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
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>
其他回答
您可以使用更通用的转换器
public class EnumBooleanConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
string parameterString = parameter as string;
if (parameterString == null)
return DependencyProperty.UnsetValue;
if (Enum.IsDefined(value.GetType(), value) == false)
return DependencyProperty.UnsetValue;
object parameterValue = Enum.Parse(value.GetType(), parameterString);
return parameterValue.Equals(value);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
string parameterString = parameter as string;
if (parameterString == null)
return DependencyProperty.UnsetValue;
return Enum.Parse(targetType, parameterString);
}
#endregion
}
在xaml部分中，您使用:
<Grid>
<Grid.Resources>
<l:EnumBooleanConverter x:Key="enumBooleanConverter" />
</Grid.Resources>
<StackPanel >
<RadioButton IsChecked="{Binding Path=VeryLovelyEnum, Converter={StaticResource enumBooleanConverter}, ConverterParameter=FirstSelection}">first selection</RadioButton>
<RadioButton IsChecked="{Binding Path=VeryLovelyEnum, Converter={StaticResource enumBooleanConverter}, ConverterParameter=TheOtherSelection}">the other selection</RadioButton>
<RadioButton IsChecked="{Binding Path=VeryLovelyEnum, Converter={StaticResource enumBooleanConverter}, ConverterParameter=YetAnotherOne}">yet another one</RadioButton>
</StackPanel>
</Grid>
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;
}
}
我已经创建了一个新类来处理绑定RadioButtons和复选框到枚举。它适用于标记的枚举(有多个复选框选择)，也适用于单个选择复选框或单选按钮的非标记枚举。它也根本不需要ValueConverters。
这可能一开始看起来比较复杂，但是，一旦您将这个类复制到您的项目中，它就完成了。它是通用的，所以可以很容易地在任何枚举中重用。
public class EnumSelection<T> : INotifyPropertyChanged where T : struct, IComparable, IFormattable, IConvertible
{
private T value; // stored value of the Enum
private bool isFlagged; // Enum uses flags?
private bool canDeselect; // Can be deselected? (Radio buttons cannot deselect, checkboxes can)
private T blankValue; // what is considered the "blank" value if it can be deselected?
public EnumSelection(T value) : this(value, false, default(T)) { }
public EnumSelection(T value, bool canDeselect) : this(value, canDeselect, default(T)) { }
public EnumSelection(T value, T blankValue) : this(value, true, blankValue) { }
public EnumSelection(T value, bool canDeselect, T blankValue)
{
if (!typeof(T).IsEnum) throw new ArgumentException($"{nameof(T)} must be an enum type"); // I really wish there was a way to constrain generic types to enums...
isFlagged = typeof(T).IsDefined(typeof(FlagsAttribute), false);
this.value = value;
this.canDeselect = canDeselect;
this.blankValue = blankValue;
}
public T Value
{
get { return value; }
set
{
if (this.value.Equals(value)) return;
this.value = value;
OnPropertyChanged();
OnPropertyChanged("Item[]"); // Notify that the indexer property has changed
}
}
[IndexerName("Item")]
public bool this[T key]
{
get
{
int iKey = (int)(object)key;
return isFlagged ? ((int)(object)value & iKey) == iKey : value.Equals(key);
}
set
{
if (isFlagged)
{
int iValue = (int)(object)this.value;
int iKey = (int)(object)key;
if (((iValue & iKey) == iKey) == value) return;
if (value)
Value = (T)(object)(iValue | iKey);
else
Value = (T)(object)(iValue & ~iKey);
}
else
{
if (this.value.Equals(key) == value) return;
if (!value && !canDeselect) return;
Value = value ? key : blankValue;
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged([CallerMemberName] string propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
至于如何使用它，假设你有一个手动或自动运行任务的枚举，可以安排在一周的任何一天，以及一些可选选项…
public enum StartTask
{
Manual,
Automatic
}
[Flags()]
public enum DayOfWeek
{
Sunday = 1 << 0,
Monday = 1 << 1,
Tuesday = 1 << 2,
Wednesday = 1 << 3,
Thursday = 1 << 4,
Friday = 1 << 5,
Saturday = 1 << 6
}
public enum AdditionalOptions
{
None = 0,
OptionA,
OptionB
}
下面是使用这个类的简单程度:
public class MyViewModel : ViewModelBase
{
public MyViewModel()
{
StartUp = new EnumSelection<StartTask>(StartTask.Manual);
Days = new EnumSelection<DayOfWeek>(default(DayOfWeek));
Options = new EnumSelection<AdditionalOptions>(AdditionalOptions.None, true, AdditionalOptions.None);
}
public EnumSelection<StartTask> StartUp { get; private set; }
public EnumSelection<DayOfWeek> Days { get; private set; }
public EnumSelection<AdditionalOptions> Options { get; private set; }
}
下面是用这个类绑定复选框和单选按钮的简单方法:
<StackPanel Orientation="Vertical">
<StackPanel Orientation="Horizontal">
<!-- Using RadioButtons for exactly 1 selection behavior -->
<RadioButton IsChecked="{Binding StartUp[Manual]}">Manual</RadioButton>
<RadioButton IsChecked="{Binding StartUp[Automatic]}">Automatic</RadioButton>
</StackPanel>
<StackPanel Orientation="Horizontal">
<!-- Using CheckBoxes for 0 or Many selection behavior -->
<CheckBox IsChecked="{Binding Days[Sunday]}">Sunday</CheckBox>
<CheckBox IsChecked="{Binding Days[Monday]}">Monday</CheckBox>
<CheckBox IsChecked="{Binding Days[Tuesday]}">Tuesday</CheckBox>
<CheckBox IsChecked="{Binding Days[Wednesday]}">Wednesday</CheckBox>
<CheckBox IsChecked="{Binding Days[Thursday]}">Thursday</CheckBox>
<CheckBox IsChecked="{Binding Days[Friday]}">Friday</CheckBox>
<CheckBox IsChecked="{Binding Days[Saturday]}">Saturday</CheckBox>
</StackPanel>
<StackPanel Orientation="Horizontal">
<!-- Using CheckBoxes for 0 or 1 selection behavior -->
<CheckBox IsChecked="{Binding Options[OptionA]}">Option A</CheckBox>
<CheckBox IsChecked="{Binding Options[OptionB]}">Option B</CheckBox>
</StackPanel>
</StackPanel>
When the UI loads, the "Manual" radio button will be selected and you can alter your selection between "Manual" or "Automatic" but either one of them must always be selected. Every day of the week will be unchecked, but any number of them can be checked or unchecked. "Option A" and "Option B" will both initially be unchecked. You can check one or the other, checking one will uncheck the other (similar to RadioButtons), but now you can also uncheck both of them (which you cannot do with WPF's RadioButton, which is why CheckBox is being used here)
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>
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/
