1

我在这个项目中使用 Prism.Unity.Forms 和 Xamarin。Client.Id属性更改时如何更新视图？当我将 XAML 从{Binding Client.Id}（一个 Guid 对象）更改为{Binding Client.Name}（一个字符串）时，视图会更新。

public class CreateClientViewModel : BindableBase
{
    private Client _client;
    public Client Client {
        get => _client;
        set => SetProperty(ref _client, value);
    }

    private async void FetchNewClient()
    {
        Client = new Client{
            Id = new Guid.Parse("501f1302-3a45-4138-bdb7-05c01cd9fe71"),
            Name = "MyClientName"
        };
    }
}

这有效

<Entry Text="{Binding Client.Name}"/>

这不

<Entry Text="{Binding Client.Id}"/>

我知道该ToString方法正在Client.Id属性上被调用，因为我将它包装Guid在一个自定义类中并覆盖了该ToString方法，但视图仍然没有更新。

public class CreateClientViewModel : BindableBase
{
    private Client _client;
    public Client Client {
        get => _client;
        set => SetProperty(ref _client, value);
    }

    //This method will eventually make an API call.
    private async void FetchNewClient()
    {
        Client = new Client{
            Id = new ClientId{
                Id = new Guid.Parse("501f1302-3a45-4138-bdb7-05c01cd9fe71")
            },
            Name = "MyClientName"
        };
    }
}

public class ClientId
{
    public Guid Id { get; set }

    public override string ToString()
    {
        //This method gets called
        Console.WriteLine("I GET CALLED");
        return Id.ToString();
    }
}
4

1 回答 1

0

使用Converter解决了问题，但我无法解释原因。Guid.ToString无论哪种方式都调用了该方法。

<Entry Text="{Binding Client.Id, Converter={StaticResource GuidConverter}}"/>

public class GuidConverter : IValueConverter
{
    public object Convert()
    {
        var guid = (Guid) value;
        return guid.ToString();
    }

    public object ConvertBack(){...}
}

然后我在App.xaml

<ResourceDictionary>
    <viewHelpers:GuidConverter x:Key="GuidConverter" />
</ResourceDictionary>
于 2017-07-13T12:56:40.667 回答