I have a binding list of Models and a DataGrid. Value can be of couple of data types (bool, double).
public class Model
{
public object Value { get; set; }
}
public void Initialize()
{
var models = new BindingList<Model>();
models.Add(new Model(){ Value = "hello"});
models.Add(new Model(){Value=true});
signals.ItemsSource = models;
}
I want to display the data in the data grid and I want to use textbox for numbers, but combo(true/false) for boolean values.So I implemented bool2string converter and DataTemplateSelector. In my example I have one text column and one template column displaying the same data. When I start the application the combo values are not initialized (nothing is selected). Once I start playing with values, everything works,the values are properly synchronized (if I change value in one column, it will propagate to the other column). Do you have any idea, what mistake I'm doing?
public class BoolToStringConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return ((bool)value == true) ? "true" : "false";
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var comboValue = (value as ComboBoxItem).Content.ToString();
return (String.Compare(comboValue, "true", StringComparison.InvariantCultureIgnoreCase) == 0);
}
}
public class DynamicDataTemplateSelector : DataTemplateSelector
{
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
var element = container as FrameworkElement;
var signal = item as Model;
if (element != null && signal != null)
{
if (signal.Value is bool)
return element.FindResource("BoolTemplate") as DataTemplate;
else
return element.FindResource("TextTemplate") as DataTemplate;
}
return null;
}
}
My xaml looks like following:
<Window.Resources>
<comboQuestion:DynamicDataTemplateSelector x:Key="DataTemplateSelector"/>
<comboQuestion:BoolToStringConverter x:Key="BoolToStringConverter"/>
</Window.Resources>
<Grid>
<DataGrid Grid.Row="1" Name="signals" AutoGenerateColumns="False" ItemsSource="{Binding}" >
<DataGrid.Resources>
<DataTemplate x:Key="BoolTemplate">
<ComboBox SelectedItem="{Binding Value, Converter={StaticResource BoolToStringConverter}, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
<ComboBoxItem>true</ComboBoxItem>
<ComboBoxItem>false</ComboBoxItem>
</ComboBox>
</DataTemplate>
<DataTemplate x:Key="TextTemplate">
<TextBox Text="{Binding Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</DataTemplate>
</DataGrid.Resources>
<DataGrid.Columns>
<DataGridTextColumn Header="TextValue" Binding="{Binding Value}"/>
<DataGridTemplateColumn Header="DynamicValue" CellTemplateSelector="{StaticResource DataTemplateSelector}"/>
</DataGrid.Columns>
</DataGrid>
</Grid>
EDIT:
I tried to change the SelectedItem to SelectedValue and I also tried to change the Convert part of the converter to:
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var cbi = new ComboBoxItem();
cbi.Content = ((bool)value == true) ? "true" : "false";
return cbi;
}
however, the behavior remains the same.
You can convert a boolean to an index number using the following converter:
public class BooleanToIndexConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return ((bool)value == true) ? 0 : 1;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return ((int)value == 0) ? true : false;
}
}
Then bind to SelectedIndex on the ComboBox:
SelectedIndex="{Binding Value, Converter={StaticResource BooleanToIndexConverter}}
First of all, I am new to WPF and Xaml, so I just hope that you understand what I am asking.
I got this situation: There is a listBox of Animals. Every Animal has Weight property. What I am trying to achieve is whenever Weight of Animal is greater then 300 kg, that Weight should be displayed red.
You could use custom converter to achieve that. If your item looks like that:
public class Animal
{
public int Weight { get; set; }
public string Name { get; set; }
}
and ItemTemplate like that:
<DataTemplate x:Key="AnimalTemplate">
<TextBlock Text="{Binding Name}" Foreground="{Binding Weight, Converter={StaticResource AnimalColorSelector}}"/>
</DataTemplate>
Your converter will be like the following one:
public class AnimalColorSelector : IValueConverter
{
private readonly Color _overweightColor = Colors.Red;
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is int)
{
return (int) value > 300 ? new SolidColorBrush(_overweightColor) : Binding.DoNothing;
}
return Binding.DoNothing;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotSupportedException();
}
}
This approach has the following pros:
You don't need to hardcode the default color, but inherit it by using Binding.DoNothing.
You don't need to store any style information in a view model.
