用于绑定TextBlock值的UWP类型转换器在设计时未在我的XAML上处理

Question

我正在使用Type Converter对UWP应用中绑定到TextBlocks的文本执行一些字符串操作。我使用了一个类型转换器类，我已经在许多UWP应用程序中使用，没有任何问题。但是在一个新的UWP应用程序中，我一直看到Binding值被传回的问题，并且类型转换器中没有对我传递的值进行任何更改。我一直在使用一个类型转换器，它接受参数来执行自定义操作，这不像我创建的简单的新类型转换器那样工作。奇怪的是，类型转换器在运行时工作，但在设计时被忽略。 以下是我的代码部分和XAML：

这是一个数据类，它为此repro创建样本数据以用于我的绑定：

public class Alerts_DataClass
{
    public string id { get; set; }
    public string severity { get; set; }
    public string status { get; set; }
    public string title { get; set; }
    public DateTime lastEventTime { get; set; }
}


public class AlertsSampleData : Alerts_DataClass
{
    public AlertsSampleData()
    {

        Alerts_DataClass myAlert = new Alerts_DataClass { id = "636531490526731751_2124891065", title = "Category Type XVI", severity = "Medium", lastEventTime = new DateTime(2018, 2, 02) };

        this.id = myAlert.id;
        this.status = myAlert.status;
        this.title = myAlert.title;
        this.lastEventTime = myAlert.lastEventTime;
        this.severity = myAlert.severity;

    }
}

这是XAML：

<Page
    x:Class="NestedBindingsTester.TypeConverterTest"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:NestedBindingsTester"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:sys="using:System"
    mc:Ignorable="d">

    <Page.Resources>

        <local:StringFormatConverterWithChangeType x:Key="StringFormatConverter"/>
        <local:DebugDataBindingConverter x:Key="DebugBinding"/>
        <local:ValueToStringConverter x:Key="valueToStringConverter" />
        <local:AlertsSampleData x:Key="data2"/>

    </Page.Resources>


    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="103*"/>
            <RowDefinition Height="897*"/>
        </Grid.RowDefinitions>

        <StackPanel Grid.Row="1" d:DataContext="{StaticResource data2}">

            <TextBlock Text="{Binding title, ConverterParameter=lower, Converter={StaticResource StringFormatConverter}, Mode=TwoWay}" Style="{StaticResource BaseTextBlockStyle}" Margin="50,0,0,0"  />

            <TextBlock Text="{Binding title, Converter={StaticResource valueToStringConverter}, Mode=TwoWay}" Style="{StaticResource BaseTextBlockStyle}" Margin="50,0,0,0" />

        </StackPanel>

    </Grid>
</Page>

最后这里是两个Type Converter模块。第一个是简单的valueToStringConverter，我只需要传递任何String文本并将其作为小写返回：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Windows.UI.Xaml.Data;

namespace NestedBindingsTester
{

    public sealed class ValueToStringConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, string language)
        {

            //return value?.ToString();
            string strThisTest = value.ToString().ToLower();
            return strThisTest;

        }

        public object ConvertBack(object value, Type targetType, object parameter, string language)
        {
            throw new NotImplementedException("Converting from string is not supported.");
        }
    }

}

我使用的原始类型转换器将参数作为各种操作的开关，称为StringFormatConverter。在我的XAML示例中，我传递了'lower'参数，告诉它将字符串值转换为小写：

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Linq;
using System.Runtime.Serialization;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Windows.UI.Xaml.Data;


namespace NestedBindingsTester
{

    public class DebugDataBindingConverter : IValueConverter
    {
        public object Convert(object value, Type targetType,
            object parameter, CultureInfo culture)
        {
            Debugger.Break();
            return "This is";
            ////return value;
        }

        public object ConvertBack(object value, Type targetType,
            object parameter, CultureInfo culture)
        {
            Debugger.Break();
            return "it";
            ////return value;
        }

        public object Convert(object value, Type targetType, object parameter, string language)
        {
            ////throw new NotImplementedException();
            return "Hello moto";
        }

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


    /// <summary>
    /// Sample usage:
    /// Text="{Binding Budget, Mode=TwoWay, Converter={StaticResource StringFormatConverterWithChangeType}, ConverterParameter='\{0:C2\}'}"
    /// </summary>
    public class StringFormatConverterWithChangeType : IValueConverter
    {
        #region IValueConverter Members


        public object Convert(object value, Type targetType, object parameter, string language)
        {
            //  Used in UWP app
            //
            if (value != null)
            {
                // Arbitrarily remove dollar sign.
                //value = value.ToString().Replace("$", "");
            }
            else
            {
                value = "**NULL**";
            }

