如何在WPF Visual Studio Designer中显示占位符值，直到可以加载实际值为止 [英] How to display placeholder value in WPF Visual Studio Designer until real value can be loaded

问题描述

我是一位经验丰富的C#开发人员，但还是WPF新手.我无法通过网络搜索找到答案的基本问题(我认为).这是简化的用例...

I'm an experienced C# developer but a WPF newbie. Basic question (I think) that I can't find an answer to by web searching. Here's the simplified use case...

我想在WPF TextBlock中显示一个字符串.所以我在XAML控件的代码后面写了一些C#代码...

I want to display a string in a WPF TextBlock. So I write some C# code in codebehind of my XAML control...

public class MyCoolControl : UserControl
{
   public void InitializeMyCoolControl()
   {
      this.DataContext = "SomeStringOnlyAvailableAtRuntime"; // Perhaps from a database or something...
   }
}

我这样设置我的XAML:

And I set up my XAML like this:

<UserControl ... snip...>
   <!-- Bind the textblock to whatever's in the DataContext -->
   <TextBlock Text="{Binding}"></TextBlock>
</UserControl>

效果很好，我在执行应用程序时可以看到值"SomeStringOnlyAvailableAtRuntime".但是，使用Visual Studio 2008的XAML设计器在设计时看不到任何东西.

Works great, I can see the value "SomeStringOnlyAvailableAtRuntime" when I execute my application. However, I don't see anything at Design Time using Visual Studio 2008's XAML Designer.

在设计时如何查看文本块的占位符值(任何值)?

How can I see a placeholder value (anything) for the textblock at design time?

谢谢！

-迈克

推荐答案

在设计用户控件时，我经常在绑定上使用FallbackValue进行查看.例如:

I often use FallbackValue on the binding to have something to look at while I design user controls. For example:

<TextBlock Text={Binding Path=AverageValue, FallbackValue=99.99} />

但是，由于FallbackValue不仅在设计时应用，因此如果出于其他原因要在运行时使用FallbackValue，这可能不合适.

However, since FallbackValue is not just applied at design time, this might not be appropriate if you want to use FallbackValue at run time for other reasons.

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