I have a complex value object class that has 1) a number or read-only properties; 2) a private constructor; and 3) a number of static singleton instance properties [so the properties of a ComplexValueObject never change and an individual value is instantiated once in the application's lifecycle].
public class ComplexValueClass
{
/* A number of read only properties */
private readonly string _propertyOne;
public string PropertyOne
{
get
{
return _propertyOne;
}
}
private readonly string _propertyTwo;
public string PropertyTwo
{
get
{
return _propertyTwo;
}
}
/* a private constructor */
private ComplexValueClass(string propertyOne, string propertyTwo)
{
_propertyOne = propertyOne;
_propertyTwo = PropertyTwo;
}
/* a number of singleton instances */
private static ComplexValueClass _complexValueObjectOne;
public static ComplexValueClass ComplexValueObjectOne
{
get
{
if (_complexValueObjectOne == null)
{
_complexValueObjectOne = new ComplexValueClass("string one", "string two");
}
return _complexValueObjectOne;
}
}
private static ComplexValueClass _complexValueObjectTwo;
public static ComplexValueClass ComplexValueObjectTwo
{
get
{
if (_complexValueObjectTwo == null)
{
_complexValueObjectTwo = new ComplexValueClass("string three", "string four");
}
return _complexValueObjectTwo;
}
}
}
I have a data context class that looks something like this:
public class DataContextClass : INotifyPropertyChanged
{
private ComplexValueClass _complexValueClass;
public ComplexValueClass ComplexValueObject
{
get
{
return _complexValueClass;
}
set
{
_complexValueClass = value;
PropertyChanged(this, new PropertyChangedEventArgs("ComplexValueObject"));
}
}
}
I would like to write a XAML binding statement to a property on my complex value object that updates the UI whenever the entire complex value object changes. What is the best and/or most concise way of doing this? I have something like:
<Object Value="{Binding ComplexValueObject.PropertyOne}" />
but the UI does not update when ComplexValueObject as a whole changes.
Your original scenario should work just fine because in most cases Bindings recognize change notifications on any part of their property path. I in fact tried out the code you posted to confirm and it does work just fine.
Are there other complexities you may not be expressing in your stripped down sample? The primary one I can think of would be collections->ItemsSource Bindings but there could be something related to the property you're assigning the bound value to (since it's obviously not an Object) or something else entirely.
You don't notify on changes to PropertyOne so UI will not update. Instead bind to ComplexValueObject and use value converter to get the property value.
<Object Value="{Binding Path=ComplexValueObject, Converter={StaticResource ComplexValueConverter}, ConverterParameter=PropertyOne}" />
public class ComplexValueConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
ComplexValue cv = value as ComplexValue;
string propName = parameter as string;
switch (propName)
{
case "PropertyOne":
return cv.PropertyOne;
case "PropertyTwo":
return cv.PropertyTwo;
default:
throw new Exception();
}
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
You need INotifyPropertyChanged on your Complex class. The only notifies if you reassign the entire property in the parent, the properties of that child class need to notify to0 if you are going to bind to them.
Related
I am attaching enum to a picker and onSelect i am binding to the actual value of the enum, not its title.
My enum is as follows:
public enum Reason
{
AnnualLeave = 12,
Emergency = 23,
MaternityLeave = 34
}
My class uses the following to bind the enum title to the picker
public Reason ReasonSelectedOption { get; set; }
public ObservableCollection<Reason> ReasonDisplay
{
get => new ObservableCollection<Reason>(Enum.GetValues(typeof(Reason)).OfType<Reason>().ToList());
}
The actual picker
<Picker
ItemsSource="{Binding ReasonDisplay}"
SelectedItem="{Binding ReasonSelectedOption}"
Title="Please Select"
HorizontalOptions="FillAndExpand" />
Everything works fine except in the actual picker, the options appear as AnnualLeave and MaternityLeave which is what's expected from my code but i want them to appear as Annual Leave and Maternity Leave (with the space inbetween) preserving the selecteditem value
Current case: When user selects AnnualLeave, selectedItem value is 12, if i convert to string the selected value becomes 0.
I am simply asking how to put spaces inbetween the enum options and also preserve the SelectedItem integer value
Here you have to keep in mind the internationalisation.
Even if you don't have localised texts now, you may have to support it in the future. So, keeping that in mind, you won't need simply to "split" the string, but to take a specific text from somewhere (i.e. translate it according to the culture).
You can achieve it with the help of some attributes, extension methods and some clever binding.
