在wpf中使用带枚举的转换器 [英] Using converters with enums in wpf
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问题描述
我想在组合框中显示之前更改枚举字符串值。在这种情况下，我希望橙子显示为Juicy oranges等。
< 窗口 x：Class = Window1
xmlns = http://schemas.microsoft.com/winfx/2006/xaml/presentation
xmlns：x = http://schemas.microsoft.com/winfx/2006/ xaml
xmlns：System = clr-namespace ：System; assembly = mscorlib
xmlns：local = clr-namespace：FruitProject
标题 = Window1 高度 = 300 W宽度 = 300 >
< Window.Resources >
< local：EnumConverter x：Key = fruitImprover > < / local：EnumConverter >
< ObjectDataProvider MethodName = GetValue s
ObjectType = {x：Type System：Enum}
< span class =code-attribute> x：Key = deliciousFruits >
< ObjectDataProvider.MethodParameters >
< x：输入 TypeName = local：Window1 + Fruit / >
< / ObjectDataProvider.MethodParameters >
< / ObjectDataProvider >
< / Window.Resources >
< 网格 > ;
< Grid.ColumnDefinitions >
< ColumnDefinition 宽度 = * > < / ColumnDefinition >
< ColumnDefinition 宽度 = * > < / ColumnDefinition >
< ColumnDefinition 宽度 = * > < / ColumnDefinition >
< /Grid.ColumnDefinitions >
< Grid.RowDefinitions >
< RowDefinition 高度 = * > < / RowDefinition >
< RowDefinition 高度 = .25 * > < / RowDefinition >
< RowDefinition < span class =code-attribute> 高度 = * > < / RowDefinition >
< / Grid.RowDefinitions >
< ComboBox Grid.Column = 1 Grid.Row = 1 ItemsSource = {Binding Source = {StaticResource deliciousFruits}，Converter = {StaticResource fruitImprover}} > < / ComboBox >
< / Grid >
< / Window >
window1后面的VB代码是
< span class =code-keyword>公开 类 Window1
公开 < span class =code-keyword> Enum Fruit
Oranges
苹果
李子
结束 枚举
结束 类
我的转换器类是：
公共 类 EnumConverter
< span class =code-keyword> Implements IValueConverter
公共 功能转换（值作为 对象，targetType 作为类型，参数作为 对象，culture As Globalization.CultureInfo）作为 对象 实施 IValueConverter.Convert
Dim f As Window1.Fruit = CType （value，Window1.Fruit）
选择 案例 f
案例 Window1.Fruit.Apples
返回 多汁苹果
案例 Window1.Fruit.Oranges
< span class =code-keyword>返回 甜橙
案例 Window1.Fruit.Plums
返回 紫色李子
结束 选择
结束 功能
公共 功能 ConvertBack（值 As 对象，targetType 作为类型，参数 As 对象，culture 作为 Globalization.CultureInfo） As 对象 实施 IValueConverter.ConvertBack
返回 4
结束 功能
结束 类
我收到以下错误消息当我尝试将值转换为水果枚举时。
从'Fruit（）'类型转换为类型'整数'无效。
有什么想法吗？
解决方案
我会看下面的文章：使用DescriptionAttribute绑定到ComboBox的枚举 [ ^ ]
< blockquote>是的，不要这样做（我从来没有设法让这种方法工作0。你可以使用一种更好的方法，我认为它更易于使用。使用枚举上的[Description（）]属性如下：
公开 枚举水果
<说明（ Juicy Oranges）>
橘子
<描述（ 嘎吱嘎嘎的苹果）>
苹果
李子
结束 枚举
然后使用转换器从绑定对象中检索描述属性。
公开 类 EnumDescriptionConverter
Implements IValueConverter
私有 功能 GetEnumDescription（enumObj As [ 枚举]）作为 字符串
Dim fieldInfo As FieldInfo = enumObj。[ GetType ]（）。GetField（enumObj.ToString（））
Dim attribArray As Object （）= fieldInfo.GetCustomAttributes（ False ）
如果 attribArray.Length = 0 那么
返回 enumObj.ToString（）
否则
Dim attrib As DescriptionAttribute = TryCast （attribArray（ 0 ），DescriptionAttribute）
返回 attrib.Description
结束 如果
结束 功能
私有 功能 IValueConverter_Convert（value 作为 Object ，targetType As 类型，参数 As < span class =code-keyword> Object ，culture As CultureInfo） As 对象 实现 IValueConverter.Convert
Dim myEnum 作为 [枚举] = DirectCast （值，[枚举]）
Dim description 正如 字符串 = GetEnumDescription（myEnum）
返回说明
< span class =code-keyword>结束 功能
私人 功能 IValueConverter_ConvertBack（值作为 对象，targetType 作为类型，参数作为 对象，culture 作为 CultureInfo）作为 对象 实现 IValueConverter.ConvertBack
返回 字符串 .Empty
结束 功能
结束 类
然后在组合框中将数据源设置为数据提供者并设置DisplayMemberPath转换器。
Combobox XAML：
< ; combobox itemssource < span class =code-keyword> = {Binding Source = {StaticResource deliciousFruits}} > ;
< combobox.itemtemplate >
< datatemplate >
< textblock text = {绑定转换器= {StaticResource fruitImprover}} > < / textblock >
< / datatemplate >
< / combobox.itemtemplate >
< / combobox >
I want to change the enum string value before I display it in a combo box. In this case I want "oranges to display as "Juicy oranges" etc.
