wpf XAML 中的布尔命令参数
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Boolean CommandParameter in XAML
提问by Matěj Zábsky
I have this code (which works just right):
我有这个代码（它工作得恰到好处）：
<KeyBinding Key="Enter" Command="{Binding ReturnResultCommand}">
<KeyBinding.CommandParameter>
<s:Boolean>
True
</s:Boolean>
</KeyBinding.CommandParameter>
</KeyBinding>
Where "s" is of course the System namespace.
其中“s”当然是系统命名空间。
But this command is called quite a few times and it really inflates otherwise rather simple XAML code. Is this really the shortest notation of boolean command parameter in XAML (other than splitting the command into several commands)?
但是这个命令被调用了很多次，它确实膨胀了其他相当简单的 XAML 代码。这真的是 XAML 中布尔命令参数的最短表示法（除了将命令拆分为多个命令）？
回答by H.B.
This might be a bit of a hack but you can derive from the KeyBindingclass:
这可能有点小技巧，但您可以从KeyBinding该类派生：
public class BoolKeyBinding : KeyBinding
{
public bool Parameter
{
get { return (bool)CommandParameter; }
set { CommandParameter = value; }
}
}
Usage:
用法：
<local:BoolKeyBinding ... Parameter="True"/>
And another not so weird solution:
另一个不那么奇怪的解决方案：
xmlns:s="clr-namespace:System;assembly=mscorlib"
<Application.Resources>
<!-- ... -->
<s:Boolean x:Key="True">True</s:Boolean>
<s:Boolean x:Key="False">False</s:Boolean>
</Application.Resources>
Usage:
用法：
<KeyBinding ... CommandParameter="{StaticResource True}"/>
回答by Gordon
The easiest is to define the following in the Resources
最简单的是在资源中定义以下内容
<System:Boolean x:Key="FalseValue">False</System:Boolean>
<System:Boolean x:Key="TrueValue">True</System:Boolean>
and use it like:
并使用它：
<Button CommandParameter="{StaticResource FalseValue}"/>
回答by Onur
I just found an even more generic solution with this markup extension:
我刚刚用这个标记扩展找到了一个更通用的解决方案：
public class SystemTypeExtension : MarkupExtension
{
private object parameter;
public int Int{set { parameter = value; }}
public double Double { set { parameter = value; } }
public float Float { set { parameter = value; } }
public bool Bool { set { parameter = value; } }
// add more as needed here
public override object ProvideValue(IServiceProvider serviceProvider)
{
return parameter;
}
}
Usage ("wpf:" is the namespace where the extension lives in):
用法（“wpf:”是扩展所在的命名空间）：
<KeyBinding Key="F8" Command="{Binding SomeCommand}" CommandParameter="{wpf:SystemType Bool=True}"/>
You even get the options Trueand Falseafter typing Bool=and type safety!
您还可以得到的选项True，并False键入之后Bool=和类型安全！
回答by javicabanas
Or, maybe that:
或者，也许是：
<Button.CommandParameter>
<s:Boolean>True</s:Boolean>
</Button.CommandParameter>
Where s is the namespace:
其中 s 是命名空间：
xmlns:s="clr-namespace:System;assembly=mscorlib"
回答by Bala R
Perhaps something like
也许像
<KeyBinding Key="Enter" Command="{Binding ReturnResultCommand}"
CommandParameter="{x:Static StaticBoolean.True}" />
where StaticBooleanis
这里StaticBoolean是
public static class StaticBoolean
{
public static bool True
{
get { return true; }
}
}
回答by Mark A. Donohoe
Here's another approach where you define your own markup extensions that return Trueor False(or any other value you wish). Then you simply use them right in XAML like any other markup extension:
这是另一种方法，您可以定义自己的标记扩展，返回Trueor False（或您希望的任何其他值）。然后，您只需像任何其他标记扩展一样直接在 XAML 中使用它们：
public class TrueExtension : MarkupExtension {
public override object ProvideValue(IServiceProvider serviceProvider) => true;
}
public class FalseExtension : MarkupExtension {
public override object ProvideValue(IServiceProvider serviceProvider) => false;
}
public class DoubleExtension : MarkupExtension {
public DoubleExtension(){};
public DoubleExtension(double value) => Value = value;
public double Value { get; set; }
public override object ProvideValue(IServiceProvider serviceProvider) => Value;
}
You then use them like this (assuming your imported namespace is mx):
然后您可以像这样使用它们（假设您导入的命名空间是mx）：
<KeyBinding Key="Enter"
Command="{Binding ReturnResultCommand}"
CommandParameter="{mx:True}" />
<Button Visibility="{Binding SomeProperty,
Converter={SomeBoolConverter},
ConverterParameter={mx:True}}">
<!-- This guarantees the value passed is a double equal to 42.5 -->
<Button Visibility="{Binding SomeProperty,
Converter={SomeDoubleConverter},
ConverterParameter={mx:Double 42.5}}">
I actually define lots of custom MarkupExtensionclasses for a lot of common things that I don't want to necessarily store in my resources.
我实际上MarkupExtension为很多我不想存储在我的资源中的常见事物定义了很多自定义类。
