I have been through this How to bind RadioButtons to an enum?
and accepted answer to this question contains use of generic Enum to Boolean converter.
my problem is that I am having two radio buttons in View and an enum
public Enum LinkType
{
A,
B,
C,
D,
E,
F
}
In ViewModel I have a property Called
public LinkType MyLinktype
{
get;set;
}
my first radio button can be true if property of enum in ViewModel is having value among A,C,E and second radio button can be true if property of enum in ViewModel is having value among.
B,D,F
So, How can I pass multiple values in the converter parameter in generic EnumTo Boolean Converter which is as following
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);
}
So what changes I have to make in converter if I want something like this in the XAML
<RadioButton IsChecked="{Binding Path=MyLinktype, Converter={StaticResource enumBooleanConverter}, ConverterParameter=A,C,F}">Odd LinkType</RadioButton>
<RadioButton IsChecked="{Binding Path=Mylinktype, Converter={StaticResource enumBooleanConverter}, ConverterParameter=B,D,E}">Even Link Type</RadioButton>
You can define an array in xaml:
<x:Array Type="LinkType" x:Key="ar">
<LinkType>A</LinkType>
<LinkType>B</LinkType>
</x:Array>
And then pass it as parameter
<RadioButton IsChecked="{Binding Path=MyLinktype, Converter={StaticResource enumBooleanConverter}, ConverterParameter={StaticResource ar}}">Odd LinkType</RadioButton>
You'll have to fix your converter tho, in order to properly handle array as converter parameter.
Firstly, I think "Flags" attribute is the key to resolve the problem:
[Flags]
public enum LinkType
{
A=1,
B=2,
C=4,
D=8,
E=16
}
And then, I implement the converter like this:
public class LinkTypeToBoolCvt : IValueConverter
{
#region | Members of IValueConverter |
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
// please refer to the implementation of "CallBack" method
throw new NotImplementedException();
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value == null || parameter == null) return DependencyProperty.UnsetValue;
var param= parameter.ToString();
int result;
if (int.TryParse(param,out result))
{
// ex: if the parameter is 11, the result will be "A|B|D"
return result;
}
else
{
// ex: if the parameter is "A|E", the result will be 17
var enums = param.Split(new []{"|"}, StringSplitOptions.RemoveEmptyEntries);
LinkType lt = 0;
LinkType ltTemp = 0;
foreach (var item in enums)
{
if (Enum.TryParse<LinkType>(item, out ltTemp)) lt |= ltTemp;
}
if (lt == 0) return DependencyProperty.UnsetValue;
else return lt;
}
}
#endregion
}
And, in Xaml you can use it like this:
<RadioButton IsChecked="{Binding .MyLinkType,Converter={StaticResource LinkTypeToBoolCvt},ConverterParameter=11}" />
Also like this:
<RadioButton IsChecked="{Binding .MyLinkType,Converter={StaticResource LinkTypeToBoolCvt},ConverterParameter=A|B|D}" />
if you dont use "Flags" attribute, you cannot transfer the result like "A|B|D" back to your model.
Finally, I should apologize for my poor english. ^-^
You can use following enum to boolean converter
[ValueConversion(typeof(Enum), typeof(bool))]
public class EnumToBooleanConverter : IValueConverter
{
public object Convert(object value,
Type targetType,
object parameter,
CultureInfo culture)
{
if (
(value == null)
||
(!(value is Enum))
||
(parameter == null)
)
{
return false;
}
foreach (Enum paramValue in ParseObjectToEnum(value.GetType(),
parameter))
{
if (value.Equals(paramValue))
{
return true;
}
}
return false;
}
public object ConvertBack(object value,
Type targetType,
object parameter,
CultureInfo culture)
{
object result = Binding.DoNothing;
if ((bool)value)
{
Enum[] parsedValues = ParseObjectToEnum(targetType,
parameter);
if (parsedValues.Length > 0)
{
result = parsedValues[0];
}
}
return result;
}
private static Enum[] ParseObjectToEnum(Type enumType,
object value)
{
var enumValue = value as Enum;
if (enumValue != null)
{
return new[] { enumValue };
}
var str = value as string;
if (string.IsNullOrEmpty(str))
{
throw new ArgumentException("parameter");
}
string[] strArray = str.Split(new[] { ';', ',' },
StringSplitOptions.RemoveEmptyEntries);
var enumArray = new Enum[strArray.Length];
for (int i = 0;
i < strArray.Length;
i++)
{
enumArray[i] = (Enum)Enum.Parse(enumType,
strArray[i],
true);
}
return enumArray;
}
}
and in xaml you can use like
<RadioButton IsChecked="{Binding Path=MyLinktype, Converter={StaticResource enumBooleanConverter}, ConverterParameter=A;C;F}">Odd LinkType</RadioButton>
where enumBooleanConverter is the above converter
Related
I have this value converter which converts a number to a brush color. What I need to do is to change the line return Brushes.Red; into return (Brush)FindResource("PrimaryHueMidBrush");, so I can return the color of the main theme. The problem is that I don't know how to declare (Brush)FindResource("PrimaryHueMidBrush");. Any help is welcome. Thank you in advance.