            if (parameter != null)
            {
                string formatString = parameter.ToString();
                if (!string.IsNullOrEmpty(formatString))
                {
                    string strValue = value.ToString();
                    if (strValue != null && !string.IsNullOrWhiteSpace(strValue))
                    {
                        switch (formatString)
                        {
                            case "%":           // Add %
                                return String.Format("{0}%", value);
                            case "mi":          // Add miles
                                return String.Format("{0} miles", value);
                            case "caps":        // Convert to Initial caps
                                return UpperCaseFirstCharacter(value.ToString());
                            case "lower":        // Convert to Initial caps
                                return value.ToString().ToLower();
                            case "LiGa":        // Convert from Liters to Gallons
                                {
                                    //
                                    // Convert kilometers to miles.
                                    //  1 liter = 0.264172052 US gallons
                                    //
                                    double lConversion = 0.264172052;
                                    double liters = System.Convert.ToDouble(strValue);
                                    double gallons = lConversion * liters;
                                    return String.Format("{0:N1} gallons", gallons);
                                }
                            case "TimeMath":      // Compute time remaining until fully charged
                                {
                                    int Minutes = System.Convert.ToInt16(value);

                                    DateTime currentTime = DateTime.Now;

                                    TimeSpan twoAndAHalfHours = new TimeSpan(0, Minutes, 0);
                                    DateTime estimatedFullChargedTime = DateTime.Now.AddMinutes(Minutes);
                                    string formattedTime = estimatedFullChargedTime.ToString("HH:mm");

                                    return formattedTime;
                                }
                            case "UTCtoShortDate":  // 02/03.2018
                                {
                                    string utcDate = value.ToString();            // "2018-01-26T02:17:23.5099802Z";
                                    DateTime dateTime;

                                    DateTime.TryParse(utcDate, CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal, out dateTime);
                                    Debug.WriteLine(dateTime.ToString());
                                    string strWDATP_Date = String.Format("{0:MM.dd.yyyy}", dateTime);
                                    return strWDATP_Date;
                                }
                            case "{0:d}":  // Short date.
                            case "{0:D}":   // Long date.
                                ////return String.Format(culture, formatString, System.Convert.ChangeType(value, typeof(DateTime), null));
                                return String.Format("US", formatString, System.Convert.ChangeType(value, typeof(DateTime), null));
                        }
                    }
                    else
                    {
                        return String.Format("US", formatString, value);
                    }
                }
            }

            return value.ToString();


        }

        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value != null)
            {
                // Arbitrarily remove dollar sign.
                //value = value.ToString().Replace("$", "");
            }

            if (parameter != null)
            {
                string formatString = parameter.ToString();
                if (!string.IsNullOrEmpty(formatString))
                {
                    string strValue = value.ToString();
                    if (strValue != null && !string.IsNullOrWhiteSpace(strValue))
                    {
                        switch (formatString)
                        {
                            case "%":           // Add %
                                return String.Format("{0}%", value);
                            case "mi":          // Add miles
                                return String.Format("{0} miles", value);
                            case "caps":        // Convert to Initial caps
                                return UpperCaseFirstCharacter(value.ToString());
                            case "LiGa":        // Convert from Liters to Gallons
                                {
                                    //
                                    // Convert kilometers to miles.
                                    //  1 liter = 0.264172052 US gallons
                                    //
                                    double lConversion = 0.264172052;
                                    double liters = System.Convert.ToDouble(strValue);
                                    double gallons = lConversion * liters;
                                    return String.Format("{0:N1} gallons", gallons);
                                }
                            case "TimeMath":      // Compute time remaining until fully charged
                                {
                                    int Minutes = System.Convert.ToInt16(value);

                                    DateTime currentTime = DateTime.Now;

                                    TimeSpan twoAndAHalfHours = new TimeSpan(0, Minutes, 0);
                                    DateTime estimatedFullChargedTime = DateTime.Now.AddMinutes(Minutes);
                                    string formattedTime = estimatedFullChargedTime.ToString("HH:mm");

                                    return formattedTime;
                                }
                            case "{0:d}":  // Short date.
                            case "{0:D}":   // Long date.
                                return String.Format(culture, formatString, System.Convert.ChangeType(value, typeof(DateTime), null));
                        }
                    }
                    else
                    {
                        return String.Format(culture, formatString, value);
                    }
                }
            }

            return value.ToString();
        }

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

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return value;
        }


        public string UpperCaseFirstCharacter(string text)
        {
            //return Regex.Replace(text, "^[a-z]", m => m.Value.ToUpper());
            return text.First().ToString().ToUpper() + text.Remove(0, 1).ToLower();
        }


        #endregion
    };



}

我正在使用Visual Studio 2017并定位Windows 10 Fall Creators Update SDK（16299）。

我无法发现为什么它不再起作用，因为这些类型转换器在其他两个UWP项目中运行良好。

注意：我在TextBlocks的绑定中使用Binding，因为x：Bind不适用于设计时数据。

感谢您看一下，我一直盯着这段代码，但找不到问题。

瑞克