<Window x:Class="Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:System="clr-namespace:System;assembly=mscorlib"
xmlns:local="clr-namespace:FruitProject"
Title="Window1" Height="300" Width="300">
<Window.Resources>
<local:EnumConverter x:Key="fruitImprover"></local:EnumConverter>
<ObjectDataProvider MethodName="GetValues"
ObjectType="{x:Type System:Enum}"
x:Key="deliciousFruits">
<ObjectDataProvider.MethodParameters>
<x:Type TypeName="local:Window1+Fruit" />
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
</Window.Resources>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height=".25*"></RowDefinition>
<RowDefinition Height="*"></RowDefinition>
</Grid.RowDefinitions>
<ComboBox Grid.Column="1" Grid.Row="1" ItemsSource="{Binding Source={StaticResource deliciousFruits}, Converter={StaticResource fruitImprover}}"></ComboBox>
</Grid>
</Window>
The VB code behind window1 is
Public Class Window1
Public Enum Fruit
Oranges
Apples
Plums
End Enum
End Class
My converter class is:
Public Class EnumConverter
Implements IValueConverter
Public Function Convert(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.Convert
Dim f As Window1.Fruit = CType(value, Window1.Fruit)
Select Case f
Case Window1.Fruit.Apples
Return "Juicy apples"
Case Window1.Fruit.Oranges
Return "Sweet Oranges"
Case Window1.Fruit.Plums
Return "Purple Plums"
End Select
End Function
Public Function ConvertBack(value As Object, targetType As Type, parameter As Object, culture As Globalization.CultureInfo) As Object Implements IValueConverter.ConvertBack
Return 4
End Function
End Class
I get the following error message when I try and convert value to a fruit enumeration.
Conversion from type 'Fruit()' to type 'Integer' is not valid.
Any ideas ?
解决方案
I would look at the following article: Using DescriptionAttribute for enumerations bound to a ComboBox[^]
Yes, don't do it like that (I never managed to get that approach to work0. There is a much better approach you can use which I think is more re-usable. Use the [Description()] Attribute on your enum like this:
Public Enum Fruit <Description("Juicy Oranges")> Oranges <Description("Crunchy Apples")> Apples Plums End Enum
Then use a converter that retrieves description attributes from the bound object.
Public Class EnumDescriptionConverter Implements IValueConverter Private Function GetEnumDescription(enumObj As [Enum]) As String Dim fieldInfo As FieldInfo = enumObj.[GetType]().GetField(enumObj.ToString()) Dim attribArray As Object() = fieldInfo.GetCustomAttributes(False) If attribArray.Length = 0 Then Return enumObj.ToString() Else Dim attrib As DescriptionAttribute = TryCast(attribArray(0), DescriptionAttribute) Return attrib.Description End If End Function Private Function IValueConverter_Convert(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.Convert Dim myEnum As [Enum] = DirectCast(value, [Enum]) Dim description As String = GetEnumDescription(myEnum) Return description End Function Private Function IValueConverter_ConvertBack(value As Object, targetType As Type, parameter As Object, culture As CultureInfo) As Object Implements IValueConverter.ConvertBack Return String.Empty End Function End Class
Then in your combo box set the datasource to your dataprovider and set the DisplayMemberPath to the converter.
Combobox XAML:
<combobox itemssource="{Binding Source={StaticResource deliciousFruits}}"> <combobox.itemtemplate> <datatemplate> <textblock text="{Binding Converter={StaticResource fruitImprover}}"></textblock> </datatemplate> </combobox.itemtemplate> </combobox>
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