ReactiveUI WPF - 获取文本框的最后一个字

Question

我知道这是一个微不足道的程序，但我正在学习 ReactiveUI，并且首先是整个 MVVN 的新手。我正在尝试从文本框中输入的全名中获取名字和姓氏，并将它们显示在单独的文本块中。

我成功了，但我的问题是，有没有一种方法可以只使用 LINQ 样式扩展来完成姓氏，或者我是否必须使用 select(GetLast) 调用另一个函数，如下所示？而且，如果有一种方法可以使用 LINQ 样式扩展来做到这一点，那么这样做更好还是使用 select(GetLast)?

如果您想提供任何其他意见，我们将不胜感激。预先感谢您提供的任何帮助。

MainWindowViewModel.cs

private string _fullName;
public string FullName
{
    get => _fullName;
    set => this.RaiseAndSetIfChanged(ref _fullName, value);
}

private readonly ObservableAsPropertyHelper<string> _firstName;
public string FirstName => _firstName.Value;

private readonly ObservableAsPropertyHelper<string> _lastName;
public string LastName => _lastName.Value;

public MainWindowViewModel()
{
    _lastName = this.WhenAnyValue(x => x.FullName)
        .Select(full => full?.Trim())
        .DistinctUntilChanged()
        .Where(full => full != null)
        .Select(GetLast)                                   //<-- Point of question
        .ToProperty(this, x => x.LastName, out _lastName);

    _firstName = this.WhenAnyValue(x => x.FullName)
        .Select(full => full?.Trim())
        .DistinctUntilChanged()
        .Where(full => full != null)
        .Select(full => full.Split(' ')[0])
        .ToProperty(this, nameof(FirstName), out _firstName);
}

private string GetLast(string name)
{
    string[] splitName = name.Split(' ');
    if (splitName.Length > 2)
        return splitName[splitName.Length - 1];
    if (splitName.Length == 2)
        return splitName[1];                
    return string.Empty;
}

MainWindow.xaml

<Label Content="_Full Name:"
    Grid.Column="1" Grid.Row="2"
    FontWeight="SemiBold"
    Target="{Binding ElementName=fullNameTextBox}"/>
<TextBlock Text="First Name:"
    Grid.Column="2" Grid.Row="2"
    FontWeight="SemiBold"
    Padding="5,5,0,5"/>
<TextBlock Text="Last Name:"
    Grid.Column="3" Grid.Row="2"
    FontWeight="SemiBold"
    Padding="5,5,0,5"/>

<TextBox x:Name="fullNameTextBox"
    Grid.Column="1" Grid.Row="3"
    MinWidth="150"/>
<TextBlock x:Name="firstNameTextBlock"
    Grid.Column="2" Grid.Row="3"
    MinWidth="75"
    Margin="5,0,0,0"/>
<TextBlock x:Name="lastNameTextBlock"
    Grid.Column="3" Grid.Row="3"
    MinWidth="75"
    Margin="5,0,0,0"/>

MainWindow.xaml.cs

this.WhenActivated(disposableRegistration =>
{
    this.OneWayBind(ViewModel,
            vm => vm.FirstName,
            v => v.firstNameTextBlock.Text)
        .DisposeWith(disposableRegistration);

    this.OneWayBind(ViewModel,
            vm => vm.LastName,
            v => v.lastNameTextBlock.Text)
        .DisposeWith(disposableRegistration);

    this.Bind(ViewModel,
            vm => vm.FullName,
            v => v.fullNameTextBox.Text)
        .DisposeWith(disposableRegistration);
});

Answer 1

*更新

怎么样

_lastName = this.WhenAnyValue(x => x.FullName)
.Select(full => full?.Trim())
.DistinctUntilChanged()
.Where(full => !string.IsNullOrWhitespace(full))
.Select(x => x.Split(' ').Last())
.ToProperty(this, x => x.LastName, out _lastName);

至于 "is this better"，老实说，那是你的决定。我认为这非常简单 - 它只是 linq - 但可能是您的同事不太会说 linq，并且更喜欢他们可以进行单元测试并轻松掌握的单独方法。

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