Let's say that you want to have a picker with 2 options - what is the property type. The PropertyType is an enum, that looks like this:
public enum PropertyType
{
House,
Apartment
}
Since the built-in Description attribute can't translate texts for us, we can use a custom attribute to assign a specific text to an enum type, like this:
public enum PropertyType
{
[LocalizedDescription(nameof(R.SingleFamilyHouse))]
House,
[LocalizedDescription(nameof(R.ApartmentBuilding))]
Apartment
}
The attribute code looks like this:
public class LocalizedDescriptionAttribute : DescriptionAttribute
{
private readonly ResourceManager resourceManager;
private readonly string resourceKey;
public LocalizedDescriptionAttribute(string resourceKey, Type resourceType = null)
{
this.resourceKey = resourceKey;
if (resourceType == null)
{
resourceType = typeof(R);
}
resourceManager = new ResourceManager(resourceType);
}
public override string Description
{
get
{
string description = resourceManager.GetString(resourceKey);
return string.IsNullOrWhiteSpace(description) ? $"[[{resourceKey}]]" : description;
}
}
}
R is my resx file. I have created a Resources folder and inside it I have 2 resx files - R.resx (for English strings) & R.de.resx (for German translation). If you don't want to have internationalisation now, you can change the implementation to get your strings from another place. But it is considered a good practice to always use a resx file, even if you only have 1 language. You never now what tomorrow may bring.
Here is my structure:
The idea behind LocalizedDescriptionAttribute class is that the built-in Description attribute isn't very useful for our case. So we'll have to take the resource key that we have provided it, translates and to override the Description attribute, which later we will reference.
Now we need to obtain the localised description text with this helper method:
public static class EnumExtensions
{
public static string GetLocalizedDescriptionFromEnumValue(this Enum value)
{
return !(value.GetType()
.GetField(value.ToString())
.GetCustomAttributes(typeof(LocalizedDescriptionAttribute), false)
.SingleOrDefault() is LocalizedDescriptionAttribute attribute) ? value.ToString() : attribute.Description;
}
}
Now, when we create the bindings for the Picker, we won't just use a simple Enum, but a specific PropertyTypeViewModel, which will have 2 properties - the Enum itself and a Name that will be displayed.
public class PropertyTypeViewModel : BaseViewModel
{
private string name;
public string Name
{
get => name;
set => SetValue(ref name, value);
}
private PropertyType type;
public PropertyType Type
{
get => type;
set => SetValue(ref type, value);
}
public PropertyTypeViewModel()
{
}
public PropertyTypeViewModel(PropertyType type)
: this()
{
Type = type;
Name = type.GetLocalizedDescriptionFromEnumValue();
}
}
The important line is the last one - Name = type.GetLocalizedDescriptionFromEnumValue();
The final thing that is left is to set your Picker's ItemsSource to your collection of PropertyTypeViewModels and ItemDisplayBinding to be pointing to the Name property - ItemDisplayBinding="{Binding Name}"
That's it - now you have a Picker with dynamic localised strings.
You could use a converter
public class EnumToStringConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value == null) return null;
var valueAsString = value.ToString();
valueAsString = valueAsString.SplitCamelCase();
return valueAsString;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
And for the SplitCamelCase I wrote this but I'm sure there are cleaner options:
public static string SplitCamelCase(this string str)
{
string result = "";
for (int i = 0; i < str.Count(); i++)
{
var letter = str[i];
var previousLetter = i != 0 ? str[i - 1] : 'A';
if (i != 0 && char.IsUpper(previousLetter) == false && char.IsUpper(letter)) result = result + " " + letter;
else result = result + letter;
}
return result;
}
Then just used it like so:
<TextBlock Text="{Binding Converter={StaticResource EnumToStringConverter}}"/>
How I can make something like this in VS properties Window (collapsible multi properties):
I tried such code:
Test z = new Test();
[ Browsable(true)]
public Test _TEST_ {
get { return z; }
set { z = value; }
}
Where "Test" class is:
[Browsable(true)]
public class Test {
[Browsable(true)]
public string A { get;set; }
[Browsable(true)]
public string B { get;set; }
}
But this gives me only grayed-out name of class
Alright, I got something to work that may satisfy your case.
To get a class to expand in the PropertyGrid, you have to add a TypeConverterAttribute to it, referencing the type of an ExpandableObjectConverter (or something else that derives from it).
[TypeConverter(typeof(ExpandableObjectConverter))]
public class Test
{
[Browsable(true)]
public string A { get; set; }
[Browsable(true)]
public string B { get; set; }
}
The only problem is that it now displays the type name (the return value of its ToString() method as the value of your class). You can either live with it (which you probably won't want to), change the ToString() return value to something more fitting or use a custom TypeConverter for that case.