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
double.TryParse(value.ToString(), out double val);
if (val == 1)
{
return Brushes.Red;
}
else if(val == 0.5)
{
return Brushes.MediumVioletRed;
}
else if(val==0)
{
return Brushes.Transparent;
}
else
{
return Brushes.Transparent;
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
Instead of calling FindResource in the converter, you'd better add one or more properties for the dynamic Brushes:
public class YourConverter : IValueConverter
{
public Brush FirstBrush { get; set; }
public Brush SecondBrush { get; set; }
public object Convert(
object value, Type targetType, object parameter, CultureInfo culture)
{
double val = (double)value;
if (val >= 1)
{
return FirstBrush;
}
if (val >= 0.5)
{
return SecondBrush;
}
return Brushes.Transparent;
}
public object ConvertBack(
object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
You would declare it in the Resources of your Application or Window like this:
<local:YourConverter x:Key="YourConverter"
FirstBrush="{StaticResource PrimaryHueMidBrush}"
SecondBrush="MediumVioletRed"/>
To access FindResource you need a FrameworkElement so the best way to do this would probably be to use a MultiValueConverter instead and pass the element that uses the converter as a second value.
Converter:
public class WhateverThisIsCalledConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
// Insert type- and sanity-checks here
double val = (double)values[0];
FrameworkElement callingElement = (FrameworkElement)values[1];
if (val >= 1)
{
return callingElement.FindResource("PrimaryHueMidBrush");
}
if (val >= 0.5)
{
return Brushes.MediumVioletRed;
}
return Brushes.Transparent;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
return Enumerable.Repeat(DependencyProperty.UnsetValue, targetTypes.Length).ToArray();
}
}
Usage in XAML:
<Window.Resources>
<local:WhateverThisIsCalledConverter x:Key="Converter"/>
<SolidColorBrush Color="Red" x:Key="PrimaryHueMidBrush"/>
</Window.Resources>
<Grid>
<Grid.Background>
<MultiBinding Converter="{StaticResource Converter}">
<Binding Path="Value"/>
<Binding RelativeSource="{RelativeSource Self}"/>
</MultiBinding>
</Grid.Background>
</Grid>
Couple of notes on your current implementation:
Try avoiding == on doubles, they are not infinitely precice.
You don't need all those elses when you return in the if before.
The ConvertBack method should be implemented (Free choice of other Exceptions, Binding.DoNothing and DependencyProperty.UnsetValue).
If you know your value is a double, simply cast it instead.
I have the following consts I use to check the database values f.e.:
public static class ConnectionConst
{
public const int NotConnected = 0;
public const int Connected = 1;
public const int Unknown = 2;
// ...
