基于对象类型的 WPF 触发器
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原文地址: http://stackoverflow.com/questions/1652341/
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WPF Trigger based on Object Type
提问by Exist
Is there a way to do a comparison on object type for a trigger?
有没有办法对触发器的对象类型进行比较？
<DataTrigger Binding="{Binding SelectedItem}" Value="SelectedItem's Type">
</DataTrigger>
Background: I have a Toolbar and I want to Hide button's depending on what subclass is currently set to the selected item object.
背景：我有一个工具栏，我想根据当前设置为所选项目对象的子类来隐藏按钮。
Thanks
谢谢
采纳答案by AndyG
Why not just use a converter that takes an object and returns a string of the object type?
为什么不使用一个接受对象并返回对象类型字符串的转换器呢？
Binding="{Binding SelectedItem, Converter={StaticResource ObjectToTypeString}}"
Binding="{Binding SelectedItem, Converter={StaticResource ObjectToTypeString}}"
and define the converter as:
并将转换器定义为：
public class ObjectToTypeStringConverter : IValueConverter
{
public object Convert(
object value, Type targetType,
object parameter, System.Globalization.CultureInfo culture)
{
return value.GetType().Name;
}
public object ConvertBack(
object value, Type targetType,
object parameter, System.Globalization.CultureInfo culture)
{
// I don't think you'll need this
throw new Exception("Can't convert back");
}
}
You'll need to declare the static resource somewhere in your xaml:
您需要在 xaml 中的某处声明静态资源：
<Window.Resources>
<convs:ObjectToTypeStringConverter x:Key="ObjectToTypeString" />
</Window.Resources>
Where 'convs' in this case is the namespace of where the converter is.
在这种情况下，'convs' 是转换器所在的命名空间。
Hope this helps.
希望这可以帮助。
回答by Greg Sansom
This is based on @AndyG's answer but is a bit safer because it's strongly typed.
这是基于@AndyG 的答案，但更安全一些，因为它是强类型的。
Implement an IValueConverter named DataTypeConverter, which accepts an object and returns its Type (as a System.Type):
实现一个名为 DataTypeConverter 的 IValueConverter，它接受一个对象并返回它的类型（作为 System.Type）：
public class DataTypeConverter:IValueConverter
{
public object Convert(object value, Type targetType, object parameter,
CultureInfo culture)
{
return value?.GetType() ?? Binding.DoNothing;
}
public object ConvertBack(object value, Type targetType, object parameter,
CultureInfo culture)
{
throw new NotImplementedException();
}
}
Change your DataTrigger to use the Converter, and set the value to the Type:
更改您的 DataTrigger 以使用转换器，并将值设置为类型：
<DataTrigger Binding="{Binding SelectedItem,
Converter={StaticResource DataTypeConverter}}"
Value="{x:Type local:MyType}">
...
</DataTrigger>
Declare DataTypeConverter in the resources:
在资源中声明 DataTypeConverter：
<UserControl.Resources>
<v:DataTypeConverter x:Key="DataTypeConverter"></v:DataTypeConverter>
</UserControl.Resources>
回答by Thomas Levesque
Using a converter as suggested by AndyG is a good option. Alternatively, you could also use a different DataTemplatefor each target type. WPF will automatically pick the DataTemplatethat matches the object type
使用 AndyG 建议的转换器是一个不错的选择。或者，您也可以DataTemplate为每个目标类型使用不同的。WPF 将自动选择DataTemplate与对象类型匹配的
回答by mYnDstrEAm
Not a trigger but this worked for me. (The trigger-approach didn't as it can't create a checkbox for a string. This is pretty much Thomas Levesque's suggestion)
不是触发器，但这对我有用。（触发器方法没有，因为它无法为字符串创建复选框。这几乎是Thomas Levesque 的建议）
using:
使用：
xmlns:mscorlib="clr-namespace:System;assembly=mscorlib"
? A CheckBox or TextBox depending on the type:
? 一个 CheckBox 或 TextBox 取决于类型：
<ContentPresenter Content="{TemplateBinding SelectedItem}">
<ContentPresenter.Resources>
<DataTemplate DataType="{x:Type mscorlib:Boolean}">
<CheckBox Height="25" Width="25" HorizontalAlignment="Left" IsChecked="{Binding Path=.}"/>
</DataTemplate>
<DataTemplate DataType="{x:Type mscorlib:String}">
<TextBox Height="25" Width="200" HorizontalAlignment="Left" Text="{Binding Path=.}"/>
</DataTemplate>
</ContentPresenter.Resources>
</ContentPresenter>
Note: for Greg Sansom's solution you either got to return the type as String or use mscorlib as above
注意：对于 Greg Sansom 的解决方案，您必须将类型返回为 String 或使用 mscorlib 如上所述
回答by sa.he
If you are in a position to modify the (base) type assigned to 'SelectedItem' by adding the property:
如果您可以通过添加属性来修改分配给“SelectedItem”的（基本）类型：
public Type Type => this.GetType();
Then you could use the DataTrigger in xaml like this:
然后你可以像这样在 xaml 中使用 DataTrigger：
<DataTrigger Binding="{Binding SelectedItem.Type}" Value="{x:Type local:MyClass}">
</DataTrigger>
Advantage compared to AndyG's good answer is, that you do not have a magic string of your type in XAML, but have everything compile safe. Disadvantage: You need to modify your model - which might not always be possible.
与 AndyG 的好答案相比的优势在于，您在 XAML 中没有您类型的魔法字符串，但所有内容都可以编译安全。缺点：您需要修改您的模型 - 这可能并不总是可行的。
