不使用代碼隱藏，從文本框中刪除“無”

Question

我有一個使用multibindings生成的運輸標簽，如下所示：

<TextBox x:Name="TextBoxShippingLabel" Margin="0,10,-2,2" TextWrapping="Wrap">
    <TextBox.Text>
        <MultiBinding StringFormat="{}{0} {1}&#x0a;{2}&#x0a;{3}&#x0a;{4}&#x0a;{5}&#x0a;{6} {7}">
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[FirstName]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[Surname]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[Department]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[Organisation]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[Street]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[Suburb]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[State]" />
            <Binding ElementName="dataGridOutstandingOrders" Path="SelectedItem[Postcode]" />
        </MultiBinding>
    </TextBox.Text>
</TextBox>

這很有效，除非組織或部門等數據回復為“無”（在個人訂單的情況下會發生）。 當發生這種情況時，標簽表示如下：

有沒有辦法我可以使用XAML來識別綁定何時返回'None'並使用備用StringFormat ？

Answer 1

我有同樣的問題，我使用了轉換器。 簡單干凈：

  <MultiBinding Converter="{StaticResource TextAlternateConverter}">

public class TextAlternateConverter: IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {

      StringBuilder myOutputText = new StringBuilder();

        foreach (string param in values)
        {
            if (param == "None")
                myOutputText.Append("Give alternate text");
            else
                myOutputText.Append(param);
        }

        return myOutputText.ToString();
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new System.NotImplementedException();
    }
}

Answer 2

我知道你要求沒有代碼隱藏的解決方案。 但是我不認為這是可能的，因為你想在你的字符串格式中有一些“ifs”。 這在后面的代碼中也是不可能的（參見我提供的擴展方法）。

如果你可以擴展SelectedItem （無論可能是什么），我會在那里放置一個屬性。 這可能在將來有用（例如，通過API發送標簽）。 如果無法訪問代碼庫，也可以使用ExtensionMethod 。

您至少有2個“變通辦法”：

代碼背后：

public partial class MainWindow
{
    public MainWindow()
    {
        this.InitializeComponent();

        List<OrderViewModel> newList = new List<OrderViewModel>();

        newList.Add(new OrderViewModel() { FirstName = "foo", LastName = "bar", Organization = "SO", ZipCode = "666" });
        newList.Add(new OrderViewModel() { LastName = "bar", Organization = "SO", ZipCode = "666" });
        newList.Add(new OrderViewModel() { FirstName = "foo", ZipCode = "666" });
        newList.Add(new OrderViewModel() { FirstName = "foo" });
        newList.Add(new OrderViewModel() { FirstName = "foo", LastName = "bar", Organization = "SO", ZipCode = "666" });

        DataContext = newList;
    }
}
public static class Extensions
{
    public static string GenerateShippingLabel(this OrderViewModel order)
    {
        StringBuilder sb = new StringBuilder();

        if (order.FirstName != "None")
        {
            sb.AppendFormat("{0} ", order.FirstName);
        }
        if (order.LastName != "None")
        {
            sb.AppendLine(order.LastName);
        }
        else
        {
            sb.AppendLine();
        }

        if (order.Organization != "None")
        {
            sb.AppendLine(order.Organization);
        }
        if (order.ZipCode != "None")
        {
            sb.AppendLine(order.ZipCode);
        }

        return sb.ToString();
    }
}

public class ShippingLabelConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is OrderViewModel)
        {
            return (value as OrderViewModel).GenerateShippingLabel();
        }
        return "None"; //isn't it ironic? ;-)
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

public class OrderViewModel
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Organization { get; set; }
    public string ZipCode { get; set; }

    public string ShippingLabel
    {
        get
        {
            return this.GenerateShippingLabel();
        }
    }
}

XAML

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <ItemsControl ItemsSource="{Binding}">
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Path=ShippingLabel, Mode=OneWay}" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
    <ItemsControl ItemsSource="{Binding}" Grid.Column="2">
        <ItemsControl.Resources>
            <local:ShippingLabelConverter x:Key="labelConverter" />
        </ItemsControl.Resources>
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <TextBox Text="{Binding Converter={StaticResource labelConverter},Mode=OneWay}" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Grid>