}
Now I don't want to show the integer values in the datagrid but the values of the const properties. F.e. 'Connected' instead of '1'.
why not using an enum:
public enum ConnectionConst
{
NotConnected = 0,
Connected = 1,
Unknown = 2
}
You can have a variable of this type:
ConnectionConst connectionState = ConnectionConst.Unknown;
and in the DataGridView the value "Unknown" should appear
EDIT:
if you are already using C# 6 or higher you could also use nameof in your example with the static class:
string value = nameof(ConnectionConst.Unknown);
If you want to display name with spaces like Not Connected instead of NotConnected you can try to use this:
public enum ConnectionConst
{
[Description("Not Connected")]
NotConnected = 0,
[Description("Connected")]
Connected = 1,
[Description("Unknown")]
Unknown = 2
}
public static string DisplayEnumName(Enum value)
{
var name = value.GetType().GetField(value.ToString());
var attributes = (DescriptionAttribute[])name.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attributes != null && attributes.Length > 0) {
return attributes(0).Description;
} else {
return value.ToString();
}
}
Then just use this:
var name = DisplayEnumName(ConnectionConst.NotConnected);
In addition to what XardasLord and DavidG suggested, I'd put that enum description getting code into an IValueConverter.
public class EnumDescriptionConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == null)
return "";
string stringRepresentation = value.ToString();
Type T = value.GetType();
if (!T.IsEnum) return stringRepresentation;
MemberInfo[] enumMembers = T.GetMember(stringRepresentation);
if (enumMembers.Length <= 0) return stringRepresentation;
DescriptionAttribute[] memberAttributes = enumMembers[0].GetCustomAttributes(typeof(DescriptionAttribute), false) as DescriptionAttribute[];
if (memberAttributes == null) return stringRepresentation;
if (memberAttributes.Length <= 0) return stringRepresentation;
return memberAttributes[0].Description;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
// Or Binding.DoNothing, or throw an Exception, whichever you prefer
return DependencyProperty.UnsetValue;
}
}
And use it in the Binding of your Column:
<DataGrid>
<DataGrid.Resources>
<local:EnumDescriptionConverter x:Key="DescriptionConverter"/>
</DataGrid.Resources>
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Path=YourMemberNameHere, Converter={StaticResource DescriptionConverter}}"/>
</DataGrid.Columns>
</DataGrid>
I have a set of classes with a set of properties like this; Each having a custom attribute indicating the possible values it could take. Is there anyway to databind these values to a combobox instead of hardcoding using <ComboBoxItem/> ?
[Values("Cash","Bank","Not Applicable")]
public Nullable<int> PaymentMethod{ get; set; }
Edit: My attribute looks like this
class ValuesAttribute:Attribute
{
public List<string> values { get; set; }
public ValuesAttribute(params String[] values)
{
this.values= new List<string>();
foreach (var v in values)
{
this.values.Add(v);
}
}
}
I would use a converter for this. Send it the underlying object and the property name as the parameter. Return a key/value array so that you can bind both the value (index/enum value) and display text:
<ComboBox ItemsSource="{Binding ConverterParameter='PaymentMethod',Converter={StaticResource AttributeConverter}}"
DisplayMemberPath="Value" SelectedValuePath="Key"
/>
The converter can then get the values using reflection:
public class AttributeConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value != null && parameter as string != null)
{
var property = value.GetType().GetProperty((string)parameter);
if (property != null)
{
var attribute = property.GetCustomAttributes(typeof(ValuesAttribute), false).OfType<ValuesAttribute>().FirstOrDefault();
if (attribute != null)
return attribute.values.Select((display, index) =>
new KeyValuePair<int, string>(index, display)
).ToArray();
}
}
return DependencyProperty.UnsetValue;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
Note: if you need to do this a lot in your application, it might be worthwhile subclassing ComboBox, or creating a Behavior that applies the relevant properties.
I am using an enum to enlist values in my combobox.
I want to write a converter that would show the "description" of the selected enum value. And, when selected, it would return the enum value.
Most of the converters online have not implemented the ConvertBack() method (which is why I am posting here).