I'll show you a quick implementation on how the latter could be done:
internal class TestConverter : ExpandableObjectConverter
{
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
if (destinationType == typeof(string))
return "";
return base.ConvertTo(context, culture, value, destinationType);
}
}
And then you would write this, instead of what I wrote above:
[TypeConverter(typeof(TestConverter))]
public class Test
{
[Browsable(true)]
public string A { get; set; }
[Browsable(true)]
public string B { get; set; }
}
This just empties the information and prevents the user to enter some other value. You probably want to show something more descriptive which is completely up to you.
It is also possible to get information and parse it into useful values. A good example would be the location, which is an object of type Point visualized with [10,5] when X is 10 and Y is 5. When you enter new values they are parsed and set to the integers that are referenced by the original string.
Because I couldn't find much about the topic, I looked up some references in ReferenceSource, because it had to be done before. In my case, I peeked into ButtonBase and FlatButtonAppearance of WindowsForms to see how Microsoft did it, back in the day.
Hope I could help.
Here is the TypeConverter Class. This allows VS properties to access your object as strings, and convert back to it from strings.
for more about TypeConversion.
class MultiPropConverter : ExpandableObjectConverter
{
public override bool CanConvertFrom(ITypeDescriptorContext context,
Type sourceType)
{
if (sourceType == typeof(string)) { return true; }
return base.CanConvertFrom(context, sourceType);
}
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture,
object value)
{
if (value is string)
{
string[] v = ((string)value).Split(new char[] { ',' });
if(v.Length == 3) // Check that there are no ',' in your string(s) A.
{
return new DropDownProperties(v[0], float.Parse(v[1]), int.Parse(v[2]));
}
}
return base.ConvertFrom(context, culture, value);
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture,
object value, Type destinationType)
{
if (destinationType == typeof(string)) // What VS properties ask for to display
{
DropDownProperties dDP = (DropDownProperties)value;
return dDP.A + "," + dDP.B.ToString() + "," + dDP.C.ToString();
}
return base.ConvertTo(context, culture, value, destinationType);
}
}
the Multi-Property Class:
[TypeConverter(typeof(MultiPropConverter))]
public class DropDownProperties
{
[Description("Description of A")]
public string A { get; set; } = "Default";
[Description("Description of B")]
public float B { get; set; } = 0f;
[Description("Description of C")]
public int C { get; set; } = 1;
}
And then class instantiation:
[Description("Category Description"), Category("ACategory")]
public DropDownProperties dropProp { get; set; } = new DropDownProperties()
{ A = "Hello World", B = "0.1", C = 0};
You do not need the Browsable attribute if you include a category or description for the item.
Cheers!
In addition to the already good answers by others.
Browseable(true/false) means it can be browsed in the property window.
Please note, the Visual Studio properties editor will only show public properties. Private properties are hidden and can't be browsed for various reasons.
Public properties are browsable by default.
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.browsableattribute?view=netcore-3.1
The designer will always only show one value per default for strings, multi-property dropdowns only work for integers afaik.
Also, there is EditorBrowsable which defines whether or not Intellisense shows your property.
You can do something like this:
public class Column
{
[EditorBrowsable(EditorBrowsableState.Always)]
public string name { get; set; }
[EditorBrowsable(EditorBrowsableState.Never)]
}
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.editorbrowsablestate?view=netcore-3.1
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.editorbrowsableattribute?view=netcore-3.1
I've created a custom converter that performs converting of values based on configured mapping. It looks like below
public class UniversalConverter : List<ConverterItem>, IValueConverter
{
private bool useDefaultValue;
private object defaultValue;
public object DefaultValue
{
get { return defaultValue; }
set
{
defaultValue = value;
useDefaultValue = true;
}
}
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
foreach (var item in this)
if (Equals(item.From, value))
return item.To;
if (useDefaultValue)
return DefaultValue;
throw new ConversionException(string.Format("Value {0} can't be converted and default value is not allowed", value));
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
foreach (var item in this)
if (Equals(item.To, value))
return item.From;
throw new ConversionException(string.Format("Value {0} can't be converted back", value));
}
}
public class ConverterItem
{
public object From { get; set; }
public object To { get; set; }
}
public class ConversionException : Exception
{
public ConversionException() { }
public ConversionException(string message) : base(message) { }
}
Sample XAML is below
<core:UniversalConverter x:Key="ItemCountToVisiblityConverter" DefaultValue="{x:Static Visibility.Collapsed}">
<core:ConverterItem To="{x:Static Visibility.Visible}">
<core:ConverterItem.From>
