我有一个这样的enum:
public enum MyLovelyEnum
{
FirstSelection,
TheOtherSelection,
YetAnotherOne
};
我在DataContext中有一个属性:
public MyLovelyEnum VeryLovelyEnum { get; set; }
我有三个电台按钮在我的WPF客户端。
<RadioButton Margin="3">First Selection</RadioButton>
<RadioButton Margin="3">The Other Selection</RadioButton>
<RadioButton Margin="3">Yet Another one</RadioButton>
现在，我如何绑定RadioButtons属性为适当的双向绑定?
当前回答
您可以进一步简化已接受的答案。你可以显式地传入枚举值而不是字符串，而不是字符串表示，正如CrimsonX所评论的那样，错误会在编译时而不是运行时抛出:
ConverterParameter = {x:静态局部:YourEnumType。Enum1}
<StackPanel>
<StackPanel.Resources>
<local:ComparisonConverter x:Key="ComparisonConverter" />
</StackPanel.Resources>
<RadioButton IsChecked="{Binding Path=YourEnumProperty, Converter={StaticResource ComparisonConverter}, ConverterParameter={x:Static local:YourEnumType.Enum1}}" />
<RadioButton IsChecked="{Binding Path=YourEnumProperty, Converter={StaticResource ComparisonConverter}, ConverterParameter={x:Static local:YourEnumType.Enum2}}" />
</StackPanel>
然后简化转换器:
public class ComparisonConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value?.Equals(parameter);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value?.Equals(true) == true ? parameter : Binding.DoNothing;
}
}
编辑(12月16 - 10日):
感谢anon建议返回Binding。DoNothing而不是DependencyProperty.UnsetValue。
注意-多个组的radiobutton在同一个容器(Feb 17 '11):
In xaml, if radio buttons share the same parent container, then selecting one will de-select all other's within that container (even if they are bound to a different property). So try to keep your RadioButton's that are bound to a common property grouped together in their own container like a stack panel. In cases where your related RadioButtons cannot share a single parent container, then set the GroupName property of each RadioButton to a common value to logically group them.编辑(4月5日至11日)
Simplified ConvertBack's if-else to use a Ternary Operator.注意-嵌套在类中的Enum类型(Apr 28 '11):
If your enum type is nested in a class (rather than directly in the namespace), you might be able to use the '+' syntax to access the enum in XAML as stated in a (not marked) answer to the question :ConverterParameter = {x:静态局部:YourClass + YourNestedEnumType。Enum1}
然而，由于这个Microsoft Connect问题，VS2010中的设计器在加载时将不再提示“Type' local:YourClass+YourNestedEnumType' was not found.”，但项目确实编译并成功运行。当然，如果能够将枚举类型直接移动到名称空间，则可以避免此问题。
编辑(2012年1月27日):
If using Enum flags, the converter would be as follows:public class EnumToBooleanConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return ((Enum)value).HasFlag((Enum)parameter);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value.Equals(true) ? parameter : Binding.DoNothing;
}
}
编辑(2015年5月7日):
In case of a Nullable Enum (that is **not** asked in the question, but can be needed in some cases, e.g. ORM returning null from DB or whenever it might make sense that in the program logic the value is not provided), remember to add an initial null check in the Convert Method and return the appropriate bool value, that is typically false (if you don't want any radio button selected), like below: public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value == null) {
return false; // or return parameter.Equals(YourEnumType.SomeDefaultValue);
}
return value.Equals(parameter);
}
注- NullReferenceException(10月10日'18):
Updated the example to remove the possibility of throwing a NullReferenceException. `IsChecked` is a nullable type so returning `Nullable` seems a reasonable solution.其他回答
你可以动态创建单选按钮，ListBox可以帮助你做到这一点，不需要转换器，非常简单。
具体步骤如下:
创建一个ListBox，并设置ListBox的ItemsSource为enum MyLovelyEnum，并将ListBox的SelectedItem绑定到VeryLovelyEnum属性。 然后为每个ListBoxItem创建单选按钮。
步骤1:将枚举添加到窗口、用户控件或网格等的静态资源中。
<Window.Resources>
<ObjectDataProvider MethodName="GetValues"
ObjectType="{x:Type system:Enum}"
x:Key="MyLovelyEnum">
<ObjectDataProvider.MethodParameters>
<x:Type TypeName="local:MyLovelyEnum" />
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
</Window.Resources>
步骤2:使用列表框和控制模板填充每个项目作为单选按钮
<ListBox ItemsSource="{Binding Source={StaticResource MyLovelyEnum}}" SelectedItem="{Binding VeryLovelyEnum, Mode=TwoWay}" >
<ListBox.Resources>
<Style TargetType="{x:Type ListBoxItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<RadioButton
Content="{TemplateBinding ContentPresenter.Content}"
IsChecked="{Binding Path=IsSelected,
RelativeSource={RelativeSource TemplatedParent},
Mode=TwoWay}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ListBox.Resources>
</ListBox>
这样做的好处是:如果有一天你的枚举类改变了，你不需要更新GUI (XAML文件)。
引用: https://brianlagunas.com/a-better-way-to-data-bind-enums-in-wpf/
UWP的双向绑定解决方案，需要使用Nullable:
c#的部分:
public class EnumConverter : IValueConverter
{
public Type EnumType { get; set; }
public object Convert(object value, Type targetType, object parameter, string lang)
{
if (parameter is string enumString)
{
if (!Enum.IsDefined(EnumType, value)) throw new ArgumentException("value must be an Enum!");
var enumValue = Enum.Parse(EnumType, enumString);
return enumValue.Equals(value);
}
return value.Equals(Enum.ToObject(EnumType,parameter));
}
public object ConvertBack(object value, Type targetType, object parameter, string lang)
{
if (parameter is string enumString)
return value?.Equals(true) == true ? Enum.Parse(EnumType, enumString) : null;
return value?.Equals(true) == true ? Enum.ToObject(EnumType, parameter) : null;
}
}
在这里，空值充当Binding.DoNothing。
private YourEnum? _yourEnum = YourEnum.YourDefaultValue; //put a default value here
public YourEnum? YourProperty
{
get => _yourEnum;
set{
if (value == null) return;
_yourEnum = value;
}
}
Xaml“:
...
