；t观测模型'；s在Prism 6 上的特性

Prism 6 DelegateCommand ObservesProperty code

1）你不能随心所欲地使用复杂的数据模型，所以试试

private myPErson _MyPerson;
    public myPErson MyPerson
    {
        get { return _MyPerson; }
        set
        {
            if (_MyPerson != null)
                _MyPerson.PropertyChanged -= MyPersonOnPropertyChanged;
            SetProperty(ref _MyPerson, value);

            if (_MyPerson != null)
                _MyPerson.PropertyChanged += MyPersonOnPropertyChanged;
        }
    }
    private void MyPersonOnPropertyChanged(object sender, PropertyChangedEventArgs propertyChangedEventArgs)
    {
        updateCommand.RaiseCanExecuteChanged();
    }

2） 更改您的构造函数

public Person()
    {
        MyPerson = new myPErson();
        updateCommand = new DelegateCommand(Execute, CanExecute);
    }

首先我要介绍一下您的命名。明确你的课程名称。调用ViewModel，例如PersonViewModel，或者在应用程序不是Person时仅调用ViewModel，因为Person显然是模型。此外，myPErson是一个非常糟糕的名称，因为它与您的其他Person类非常相似，您应该使用PascalCase作为类名。

现在转到您的代码。我对Prism一无所知，所以我的代码只依赖于MVVM模式，而没有Prism库的支持。

首先，我想更改模型Person。这个类在我的代码中看起来很简单（只使用自动属性）：

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Person()
    {
        this.LastName = string.Empty;
        this.FirstName = string.Empty;
    }
}

PersonViewModel稍微复杂一点，因为它实现了INotifyPropertyChanged接口。我也在使用非常常见的RelayCommand，你可以在接受答案下的链接中找到它。

public class PersonViewModel : INotifyPropertyChanged
{
    private Person person;
    private ICommand updateCommand;
    public PersonViewModel()
    {
        this.Person = new Person();
    }
    public event PropertyChangedEventHandler PropertyChanged;
    public Person Person
    {
        get
        {
            return this.person;
        }
        set
        {
            this.person = value;
            // if you use VS 2015 or / and C# 6 you also could use
            // this.OnPropertyChanged(nameof(Person));
            this.OnPropertyChanged("Person");
        }
    }
    public ICommand UpdateCommand
    {
        get
        {
            if (this.updateCommand == null)
            {
                this.updateCommand = new RelayCommand<Person>(this.OpenMessageBox, this.OpenMessageBoxCanExe);
            }
            return this.updateCommand;
        }
    }
    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    private void OpenMessageBox(Person person)
    {
        MessageBox.Show("Hola");
    }
    private bool OpenMessageBoxCanExe(Person person)
    {
        if (person == null)
        {
            return false;
        }
        if (string.IsNullOrWhiteSpace(person.FirstName) || string.IsNullOrWhiteSpace(person.LastName))
        {
            return false;
        }
        return true;
    }
}

我把你的观点澄清了一点，因为它现在短多了。但总的来说，一切都保持不变。我刚刚将属性和内容重命名为：

<Window ...>
    <Window.Resources>
        <wpfTesst:PersonViewModel x:Key="ViewModel" />
    </Window.Resources>
    <Grid DataContext="{StaticResource ViewModel}">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <TextBox Grid.Row="0" TextWrapping="Wrap" Text="{Binding Person.FirstName, UpdateSourceTrigger=PropertyChanged}" />
        <TextBox Grid.Row="1" TextWrapping="Wrap" Text="{Binding Person.LastName, UpdateSourceTrigger=PropertyChanged}" />
        <Button Grid.Row="2" Content="Button" Command="{Binding UpdateCommand}" CommandParameter="{Binding Person}"/>
    </Grid>
</Window>

总而言之，我建议您使用没有Prism库的通用MVVM模式。当你理解MVVM很好的时候，你仍然可以选择Prism。希望能有所帮助。

查看Xaml代码

<Window x:Class="Prism6Test.Views.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:myVM="clr-namespace:Prism6Test.ViewModel"
    Title="MainWindow" Height="350" Width="525">

您缺少ViewModelLocator

    xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
    prism:ViewModelLocator.AutowireViewModel="True"
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