You could create a ViewModel for Animals that would contain necessary logic for color setting. Like this:
public class VMAnimal : INotifyPropertyChanged
{
private int _weight;
public int Weight
{
get { return _weight; }
set
{
_weight = value;
RaisePropertyChanged("Weight");
RaisePropertyChanged("Color");
}
}
public Brush Foreground
{
get
{
if (Weight > 300)
return new SolidColorBrush(Color.Red);
return new SolidColorBrush(Color.Black);
}
}
}
And use it with binding like this:
<TextBlock Text="{Binding Weight}" Foreground="{Binding Foreground}" />
I've got an enum like this:
public enum MyLovelyEnum
{
FirstSelection,
TheOtherSelection,
YetAnotherOne
};
I got a property in my DataContext:
public MyLovelyEnum VeryLovelyEnum { get; set; }
And I got three RadioButtons in my WPF client.
<RadioButton Margin="3">First Selection</RadioButton>
<RadioButton Margin="3">The Other Selection</RadioButton>
<RadioButton Margin="3">Yet Another one</RadioButton>
Now how do I bind the RadioButtons to the property for a proper two-way binding?
You can further simplify the accepted answer. Instead of typing out the enums as strings in xaml and doing more work in your converter than needed, you can explicitly pass in the enum value instead of a string representation, and as CrimsonX commented, errors get thrown at compile time rather than runtime:
ConverterParameter={x:Static local: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>
Then simplify the converter:
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;
}
}
Edit (Dec 16 '10):
Thanks to anon for suggesting returning Binding.DoNothing rather than DependencyProperty.UnsetValue.
Note - Multiple groups of RadioButtons in same container (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.
Edit (Apr 5 '11):
Simplified ConvertBack's if-else to use a Ternary Operator.
Note - Enum type nested in a class (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:Static local:YourClass+YourNestedEnumType.Enum1}
Due to this Microsoft Connect Issue, however, the designer in VS2010 will no longer load stating "Type 'local:YourClass+YourNestedEnumType' was not found.", but the project does compile and run successfully. Of course, you can avoid this issue if you are able to move your enum type to the namespace directly.
Edit (Jan 27 '12):
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;
}
}
Edit (May 7 '15):
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);
}
Note - NullReferenceException (Oct 10 '18):
Updated the example to remove the possibility of throwing a NullReferenceException. `IsChecked` is a nullable type so returning `Nullable` seems a reasonable solution.
You could use a more generic converter
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
}
And in the XAML-Part you use:
<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>
For the EnumToBooleanConverter answer:
Instead of returning DependencyProperty.UnsetValue consider returning Binding.DoNothing for the case where the radio button IsChecked value becomes false.
The former indicates a problem (and might show the user a red rectangle or similar validation indicators) while the latter just indicates that nothing should be done, which is what is wanted in that case.
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
I would use the RadioButtons in a ListBox, and then bind to the SelectedValue.
This is an older thread about this topic, but the base idea should be the same: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/323d067a-efef-4c9f-8d99-fecf45522395/
For UWP, it is not so simple: You must jump through an extra hoop to pass a field value as a parameter.
Example 1
Valid for both WPF and UWP.
<MyControl>
<MyControl.MyProperty>
<Binding Converter="{StaticResource EnumToBooleanConverter}" Path="AnotherProperty">
<Binding.ConverterParameter>
<MyLibrary:MyEnum>Field</MyLibrary:MyEnum>
</Binding.ConverterParameter>
</MyControl>
</MyControl.MyProperty>
</MyControl>
Example 2
Valid for both WPF and UWP.
...
<MyLibrary:MyEnum x:Key="MyEnumField">Field</MyLibrary:MyEnum>
...
<MyControl MyProperty="{Binding AnotherProperty, Converter={StaticResource EnumToBooleanConverter}, ConverterParameter={StaticResource MyEnumField}}"/>
Example 3
Valid only for WPF!
<MyControl MyProperty="{Binding AnotherProperty, Converter={StaticResource EnumToBooleanConverter}, ConverterParameter={x:Static MyLibrary:MyEnum.Field}}"/>
UWP doesn't support x:Static so Example 3 is out of the question; assuming you go with Example 1, the result is more verbose code. Example 2 is slightly better, but still not ideal.