Here is ConvertBack method:
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value;
}
Full Converter Code:
public class EnumConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value == null) return DependencyProperty.UnsetValue;
return GetDescription((Enum)value);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value;
}
public static string GetDescription(Enum en)
{
Type type = en.GetType();
MemberInfo[] memInfo = type.GetMember(en.ToString());
if (memInfo != null && memInfo.Length > 0)
{
object[] attrs = memInfo[0].GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attrs != null && attrs.Length > 0)
{
return ((DescriptionAttribute)attrs[0]).Description;
}
}
return en.ToString();
}
}
EDIT
Here is my ComboBox XAML:
<ComboBox ItemsSource="{Binding SampleValues}"
SelectedItem="{Binding SelectedValue, Converter={StaticResource enumConverter}}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=., Converter={StaticResource enumConverter}}" />
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
I know this is an old question, but for some reason, this is rather complicated, even though it seems like it'd be a pretty common task (I'm currently doing this on a UWP app). Using a combination of the accepted answer, some other items I found, and a bit of my own work, here's the simplest way I've found to accomplish this menial task. In short:
Define your enum along w/ setting the description in the Display attribute
Create a converter that converts from an enum value to the description
In your viewmodel, expose a collection of enum values from which to choose, the selected enum value, then initialize those
Define a couple of handy enum extension methods
Finally, some simple binding to the ComboBox, just overriding its ItemTemplate to use the converter.
Enum
public enum EnumOptions
{
[Display(Description = "Option 1")]
OptionOne= 1,
[Display(Description = "Option 2")]
OptionTwo,
[Display(Description = "Option 3")]
OptionThree
}
Converter
public class EnumToDisplayConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, string language)
{
var enumValue = value as Enum;
return enumValue == null ? DependencyProperty.UnsetValue : enumValue.GetDescriptionFromEnumValue();
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
return value;
}
}
Viewmodel (partial)
public IReadOnlyList<EnumOptions> Options { get; }
private EnumOptions _selectedOption;
public EnumOptions SelectedOption
{
get { return _selectedOption; }
set
{
_selectedOption = value;
OnPropertyChanged(() => SelectedOption);
}
}
// Initialization in constructor
Options = EnumExtensions.GetValues<EnumOptions>().ToArray();
// If you want to set a default.
SelectedOption = Options[0];
Extensions
public static class EnumExtensions
{
public static string GetDescriptionFromEnumValue(this Enum value)
{
var attribute = value.GetType()
.GetField(value.ToString())
.GetCustomAttributes(typeof(DisplayAttribute), false)
.SingleOrDefault() as DisplayAttribute;
return attribute == null ? value.ToString() : attribute.Description;
}
/// <summary>
/// Enumerates all enum values
/// </summary>
/// <typeparam name="T">Enum type</typeparam>
/// <returns>IEnumerable containing all enum values</returns>
/// <see cref="http://stackoverflow.com/questions/972307/can-you-loop-through-all-enum-values"/>
public static IEnumerable<T> GetValues<T>()
{
return Enum.GetValues(typeof (T)).Cast<T>();
}
}
XAML (partial)
<TextBlock Grid.Row="1">Choose an option</TextBlock>
<ComboBox Grid.Row="2"
ItemsSource="{Binding Options}"
SelectedItem="{Binding SelectedOption, Mode=TwoWay}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Converter={StaticResource EnumToDisplayConverter}}"></TextBlock>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
[ValueConversion(typeof(MyEnum), typeof(String))]
public class MyEnumConverter : IValueConverter
{
public object Convert(object value,
Type targetType,
object parameter,
CultureInfo culture)
{
var enumVal = (MyEnum)value;
// in this example, this is an extension method
return enumValue.Description();
}
public object ConvertBack(object value,
Type targetType,
object parameter,
CultureInfo culture)
{
var enumDesc = value as string;
MyEnum val;
if (Enum.TryParse(typeof(MyEnum), strValue, out val))
{
return val;
}
return DependencyProperty.UnsetValue;
}
}
The extension method in the example might look like this:
public static string Description(this MyEnum enumVal)
{
// you could use a switch statement here;
// or maybe a Dictionary
}
Supplement to the above examples to show decorating the enum with attributes.
sealed class DescriptionAttribute : Attribute
{
readonly string description;
public DescriptionAttribute(string description)
{
this.description = description;
}
public string Description
{
get { return description; }
}
}
enum Vehicle
{
[Description("Benz")]
Car,
[Description("Volvo")]
Bus,
[Description("Honda")]
Bike
}
BTW, I wonder why you needed to convert back the description to enum. If you provide the enums itself as ItemSource, you can use the description technique to show the display value in the ComboBox, however, once an item is selected you can directly have an enum as selected item.
