将控件的可见性绑定到IEnumerable的“Count” [英] Binding visibility of a control to 'Count' of an IEnumerable

问题描述

我有一个包含在IEnumerable中的对象列表。
我想根据此列表的计数设置控件的可见性。我试过：

  Visibility ={Binding MyList.Count> 0？Collapsed：Visible，Mode = OneWay}
  

但这不行。我尝试将MyList.Count绑定到文本块中的文本，以确保计数值正确，它是。它似乎没有正确设置可见性。

解决方案

你不能在绑定中使用逻辑或代码表达式（它期望一个 PropertyPath ）。使用转换器或触发器，这是我会做的：

 < YourControl.Style> 
< Style TargetType =YourControl> 
< Setter Property =VisibilityValue =Collapsed/> 
< Style.Triggers> 
< DataTrigger Binding ={Binding MyList.Count}Value =0> 
< Setter Property =VisibilityValue =Visible/> 
< / DataTrigger> 
< /Style.Triggers> 
< / Style> 
< /YourControl.Style> 
  

（您当然可以将风格重构为资源，如果你愿意的话。）

I have a list of objects contained in an IEnumerable<>. I would like to set the visibility of a control based on the count of this list. I have tried:

 Visibility="{Binding MyList.Count>0?Collapsed:Visible, Mode=OneWay}"

But this doesn't work. I tried binding MyList.Count to the text in a text block to ensure that the count value was correct, and it is. It just doesn't seem to set the visibility correctly.

解决方案

You cannot use logical or code-expressions in bindings (it expects a PropertyPath). Either use a converter or triggers, which is what i would do:

<YourControl.Style>                     
    <Style TargetType="YourControl">
        <Setter Property="Visibility" Value="Collapsed" />
        <Style.Triggers>
            <DataTrigger Binding="{Binding MyList.Count}" Value="0">
                <Setter Property="Visibility" Value="Visible" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</YourControl.Style>

(You can of course refactor the style into a resource if you wish.)

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