Solution
public abstract class EnumToBooleanConverter<TEnum> : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, string language)
{
var Parameter = parameter as string;
if (Parameter == null)
return DependencyProperty.UnsetValue;
if (Enum.IsDefined(typeof(TEnum), value) == false)
return DependencyProperty.UnsetValue;
return Enum.Parse(typeof(TEnum), Parameter).Equals(value);
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
var Parameter = parameter as string;
return Parameter == null ? DependencyProperty.UnsetValue : Enum.Parse(typeof(TEnum), Parameter);
}
}
Then, for each type you wish to support, define a converter that boxes the enum type.
public class MyEnumToBooleanConverter : EnumToBooleanConverter<MyEnum>
{
//Nothing to do!
}
The reason it must be boxed is because there's seemingly no way to reference the type in the ConvertBack method; the boxing takes care of that. If you go with either of the first two examples, you can just reference the parameter type, eliminating the need to inherit from a boxed class; if you wish to do it all in one line and with least verbosity possible, the latter solution is ideal.
Usage resembles Example 2, but is, in fact, less verbose.
<MyControl MyProperty="{Binding AnotherProperty, Converter={StaticResource MyEnumToBooleanConverter}, ConverterParameter=Field}"/>
The downside is you must define a converter for each type you wish to support.
I've created a new class to handle binding RadioButtons and CheckBoxes to enums. It works for flagged enums (with multiple checkbox selections) and non-flagged enums for single-selection checkboxes or radio buttons. It also requires no ValueConverters at all.
This might look more complicated at first, however, once you copy this class into your project, it's done. It's generic so it can easily be reused for any enum.
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));
}
}
And for how to use it, let's say you have an enum for running a task manually or automatically, and can be scheduled for any days of the week, and some optional options...
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
}
Now, here's how easy it is to use this class:
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; }
}
And here's how easy it is to bind checkboxes and radio buttons with this class:
<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)
This work for Checkbox too.
public class EnumToBoolConverter:IValueConverter
{
private int val;
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
int intParam = (int)parameter;
val = (int)value;
return ((intParam & val) != 0);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
val ^= (int)parameter;
return Enum.Parse(targetType, val.ToString());
}
}
Binding a single enum to multiple checkboxes.
You can create the radio buttons dynamically, ListBox can help you do that, without converters, quite simple.
The concrete steps are below:
create a ListBox and set the ItemsSource for the listbox as the enum MyLovelyEnum and binding the SelectedItem of the ListBox to the VeryLovelyEnum property.
then the Radio Buttons for each ListBoxItem will be created.
Step 1: add the enum to static resources for your Window, UserControl or Grid etc.
<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>
Step 2: Use the List Box and Control Template to populate each item inside as Radio button
<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>
The advantage is: if someday your enum class changes, you do not need to update the GUI (XAML file).
References:
https://brianlagunas.com/a-better-way-to-data-bind-enums-in-wpf/
One way to handle this would be to have separate bool properties in your ViewModel class. Here is how I've handled with such a situation:
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>
It's not as robust or dynamic as some of the other solutions, but the nice thing is it's very self-contained and doesn't require creating custom converters or anything like that.
Based on the EnumToBooleanConverter from Scott.
I noticed that the ConvertBack method doesn't work on the Enum with flags code.
I've tried the following code:
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;
}
}
}
}
The only thing that I can't get to work is to do a cast from int to targetType so I made it hardcoded to NavigationProjectDates, the enum that I use. And, targetType == NavigationProjectDates...
Edit for more generic Flags Enum converter:
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;
}
}
A TwoWay Binding solution to UWP that takes the usage of Nullable:
C# Part:
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;
}
}
Here the null value acts as the 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 Part:
...
<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>
I am using MVVM in my Silverlight app. When control visibility is need to be managed by data, I am connecting its 'Visibility' property to object's corresponding property:
XAML:
<TextBlock Text="Price" Visibility="{Binding PriceVisibility, Mode=OneWay}"/>
<TextBox Text="{Binding TicketPrice, Mode=TwoWay}" Visibility="{Binding PriceVisibility, Mode=OneWay}"/>
CodeBehind (C#):
public string PriceVisibility { get { return PriceVisible ? "Visible" : "Collapsed"; } }
But from my perspective, returning string representation of the Visibility property is not a best approach.
Could you please advise if there are any better way?
Thanks!
I just used Reflector to inspect the type converters in the PresentationFramework.dll
There is already an implementation that can convert between boolean and visibility. You should be able to make use of this in your silverlight application.
public sealed class BooleanToVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
bool flag = false;
if (value is bool)
{
flag = (bool) value;
}
else if (value is bool?)