<Page.Resources>
<ResourceDictionary>
<helper:EnumConverter x:Key="YourConverter" EnumType="yournamespace:YourEnum" />
</ResourceDictionary>
</Page.Resources>
...
<RadioButton GroupName="YourGroupName" IsChecked="{Binding Converter={StaticResource YourConverter}, Mode=TwoWay, Path=YourProperty, ConverterParameter=YourEnumString}">
First way (parameter of type string)
</RadioButton>
<RadioButton GroupName="LineWidth">
<RadioButton.IsChecked>
<Binding
Converter="{StaticResource PenWidthConverter}"
Mode="TwoWay" Path="PenWidth">
<Binding.ConverterParameter>
<yournamespace:YourEnum>YourEnumString</yournamespace:YourEnum>
</Binding.ConverterParameter>
</Binding>
</RadioButton.IsChecked>
Second way (parameter of type YourEnum (actually it was converted to int when passed to converter))
</RadioButton>
处理这种情况的一种方法是在ViewModel类中使用单独的bool属性。以下是我处理这种情况的方法:
ViewModel:
public enum MyLovelyEnum { FirstSelection, TheOtherSelection, YetAnotherOne };
private MyLovelyEnum CurrentSelection;
public bool FirstSelectionProperty
{
get
{
return CurrentSelection == MyLovelyEnum.FirstSelection;
}
set
{
if (value)
CurrentSelection = MyLovelyEnum.FirstSelection;
}
}
public bool TheOtherSelectionProperty
{
get
{
return CurrentSelection == MyLovelyEnum.TheOtherSelection;
}
set
{
if (value)
CurrentSelection = MyLovelyEnum.TheOtherSelection;
}
}
public bool YetAnotherOneSelectionProperty
{
get
{
return CurrentSelection == MyLovelyEnum.YetAnotherOne;
}
set
{
if (value)
CurrentSelection = MyLovelyEnum.YetAnotherOne;
}
}
XAML:
<RadioButton IsChecked="{Binding SimilaritySort, Mode=TwoWay}">Similarity</RadioButton>
<RadioButton IsChecked="{Binding DateInsertedSort, Mode=TwoWay}">Date Inserted</RadioButton>
<RadioButton IsChecked="{Binding DateOfQuestionSort, Mode=TwoWay}">Date of Question</RadioButton>
<RadioButton IsChecked="{Binding DateModifiedSort, Mode=TwoWay}">Date Modified</RadioButton>
它不像其他解决方案那样健壮或动态，但优点是它是非常自包含的，不需要创建自定义转换器或类似的东西。
基于Scott的EnumToBooleanConverter。 我注意到ConvertBack方法在带有标志的Enum代码上不起作用。
我尝试了以下代码:
public class EnumHasFlagToBooleanConverter : IValueConverter
{
private object _obj;
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
_obj = value;
return ((Enum)value).HasFlag((Enum)parameter);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value.Equals(true))
{
if (((Enum)_obj).HasFlag((Enum)parameter))
{
// Do nothing
return Binding.DoNothing;
}
else
{
int i = (int)_obj;
int ii = (int)parameter;
int newInt = i+ii;
return (NavigationProjectDates)newInt;
}
}
else
{
if (((Enum)_obj).HasFlag((Enum)parameter))
{
int i = (int)_obj;
int ii = (int)parameter;
int newInt = i-ii;
return (NavigationProjectDates)newInt;
}
else
{
// do nothing
return Binding.DoNothing;
}
}
}
}
唯一一件我不能得到的工作是做一个类型转换从int到targetType，所以我把它硬编码到NavigationProjectDates，我使用的enum。并且，targetType == NavigationProjectDates…
编辑更多通用Flags Enum转换器:
public class FlagsEnumToBooleanConverter : IValueConverter {
private int _flags=0;
public object Convert(object value, Type targetType, object parameter, string language) {
if (value == null) return false;
_flags = (int) value;
Type t = value.GetType();
object o = Enum.ToObject(t, parameter);
return ((Enum)value).HasFlag((Enum)o);
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
if (value?.Equals(true) ?? false) {
_flags = _flags | (int) parameter;
}
else {
_flags = _flags & ~(int) parameter;
}
return _flags;
}
}
对于EnumToBooleanConverter的答案: 而不是返回DependencyProperty。考虑返回Binding。对于单选按钮IsChecked值变为false的情况不做任何事情。 前者表示有问题(可能会向用户显示一个红色矩形或类似的验证指示器)，而后者只是表示不应该做任何事情，这正是在这种情况下所需要的。
http://msdn.microsoft.com/en-us/library/system.windows.data.ivalueconverter.convertback.aspx http://msdn.microsoft.com/en-us/library/system.windows.data.binding.donothing.aspx