<system:Int32>0</system:Int32>
</core:ConverterItem.From>
</core:ConverterItem>
</core:UniversalConverter>
Now everything builds and works fine, but if I use it XAML Visual Studio underscores the whole file with curvy blue lines and shows two kind of mistakes:
1) If converter is put into ResourceDictionary AND is assigned an x:Key attribute it shows Missing key value on 'UniversalConverter' object
2) If I assign DefaultValue property any value (e.g {x:Null}) the message is XAML Node Stream: Missing EndMember for 'StuffLib.UniversalConverter.{http://schemas.microsoft.com/winfx/2006/xaml}_Items' before StartMember 'StuffLib.UniversalConverter.DefaultValue'
What is the reason for those messages? I can live with them but they hide all other compiler and ReSharper markings
Don't inherit from list, just create Items property in your converter:
[ContentProperty("Items")]
public class UniversalConverter : IValueConverter
{
public ConverterItem[] Items { get; set; }
public object DefaultValue { get; set; }
//all other stuff goes here
}
and xaml:
<l:UniversalConverter x:Key="MyConverter">
<x:Array Type="l:ConverterItem">
<l:ConverterItem From="..." To="..." />
Based on answer given by #Leiro
[ContentProperty("Items")]
public class UniversalConverter : IValueConverter
{
public UniversalConverter()
{
Items = new List<ConverterItem>();
}
public List<ConverterItem> Items { get; private set; }
//All other logic is the same
}
Note that this way you won't need to wrap items in collection in XAML
Resulting XAML
<core:UniversalConverter x:Key="ItemCountToVisiblityConverter" DefaultValue="{x:Static Visibility.Collapsed}">
<core:ConverterItem To="{x:Static Visibility.Visible}">
<core:ConverterItem.From>
<system:Int32>0</system:Int32>
</core:ConverterItem.From>
</core:ConverterItem>
</core:UniversalConverter>
It's because it is being used at design time but there is no data so I suspect a NullReferenceException is being thrown. Try checking for design time mode as follows at the top of the IValueConverter.Convert() method body:
// Check for design mode.
if ((bool)(DesignerProperties.IsInDesignModeProperty.GetMetadata(typeof(DependencyObject)).DefaultValue))
{
return false;
}
I have view-model with ObservableCollection<string> that's bound to a TextBox. Users must be able to enter textual data with some separators (say a comma or a semicolon), and have the change reflected to the ObservableCollection<string>, so if I type in the box abc,123,one, the ObservableCollection<string> will have three items: abc, 123 and one.
My examplary ViewModel:
class ViewModel {
public ObservableCollection<string> MyObservableCollection { get; set; }
}
My TextBox:
<TextBox Text="{Binding MyObservableCollection, Converter={StaticResource Conv}, Mode=TwoWay}"/>
My value-converter:
public class ObservableCollectionToAndFromString : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
ObservableCollection<string> oc;
if (targetType != typeof (string) || (oc = value as ObservableCollection<string>) == null)
return Binding.DoNothing;
return string.Join(",", oc);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
var str = value as string;
return str == null
? Binding.DoNothing
: str.Split(',');
}
}
But it doesn't work from understandable reason - WPF doesn't know how to replace an ObservableCollection<string> with string[].
But I don't want the framework to replace my ObservableCollection<string> object with new ObservableCollection<string> object (in that case I could have just created new one and return it in the ConvertBack method). I want it to add/remove items to/from the existing ObservableCollection<string>.
How can I accomplish this (without another model-view string property that will do the work in code-behind)?
Edit:
Ok, I give up... movel-view is the way to go... I hoped to make it work on several fields in one time, but that just to awkward.
I think it's better to add a string representation of data to your viewmodel.
internal class ViewModel
{
public ObservableCollection<string> MyObservableCollection { get; set; }
public string MyString
{
get { return string.Join(",", MyObservableCollection); }
set { // update observable collection here based on value }
}
}
<TextBox Text="{Binding MyString, Mode=TwoWay}"/>
I tried to search for an answer for this problem but could not find much, most probably because I do not know how to look for it properly, so here it goes. All help is very much appreciated.
With the base class that looks like
abstract public class Property
{
private String name;
public Property(String propertyName)
{
name = propertyName;
}
public String Name
{
get { return name; }
}
abstract public override String ToString();
}
And derived classes that look like
public class StringProperty : Property
{
private String value; // different properties for different types
public StringProperty(String propertyName, String value) : base(propertyName)
{
this.value = value;
}
public String Value // different signature for different properties
{
get { return value; }
}
public override String ToString()
{
return base.Name + ": " + value;
}
}
During runtime, the function receives a collection of "Property" objects. What do I need to do to be able to obtain the "Value" of each? Do I need to have a big if statement to query the type of each "Property" object? If not, is there a more elegant solution?