{
bool? nullable = (bool?) value;
flag = nullable.HasValue ? nullable.Value : false;
}
return (flag ? Visibility.Visible : Visibility.Collapsed);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return ((value is Visibility) && (((Visibility) value) == Visibility.Visible));
}
}
I've faced the problem of binding a Boolean value to the visibility property, so I've implemented my own Boolean to Visibility Converter, I'm using it with most of my applications.
Add the Following Class to your application:
public class BoolVisibilityConverter : IValueConverter{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture){
bool isVisible = (bool)value;
return isVisible ? System.Windows.Visibility.Visible : System.Windows.Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture){
System.Windows.Visibility currVisibility = (System.Windows.Visibility)value;
return (currVisibility == System.Windows.Visibility.Visible);
}
}
Now To Use it you'll need to add it as a resource in your XAML Code.
<UserControl.Resources>
<Helpers:BoolVisibilityConverter x:Key="boolVisibilityConverter" />
</UserControl.Resources>
In your example use the following:
<TextBlock Text="Price" Visibility="{Binding PriceVisibility, Mode=OneWay, Converter={StaticResource boolVisibilityConverter}}"/>
<TextBox Text="{Binding TicketPrice, Mode=TwoWay}" Visibility="{Binding PriceVisibility, Mode=OneWay, Converter={StaticResource boolVisibilityConverter}}"/>
I have a Collection of Model-objects in my ViewModel. I would like to be able to bind a TabControl to these and use a DataTemplate to extract the information from the Model-objects. When I try to do this I get the errormessage: Unable to cast object of type Model to object of type TabItem. After spending some time looking for a solution I found the following:
The Silverlight TabControl is
broken. Use a combination of ListBox
and ContentControl to mimic the
behaviour of a TabControl. (Means
that I have to skin the ListBox to
look like a TabControl)
TabControl does not override
PrepareContainerForItemOverride and
the solution is to make a
Converter. (Not so good because I
then need to specify the type of the
convertee in the Converter)
Anyone know any better solution?
XAML
<sdk:TabControl ItemsSource="{Binding Items, ElementName=MyControl}">
<sdk:TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" />
</DataTemplate>
</sdk:TabControl.ItemTemplate>
</sdk:TabControl>
C#
public ObservableCollection<Model> Items { get; set; }
public ViewModel()
Items = new ObservableCollection<Model>{
new Model { Name = "1"},
new Model { Name = "2"},
new Model { Name = "3"},
new Model { Name = "4"}
};
}
Suggested Converter:
public class TabConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
List<TabSource> source = value as List<TabSource>;
if (source != null)
{
List<TabItem> result = new List<TabItem>();
foreach (TabSource tab in source)
{
result.Add(new TabItem()
{
Header = tab.Header,
Content = tab.Content
});
}
return result;
}
return null;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
Create converter
public class SourceToTabItemsConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
try
{
var source = (IEnumerable)value;
if (source != null)
{
var controlTemplate = (ControlTemplate)parameter;
var tabItems = new List<TabItem>();
foreach (object item in source)
{
PropertyInfo[] propertyInfos = item.GetType().GetProperties();
//тут мы выбираем, то поле которое будет Header. Вы должны сами вводить это значение.
var propertyInfo = propertyInfos.First(x => x.Name == "name");
string headerText = null;
if (propertyInfo != null)
{
object propValue = propertyInfo.GetValue(item, null);
headerText = (propValue ?? string.Empty).ToString();
}
var tabItem = new TabItem
{
DataContext = item,
Header = headerText,
Content =
controlTemplate == null
? item
: new ContentControl { Template = controlTemplate }
};
tabItems.Add(tabItem);
}
return tabItems;
}
return null;
}
catch (Exception)
{
return null;
}
}
/// <summary>
/// ConvertBack method is not supported
/// </summary>
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotSupportedException("ConvertBack method is not supported");
}
Create ControlTemplate:
<ControlTemplate x:Key="MyTabItemContentTemplate">
<StackPanel>
<TextBlock Text="{Binding Path=name}" />
</StackPanel>
</ControlTemplate>
And binding convert, controltemplate
<controls:TabControl x:Name="tabControl"
ItemsSource="{Binding ElementName=tabControl,
Path=DataContext,
Converter={StaticResource ConverterCollectionToTabItems},
ConverterParameter={StaticResource MyTabItemContentTemplate}}">
</controls:TabControl>
taken from the blog binding-tabcontrol