Here is my working well example:
Enum definition:
public enum MyEnum
{
[Description("Exchange 2007")]
E2007,
[Description("Exchange 2010")]
E2010,
[Description("Exchange 2013")]
E2013,
};
Helper class:
public static class cHelperClass
{
#region GetValuesAndDescriptions
public static object[] GetValuesAndDescriptions(Type enumType)
{
var kvPairList = new List<KeyValuePair<string, string>>();
var listValue = Enum.GetValues(enumType);
for (var i = 0; i < listValue.Length; i++)
{
var value = listValue.GetValue(i);
var enumValue = (Enum)listValue.GetValue(i);
kvPairList.Add(new KeyValuePair<string, string>(value.ToString(), GetDescription(enumValue)));
}
var valuesAndDescriptions = from kv in kvPairList select new
{
Value = kv.Key,
Description = kv.Value
};
return valuesAndDescriptions.ToArray();
}
public static string GetDescription(this Enum value)
{
var fieldInfo = value.GetType().GetField(value.ToString());
var attributes = (DescriptionAttribute[])fieldInfo.GetCustomAttributes(typeof(DescriptionAttribute), false);
return (attributes.Length > 0) ? attributes[0].Description : value.ToString();
}
public static string GetStringValue(this Enum enumItem)
{
return enumItem
.GetType()
.GetField(enumItem.ToString())
.GetCustomAttributes<StringValueAttribute>()
.Select(a => a.Value)
.FirstOrDefault() ?? enumItem.ToString();
}
public static string GetName(Type enumType, object value)
{
return Enum.GetName(enumType, value);
}
#endregion
}
XAML:
<UserControl.Resources>
<!-- ObjectDataProvider für WindowStyles -->
<ObjectDataProvider x:Key="myEnumResource" MethodName="GetValuesAndDescriptions" ObjectType="classes:cHelperClass">
<ObjectDataProvider.MethodParameters>
<x:Type TypeName="classes:MyEnum" />
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
</UserControl.Resources>
<ComboBox ItemsSource="{Binding Source={StaticResource myEnumResource}}" DisplayMemberPath="Description" SelectedValuePath="Value" SelectedValue="{Binding MyEnum, Mode=TwoWay}" />
I want to implement a converter so that certain XAML elements only appear/disappear if there are items in an ObservableCollection.
I have referenced How to access generic property without knowing the closed generic type but cannot get it to work with my implementation. It build and deploys OK (to Windows Phone 7 emulator and device) but does not work. Moreover Blend throws an exception and will no longer render the page,
NullReferenceException: Object reference not set to an instance of an
object.
Here is what I have so far,
// Sets the vsibility depending on whether the collection is empty or not depending if parameter is "VisibleOnEmpty" or "CollapsedOnEmpty"
public class CollectionLengthToVisibility : System.Windows.Data.IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo cultureInfo)
{
// From https://stackoverflow.com/questions/4592644/how-to-access-generic-property-without-knowing-the-closed-generic-type
var p = value.GetType().GetProperty("Length");
int? length = p.GetValue(value, new object[] { }) as int?;
string s = (string)parameter;
if ( ((length == 0) && (s == "VisibleOnEmpty"))
|| ((length != 0) && (s == "CollapsedOnEmpty")) )
{
return Visibility.Visible;
}
else
{
return Visibility.Collapsed;
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo cultureInfo)
{
return null;
}
}
Here is how I referenced the converter on Blend/XAML
<TextBlock Visibility="{Binding QuickProfiles, ConverterParameter=CollapsedOnEmpty, Converter={StaticResource CollectionLengthToVisibility}}">Some Text</TextBlock>
I would use the Enumerable.Any() extension method. It will work on any IEnumerable<T> and avoids you having to know what sort of collection you're dealing with. Since you don't know T you can just use .Cast<object>()
public class CollectionLengthToVisibility : System.Windows.Data.IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo cultureInfo)
{
var collection = value as System.Collections.IEnumerable;
if (collection == null)
throw new ArgumentException("value");
if (collection.Cast<object>().Any())
return Visibility.Visible;
else
return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo cultureInfo)
{
throw new NotImplementedException();
}
}