I tried to define an abstract "Value" property to be overridden but since the return types are different, it did not work. I also tried playing with shadowing the "Value" property, but I could not make it work. The idea of using an COM-like Variant does not sound very appropriate, either.
Thanks a lot in advance.
EDIT:
I should have added details as to what I am trying to do. The properties are displayed in a Winforms app. Different "TextBox"es represent different properties and are filtered for proper input (depending on the type). The updated values are read back and stored. The container object will be serialized into JSON and deserialized on an Android and iPhone client and eventually these values will be passed into a layer running native C++ code doing OpenGL stuff. I don't know in advance the kind of all needed properties so as the middleman, I wanted to make my code as robust as possible while being able to feed the OpenGL engine.
You can use a generic class:
public class AnyProperty<T> : Property
{
private T value;
// ... etc
I'd really recommend making the base class an Interface by now:
public interface IProperty
{
public String Name { get; }
}
public class Property<T> : IProperty
{
public Property(String name, T value)
{
Name = name;
Value = value;
}
public String Name { get; private set; }
public T Value { get; private set; }
public override String ToString()
{
return string.Format("{0}: {1}", Name, Value)
}
}
Here is sample usage:
var intProp = new Property<int> ("age", 32);
var strProp = new Property<string> ("name", "Earl");
var enumProp = new Property<ColorEnum> ("eye color", ColorEnum.Magenta);
To make the construction even simpler, you could have a factory method:
public static Property<T> MakeProperty(string name, T value)
{
return new Property<T>(name,value);
}
var intProp = MakeProperty("age", 32);
var strProp = MakeProperty("name", "Earl");
var enumProp = MakeProperty("eye color", ColorEnum.Magenta);
Not necessarily recommended, and a bit OT:
You could make it even funkier with an extension method:
public static Property<T> AsProp<T>(this T value, string name)
{
return new Property<T>(name,value);
}
var intProp = 32.AsProp("age");
var strProp = "Earl".AsProp("name");
var enumProp = ColorEnum.Magenta.AsProp("eye color");
You would have to simply use the object type. What are you trying to accomplish? The problem here isn't the structure of your classes, it's the function that receives the collection of Property objects. It's impossible to even cast something to an unknown type, since you don't know what type of variable it needs to be stored in.
So basically, your Property.Value property needs to be of type object. In your method that uses the Property objects, you need to do something with them, and what you're doing will decide how it should be structured. Are you printing values out? Have a *Value class inheriting from an abstract PropertyValue class and override ToString() to return an appropriate string represention.
I made a few changes to your sample code and got this result...
abstract public class Property
{
private readonly String _name;
public Property(String propertyName)
{
_name = propertyName;
}
public String Name
{
get { return _name; }
}
abstract public override String ToString();
}
public class StringProperty : Property
{
private readonly dynamic _value; // different properties for different types
public StringProperty(String propertyName, dynamic value)
: base(propertyName)
{
this._value = value;
}
public dynamic Value // different signature for different properties
{
get { return _value; }
}
public override String ToString()
{
return base.Name + ": " + _value;
}
}
static void Main(string[] args)
{
StringProperty sp = new StringProperty("A double", 3.444);
StringProperty sp2 = new StringProperty("My int", 4343);
StringProperty sp3 = new StringProperty("My directory", new DirectoryInfo("Some directory"));
StringProperty sp4 = new StringProperty("My null", null);
Console.WriteLine(sp);
Console.WriteLine(sp2);
Console.WriteLine(sp3);
Console.WriteLine(sp4);
}
}
Values are properly printed to the console in the expected way.
It would require a bit of a rethink, but have you considered using the dynamic type (introduced in .net4)
Doesn't really solve your problem, but sidespteps it.
Your properties can bascically just be a
Dictionary<String, dynamic>
, the gotcha is they don't get evaluated until runtime, so you get no compiler support for typing.
so given you want
int SomeValue = MyProperties[SomePropertyName] + 10;
So if
MyProperties[SomePropertyName] = 10; // all is good
if its 76.52 or Fred, the addition will throw an exception at the point it executes.
Code is much simpler and cleaner, no extra casting and the amount of scaffolding required is minimal, BUT, you'll need to unit test code that uses the dictionary extensively and religiously.