如何通过一个静态值在XAML来的IValueConverter [英] How to pass a static value to IValueConverter in XAML

问题描述

我想用我的WP7应用程序从Web服务获取静态文本。每个文本具有一个名称（indetifier）和Content属性。

例如文本看起来是这样的：

  NAME =M43; 
含量=这是要显示的文字; 
  

然后，我会想将名字传下去的文字（即标识符）到<$ C 。$ C>的IValueConverter ，然后将查找名称和返回文本

我想转换器是这个样子：

 公共类StaticTextConverter：的IValueConverter 
 {
公共对象转换（对象的值，类型TARGETTYPE，对象参数，CultureInfo的文化）
 {
如果（值= NULL）
 {
返回App.StaticTexts.Items.SingleOrDefault（T =>！t.Name.Equals（值） ）。内容; 
} 
 
返回NULL; 
} 
} 
  

然后在XAML：

 <电话：PhoneApplicationPage.Resources> 
<助手：StaticTextConverter X：NAME =StaticTextConverter/> 
< /电话：PhoneApplicationPage.Resources> 
 
：
 
< TextBlock的文本={结合'M43'，转换器= {StaticResource的StaticTextConverter}}/> 
  

不过，这似乎并没有工作，我不知道我在值传递给变频器正常。

有没有人有一些建议吗？

解决方案

我终于找到了答案。答案是@Shawn Kendrot和另外一个问题我问这里的混合体：的IValueConverter在某些情况下 <没有被调用/ p>

要总结了使用该解决方案的的IValueConverter 我要绑定我在下面的庄园控制：

 <电话：PhoneApplicationPage.Resources> 
<助手：StaticTextConverter X：NAME =TextConverter/> 
< /电话：PhoneApplicationPage.Resources> 
 
< TextBlock的文本={结合转换器= {StaticResource的TextConverter}，ConverterParameter = M62}/> 
  

由于文本的ID与转换器参数传递中，转换器看起来几乎是相同的：

 公共类StaticTextConverter：的IValueConverter 
 {
公共对象转换（对象的值，类型TARGETTYPE，对象参数，CultureInfo的文化）
 {
如果（参数= NULL&放大器;！&放大器;参数是字符串）
 {
返回App.StaticTexts.Items.SingleOrDefault（T =>吨。.Name.Equals（参数））内容; 
} 
 
返回NULL; 
} 
} 
  

然而，事实证明，绑定，从而如果这样做的转换器不调用的不的有的DataContext 。为了解决这个问题，控制的的DataContext 属性只是必须设置的东西随意：

 < TextBlock中的DataContext =任意
文本={结合转换器= {StaticResource的TextConverter}，ConverterParameter = M62}/> 
  

然后一切按预期工作！

I would like to use static texts fetched from a web service in my WP7 app. Each text has a Name (the indetifier) and a Content property.

For example a text could look like this:

Name = "M43";
Content = "This is the text to be shown";

I would then like to pass the Name (i.e. the identifier) of the text to an IValueConverter, which would then look up the the Name and return the text.

I figured the converter to look something like this:

public class StaticTextConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value != null)
        {
            return App.StaticTexts.Items.SingleOrDefault(t => t.Name.Equals(value)).Content;
        }

        return null;
    }
}

Then in the XAML:

<phone:PhoneApplicationPage.Resources>
    <Helpers:StaticTextConverter x:Name="StaticTextConverter" />
</phone:PhoneApplicationPage.Resources>

...

<TextBlock Text="{Binding 'M43', Converter={StaticResource StaticTextConverter}}"/>

However, this does not seem to work and I am not sure that I pass in the value to the converter correctly.

Does anyone have some suggestions?

解决方案

I finally found the answer. The answer was a mix between that of @Shawn Kendrot and another question I asked here: IValueConverter not getting invoked in some scenarios

To summarize the solution for using the IValueConverter I have to bind my control in the following manor:

<phone:PhoneApplicationPage.Resources>
    <Helpers:StaticTextConverter x:Name="TextConverter" />
</phone:PhoneApplicationPage.Resources>

<TextBlock Text="{Binding Converter={StaticResource TextConverter}, ConverterParameter=M62}" />

Since the ID of the text is passed in with the converter parameter, the converter looks almost the same:

public class StaticTextConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (parameter != null && parameter is string)
        {
            return App.StaticTexts.Items.SingleOrDefault(t => t.Name.Equals(parameter)).Content;
        }

        return null;
    }
}

However, as it turns out, the binding and thus the converter is not invoked if it does not have a DataContext. To solve this, the DataContext property of the control just has to be set to something arbitrary:

<TextBlock DataContext="arbitrary" 
           Text="{Binding Converter={StaticResource TextConverter}, ConverterParameter=M62}" />

And then everything works as intended!

这篇关于如何通过一个静态值在XAML来的IValueConverter的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！